Pro Cast 20091

ProCAST User Manual

Version 2009.1

ProCAST User Manual Version 2009.1

Revised version (July 2009) - CL/PRCA/09/05/01/A

ProCAST User Manual

Version 2009.1

INTRODUCTION 9

SOFTWARE CAPABILITIES 9

SOFTWARE ORGANIZATION 11

USER MANUAL PRESENTATION 13

WHAT'S NEW 14

VERSION 2009.1 14

VERSION 2009.0 17

VERSION 2008.0 24

VERSION 2007.0 30

VERSION 2006.1 34

VERSION 2006.0 38

VERSION 2005.0 45

VERSION 2004.1 50

VERSION 2004.0 55

IDENTIFIED BUGS, PROBLEMS AND LIMITATIONS 59

SOFTWARE MANAGER 62

FILE MANAGER 62

MODULE CALLS 66

ADVANCED MODULE CALLS 74

RUN LIST 77

SOFTWARE CONFIGURATION 80

CUSTOMIZED INSTALLATION 84

FLEXLM 85

GETTING STARTED 89

SOFTWARE LAUNCH 89

PROBLEM SET-UP 91

CALCULATION 99

RESULTS DISPLAY 101

PRE-PROCESSING 104

INTRODUCTION 104

GEOMETRY IMPORT 108

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THERMAL 110

GEOMETRY ASSIGNMENTS 111

MATERIALS ASSIGNMENT 111

INTERFACES ASSIGNMENT 116

BOUNDARY CONDITIONS ASSIGNMENT 122

PROCESS CONDITIONS ASSIGNMENT 127

INITIAL CONDITIONS ASSIGNMENT 128

RUN PARAMETERS ASSIGNMENT 129

FLUID FLOW & FILLING 130

RADIATION 134

STRESS 149

DATABASES 158

MATERIAL DATABASE 158

MATERIAL PROPERTIES 162

THERMODYNAMIC DATABASES 169

INTERFACE DATABASE 198

BOUNDARY CONDITIONS DATABASE 201

PROCESS DATABASE 218

STRESS DATABASE 224

STRESS MODELS AND PROPERTIES 227

EXTRACT AND MAPPING 269

RESULTS EXTRACTION 270

RESULTS MAPPING 273

DOMAIN REMOVAL 275

DOMAIN ADDITION 277

EXTRACT EXAMPLES 281

RUN PARAMETERS 302

GENERAL RUN PARAMETERS 304

THERMAL RUN PARAMETERS 311

CYCLING RUN PARAMETERS 317

RADIATION RUN PARAMETERS 320

FLOW RUN PARAMETERS 324

TURBULENCE RUN PARAMETERS 337

STRESS RUN PARAMETERS 339

MICRO RUN PARAMETERS 344

PRE-DEFINED RUN PARAMETERS 348

RUN PARAMETERS RECOMMENDATIONS 350

POROSITY MODELS 353

POROS=1 354

POROS=4 358

POROS=8 358

DENSITY DEFINITION 359

ACTIVE FEEDING 360

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CAST IRON POROSITY MODEL 361

VIRTUAL MOLD 369

FILTERS 374

EXOTHERMIC 377

CYCLING 379

LOST FOAM 382

THIXO CASTING 387

CENTRIFUGAL CASTING 390

LARGE INGOT FILLING 393

MULTIPLE MESHES AND NON-COINCIDENT MESHES 395

GEOMETRY MANIPULATION 399

MESH OPTIMIZATION 403

USER FUNCTIONS 404

USER FUNCTIONS TEMPLATES 410

BATCH PRE-PROCESSING 424

INTRODUCTION 424

PRS USER INTERFACE 425

SCRIPT LANGUAGE 435

RUN OF THE CALCULATION 446

SOLVER 446

TROUBLESHOOTING 449

RESULTS VIEWING 453

INTRODUCTION 453

FIELD SELECTION 459

DISPLAY TYPES 463

DISPLAY PARAMETERS 473

TAPE PLAYER 491

CURVES 492

GEOMETRY MANIPULATION 498

RESULTS ANALYSIS 507

CRITERION FUNCTIONS 507

POROSITY 517

FATIGUE LIFE INDICATOR 518

HOT TEARING INDICATOR 519

CRACKING INDICATOR 520

FRECKLES INDICATOR 521

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FLUID FRONT TRACKING 522

RESULTS EXPORTS 530

INTRODUCTION 530

GEOMETRY 531

RADIATION FACES 532

TEMPERATURE 533

HEAT FLUX 536

DISPLACEMENTS 537

STRESS 538

ABAQUS IMPORT 542

SYSWELD IMPORT 545

PARALLEL SOLVER (DMP) 547

INTRODUCTION 547

HOW DOES PROCAST PARALLEL WORKS ? 550

USE OF THE PARALLEL SOLVER 555

REPEATABILITY 561

LIMITATIONS 562

MACHINE CONFIGURATION 563

HARDWARE AND OS 565

ADVANCED POROSITY MODULE 567

INTRODUCTION 568

ADVANCED POROSITY PRE-PROCESSING 571

MATERIAL PROPERTIES 572

GAS AND BUBBLE PROPERTIES 577

PROCESS INFORMATION 581

CALCULATION SETTINGS 589

EXAMPLES OF PREFIX_PORO.D INPUT FILE 596

APM EXAMPLES 600

ADVANCED POROSITY SOLVER 611

ADVANCED POROSITY POST-PROCESSING 614

APM APPENDIX 619

APM FLOW CHART 619

GROWTH MODEL OF A PORE 620

GAS THERMODYNAMIC DATABASE 623

LIST OF THE APM PARAMETERS 625

APM REFERENCES 628

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MICROSTRUCTURES 629

INTRODUCTION 630

CASE SET-UP AND RESULTS 633

EXAMPLES 639

IRON AND STEEL 646

INTRODUCTION TO IRON AND STEEL 646

IRON AND STEEL MODELS 653

CASE STUDIES 659

TTT/CCT MODELS 680

MICROSTRUCTURES - STRESS COUPLING 687

STRESS PROPERTIES DEPENDING UPON MICROSTRUCTURE 688

FINAL STRESS PROPERTIES AS FUNCTION OF MICROSTRUCTURE 695

"2-D" 698

INTRODUCTION 699

MESHING 701

CASE SETTING 708

CAFE-3D 711

INVERSE MODELING 718

INTRODUCTION 718

MODEL SET-UP 720

INVERSE RUN 727

FILE FORMATS 731

INVERSE APPENDIX 735

CONTINUOUS CASTING 745

PRINCIPLES 746

PRE-PROCESSING 752

STEADY STATE CASES 752

NON STEADY STATE CASES (MILE) 768

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MILE EXAMPLES 779

THERMAL + FLOW 779

THERMAL + STRESS 783

CORE BLOWING 786

HOT CRACKING (FOR CONTINUOUS CASTING) 794

INTRODUCTION 794

THE RDG HOT TEARING CRITERION 795

STRUCTURE OF THE INPUT FILES 799

RUNNING A CASE 803

VIEWING OF THE RESULTS 806

REFERENCES 811

INPUT-OUTPUT FILES 812

TIPS & TRAPS 817

INLET VELOCITY 817

LPDC RECOMMENDATIONS 819

RESTART 828

CONVERGENCE PROBLEMS 829

STRESS CALCULATIONS 830

GAPS IN STRESS MODELS 831

STRESS VISUALIZATION 835

RESULTS COMPARISONS BETWEEN VERSIONS 838

RESULTS COMPARISONS (2009.0) 838

GRAVITY-1 839

GRAVITY-2 841

GRAVITY-3 843

HPDC-1 846

LPDC-1 848

INVESTMENT-1 851

STRESS-1 853

MICROSTRUCTURE-1 857

THIXO-1 860

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CENTRIFUGAL-1 862


GRAVITY-1 866

GRAVITY-2 868

GRAVITY-3 870

HPDC-1 872

LPDC-1 874

INVESTMENT-1 877

STRESS-1 879


THIXO-1 886

CENTRIFUGAL-1 888


GRAVITY-1 892

GRAVITY-2 894

GRAVITY-3 896

HPDC-1 898

LPDC-1 901

INVESTMENT-1 904

STRESS-1 906


THIXO-1 913

CENTRIFUGAL-1 915

TUTORIALS 917

ProCAST User Manual

Version 2009.1

INTRODUCTION SOFTWARE CAPABILITIES

ProCAST is a software using the Finite Elements Method (FEM). It allows the modeling of Thermal heat transfer (Heat flow), including Radiation with view factors, Fluid flow, including mold filling, Stresses fully coupled with the thermal solution (Thermomechanics). Beside that, it includes also microstructure modeling and porosity modeling. Special models are included in order to account for thixo casting and lost foam. Specific features are included to account for processes such as high pressure die casting, centrifugal, tilt. Finally, customized models for foundry processes, such filters, sleeves are included.

Thermal calculation

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Mold filling and Fluid flow calculation

Thermomechanical calculation

ProCAST User Manual

Version 2009.1

SOFTWARE ORGANIZATION

The software is organized around a Manager, which calls the different modules :

• MeshCAST : the mesh generator • PreCAST : the pre-processor, coupled with databases • DataCAST / ProCAST : the solvers • ViewCAST : the post-processor and data export unit

The following figure is presenting the structure of the software. First, the geometry, in the form of a CAD model is loaded into MeshCAST, to generate a FEM mesh. Then, the calculation is configured in PreCAST, the Pre-processor. PreCAST is linked to Thermodynamic Databases for the automatic determination of the material properties from thermodynamic databases. Before the solver ProCAST is launched, a "data conditioner" named DataCAST is run. Finally, the results can be viewed or exported (for further processing) in the Post-processor ViewCAST.

The ProCAST solvers are divided in "Physical modules" with the following capabilities :

ProCAST User Manual

Version 2009.1

Thermal module • Heat conduction (Fourier equation) • Latent heat release during solidification • Cycling in die casting • Sleeves (insulating and exothermic) • Non-coincident meshes • Solidification time • Secondary Dendrite Arm spacing • Porosity indicator

Radiation module • Net radiation method • Full view factors capabilities • Mirror and rotational symmetries • Relative motion of materials • Solid or surface enclosures

Fluid flow module • Navier-Stokes equation • Penalization of the flow in the mushy zone and in the solid • Mold filling algorithm, with free surface • Filter model • Newtonian and Non-Newtonian flow • Thixo casting models • Lost Foam model • Tilt pouring • Centrifugal casting • Turbulent models

Stress module • Elastic, Elastic-plastic, Elasto-visco-plastic • Rigid or vacant materials • Automatic calculation of the air gap heat transfer • Contact algorithm between the different materials • Contact pressure • Die Fatigue prediction • Hot Tearing indicator

The features linked to specific processes (e.g. cycling, tilt, ...) are embedded in the corresponding physical modules.

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Version 2009.1

USER MANUAL PRESENTATION

After a "Getting started" chapter, which presents briefly the set-up of a simple thermal case, the different modules of the software, starting by the "Software Manager" are presented. The "Pre-processing" chapter is probably the most important as it describes the setting up of a case, from the FEM mesh to the run of the calculation. After an introduction on common features, this chapter is divided according to the "Physical modules", i.e. Thermal, Fluid Flow & Filling, Radiation and Stress. Then, the Databases, Run Parameters and Advanced features are presented. After the Run of the calculation chapter, three chapters are dedicated to the Results viewing, the Results analysis and the Results exports. Finally, Tips & Traps and Tutorials will illustrate the use of the software. MeshCAST, the mesh generator, is presented in a separate manual.

ProCAST User Manual

Version 2009.1

WHAT'S NEW VERSION 2009.1

This section is describing the main news of ProCAST v2009.1. This version is an update of version 2009.0 which corresponds to the first release of the new STL Mesh Generator. It also includes bugs and problems correction. The links are referring to the corresponding section of the manual for more details.

MeshCAST. • STL Meshing : a new meshing algorithm has been introduced in MeshCAST.

It allows to mesh fully automatically multiple cavities (assemblies) defined by one or several STL files (see the MeshCAST Manual for more details).

PreCAST • A new mapping tool is now available. It allows to extract Temperature, FVOL

(filling information) and Porosity results from one calculation to an other, in the case where the two calculations were made with different meshes (see the "Extract and Mapping/Results Mapping" section for more details).

• New commands were added in the PreCAST Batch script (see the "Batch Pre-processing/Script language" section for more details).

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Thermodynamic Databases • The Ni database was improved by the addition of Mn (up to 3%) and Cu. In

addition, the quality of the calculations of the liquidus and of the gamma prime solvus were improved.

• The Fe database was improved in the case of alloys containing Nb (in conjunction with C).

• A new section was added to the manual to illustrate the effect of the alloy composition on the computed liquidus temperature, for Ni alloys (see the "Influence of alloying elements/Ni alloys" section for more details).

• The model for the calculation of the Yield stress of Al alloys was improved. Comparisons with experimental data are giving good results. Accordingly, the Yield stress of the "A356-Stress" and "A356-Visco-Stress" entries of the PreCAST database (stress.db) were modified to take into account this improvement. As the Yield stress is depending strongly on the microstructure, which is a result of different cooling rates, the A356-Stress single entry was replaced by four entries, which are valid for 4 typical cooling rates of 0.1, 1, 10 and 100 K/s.

• The calculation of the Young's modulus of Cast iron was improved in order to take into account the influence of the graphite shape (i.e. for gray, compact or ductile iron). For this Young's modulus calculation, the effect of the graphite shape is triggered by the Mg content, according to the following amounts : Gray iron for Mg > 0.01%; Compact for 0.01% < Mg < 0.03%; Ductile iron for Mg > 0.03%.

VisualCAST (please refer to the Visual 5.5 Release notes for full details) • The "Scale dialog box" (e.g. to change the temperature scale for instance) can

be opened automatically by a double-click on the scale. • The liquidus and solidus are now displayed on the temperature scale. This

display can be deactivated in the Scale dialog box (under Preferences - Datum Line)

• The plot of free surface information (like temperature, velocity, ...) was improved.

• Improvements in the Exports are now available. Solver • The limitation of 10000 steps in Radiation calculation has been removed. • A bug in the reinitialisation of the displacement in the case of stress and

cycling was corrected. • In the case of a FLOW only calculation, the viscosity (if defined as a function

of temperature) is taken at the temperature corresponding to the Tinitial value defined by the user.

Parallel processing (DMP) • The THERMAL 2 option is now available in DMP. • A problem of LPDC filling in DMP (where the inlet tube was getting empty)

was corrected.

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Manual • A new section was added to the manual to illustrate the effect of the alloy

composition on the computed liquidus temperature, for Ni alloys (see the "Influence of alloying elements/Ni alloys" section for more details).

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VERSION 2009.0

This section is describing the main news of ProCAST v2009.0. The links are referring to the corresponding section of the manual for more details.

General / Manager • When the APM, the CAFE or the HCS solvers are called from the Manager, it

is possible to run the ProCAST solver first (for the thermal calculation for instance). The script used by the Manager has been complemented in order to allow the usage of "User functions" in the ProCAST run.

• The printout of the Wall clock time and Solid fraction has been corrected in the "Status" in the case the "statpro" directory was not defined.

• VisualCAST is now the default post-processor. It is still possible to activate ViewCAST in the "Installation Settings" of the Manager. If activated, ViewCAST will be accessible with a right click on the "VisualCAST" menu.

• "Pyramid elements" have been introduced (i.e. elements with one quadrilateral face and four triangular faces). At this stage, no ESI software is able to generate such elements (but this will come in the future, especially for boundary layer meshing), but PreCAST, DataCAST, ProCAST, VisualCAST and ViewCAST are now compatible with this new element type.

PreCAST • The writing of the d.dat file is performed after the completion of the

optimization (previously, if an old d.dat file was loaded and the optimization was failing, the d.dat file was erased).

• New export capabilities of the stress results have been added. It is now possible to perform a direct export in the Abaqus, ANSYS and Sysweld format, as well as in a Neutral format (see the "Results Exports/Stress" section for more details).

• The "Extract" capability allows now to extract also the Porosity results (in addition to the free surface (FVOL) and the stress results) (see the "Extract/Results Extraction" section for more details).

• The Die Combo capability was extended in order to allow distinct opening, closing and spraying times for different parts of the molds. It will be possible to define TOPEN, TCLOSE, TBSPRAY and TESPRAY with different values, in each Die Combo Entry. However the possibility to have centralized values in the Run Parameters will be still available if desired (see the "Interface Database" section for more details).

• The model describing the nucleation and growth of the pearlite was improved and a bug was corrected (to predict more accurate ferrite and pearlite fractions). Two new Run Parameters (PERNUCL and PERGROW) were introduced which allow to well calibrate calculated and measured pearlite/ferrite fractions (see the "Micro Run Parameters" section for more details).

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• In stress calculations, the possibility to take into account the mechanical behavior of the alloy during annealing has been introduced (see the "Stress Models and Properties" section for more details).

• A new TTT/CCT database containing 8 different steel alloys, coming from Sysweld, has been introduced (see the "TTT/CCT models" section for more details).

• The possibility to define mechanical properties as a function of the microstructure to be used during a Stress calculation has been introduced. This allows a full coupling between Thermal, Stress and Microstructure calculations (see the "Stress properties depending upon microstructure" sections for more details).

• In continuous casting, when a Thermal + Flow calculation is defined, it was found that one should set FREESF = 0 in order to have a good flow solution.

• PreCAST can now be used in Batch mode. The set-up is done through a script, which can be applied automatically to different meshes (see the "Batch Pre-processing" chapter for more details).

• A bug in the Inlet BC calculator was corrected. It is now possible to set an inlet temperature outside the range of temperature definition of the density.

• The symmetry plane check was improved to guarantee good stresses on symmetry planes.

Thermodynamic Databases • The Ni database was improved by adding Re and Hf. In particular the density

calculation was improved. • The Fe database was modified. The element "B" was added. In addition, the

database quality was further developed and improved by the addition of 13 new binary and 10 new ternary systems.

VisualCAST • A Context based help is available in VisualCAST. The user can now press F1

key to get context based help, corresponding to the active panel. • Information about the Free surface can be obtained as x-y plots. Time

evolution of the following quantities during the filling can be calculated (min, max and average) : Temperature / Fraction Solid / Fluid Velocity-Magnitude / Fluid Velocity-U / Fluid Velocity-V / Fluid Velocity-W / Pressure / Front Tracking (i.e. Junction) / Area.

• The display of the SDAS can now be seen in microns. • A bug which was creating a crash in the RGL calculation was corrected. • The Contour scale is removed when the selected Contour is "None". • The step frequency of the "Calculate New Particles" can now be set to values

lower then 10. • The "Entity selector" and the Display control can now work together. This

means that while picking nodes for plotting temperatures, the user can switch on/off parts in the same time.

• The scale of the porosity is now in % (instead of fraction). • By default, the velocity magnitude results are shown for vectors when the

Results are "none".

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• The calculation of the Alpha case (for Ti alloys) was improved and better documented (see the "Criterion functions" section for more details). It is now possible to use the Alpha case without a mold (this was not possible before). In previous version it was needed that the casting material name was starting by "TI". This limitation was removed and any material name can be used now.

• The pick node was improved in sections or cut-off contours. The nearest node to section plane or cut-off iso-surface is now selected.

• Scan can now be exported as AVI animations. • In the "Save Page as", it is now possible to save the Current window, the

current page, selected pages or all the pages. • Each window has the "standard" icons on the top right to "iconize",

"maximize" or "delete" the window. • In the "Entity selector list", it is possible to select a range with the Shift and

Control keys. For instance, it is possible to select several nodes (or a range of the list) if required.

• The "Measure" panel was improved. • In the "Save Page As" panel, it is now possible to export Animated GIF

movies.

ViewCAST • The calculation of the Alpha case (for Ti alloys) was improved and better

documented (see the "Criterion functions" section for more details). It is now possible to use the Alpha case without a mold (this was not possible before). In previous version it was needed that the casting material name was starting by "TI". This limitation was removed and any material name can be used now.

• A bug which was creating a crash in the RGL calculation was corrected.

Solver • DataCAST was modified in order to allow spaces and special characters in

material names. • When the APM, the CAFE or the HCS solvers are called from the Manager, it

is possible to run the ProCAST solver first (for the thermal calculation for instance). The script used by the Manager has been complemented in order to allow the usage of "User functions" in the ProCAST run.

• A problem of Restart in the case of FLOW = 9 has been fixed. • The mass balance correction algorithm at the free surface in the case of

multiple free surface (e.g. multiple inlets) was significantly improved. This allows to obtain now well balanced filling in the case of multiple inlets. This new algorithm is now activated with FGROUP=2 (which is the default value for both the Scalar and the DMP solvers) (see the "Run Parameters/Flow" section for more details on FGROUP).

• A Restart problem (when a value of INILEV different or higher than the last available step was specified) has been corrected. This was affecting restarts when time dependant functions were used.

• In some cases, the flow solution was different when JUNCTION = 1 or JUNCTION = 2 were used. This abnormal behavior was corrected and now

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the flow solution is in dependant from the fact that JUNCTION is calculated or not.

• The stress solver was modified in order to reset stress and strain data when remelting was occurring (i.e. fs < CRITFS). This is correcting odd behavior in the stress results which were occurring in the case of remelting.

• The free surface algorithm was further improve in order to prevent some undesired flow patterns observed in some rare cases.

• In the case of a stress calculation, the stresses are now also stored at step 0. This allows to visualize a stress calculation which have not started yet as well as to have the right stresses and deformations at step 0.

• The version 2.3.3 of the PETSC library is now used, as well as the Intel compiler 9.1 for both Linux and Windows.

• In the case of Stress calculations, when deformations become quite important, some elements may become too distorted, leading to Negative Jacobian's. A new procedure of "Mesh smoothing" has been introduced in order to cure this kind of problem. This algorithm will only move "interior nodes", keeping the same mesh topology (no surface nodes are moved, no new nodes or elements are created). The Mesh smoothing is activated in the following situations : a) globally at the beginning of each cycle, b) globally upon "restart" and c) locally, when a negative Jacobian does appear. The Mesh smoothing is totally transparent for the user as the post-processor is automatically taking these movements into account (i.e. the displacements shown in the post-processor are only the real "physical" displacements).

• When stress calculation during cycling are performed, often the deformations can be rather large which can lead to highly distorted elements (and thus to Negative Jacobian's). In order to prevent such problems, the mesh can be reset to the original mesh at the beginning of each cyle, but the deformation is still accumulated. Thus, the result is still correct, but without having the problem of too important accumulated mesh distortions. If the calculation is able to go through the first cycle, the calculation of the other cycles should be then possible without problems. However, in the post-processing, we will still be able to see a mesh which is distorting more and more along the cycles. To activate this algorithm, the Run Parameter "CYCLE_ALGM" should be set to 2 (the default value is 1, which correspond to no special action and thus no re-alignment) (see the "Stress Run Parameters" section for more details).

• The possibility to compute the final stress properties of a part, as a function of its final microstructure and defects has been added (see the "Final Stress properties as function of microstructure" section for more details).

• A bug was corrected in the writing of the p.out file. The translation information of an enclosure is now well written.

• A bug about the flow restart when TFREQ > VFREQ was corrected. • A true 64 bits DataCAST is now available on Windows. • In the case of stress calculations, the heat transfer coefficient is automatically

affected by the gap width. In previous version, the gap was considered automatically as air or as vacuum. In the case the gap is filled with something else (e.g. flux or water), it is possible to define the gap properties in the "interhtransfer.c" user function

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• New variables are available in the User functions and in the "externalcompute.c" function (see the "External function" section for more details). This allows in particular to define an interface heat transfer coefficient which is a function of the liquid pressure.

• In the case of a stress calculation, the stresses are now also stored at step 0. This allows in particular to see the initial stress state after an extract (which would well correspond to the extracted state).

Parallel processing (DMP) • The dynamic partitioning was extended to the case of filters. This means that

the DMP performances of filling in the presence of filters will be greatly improved.

• A bug was corrected in the case of a restart (with the DMP version) in the presence of a Virtual mold.

• A memory leak was corrected in the DMP solver. • A problem in the Linux HPMPI DMP launch script (used in the case of Micro

modeling), about the export of the Environment variable, has been corrected. • The usage of "Tabulated hardening" (or "Digitized hardening") is now also

possible with the DMP version. • The mass balance correction algorithm at the free surface in the case of

multiple free surface (e.g. multiple inlets) was significantly improved. This allows to obtain now well balanced filling in the case of multiple inlets. This new algorithm is now activated with FGROUP=2 (which is the default value for both the Scalar and the DMP solvers). In the previous version, the FGROUP algorithm was not available at all in the DMP version (see the "Run Parameters/Flow" section for more details on FGROUP).

• The version 2.3.3 of the PETSC library is now used, as well as the Intel compiler 9.1 for both Linux and Windows.

• The User Functions are now available in the DMP version too (except the new User functions for Stress properties as a function of the microstructure).

• The Turbulence model is now available in the DMP version too. • A problem occurring during centrifugal casting in DMP was corrected. • The pressure solver was improved in order to speed-up the filling calculations

(by about 10%). Advanced Porosity Module (APM) • In the previous version, in order to allow a smooth transition, the two APM

algorithms were available to the user : the "standard" and the "multigas" ones. The "multigas" model being more advanced (no more developments are made in the "standard" algorithm since a few years), it is now the only available algorithm. Thus, the "standard" algorithm is removed from this version (see the updated version of the "APM Multigas manual").

• The possibility to assign more than one injection point has been introduced. This can allow "gate feeding" in the case of multiple gates which are not anymore connected (i.e. separated by solid). This allows also the possibility to model only the casting, without the gating system and still account for the pressure applied to the biscuit which is transmitted to each gate (see the

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"Advanced Porosity Pre-processing/Process Information" section for more details).

• The APM solver was significantly optimized in order to reduce the CPU time for large cases (i.e. cases with several millions of cells). This was done mainly by optimizing the mushy and liquid pocket detection algorithm. Speed-up up to a factor 5 to 7 were observed for cases with 2 and 5 millions cells. It should be noticed that in previous versions, it was almost impossible to consider calculations above 2 millions cells.

• When a ProCAST calculation is run with POROS = 1, pipe shrinkage or macroporosity may appear (which is viewed as empty when a temperature contour is plotted). If the APM is not calculating a hole at this same location, the post-processing has been modified in order to show the real APM result at this location (in previous versions, it was displaying a hole), thus ignoring the FVOL information. Please note however, that, if significant macroshrinkage are observed, it is strongly recommended to use POROS = 0 for the thermal calculation to be used with the APM, as the temperature in an empty volume will remain constant and thus it will not represent the exact reality in the APM calculation. In any case, PIPEFS should be set to 0 in the perspective of APM calculations.

• The memory usage of the APM solver (multi-gas) was decreased by about 20 %.

• The APM solver is creating a new result file (named "prefix_res.log") which contains information about the amounts of micro and macroporosity in the full casting, as well as in each domain (see the "APM manual/Calculation Settings" section for more details).

• A new result file is now created at the end an APM calculation. This file, named "prefix_res.log" is containing information about the amount of micro and macroporosity in the different domains, including the amount and volume of "porous" locations which are above a given critical user defined value (see the end of the section "Advanced Porosity Solver" for more details).

• The gas database (gas.db) has been improved.

2D • A bug has been fixed for 2D quadrilateral meshes in the DMP flow solver. • The possibility to perform an "Extract" in 2D axisymetric cases has been

activated. • The problems of colors in ViewCAST while displaying 2D models were fixed.

Manual • The description of the usage of the "Digitized hardening" was improved. • A new description for FGROUP was added (see the "Run Parameters/Flow"

section for more details). • APM : the multigas model is now fully described in the On-line manual

(previously it was only available in PDF) (see the updated version of the "APM Multigas manual").

• APM : Information on the requirements about the possibilities for the Thermal calculation to use "Restart" or "Extract" in conjunction with the APM were

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added (see the "APM/Advanced Porosity Pre-processing" section for more details).

• A new TTT/CCT Models chapter for Heat Treatments was added (see the "TTT/CCT Models" chapter for more details).

• A new chapter was added about the coupling between Microstructures and Stress properties (i.e. to define stress properties which are depending upon the microstructure) (see the "Microstructures-Stress coupling" chapter for more details). This chapter contains two different new sections : a) Stress properties depending upon microstructure and b) Final Stress properties as function of microstructure.

• A new section was added about Batch Pre-processing (see the "Batch Pre-processing" chapter for more details).

• The calculation of the Alpha case (for Ti alloys) was better documented (see the "Criterion functions" section for more details).

• The Run Parameter COLDSHUT is described, as well as the occurrences when the "cold shut switch off" is activated (see the "Flow Run Parameters" section for more details).

• The section "Use of the Parallel solver", describing the launch of DMP calculation using HPMPI, has been adapted and detailed.

• The following remark has been added at the end of the "Extract/Domain removal" section : In the case of stress extraction with domain(s) removal, one should make sure that all the remaining domain(s) are well defined as "CASTING". For instance, if the original model has a CASTING, a MOLD and a CORE and only the MOLD has to be deleted first (i.e. to run a stress calculation with the CASTING and the CORE), the CORE must be switched to CASTING (ignore the Warning message saying that two different materials are assigned to the different CASTING domains) in order to have a successful Extract. This is due to the "renumbering" algorithm applied to the Extract which is currently made only on the CASTING domains.

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VERSION 2008.0


General / Manager • When the ProCAST solver is called before a CAFE or an APM calculation on a

64 bits Windows machine, the 64 bits ProCAST solver is now used. • For large screens, it was necessary in the past to change the font sizes. The file

"procastFonts.tcl" (in the bin directory of the software installation) was modified in order to allow an easy adaptation. Fonts can be adapted to large screens by setting the variable "adaptFontsLargeScreen" to 1 (line 11 of the procastFonts.tcl file).

MeshCAST. • It is now possible to import large Patran meshes into MeshCAST (meshes with

more than 10 million elements). • The "show feature" display is now remaining active during graphical

manipulations. • It is now possible to restart an Assembly with different parameters (i.e.

different tolerances, ...). • The Assembly algorithm was further improved. The feature lines are better

taken into account.

PreCAST • A "Velocity calculator" has been introduced in both the "velocity BC" and the

"inlet BC". The calculator is now also applicable if time functions are used (see the "Pre-processing/Databases/Boundary Conditions Database" section for more details).

• It is now possible to automatically chain a cycling and a filling calculation. To do so, a new run parameter CYCLEF has been introduced to activate the filling at the last cycle only. At the beginning of each cycle, except the last one, casting volumes will be set to full (see the "Cycling Run Parameters" section for more details).

• It is now possible to automatically restart a calculation by setting INILEV to an arbitrary large value. The last complete step corresponding to TFREQ, VFREQ and SFREQ will be selected and the calculation will be restarted with this last time step. It is assumed that MFREQ=TFREQ (see the "General Run Parameters" section for more details).

• A new method to Extract data from one model to an other one has been introduced in order to add flexibility in the use of ProCAST (see the new "Extract" chapter for more details). In particular, it is possible now to Delete/Add materials or domains while preserving the model set-up (with

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some exceptions) (see the "Extract/Domain removal" and "Extract/Domain addition" sections for more details).

• It is now possible not only to Extract the temperature as initial conditions, but also the Free surface information (FVOL) as well as the Stress Fields (see the new "Extract/Results extraction" section for more details). As a consequence, when an Extract is used (even for Temperature only), a new file called "prefix.ini" (automatically created by PreCAST during the Extract) must be present in the working directory when DataCAST is run. Moreover, when an Extract is made in a model which has encountered a "Delete/Add" operation, a special care should be taken with respect to the created file prefix.nnc and prefix.enc (see the "Extract" chapter for more details).

• In the "Extract" window, it is now possible to make multiple selections of domains (i.e. to apply an extract case and timestep to more than one domain at a time) (see the new "Extract/Results extraction" section for more details).

• For LPDC, it is now possible to "drain" the remaining liquid in the inlet sprue region which is still liquid when the pressure is released. To do so, two new Run parameters were introduced : DRAINFS and DRAINTIME (see the "Thermal/Run Parameters" and the "LPDC recommendations" sections for more details).

• The possibility to define "visco-elastic" materials has been introduced (see the "Visco-elasticity" section for more details). Such properties are useful for the modeling of waxes used in investment casting.

• In the case of thixo casting (with the Power cut-off model), the file prefixg0.dat is now read and written by the pre-processor and it is thus not reinitialized. .

• The Clip in PreCAST is now fully operational. This allows easy selection of faces and nodes inside a model (for instance for selections in cooling channels). .

• It is now again possible to define three orthogonal symmetry planes and to have the automatic checking whether all the nodes are well aligned on the symmetry planes (see the "Pre-processing/Radiation" section for more details).

• By default, when a new mesh is loaded in PreCAST, all the domains are set to "MOLD" (previously it was CASTING).

• In the stress database, the contribution of the liquid contraction in the mushy zone (in the thermal expansion coefficient) is now removed. This was done as one can considers that the contribution of the liquid contraction in the mushy zone is not leading to stresses, but is compensated by liquid movement.

Thermodynamic Databases • The Yield stress can now be automatically calculated (for Al alloys only),

together with the Young's modulus, the Poisson ration and the Thermal expansion coefficient. This option is only available with the "Back diffusion model" (see the "Calculation of Stress Properties" section for more details).

• The Ni Database was improved with respect to the previous version. In particular, the liquidus temperature are now much predicted. The difference between the database of this version and the one of version 2007.0 can be summarized briefly in the following way. Version 2007.0 did include many

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new measurements provided by a reknown US Agency. It was assumed that these data were of very good quality (as they were coming from a reknown US Agency) and thus, an important "weight" was allocated to these measurements. However, further comparisons with independant experiments have shown that the quality of these measurements were not as good as thought. Thus, this 2008.0 database is giving back "more" weight to the previous measurements leading to more accurate results.

• The Ni database was improved with the addition of Pt, Ru and Ir elements. • In addition to Ni (see above), a new database is also available for Fe alloys. A

document from CompuTherm, entitled "Computherm_Release_notes_2008.pdf", is available in the software installation in the dat/manuals/PDF directory.

• In the Fe database, the description for the Fe-S system was improved. • On Linux, the thermodynamic databases were corrected (there was a problem

in the previous version). • In the stress database, the contribution of the liquid contraction in the mushy

zone (in the thermal expansion coefficient) is now removed. This was done as one can considers that the contribution of the liquid contraction in the mushy zone is not leading to stresses, but is compensated by liquid movement.

VisualCAST (see the VisualCAST 4.0 on-line Release Notes for more details) • The algorithms have been improved in order to reduce the memory

consumption. Depending upon the cases, the memory needed to display a given model has been reduced by 20-30%.

• The zoom is now maintained when the "Export Page movie" is used. • It is now possible to maintain the "View settings" in Page Export. • When an export is done, it is now possible to define a new folder location. • The Void Pressure contour is not anymore active when a calculation was run

without the GAS model. • An option to "Save the image to the Clipboard" has been introduced. • When AVI movies are generated, it is now possible to select the compression

algorithm. • To select nodes for XY plots, it is now possible to either pick the node

interactively or to use the coordinates (the selection mode is the same for both evolutions and profiles).

• In the Scale definition panel, it is now possible to set negative delta values. • All the contours can now be plotted with XY graphs. • The calculated particles can now be stored/deleted/modified. • In the case of a cycling calculation, the cycle information are now displayed in

the Contour and Plot windows. Tcycle, Topen and Tclose are indicated on evolution graphs.

• The Plot interval definition is now only applied to visible parts. • A new option to set the number of colors in the color scale has been

introduced. • A new option to couple windows in order to apply the same graphical

transformations simultaneously in all windows has been introduced.

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• The initial view when gravity was along a positive direction was corrected. • A bug in the gap width export was corrected. • A bug was corrected in the case of the display of a non-time dependant "usf"

file (i.e. with an output frequency of 0). • A bug in the display of Tilt casting cases with stress has been fixed. • A bug was corrected for the display of cases having solid rotations.

ViewCAST • In the "Pick node", a 3rd digit was added in the display of the values. • A bug was corrected for the display of cases having solid rotations. • The -T2, -T2 and -T3 options (to change the display from seconds to

milliseconds or hours, minutes, seconds) have been re-introduced in the manager.tcl file.

Solver • Interpenetrating meshes can now be used together with cycling (e.g. cycling

with shot piston). This is available both with the Scalar and the DMP solver. • In continuous casting simulations (steady state algorithm), the solid transport

term can now be applied to more than one domain. • For the modeling of stress in large heavy castings, the solver was improved to

account for the casting weight on the mold, with the new Run Parameter GLOAD = 1 (see the "Stress/Run parameters" section for more details).

• In the case of a stress calculation where the casting is not fully constraint by the mold, a new Run Parameter GLOAD = 2 was introduced. This allows to guarantee that the casting will stay in contact with the mold in the direction of the gravity (see the "Stress/Run parameters" section for more details).

• A new Run parameter, named CLAYERS, has been introduced to adjust the number of constraint layers used by GLOAD = 1. This allows to reduce the effect of the constraints linked to the liquid nodes (see the "Stress/Run parameters" section for more details).

• The stress solver was improved in order to handle the situation where one solid is separating into two distinct volumes. This can happen during piping, where a few solid elements can be separated from the main casting due to piping.

• The possibility to define "visco-elastic" materials has been introduced (see the "Visco-elasticity" section for more details). Such properties are useful for the modeling of waxes used in investment casting.

• The new functionnality for the calculation and viewing of the "metal front tracking" (also called the "JUNCTION" model), which has been introduced in the previous version, has been significantly improved. It is now possible to view the "accumulated free surface volume" (free surface multiplied by the travelled distance), the "accumulated free surface time" (free surface multiplied by the time), the "Free surface age" and the "Flow length" (see the "Results analysis/Fluid Front Tracking" section and the "Run Parameters/Flow" section for more details about this new functionnality and about the Run Parameter JUNCTION).

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• It is now possible to automatically chain a cycling and a filling calculation. To do so, a new run parameter CYCLEF has been introduced to activate the filling at the last cycle only. At the beginning of each cycle, except the last one, casting volumes will be set to full (see the "Cycling Run Parameters" sectoin for more details).

• For LPDC, it is now possible to "drain" the remaining liquid in the inlet sprue region which is still liquid when the pressure is released. To do so, two new Run parameters were introduced : DRAINFS and DRAINTIME (see the "Thermal/Run Parameters" and the "LPDC recommendations" sections for more details).

• It is now possible to automatically restart a calculation by setting INILEV to an arbitrary large value. The last complete step corresponding to TFREQ, VFREQ and SFREQ will be selected and the calculation will be restarted with the last time step. It is assumed that MFREQ=TFREQ (see the "General Run Parameters" section for more details).

• A small improvement was made in the porosity model (POROS=1) which can lead to very small differences in the piping.

• A problem in the NodNum User function was corrected. • A problem in the DTMAXFILL algorithm was corrected. • In the case of stress calculation, the contact algorithm was slightly improved in

order to better calculate the gap width in certain specific situations (where a node on one side could not see a node in front due to a too tight tolerance).

Parallel processing (DMP) • Cycling with interpenetrating mesh (shot piston) is available in DMP. • The performance of the stress solver in DMP was improved. This is mainly

due to the elimination of unnecessary zeros in the matrix. It is also due to a better assembly technique for contact and rigid/vacant domains.

• In the case of filling of large casting with long ingate tubes, the logic of the re-partitioning was not appropriate (leading to poor scalability). The repartioning algorithm was improved in order to well take into account this specific situation. As a result, the scalability of such filling is now much better.

• The repartitioning algorithm was modified in order to allow multiple inlets which are activated at different times (delayed inlet BC).

• A bug was corrected in the repartitioning algorithm in the case of equivalent interfaces.

• It is now possible to run a DMP calculation with THERMAL = 0 and POROS = 1.

• A bug was corrected when a casting only was modeled with CRACK = 1. • A bug in the temperature reset of Cores during cycling has been corrected. • A problem was fixed in the case of centrifugal casting with a revolution

velocity controlled by a time function.

Advanced Porosity Module (APM) • The Multi-gas APM is now fully available. Since this version 2008.0, it is

strongly advised to use the Multi-gas APM, which is more advanced and which have been further optimized (reduced CPU time, available in 64 bits allowing

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larger models). Please note that the input data (defined in the prefix_poro.d file) are different from the standard version and have been simplified. In particular the gas properties are now defined in a database and do not need to be specified in the input data.

• The Advanced Porosity solver (multi-gas version) is now available on 64 bits machines (Windows and Linux). This allows to release the limitation of a maximum of cells of 1-2 milions.

• The algorithm (multi-gas version) has been improved in order to reduce the CPU time quite significantly.

Inverse • The Inverse solver is now launched via a script file. This allows to customize it

in order to use the ProCAST DMP solver, if desired, (instead of the scalar one) for the direct calculations of the inverse solve.

2D • The 2D solver of ProCAST was reactivated (beside the pseudo-2D solver). In

MeshCAST 2D, it is possible now to create real 2-D meshes (and not only 3D extruded meshes). PreCAST, ViewCAST, VisualCAST and the solvers were adapted.

• In order to use the 2D version, nothing special has to be done, except to load in PreCAST a 2D mesh instead of a 3D one (if a "planar" surface mesh *.sm is to be used, just rename it as *.mesh before loading it into PreCAST).

• As this is the first release of the 2D, it is possible that some functionnalities are not yet available or may exhibit problems (e.g. Radiation in DMP, stress axisymmetric, ...).

Manual • The on-line help manual is now working in the MeshCAST 64bits Windows

version. • A new section about all the new possibilities of the Extract has been added

(see the "Extract" section for more details) including examples illustrating how it can be used (see the "Extract examples" section for more details).

• A new section was added in the Tips & Traps chapter about LPDC recommendations (see the "LPDC recommendations" section for more details).

• A new section about Viscoplastic properties recommendations has been added (see the "Viscoplastic Properties Recommendations" section for more details).

• A new section on Visco-elastic models has been added (see the "Visco-elasticity" section for more details).

• The section about how to launch DMP calculations with HP-MPI on clusters was updated (see the "Use of the Parallel solver" section for more details).

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VERSION 2007.0


General / Manager • The possibility to select true 64bits executables for Windows platforms has

been added in the Manager (see the "Software Manager/Software configuration" section for more details). 64 bits executables are available for MeshCAST, ProCAST scalar and DMP solvers on Windows (please note that the 64 bits executables are available on Linux, as before).

• The manager has been changed in order to allow the selection of pre-defined nodes for DMP calculations (see the "Use of the Parallel solver" section for more details.

MeshCAST (see the "What's new in MeshCAST 2007.0" section in the MeshCAST manual for more details). • True 64 bits executables of MeshCAST are now available for Windows and

Linux platforms (see the "Software Manager/Software configuration" section for more details).

• The Assembly algorithm has been improved in order to be more automatic and powerful :

• the error detection has been greatly simplified with the introduction of a "Show critical errors" button

• the display of the Master/Slave has been improved • the Feature angle can be defined by the user • the handling of the "*_feat.sm" files has been simplified

• The reading of the Parasolid interface has been improved • A new option to locally refine the mesh (denser mesh) has been added • A tolerance was changed in the New Shell generation, in order to improve the

quality of the shell • The actions of the "Check Mesh" button has been modified • The "modulus calculation" is now only active in the presence of a volume

mesh. • A specific situation where volume meshing was failing has been corrected.

PreCAST • Automatic alignment of nodes along symmetry planes for rotational and mirror

symmetries (see the "Pre-processing/Radiation/Check of the symmetry planes" section for more details.

• Introduction of FADING, a new microstructure Run parameter for the modeling of Graphite fading in SGI (see the "Microstructure Run Parameters" section for more details).

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Thermodynamic Databases • Improved description of Fe-S binary systems. • Introduction of Sn element for Fe-Si-Sn systems (only for small addition of

Sn).

VisualCAST (see the VisualCAST 3.5 on-line Release Notes for more details) • Customizable menus and toolbars • Possibility to define visibility and color attributes in Part Table menu • Possibility to save and restore page templates • Improvement of foreground/background handling in the slice menu • Option to display the complete study path information in graphics window • Definition of symmetries • Model explode and move options • Possibility to visualize relative displacements (w.r.t a plane) • Possibility to visualize relative velocities in centrifugal casting • Possibility to visualize a different contour on a Cut Off display • New Cut Off info option to show average results based on selection • Arithmetic and logical operators to create user defined contours • Possibility to select different abscissa for curves (e.g. Plot of the Density as

function of the temperature when using Cast iron micro module) • Quick results template • Handling of time units • Mesh export in various new formats including PAM-CRASH • A bug in the calculation of the SDAS has been corrected. • A bug in the "contact pressure" display has been fixed.

ViewCAST • A problem in the visualisation of TILT + STRESS calculations has been fixed. • The FACE-TO-GROUP information can be displayed also on the enclosure. • A new functionnality for the calculation and viewing of the "metal front

tracking" is now available. This allows to view where the oxydes and impurities trapped at the free surface are most likely to end-up as well as to study the flow junctions (see the "Results analysis/Fluid Front Tracking" section for more details).

• User defined contours in a new "Additional" contour panel are now available (see the "Results viewing/Field Selection" section for more details).

Solver • True 64bits executables for ProCAST solver are now available on Windows

for both scalar and DMP versions (please note that the 64 bits executables are available on Linux, as before)

• In the scalar version (Windows and Linux) the PETSC solver was introduced for stress calculations. This leads to better convergence and quality results. In some cases, significant speed-up (30% to 100%) were observed.

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• Improved core blowing option (NNEWTON=7) (see the new "Core Blowing" chapter for more details).

• A new functionnality for the calculation and viewing of the "metal front tracking" is now available. This allows to view where the oxydes and impurities trapped at the free surface are most likely to end-up as well as to study the flow junctions (see the "Results analysis/Fluid Front Tracking" section and the "Run Parameters/Flow" section for more details about this new functionnality and about the Run Parameter JUNCTION).

• Introduction of a new FADING parameter affecting the time during which the Mg treatment has an effect (see the "Microstructures/Iron and Steel/Iron and Steel models" section for more details).

• A new Run parameter (FREESFBAL) was introduced to stabilize large free surfaces in gravity filling (See the "Flow Run parameters" section for more details).

• For stress calculation, the handling of the penalty (for the contact algorithm) has been improved by the introduction of the new Run parameter PENMOD (see the "Stress Run Parameters" section for more details).

• The HCS solver (Hot cracking sensitivity calculation for continuous casting which was available in calcosoft-3D) is now integrated in ProCAST (see the "Hot Cracking (for continuous casting)" chapter for more details).

• A bug in the usage of FREESFOPT = 1 together with GAS = 1 was corrected. • A problem in the TOPFILL algorithm has been fixed.

Parallel processing (DMP) • The Microstructure module (MICRO = 1) is now available in the DMP solver. • The Freckle calculation (FRECK = 1) is now available in the DMP solver. • The HIVISC algorithm is now available in the DMP solver. • The Core blowing option (NNEWTON = 7) is now available in the DMP

solver (see the new "Core Blowing" chapter for more details). • Improved performance of the stress parallel solver. • Improvements in lost foam modeling and interpenetrating mesh option. • HP-MPI used by default in standard Linux 64bits version. • A bug in the treatment of the units of moving solids was corrected. • It is now possible to start a calculation with a zero inlet velocity or a zero inlet

mass. • The manager has been changed in order to allow the selection of pre-defined

CPU's.

Innovations This section was added in order to describe new innovative developments which are included in the version although still in the industrialization/validation stage. If you are interested to have access to such developments, please contact your local support. Manuals about these subjects (in PDF format) are available in the software installation (dat/manuals/Pdf directory). See the "Innovations" section for more details. • A new approach for Multi gas systems has been developed for the Advanced

Porosity Module (APM).

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• The possibility to calculate heat treatment, based upon TTT diagrams has been developed.

• User functions for material properties. • Mold removal and Gate cutting in stress.

Manual • A new section about Core Blowing (NNEWTON = 7) was introduced (see the

"Core Blowing" chapter for more details). • A new section about Fluid Front Tracking has been added (see the "Results

analysis/Fluid Front Tracking" section for more details). • The 2007 Release notes of CompuTherm are available in PDF format in the

software installation (in ../dat/manuals/PDF/CompuTherm_Release_notes_2007.pdf

• A new chapter about the HCS solver (Hot cracking sensitivity calculation for continuous casting which was available in calcosoft-3D) was added (see the "Hot Cracking (for continuous casting)" chapter for more details).

• An Innovation section was added (See the "Innovations" section for more details).

• A section presenting comparisons of results between version 2006.1 and 2007.0, as well as Scalar and Parallel calculations (2007.0) has been added (see the "Results comparisons between versions" section for more details).

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VERSION 2006.1


General / Manager • The possibility to launch the VisualCAST post-processor from the manager

(see the "Software Manager/Module calls" section for more details).

MeshCAST • A new shell mesher algorithm has been designed in order to improve greatly

the quality of shells (see the MeshCAST manual for more details). • The handling of symmetries with the shell mesher has been totally revisited

(see the MeshCAST manual for more details). • Boolean operations algorithms have been improved and made more robust. In

particular, it now accommodates models with enclosures (enclosures should belong to the master part).

• The mesh smoothening operation following mesh assembly and Boolean operations has been improved so as to better preserve geometry features.

• The logic of the "Check Mesh button" has been changed : A left mouse click action will display cracks and multiple edges while a right click will display bad triangles only.

• In the Assembly, the Master and Slave domains can be viewed with different colors (with a right click).

• An option has been added to calculate the geometrical modulus from a volume mesh. The geometrical modulus is printed for clip selections (see the MeshCAST manual for more details).

• The Export of a volume mesh in SYSWELD format is now available. • In Geomesh, it is now possible to save a model in "tos" format.

PreCAST • A bug in the translation defintion x(t) was corrected. • A problem of units when using a translation defined by v(x) has been

corrected. • It is now possible to define a velocity BC with only one component (leaving

the other components empty, thus free). • A bug in the use of Die Combo interface (with a temperature dependant table,

multiplied by a constant different than 1) was corrected. The constant was not multiplying the table.

• It is now allowed to set an emissivity value of 1.0 (before this was creating problems).

• The GRAPHITE and MGTREAT Run parameters have been added to the "Micro" tab (see the "Micro Run Parameters" section for more details).

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• The MOLDRIG Run parameter has been added to the "Thermal" tab (see the "Thermal Run Parameters" section for more details).

Thermodynamic Databases • The Cu thermodynamic database has been introduced (see the

"Thermodynamic Databases" section for more details). Please note that the Cu database (provided by CompuTherm) corresponds to a first version and some compositions (especially with Pb) may encounter problems (see the "Databases limitations" section for more details). A document from CompuTherm, entitled "CompuTherm_Copper_Database.pdf", describing the Cu database is available in the software installation in the dat/manuals/PDF directory.

• A back-diffusion model has been introduced for a better prediction of the material properties as a function of the cooling rate (see the "Thermodynamic Databases" section for more details).

• The Ni database was improved. A thermodynamic description of the gamma'' phase was developed. Many ternary systems, such as Ni-Al-Co, Ni-Co-Cr, Ni-Al-Ta, Ni-Al-W, Ni-Co-Re and Ni-Co-Ta were modified in order to have better properties prediction, including a better gamma'' solvus prediction. The thermodynamic description of the eta phase was modified based upon exprimental data.

• The Ti database was improved. Ternary systems, such as Ti-Al-V, Ti-Al-Mo, Ti-Al-Sn, Ti-Al-Cr, Ti-Cr-Nb or Ti-Al-O were modified in order to better predict commercial alloys. The thermodynamic description of the Ti-Si-Zr system was developed including the ternary S2 phase.

• A document entitled "CompuTherm_Release_Notes_2006.pdf", available in the software installation in the dat/manuals/PDF directory, is describing the improvements of the databases.

• The prediction of the Youngs modulus for cast iron was improved in order to take into account the effect of the magnesium on the microstructure.

• A problem encountered in the calculation of alloy properties (with Computherm) on Windows when the software was installed in an other location than the C:/ drive was corrected.

• A problem when calculating properties of Al alloys with Mn on Linux was corrected.

• The Computherm databases on Linux were updated (the update was not well done on version 2006.0).

• Problems encountered when erasing an element from the chemical composition and re-calculating material properties have been corrected.

ViewCAST - VisualCAST • A new post-processor called VisualCAST is introduced in this version in

addition to ViewCAST (see the separate VisualCAST DVD for more information). A VisualCAST 3.0 Tutorial is available in PDF format in the dat/manuals/PDF directory of the installation.

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• The PATRAN export format of a mesh was slighty changed (a minus sign in the material ID was removed) in order to allow a better compatibility with other softwares.

• When the Heat flux, velocity, voids, stresses and displacement results are exported, only the results of the active domain(s) are exported (and not the results of all the domains).

• The export format (when using the PATRAN neutral file format) was changed in order to account for exponents with 3 digits (in order to have a space between values).

• A bug in the export of heat flux results has been corrected. • The display of "Face to Group" view factors has been corrected and is also

available for enclosures. • For centrifugal casting, the relative velocities can be calculated (in order to

remove the rotational component of the vectors) (see the "Centrifugal casting" section for more details).

Solver • A new option has been introduced in the micro module to allow for

coupled/uncoupled calculations (see the "Microstructures/Case set-up and Results" section for more details).

• The Fading effect of the Magnesium treatment has been added to the SGI micro model. A new Run parameter MGTREAT has been introduced in order to account for the delay between the Mg treatment and the beginning of the casting process (see the "Microstructures/Iron and Steel/Iron and Steel models" and the "Micro Run Parameters" sections for more details).

• The density calculation for cast iron in the micro module has been improved. • The effect of the white iron on the mechanical properties of grey iron was

introduced (when a micro calculation is performed). • The filling algorithm was improved in the case of large ingots filling (no

change for other filling situations) (see the "Large Ingot Filling" section for more details).

• A new algorithm (MiLE) has been introduced to address non-steady state continuous casting problems (see the "Continuous Casting" chapter for more details).

• The possibility to address steady state continuous casting processes has been introduced (see the "Continuous Casting" chapter for more details).

• A bug was corrected in DataCAST in the case of time-dependant temperature assignments to enclosures (occuring when more then 10 assignments were made).

• Possibility to define the maximum timesteps DTMAX in a table, as well as the maximum timestep during the filling DTMAXFILL (see the "General Run Parameters" section for more details).

• The Freckles prediction was improved. This was done both by an improvement of the Computherm database and by the introduction of the back diffusion model (which both lead to a better prediction of the phases and thus of the solidification path).

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• The solver was modified in order to allow the viewing of results (in VisualCAST only) every X% of filling or X% solidified. As a consequence, the results calculated with ProCAST 2006.1 are not anymore fully compatible with earlier versions of ViewCAST.

• Problems in processing datasets containing large numbers of temperature dependant assignments have been corrected.

• A problem in the resetting of contact pressures in case of mold opening has been corrected.

• A problem in the calculation of thixo casting has been corrected.

Parallel processing (DMP) • The Thixocasting module has been parallelized (HIVISC = 2 and NNEWTON

= 2), including the cut-off model. • The interpenetrating mesh option (PENETRATE = 1) (e.g. for HPDC shot

piston) has been parallelized. • A bug was corrected in the contact algorithm (stress module) in the case of a

Restart. • A bug related to part ejection and Die Combo interface has been corrected. • The Windows DMP version is now using the HPMPI libraries for better

performances (please note that no special license or installation is necessary in addition to the ProCAST installation and license). Due to the use of HPMPI, the launch command of the DMP version on Windows has changed (see the "Parallel Solver/Use of the Parallel solver" section for more details).

• The DMP versions (Linux and Windows) are now included in the Installation CD and are automatically installed with the scalar version.

CAFE / Advanced Porosity module • A bug in the storage of the Cut files in the full coupling solver was corrected.

Manual • A new section about recommendations for inlet velocities has been added (see

the "Tips and Traps/Inlet velocity" section for more details). • The TPROF and WSHEAR Run parameters have been described in details

(see the "Flow Run Parameters" section for more details). • The Tutorials are now stored in a separate document.

ProCAST User Manual

Version 2009.1

VERSION 2006.0


General / Manager • In the "Copy" panel, the possibility to access directly to the "Template"

directory of the installation was added (see "Software Manager/File Manager" section for more details).

• The access to the CAFE pre-processor and post-processor were introduced in the Manager, as well as to the Advanced Porosity post-processor (see the "Software Manager/Module calls" and "Software Manager/Advanced module calls" sections for more details).

• A bug in the "Copy" functionnality was corrected. • The possibility to launch DMP calculations on Linux in Batch was introduced

(see the "Parallel Solver/Use of the Parallel solver" section for more details). • The FlexLM libraries were upgraded from 9.2 CRO to 10.1.3 STL. • A bug in the status window (wrong update of the number of cycles) was

corrected.

MeshCAST • A link between GEOMESH and MeshCAST was created in order to speed-up

the repair and surface meshing process (especially to account for the more efficient readers of GEOMESH) (see the MeshCAST manual for more details).

• Surface mesh Assembly (see the MeshCAST manual for more details). • Boolean Assembly (see the MeshCAST manual for more details). • The Surface mesh algorithm was improved in order to have a better quality

surface mesh. Especially, cylinders defined by only one surface can now be meshed automatically. Thin cylinders (e.g. cooling chanels) are not collapsed anymore when the mesh size is coarse.

• The Autofix is now fully automatic (no more need to specify a length) • A functionnality to remove automatically filets was introduced (see the

MeshCAST manual for more details). • The Layered shell mesher was re-introduced in MeshCAST (see the

MeshCAST manual for more details). • The format of the volume mesh has been adapted to allow the handling of files

with more than 10 millions elements. • When a Volume mesh is loaded, new buttons "Select All" and "Deselect All"

were introduced in order to select/deselect automatically all the domains. • The "Partial layer" option was corrected (it was giving the same results are the

Full layer option). • The "*.bstl" files can now be read on Linux.

ProCAST User Manual

Version 2009.1

PreCAST • Time-dependant Inlet boundary conditions were introduced (see the

"Boundary Conditions Database" section for more details). • In the case of shot piston, it is possible now to define the position of the piston

in three different ways : position vs time, velocity vs time, velocity vs position (see the "Process Database" section for more details).

• Wall BC and Velocity BC are now exclusive (i.e. if a Wall BC with a "Select All" is set, the previously defined Velocity BC's will be preserved).

• Now, it is not anymore possible to set BC's on Periodic BC faces (the Periodic BC faces are "protected", like Symmetry faces).

• A new "Pick" function has been introduced, to pick the coordinates and the node number of a given point selected interactively on the model (see the "Geometry Manipulation" section for more details).

• Stress properties (Youngs modulus, Poisson Ratio, Expansion coefficient) are now automatically calculated, based upon the Thermodynamic databases (see "Calculation of Stress Properties" section for more details).

• When defining the interfaces, the "Wireframe" mode has been reactivated (in order to see a domain which is inside an other one).

• The Plastic stress properties (i.e. the Hardening) can now also be defined as a set of tabulated tensile tests curves in an ASCII file (see "Digitized Hardening" section for more details).

• In the case of Microstructure modelling, the default values of the Run parameters were removed (see the "Micro Run Parameters" section for more details).

• The mesh can be now optimized also in the case of Periodic BC. • If a non-coincident mesh is used, a warning prevents the definition of a virtual

mould. • New User functions have been introduced (see "User Functions" section for

more details). • A problem in the initialization of CORE materials during cycling has been

corrected. • A problem of Extract of temperatures with the prefix_t.unf file larger then 2

GB has been corrected. • Enclosures can now again be defined by QUAD elements • A new Run Parameter (GATEFS) was introduced for the handling of the third

stage pressure in HPDC (see the "Thermal Run Parameters" and "Active Feeding" sections for more details).

• The set-up of Centrifugal cases was changed for more accuracy and the RELVEL Run Parameter was introduced (see the "Centrifugal casting" and the "Flow Run Parameters" sections for more details).

• Due to the changes in PreCAST and DataCAST, it is advised to reload the d.dat and p.dat files generated on previous versions and save them before re-running the cases with the version 2006.0.

• The Run Parameters Recommendations have been updated in order to account for the changes in the algorithm (see the "Run Parameters Recommendations" section for more details).

ProCAST User Manual

Version 2009.1

Thermodynamic databases • Stress properties (Youngs modulus, Poisson Ratio, Expansion coefficient) are

now automatically calculated, based upon the Thermodynamic databases (see "Calculation of Stress Properties" section for more details).

• The latest available Computherm databases are included in this version. The material properties calculated with these databases will be more accurate than the previous ones.

• The Computherm manual (from Computherm LCC) is added in the Software installation (in the dat/manuals/PDF direcrtory). This manual describes for each alloying system the phases which are calculated, the limitations as well as the validations which have been made.

ViewCAST • A new "Pick" function has been introduced, to pick the coordinates, node

number and values (e.g. Temperature, Pressure, ...) of a given point selected interactively on the model (see the "Geometry Manipulation" section for more details).

• The liquidus and solidus temperature are now shown on the Temperature scale (see the "Results Viewing/Display Parameters" section for more details).

• The previously defined scales (i.e. the scales defined manually during a previous session) are now automatically stored and loaded (see the "Results Viewing/Display Parameters" section for more details).

• Stored views were introduced (see the "Results Viewing/Geometry Manipulation" section for more details).

• When a model is loaded for the first time (or when no view was stored), the model is displayed in isometric view, with the gravity pointing downwards.

• In case of a Stress calculation, it is now possible to calculate all the Stress results (e.g. Effective Stress, Principal Stress, SigmaX, ...) all at once before viewing them (see the "Results Viewing/Field selection" section for more details).

• In the case of stress calculation, the possibility to view the total displacement was introduced (see the "Results Viewing/Field selection" section for more details).

• The displacements relative to a plane were introduced for the visualization of deformed geometries (stress calculation) (see the "Results Viewing/Field selection" section for more details).

• When a stress calculation is performed, it is possible to display the underformed geometry in wireframe together with the deformed contours (see the "Results Viewing/Display Parameters" section for more details).

• The calculation of the solidification time was improved in order to account for remelting (if any).

• The calculation of the Filling time was changed in order to ignore the piping area.

• The pressures calculated by the "Advanced Porosity module" can now be visualized in ViewCAST (see the "Advanced Porosity Post-processing" section for more details).

ProCAST User Manual

Version 2009.1

• In order to better visualize pockets of air, a new display mode of the free surface ("Foreground") was added (see the "Results Viewing/Display Parameters" section for more details).

• Stress results can be viewed also when the directory is in Read-only mode (on Windows only). This is especially useful to view stress cases stored on a CD or a DVD. The stress results are computed and stored in a temporary file on the local disk of the computer (see the "Results Viewing/Field selection" section for more details).

• If more than one symmetry is defined in the model, it can be automatically retrieved (it was previously working only with one symmetry).

• In the case of a Tilt casting, it was mandatory to have the p.dat file present in the directory to view the case. This obligation was removed.

• In the XYPlot window, when nodes were selected interactively, the selection window (with the cursors) was disappearing each time the model had to be rotated or moved. This limitation is now removed.

Solver • The filling algorithm was improved. A new Run Parameter FREESFOPT was

introduced (see the "Flow Run Parameters" section for more details). • The filling solver was improved in order to better handle Tilt pouring models.

A new Run parameter "TILT=1" was introduced in the case of Tilt models (see the "Flow Run Parameters" section for more details).

• For centrifugal casting, the algorithm was improved by the introduction of the RELVEL Run Parameter (see the "Centrifugal casting" and the "Flow Run Parameters" sections for more details).

• The convergence, the accuracy and the CPU time of the Stress module was significantly improved.

• Two new models (Norton law and Strain Hardening Creep) were introduced in the Stress module to account for viscoplasticity and creep (see "Stress models and Properties" section for more details).

• The Plastic stress properties (i.e. the Hardening) can now also be defined as a set of tabulated tensile tests curves in an ASCII file (see "Digitized Hardening" section for more details).

• In the case of Stress calculations with Vacant or Rigid materials, the memory management was changed in order to reduce the amount of memory needed (in the scalar version only).

• Stress calculations can now be run with piping (i.e. it is now allowed to set PIPEFS<1 in the case of stress calculations).

• The POROS=1 model was extended to allow the treatment of the Graphite expansion in the case of SGI (see "Cast Iron Porosity model" section for more details).

• The POROS=1 model was improved for the treatment of the third phase in HPDC. A new Run Parameter (GATEFS) was introduced (see the "Thermal Run Parameters"and "Active Feeding" sections for more details).

• A bug in the POROS=1 model was corrected (in the identification of the independant liquid pockets).

• A problem in the POROS=1 model with FREESF=2 filling was corrected.

ProCAST User Manual

Version 2009.1

• Microstructure models were improved (see "Microstructures" section for more details).

• The memory requirement was significantly reduced when running a case with many materials.

• Time-dependant Inlet boundary conditions were introduced (see the "Boundary Conditions Database" section for more details).

• New User functions have been introduced (see "User Functions" section for more details).

• A problem of Restart in the case of gravity casting was corrected. • The problem of heat transfer between a shot piston and the casting (there was

no heat transfer) has been solved. • The logic of the flow Switch Off was changed in order to avoid some

unexpected situations. If LVSURF < 1, the value of PIPEFS can not be set to 1.

• A problem in the FLOW=9 option was corrected. • It is possible now to run Stress models with materials which have no phase

change. • A bug in the case of Stress calculation in the presence of filters has been

corrected. • It is possible now to run a Microstructure calculations together with the

Turbulent model. • A problem in Cycling with FREESF=1 was corrected. • In the case of moving solids, the translation is also called at step 0. • A problem in the case of DIE COMBO was corrected. • A problem in the calculation of the piping when using Periodic Boundary

conditions was fixed. • A problem in the calculation of the "Freckles predictor" has been corrected, as

well as a problem of Restart with Freckles prediction. • If the "statpro" directory (where the status file is written) is momentarily not

available, the calculation will not crash anymore. • In the case of delayed filling (i.e. if the filling does not start since the

beginning of the analysis), the DTMAXFILL timestep will not be active before the filling starts.

• A bug in the treatment of the TOPEN has been corrected. • A problem in the Units of the user function "externalcompute.c" was

corrected. • A problem of "datacast -u" in the case of stress was fixed (the stresses of

vacant domains were lost). • A problem of convergence with non-coincident meshes was fixed. • A problem of memory allocation was corrected in the case of Radiation

problems. • The Run Parameters Recommendations have been updated in order to account

for the changes in the algorithm (see the "Run Parameters Recommendations" section for more details).

ProCAST User Manual

Version 2009.1

Parallel processing (DMP) • The Stress module has been parallelized. Please note that no specific set-up

should be done for parallel processing of Stress calculations. The set-up exactly the same as the scalar version.

• The "DataCAST" module is now the same between Scalar and DMP (e.g. one can run DataCAST on a scalar machine and then launch the calculation on N CPU's with the DMP version or vice-versa).

• ProCAST 2006.0 contains the first release of the Windows DMP version (see the "Parallel solver" chapter for more details).

• The Lost Foam and the Non-Newtonian module has been parallelized (same set-up as the scalar version).

• The TRI2QUAD=1 functionnality (for radiation) has been parallelized. • Some problems encountered in the DMP versions were fixed.

CAFE • The CAFE pre-processor and post-processor were introduced in the Manager

(it is no longer needed to have the calcosoft-3D installation to set-up and visualize CAFE calculations) (see the "CAFE-3D" chapter for more details).

• The CAFE solver (in post-processing mode) was introduced in the ProCAST 2006.0 distribution (it is no longer needed to have the calcosoft-3D installation to run CAFE calculations) (see the "CAFE-3D" chapter for more details).

Advanced Porosity module • The quality of the solver was significantly improved in order to have a better

convergence (robustness) and a better accuracy of the results. • The defalult value for the "convergence.tolerance" was modified (from 1e-12

to 1e-10) in order to be compatible with the modified algorithm. • A bug in the storage frequency was corrected. • The pressures calculated by the "Advanced Porosity module" can now be

visualized in ViewCAST (see the "Advanced Porosity Post-processing" section for more details).

• It is possible to view Advanced Porosity results (with the calcososft post-processor) across plateforms (automatic swap option).

• The calcosoft post-processor allows now to view results calculated using Hex or Wedges mesh.

• A bug in the viewing of Advanced Porosity results in the presence of enclosures has been corrected.

• Template files of the poro.d input file were added in the software installation (see the Template button in the "Copy" of the Manager in the end of the "Software Manager/File Manager" section for more details)

Manual (The following sections of the manual were added or changed) • The Stress properties recommendations were modified. One should note that it

is very important to set stress properties according to the "rules" described in the manual. Othewise, one could have convergence problems (see the "Stress Models and Properties" section for more details - end of the section).

ProCAST User Manual

Version 2009.1

• The Computherm manual (from Computherm LCC) is added in the Software installation (in the dat/manuals/PDF direcrtory). This manual describes for each alloying system the phases which are calculated, the limitations as well as the validations which have been made.

• The Run Parameters Recommendations have been updated in order to account for the changes in the algorithm (see the "Run Parameters Recommendations" section for more details).

• A new section was added in the "Microstructure Module" chapter (see the "Iron and Steel" section for more details).

ProCAST User Manual

Version 2009.1

VERSION 2005.0


General / Manager • The manager was modified in order to allow the launch of Parallel

calculations, of the Advanced Porosity module and of the Inverse module (see the "Software Manager/Advanced module calls" section for more details).

• A "Run list" functionality was added in order to launch automatically a serie of calculation (batch processing) (see the "Software Manager/Run list" section for more details).

• A Graphical status was introduced in the Manager (see the "Software Manager/Module calls" section for more details).

• The F2 key can be used to scroll between the different case names which are present in the same directory (see the "Software Manager/File manager" section for more details).

• The case name was added in the top bar of all the modules (MeshCAST, PreCAST, ViewCAST).

• The suffix ".mesh" has been added to the Filter of the "File Manger". • The FlexLM locking system was upgraded to FlexLM 9.2 CRO, for a better

security. This version will work with 2005 CRO license keys. • LMtools can be accessed directly from the Manager (see the "Software

Manager/Software configuration" section for more details).

MeshCAST • The call of the Volume mesher of MeshCAST in batch was re-introduced (see

the end of the "Software Manager/Module calls" section for more details). • The possibility to read Parasolid files with the .x_t suffix was added. • The automatic "zoom-out" was suppressed when the ADDLINE operation was

performed. • A units problem in MeshCAST-2D was corrected.

PreCAST • A GATENODE Run parameter was introduced in order to handle "Gate

feeding" with a shot piston (see the "Active Feeding" and "Thermal Run Parameters" sections for more details).

• The computation algorithm of the Virtual mold was modified (to avoid odd behavior in some cases).

• The virtual mold size can be defined automatically (see the "Virtual mold" section for more details).

• The possibility to activate User functions was introduced in PreCAST (see the "User Functions" section for more details).

ProCAST User Manual

Version 2009.1

• A bug in the units of the "Tilt" axis was corrected. • A bug in the storage of the "K-factor" (non-Newtonian model) was corrected. • The "Extract" was extended in order to allow it in the presence of filters. • The "automatic" setting of FLOW=3 was reviewed. • A "Erase line" was added in the "Chemical Composition" definition of the

material properties. • The TENDFILL Run parameters was introduced in order to automatically stop

a calculation at the end of the filling (see the "General Run Parameters" section for more details).

• New alloys were introduced in the Material database. Some properties of existing alloys were improved.

• The Stress material properties database was complemented. • A bug in the treatment of non-coincident interfaces was corrected (it was

creating a double heat transfer on some nodes in some specific cases). • The COARSEC and COARSEP Run parameters were removed from the

interface as they are no longer used. • When PreCAST is opened, the model is oriented according to the ISO

orientation.

Thermodynamic databases • The automatic calculation of the "Thermal conductivity" from the

thermodynamic databases was introduced for all databases (see the "Thermodynamic Databases" section for more details)

• The content of the Computherm databases was improved. This will lead to more accurate properties predictions. Moreover, the computation of some alloys (which was not possible with previous versions) was improved. This means that the properties calculated with this version will be different (but more accurate) than the previous ones (e.g. the solidus temperature of Ni-based alloys is now much more realistic than before).

• A problem in the Mg database was fixed, giving now the right results. • The liquid density of Pure Aluminium was changed in order to give more

accurate density predictions of Al-alloys (e.g. in the previous version, the solidification shrinkage of an A356 alloy was about 9.15%, whereas it is now 5.45%). This will affect the density calculations for all Al alloys.

ViewCAST • ViewCAST was adapted in order to allow the viewing of result files coming

from a different platform (e.g. viewing on Windows results computed on UNIX) (see the "Software Manager/Software configuration" section for more details).

• Automatic creation of AVI animations was introduced (see the "Resultsviewing/Introduction" section for more details).

• The GIF/AVI capture action can also be started from the "File" menu. • Export of the "Shrinkage porosity" and of the "Advanced porosity" fields has

been introduced. • An automatic pre-defined setting for "Shrinkage porosity" was introduced (see

the end of the "Results viewing/Display types" section for more details).

ProCAST User Manual

Version 2009.1

• Short cuts for the different display modes were introduced (see the "Results viewing/Display types" section for more details).

• The export of "Reversed displacements" was corrected, as well as the X-Y plots of displacements.

• The maximum number of timesteps which could be exported was increased from 200 to 5000.

• In Tilt casting, the particles are now "tilting" with the part. In addition, a new "Tilt" option in the "Parameters" menu was introduced in order to deactivate the tilt during the viewing (see the "Display Parameters" section for more details).

• The "Fill time" plot was introduced. • A problem with the calculation of RGL on Linux was fixed.

Solver • User functions were introduced for "interface heat transfer coefficients" and

"Heat boundary conditions" (see the "User Functions" chapter for more details).

• A bug with the TCLOSE (DIE COMBO cycling) was corrected. • A problem in the cementite formation of cast iron (microstructure module)

was fixed. • The interpolation of the linear thermal expansion coefficient (stress module)

was changed from linear by intervals to piecewise linear. • A problem with the calculation of stress in the presence of piping (stress

module) was corrected. In such case, one should set PIPEFS = 0 (see the "Thermal Run Parameters" section, under PIPEFS for more details).

• A new possibility was included in order to handle the "Gate feeding" in hpdc in the presence of a shot piston (see the "Active Feeding" and "Thermal Run Parameters" sections for more details about the GATENODE Run Parameter).

• A bug in the POROS 1 model was corrected (to avoid unexpected behaviors in some specific cases). Moreover, the display of the macroshrinkage (i.e. holes inside the casting) has been changed (one will have shrinkage porosity values of 1, but no internal "Voids" will be shown. "Voids" will be used only for pipe shrinkage at the surface of the model). Please note that the value of FVOL has no meaning for the viewing of porosity results.

• A problem in the Surface load (stress module) which was appearing in some cases was corrected.

• The influence of the gap width on the interface heat transfer coefficient, with non-coincident meshes, was introduced.

• The viscoplastic model (stress module) was improved, for a better accuracy. • The stress module was extended in order to allow the use of filters. • DIE COMBO was extended for the use with non-coincident meshes. • A problem in the handling of the "RESERVOIR" was corrected in order to

allow to fully empty the reservoir. • A problem with the Freckles indicator was fixed. • A new stop criterion (TENDFILL) was introduced. It allows to stop the

calculation N seconds after the end of filling (see the "General Run Parameters" section for more details).

ProCAST User Manual

Version 2009.1

• The CAFE-3D coupled solver was introduced in the standard ProCAST solver executable (see the "CAFE-3D" section for more details).

• Undesired "Sticking" in the pouring cup during Tilt pouring was improved. For that purpose a new TILT Run Parameter was introduced (see the "Flow Run Parameters" section for more details).

• A "loading increment" Run Parameter LOADSCL was introduced for more accuracy in structure analysis type of problems (see the "Stress Run Parameters" section for more details).

• A problem with RDEBUG=2 was fixed.

Parallel processing • The Parallel processing solver was introduced in this version for selected

platforms (see the "Parallel Solver" chapter for more details).

Advanced Porosity module • The Advanced Porosity module (originally developed in CALCOSOFT-3D)

was introduced in the ProCAST distribution (see the "Advanced Porosity Calculations" chapter for more details).

• The module was improved (with respect to one of the CALCOSOFT-3D 2004.0 distribution).

• Extension of the Advanced Porosity module in order to allow the calculation of the porosity in more than one casting domain.

• Direct reading of the ProCAST files was introduced (no more result files conversion needed).

• Storage of the porosity results at FEM nodes, allowing the visualization of the results in ViewCAST.

• Removal of the enthalpy conversion, allowing for a direct compatibility of the data between the ProCAST and the Advanced Porosity module.

• Possibility to define directly a density curve (instead of expansion coefficients of the different phases) and thus to use the same density curve as in the ProCAST calculation (the density curve of ProCAST is automatically used and thus, the definition of this curve is not anymore necessary in the porosity module).

• Direct reading of the fraction of solid and density curves in the ProCAST data files (the definition of these curves is not anymore necessary for the porosity module).

Manual (The following sections of the manual were added or changed) • A new section was added to list the limits in the chemical compositions for the

Thermodynamic databases (see the "Databases limitations" section for more details).

• A section on the "Influence of alloying elements" on thermophysical properties obtained with thermodynamic databases was added.

• A new "Software Manager/Advanced module calls" section was added. • A new "Software Manager/Run list" section was added. • The "Software Manager/Software configuration" section was complemented.

ProCAST User Manual

Version 2009.1

• A new "Parallel Solver" chapter was added. • A new "Advanced Porosity Calculations" chapter was added. • A new "User Functions" section was added in the "Pre-processing" chapter. • A new "CAFE-3D" chapter was added. • The "Virtual mold" section was modified in order to account for the automatic

definition of the box size. • The description of the new Run Parameter TENDFILL was added in the

"General Run Parameters" section. • The description of the new Run Parameter GATENODE was added in the

"Active Feeding" and "Thermal Run Parameters" sections. • Updates in the "Results viewing/Display types" section were made. • Details about non-coincident tolerances were added at the end of the "Multiple

Meshes and non-coincident meshes" section. • The description of how to disable both the porosity and the piping calculation

(by setting POROS = 0 and PIPEFS = 0) is now included in the "Thermal Run Parameters" section (under PIPEFS).

• The set-up of a cycling calculation including a Porosity calculation is now described at the end of the "Cycling" section.

• The transition between plastic and viscoplastic models was revised in the "Stress Models and Properties" section.

• Advices about the setting of Yield stress values in the liquid have been added at the end of the "Stress Models and Properties" section.

• The principles of plastic and viscoplastic properties determination from experimental measurements are now described.

ProCAST User Manual

Version 2009.1

VERSION 2004.1


General • On some platforms, the graphics performances were very poor (in terms of

display speed). This was corrected. However, it may still happen that on some graphics cards, the graphical performances are not optimum (in terms of display refresh). In such cases, the configuration of the X-Server may need to be adjusted.

• The installation structure of the software was complemented in order to allow the installation in a Read only location. Each user has now the possibility to set a customized directory for his Preferences (including the MeshCAST user customized icons) and databases. (Customized installation).

MeshCAST • On some platforms (mainly Windows), MeshCAST was not always able to use

all the available memory (e.g. it was crashing at 1.1 GB, whereas the computer had 2 GB of RAM). This problem was due to the way "reallocation" of memory was done in the code and how the operating system was managing the memory allocation. The memory "reallocation" technique was modified in order to prevent such problems, allowing to use all (or most) of the available memory. In such situation, temporary files will be created in the working directory (see the MeshCAST manual for more details about this option and the "Module calls" section for the activation of this option).

• In the case of problems with Shell meshing with symmetry, a new functionality was added in order to allow the curing of the problem (see the MeshCAST manual for more details about this option).

• The User defined icons can now be stored in a central location (or in a customized user defined location) (Customized installation).

• Some corrections when reading Parasolid files were made. • ANSYS surface mesh input is now available.

PreCAST • The viscosity and density can be automatically calculated from the

thermodynamic databases, based upon the chemical composition (Thermodynamic Databases).

• The thermal conductivity for Aluminium alloys can be determined automatically from the thermodynamic databases, based upon the chemical composition (Thermodynamic Databases).

ProCAST User Manual

Version 2009.1

• A new Run Parameter was introduced (DTMAXFILL) in order to define the maximum timestep to be applied during the filling stage. This run parameter is optional (General Run Parameters).

• A "Die close" was introduced in the Die Combo definition. This allows to account for a closed period of the die before the next filling starts (Interface Database, Cycling Run Parameters)

• A special effort in the "Standard" Run Parameters definition was made (in PreCAST and in the Solver). Thus, it is now possible to set "Standard" sets of Run parameters for each process (see the "Run parameters Recommendations" section for more details).

• The automatic Mesh Optimization was introduced in PreCAST. This means that it will not be necessary anymore to optimize meshes in MeshCAST and that the optimization will automatically take into account the interface set-up (Warning : the Optimization should not be used on a model which contains Extracted initial conditions coming from a non-optimized model).

• A more sophisticated model (but simple to use) to define filters (with pressure drop information) was introduced, aside from the current filter model (see the definition of Filters in the "Material Properties" section).

• The inverse set-up was re-introduced in PreCAST. This was the opportunity to simplify it to make it more user friendly.

• The Microstructure Run Parameters were introduced in PreCAST. • The size of the model (and not only the min-max) is now displayed when the

case is loaded. • A correction in the "Extract menu" was done. • A correction of the Virtual mold scale display was done. • A bug in the definition of time-dependent displacements was corrected. • The "Select Remain" was selecting both outside faces and faces at interfaces.

This was corrected. Only the outside surfaces are selected. • The direct access in databases with a Right Mouse click was extended to all

databases. • Units in the "Thermal Expansion coefficient" (Stress database) were corrected.

ViewCAST • A new "Particle tracing" has been introduced. The streamlines are

automatically computed during the calculation and thus the display in ViewCAST is fast (see "Display parameters" for the viewing and "Flow Run Parameters" for the set-up).

• When a case is viewed during the calculation, the timesteps can be automatically updated during the ViewCAST session (see the Display parameters section for more details).

• In XY-Plots, the Import/Export of the node numbers (as well as the scale) was not working well. This was corrected. See the "Curves" section for the format of the Import/Export.

• The GIF capture was not always working with screen resolutions different from 1280x1024. This was corrected.

• When capturing a GIF picture/animation, if the ".gif" extension is not specified, it will be automatically added.

ProCAST User Manual

Version 2009.1

• The units of the SDAS display were wrong. It was corrected. • The node numbers and elements numbers can now be displayed (see the

"Geometry manipulation" section). • During the filling calculation, a "smoothing" algorithm of the free surface was

suppressed (as it was causing some problems in some filling situations). Thus, in the case of coarse mesh or strong zoom, one could see a more "rough" free surface than in previous versions (this does not affect the quality of the filling pattern).

• A bug in the stress solver, in the presence of non-coincident meshes was corrected.

Solver • Although many improvements were made in version 2004.0 in the filling

algorithm, in order to reduce numerical diffusion (to have "less viscous" liquid), this did create some detrimental behaviors in some situations. Thus, the filling algorithm was further refined and tests have shown much better results in all the geometries and processes which were calculated. A special effort was put in the Run Parameters settings for filling simulation. Now, the default values can be used for all processes (only WALLF should be customized in order to account for the "friction" of the liquid at the mold wall) (Flow Run Parameters, Run Parameters Recommendations).

• In LPDC, the stability of the filling with a pressure boundary condition was totally reviewed and now good results are obtained also with pressure filling (Flow Run Parameters, Run Parameters Recommendations)

• The POROS=1 model was improved and a few bugs were corrected. The description of the POROS=1 model was also improved (see in particular the description of the effect of FEEDLEN)

• The visco-plastic model was slightly changed in order to allow a more straightforward definition of the input parameters from measured data and the possibility to set a Norton law (with threshold) for creep (Stress models and properties). One should be careful that viscoplastic models which have been set in previous version should be modified in PreCAST in order to add the normalization stress. Otherwise, the solver will not work.

• Porosity calculations can now be done together with cycling. • In the Lost Foam model, there was situations where small bits of foam were

not burning. This situation was corrected. • The stress solver was extended in order to account for moving solids. • A bug in the Restart of Stress calculation was corrected, leading to a much

improved convergence of the restarted step. • A bug in the GATEFEED=1 option was corrected in the case of

time-dependant pressure or inlet velocity (GATEFEED was not activated in this cases)

• A check was introduced at the beginning of the calculation in order to prevent a missing pressure BC when GATEFEED is set to 1 (to prevent piping in pressure die casting, in thermal only calculations).

• A bug was corrected in the "inlet BC" algorithm when nodes at the interface between the casting and the mold were selected. One should be careful in such

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cases that the filling time may not be exactly correct (if interface nodes are selected).

• A bug in the micro module for hyper-eutectic cast iron was corrected. • When the microstructure module is used, the material properties definition has

slightly changed (as some data can be automatically obtained from the thermodynamic databases) - see the "Microstructures/Case set-up and Results" section for more details.

• A print-out bug was corrected in the d.out file. • On some platforms, it was still not possible to generate files larger than 2 GB.

This is now corrected. One should be careful however that the file system (kernel) should be well configured in order to accept such large files. However, as it was not possible to generate a 64 bits version of the User interfaces (and especially ViewCAST) on IBM (due to Tcl/Tk problems), it is not possible to visualize such large models on IBM at this stage. Work around : visualize these results on a different platform.

• A bug in the calculation of the permeability of a mushy zone at low fraction of solid was corrected. This has an effect on cold shots or early solidification during filling (in case of very large interface heat transfer coefficients).

• DataCAST execution time was reduced for large models.

Manual (The following sections of the manual were added or changed) • New Microstructures module chapter • New Inverse module chapter • New Thixo casting chapter • New Lost Foam chapter • New section on Thermodynamic databases for automatic computation of

density, viscosity and thermal conductivity • New section on Mesh Optimization in PreCAST • New section on Particle tracing (see "Display parameters" for the viewing and

"Flow Run Parameters" for the set-up) • New section on "customized installation" with a Read/Write zone • New section on the Input-Output files • New section and changes in the Filter definition (see the "Material Properties"

section for more details) • New "Run parameters Recommendations" section • New Run parameter DTMAXFILL (General Run Parameters) • New Run parameter TCLOSE for Die Combo (Interface Database, Cycling

Run Parameters) • New Run parameter VACUUM for stress calculations (Stress Run Parameters) • Changes in the material properties definition in the case of Microstructure

calculations have been made ("Microstructures/Case set-up and Results") • Correction of the GAPMOD Run parameter definition (Stress Run Parameters) • Correction of the definition of the modified interface heat transfer coefficient

during stress calculations, when air gaps are formed or when there is a contact pressure (Gaps in stress models)

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• Changes in the definition of the visco-plastic and creep model (Stress models and properties)

• Correction in the description of the FEEDLEN effect in the POROS=1 porosity model.

• New tutorial for LPDC.

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VERSION 2004.0


General • All the user interfaces have been re-developed, using the Tcl/Tk and OpenGL

technology. Thus, NutCracker is not anymore necessary to run the software on Windows machines

• The software is licensed using the FlexLM tool (FlexLM). This gives the possibility to have floating licenses

• Direct access to the on-line help

Manager • A new Software Manager was introduced (to replace "PCS") • Directories can be created and managed (File Manager) • Cases can be automatically copied, with prefix changes (File Manager) • The different modules can be called interactively (Module calls) • The calculation can be monitored with a direct status access (Module calls) • The software configuration can be tailored in the Manager (Software

configuration)

MeshCAST • The volume meshing algorithm is significantly improved in order to generate

less elements and nodes with a better quality • The 2-D mesh generator is replaced by a new 2-D mesh generator based upon

the one of calcosoft-2D. It is extended in order to automatically generate 3-D meshes of one slice for both cartesian and axisymmetric modeling

• The maximum number of surfaces which can be allocated to an enclosure was increased to 5000

• The new user interface is available for UNIX/Linux users

PreCAST • PreCAST was totally re-developed in a new user interface, based upon the

same fundamental principles as the previous version (Pre-processing) • Interactive tools to manipulate the geometry (rotate, zoom, center, drag)

(Geometry manipulation) • Different display types (wireframe, hidden, hidden mesh, shade) (Geometry

manipulation) • New symmetry definition, with interactive pick of the coordinates (see the

Radiation section)

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• Enhanced definition of the Virtual mold, with possibility to view the thermal depth and the mold box (Virtual Mold)

• Display of the size of the model (Geometry Assignment) • New Material database design (Material Database) • Coherency about material properties definition (enthalpy, Cp, fs and L)

(Material Properties) • Direct visualization of tables (Material Database) • Direct access to material and boundary condition databases (Materials

assignment, Boundary conditions assignment) • Search and Sort tools for each database (Material Database) • Exothermic material definition (Exothermic) • More explicit definition of the material domain types (casting, mold, foam,

filter, exothermic, ...) (Materials assignment) • Definition whether a material domain is empty or not in the "Materials

assignment" menu • Possibility to remove interfaces which have been previously created

(Interfaces assignment) • More flexible way to define non-coincident interfaces (Interfaces assignment) • Possibility to change interactively the non-coincident interface tolerance

(Interfaces assignment) • In all databases, possibility to Import or Export the tables (Material Database) • Enhanced selection of boundary conditions, automatic propagation, selection

of remainder, selection of interfaces (Boundary conditions assignment) • Copy, Paste and Clip capabilities in the Boundary conditions selection

(Boundary conditions assignment) • A "velocity calculator" was introduced in order to calculate the desired inlet

velocity boundary condition (Boundary Conditions Database) • For radiation problem with an enclosure, the alignment of the surface vectors

is simplified (Radiation) • For all databases, the database management (add, read, copy, delete) can be

done in the same window as the assignments (Material Database) • New design of the Run Parameters layout (Run Parameters) • Automatic settings of up to nine Run Parameters Templates (Pre-defined Run

Parameters)

ViewCAST • ViewCAST was totally re-developed in a new user interface, based upon the

same fundamental principles as the previous version (Results viewing, Results analysis, Results export)

• Better rendering of the models and of the free surface, including shading and transparency

• Interactive tools to manipulate the geometry (rotate, zoom, center, drag) (Geometry manipulation)

• Full capability "Tape player" to step forward and backwards in single steps or animated mode (Tape Player)

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• More comprehensive way to select the different view modes of the material domains (solid, invisible, wireframe, hidden mesh, shaded, transparent) (Geometry manipulation)

• Direct access to the different view modes (snapshot, slice, scan, cut-off) (Display types)

• Interactive slicing is available at any time (Display types) • Enhanced timestep display definition, with the possibility to define time

intervals for the display (in addition to step intervals) (Display parameters) • Full export of stress results (in a Neutral format which can be imported in any

stress software) (Results Export/Stress) • Full export of the displacements (in a case of stress calculation), with the

possibility to "reverse" the displacements in order to perform reverse engineering of distorted molds (Results Export/Displacements)

• Automatic calculation of the solidification time (Field selection) • Enhanced symmetries settings (same panel as in PreCAST) (Display

parameters) • Merge of the former PostCAST capabilities into ViewCAST. This allows to

have only one post-processor for the snapshots and the time evolutions curves (Results viewing/Curves), as well as for the generation of outputs, such as Niyama, cooling rates, SDAS, ... (Results analysis/Criterion functions)

• The XYPlots settings have been totally reviewed (Results viewing/Curves) • The node selection for XYPlots can now be stored, as well as the scale of the

graph for further use (Results viewing/Curves) • Three different modes for the viewing of the free surface have been introduced

(On, Off, Only) (Display parameters) • The definition of the scale is totally new and interactive. The scale is kept in

memory for each field (Display parameters) • The materials can be "exploded" for a better viewing (Geometry manipulation) • The display of vectors is improved. It is possible to define the length of the

arrows, as well as to have a unique length for all the arrows (Display parameters). The unit vector length is now shown on the screen during snapshots and slices

• An automatic scan of slices (scanning along the X-, Y- or Z-direction) can be done at a given step (Display types)

• The definition of slices (cuts) is improved. It is now possible to view or not the geometry behind (or ahead) of a slice (Display types)

• The "cut-off" capabilities were improved. It is now possible to specify two cut-off values (Display types)

• The display in cut-off mode in the presence of a free surface is now well treated (Display types)

• The information about the case status (prefix, displayed field), time, timestep has been reviewed and is now shown on the bottom of the screen (Results viewing/Introduction)

• The free faces information is now generated in DataCAST and thus the loading of a case is much faster

• Full viewing capabilities are now available when symmetries are activated (cut-off, free surface, ...)

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Solver • The flow solver for filling was extensively reviewed. In particular the flow

along walls was significantly enhanced (WSHEAR=2). The stability of the solver was thus improved for filling (Flow Run Parameters)

• A new Run Parameter (WALLF) was introduced in order to better account for the surface quality of the mold (Flow Run Parameters)

• The EDGE Run parameter was suppressed (due to the WALLF introduction) • The end of the filling can be shortcut with the new Run parameter ENDFILL

(Flow Run Parameters) • A new "Pool" model was introduced (RESERVOIR type) in order to facilitate

the modeling of cases with large horizontal free surfaces, such as tundishes (Materials assignment)

• Improved lost foam model • The inlet boundary condition was improved in order to preserve the right

amount of incoming mass • The Porosity model (POROS=1) was significantly improved in order to give

more accurate predictions (Porosity models) • The density definition in the case of porosity calculations was extended

(Density definition) • The gate feeding (in the case of injection - hpdc - lpdc) was changed in order

to be fully automatic (Active feeding) • Enhanced enthalpy formulation for more accuracy of the thermal solver • Exothermic materials can be modeled (Exothermic) • Large files (over 2 GB) can now be handled • The visco-plastic model for stress was adapted to account for creep (Stress

models and properties) • Fatigue prediction is available (Fatigue life indicator) • Hot tearing calculations are available (Hot tearing indicator) • Cracking indicator is introduced (Cracking indicator)

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IDENTIFIED BUGS, PROBLEMS AND L IMITATIONS

This section contains the identified bugs and problems which could not be corrected in this version.

General • On UNIX, the command window which is used to launch the manager is not

available for any further operations (as long as the manager is open). • On some platforms, there may be an error message when exiting the different

modules. This message can be ignored.

Manager • Problems may be encountered if the working directory name contains dots

("."). • If the Status is refreshed too often (by clicking on the "Status" button), a Tcl

error may be encountered. This happens if the refresh is done exactly in the same time than the writing of the stat file by the solver. This can also happen if two refresh are done in a very short time interval.

PreCAST • On some platform, the "Get coords" functionality to define symmetries is not

working properly. • On Sun, windows are opened behind the application, which can not be

accessed. • The display of the Virtual mold thermal depth has some problems. • If GATEFEED is set to 1 and POROS to 0, the calculation does not start if no

pressure BC is set (as there is a mistake in the logic of such testing). Work around : one should set GAFEFEED = 0 when POROS = 0.

• When a case is opened directly from PreCAST (and not from the Manager), if this case is located in a different directory (from the directory where PreCAST was launched) and if this directory contains a ".", the case can not be opened. Work around : open the case directly from the Manager.

• The material names should not contain blank spaces (this will generate an error in DataCAST : "An enthalpy function is referenced in 5 0 data

set 1 which has not been given" . Work around : if an old "d.dat" file is containing such a material name, one can edit the d.dat file and change the material name in the "card 5.0" to suppress the blanks ( 5 0 1 NICKEL_IN_718 1 )

• When a translation velocity as a function of position, v(x), is defined by a table, the velocity values should not contain any zero values.

ViewCAST • Some problems were observed in the visualization of stresses on SGI. • When displaying a slice with vectors, some problems may occur.

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• When displaying vectors in a slice, the contour of the slice does not appear. • It is not possible to superimpose a contour and vectors (in slices). • Sometimes, the particle tracing is giving wrong results at the last steps of the

filling. • In same cases, the automatic timestep update is freezing ViewCAST on SGI.

Work around : do not activate the automatic timestep update on SGI. • The visualization of result files larger then 2 GB is not possible on IBM (as the

executable of ViewCAST is 32 bits). Due to Tcl/Tk problems on IBM 64 bits, it was not possible to create an executable of ViewCAST 64 bits. Work around : use an other platform to visualize such results.

• On UNIX, depending on the configuration of the X-Server, it was observed that the performances of the graphics may be not optimum.

• When a case is opened directly from ViewCAST (and not from the Manager), if this case is located in a different directory (from the directory where ViewCAST was launched) and if this directory contains a ".", the case can not be opened. Work around : open the case directly from the Manager.

• Particle tracing is not available in Tilt and Reservoir cases (i.e. when there is no inlet velocity, inlet pressure on inlet BC).

• In Tilt casting the velocity vectors will not "rotate" with the part and thus they will appear in the wrong direction. Work around : deactivate the tilt rotation in ViewCAST when viewing at velocity vectors.

• It is not possible to visualize only a filter. Work around : select also an other material.

• In Lost foam calculations, one see non-zero velocities in the mould at step zero. Just ignore these velocities which are meaningless.

• It is not possible to view the Particle tracing with symmetries (i.e. the traces are not replicated).

Solver • It is not possible to fill simultaneously two separated cavities. One should fill

only one cavity at a time or set (by hand in the p.dat file) the Run parameter COLDSHUT = 0 (this will deactivate the cold shut detection algorithm).

• In models where there are more than one RESERVOIR domain, they should all touch each other and they should be all full at the beginning. Otherwise, problems may be encountered.

• PIPEFS must be set to zero if it is to be followed by an Advanced Porosity calculation.

• It is not possible to model temperatures below -273°C (below absolute zero) with the THERMAL=2 model. Work around : use THERMAL = 1.

• When a domain defined as RESERVOIR is remaining full during the whole filling, the Pool model will be activated at the wrong fill fraction (i.e. at LVSURF minus the volume of the reservoir). Work around : set this domain to CASTING instead of RESERVOIR, as if this domain remains full, it is useless to define it as RESERVOIR.

• When the data files are stored on a remote disk (accessed through a network), it may be possible to have problems with DataCAST on large problems (DataCAST is in fact running well, however, the g.unf file is not written

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properly and thus ProCAST will crash right at the beginning). In such case, it is worth to run DataCAST on the local disk of the machine and then transfer the files (or at least the g.unf file) on the remote disk. This is due to the fact that the writting of large files (with large record length) through a network may encounter problems. This is a system problem which has nothing to do with the software. This was observed only when DataCAST was run on Windows.

• If we have piping which results in a part of the casting being separated from the main body, this will lead to problems in the stress calculation (i.e. the stress calculation will diverge). Work around : use the PETSC_SOLVER = 0 option.

MeshCAST • On some Windows OS, the Open in MeshCAST is not done in the current

working directory.

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SOFTWARE MANAGER

FILE MANAGER

When the ProCAST software is started, the Manager is launched, as seen in the figure below. The Manager allows to browse in the desired working directory, to create new directories and cases, to copy files from one directory to an other and to launch the different modules of the software.

The default starting directory can be set in the "Installation settings" (see the "Software configuration" section).

Firstly, the working directory should be defined (with the "browse" and

"create directory" icons) and secondly, the name of the case (prefix name) should be defined.

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When several cases are present in the same working directory, the prefix of the first one (in alphabetical order) is selected. In order to scroll through the other cases, one can use the F2 key. The File Manager allows to perform some actions on the files, such as "Refresh"

(to refresh the file list), "create new text file" , "Rename file" ,

"Duplicate file" and "Delete file" . A set of files can be copied from one directory to the other, using the

button. Then, two windows are opened (see figure below) and files can be copied from the left window to the right one. If the "Keep Prefix" check box is activated, the prefix remains unchanged, otherwise, the prefix is changed to the one defined under "Case" in the lower orange section.

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The extensions "d.dat", "p.dat", "d.out" and "p.out" are well handled by the copy. However, if it is desired to copy "unf" files, the user is prompted for the "old prefix" and the "new prefix", as shown below :

In the "Copy" panel, the icon gives a direct access to Template files (for the user functions and for the porosity input file).

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MODULE CALLS

The different modules of ProCAST can be called from the top bar buttons :

Firstly, the FEM mesh should be generated with MeshCAST. Then the case should be set-up with the pre-processor (PreCAST). Once all the parameters and conditions are defined, the calculation files should be prepared with DataCAST. The calculation can be run at this time by calling the ProCAST solver. Finally, the results can be visualized with the post-processor VisualCAST. At any time during and after the modeling, the status of the calculation can be monitored with Status. MeshCAST, the meshing module of ProCAST, is launched with the "MeshCAST" button. Then the desired case should be opened into MeshCAST (there is no automatic launch as the software does not know whether the .gmrst, the .sm or the .mesh file should be opened). Please refer to the MeshCAST User Manual for further details. A Command window is opened in the background in order to allow the viewing of error messages if necessary. This Command window can be closed at the end by a simple <RETURN>.

The Manager allows also to launch the "2-D mesh generator" or MeshCAST with the -M option. To do so, a "right click" on the "MeshCAST" button should be

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done. This opens a sub-menu, where one can select between MeshCAST-2D or MeshCAST-3D and MeshCAST-3D with the -M option.

When "MeshCAST-3D -M" is selected, the following window opens :

This special mode of MeshCAST should be used only in the case of large memory requirements (see the MeshCAST manuals for more details). When PreCAST is launched, if a "d.dat" file is present, it will automatically be loaded. Otherwise, the browser will prompt in order to select a ".mesh" file.

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When a right click in made on the "PreCAST" button, it gives access to a sub-menu in order to activate the "CAFE pre-processor"

Interfaces assignmentThe DataCAST module is translating one input file generated by the pre-processor PreCAST (i.e. the d.dat file) into binary files (*.unf) which will be used by the calculation. Some error checking is also performed at this stage. When the DataCAST button is activated, a Command Window appears. This allows to view potential warnings or error messages. The operation is finished when the PAUSE appears on the window. Then, one should just hit any key (e.g. RETURN) in order to close this Command window and proceed with the calculation itself.

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When the DataCAST module is launched, a confirmation window is prompted to the user in order to confirm the launch of DataCAST (as DataCAST is erasing existing result files, this confirmation allows to prevent any undesired results loss).

Moreover, the "Update option" of DataCAST (see the "Run the Calculation/Solver" section for more details) can be activated from this window. Once the data are ready (after PreCAST and DataCAST), the ProCAST solver can be launched, with the "ProCAST" button. The following window is then opened in order to "Confirm" the start of the calculation. Moreover, it is possible to automatically launch "DataCAST" before the ProCAST solver, by checking the "Execute DataCAST first" box.

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Upon "Run", a Command Window will be automatically opened and the solver will be started. As this window is independent from the Manager, it is possible to use the Manager (and the other modules, such as the post-processing for instance) while the calculation is running. When the calculation is finished, a PAUSE will be prompted and one has to hit any key (e.g. RETURN) to make the window disappear. If there is a problem during the execution, a warning or an error message may be printed in this window.

The inverse solver can also be called from the "ProCAST" button (see the Software configuration section for more details about how to activate the Inverse option):

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Results can be viewed at any time (even during the run of the calculation), with the VisualCAST button. If the case name is set, as well as the current working directory, the case is automatically loaded in the post-processor, as shown below.

A right click on the "VisualCAST" button gives also access to "ViewCAST", the "Advanced Porosity" and the "CAFE" post-processors (i.e. the calcosoft post-processor) :

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Please note that VisualCAST should be installed in order to use this button (the installation of VisualCAST is distinct from the ProCAST installation. To monitor the calculation, the "Status" button can be used at any time. A graphical status of the case will be shown with the relevant information concerning the calculation (i.e. percent filled, solid fraction, timestep, current time, cpu time, ...) corresponding to the case name indicated in the lower orange window. The status is refreshed every 15 seconds, unless the "Status" button is pressed again. To exit the Status window, press the "Return to File Manager" button. Please note that the Graphical status is working only when activated in the working directory of the case (as the prefixp.dat file is read).

Finally, all these modules can be called manually from a Command Window. The "Command Window" button opens automatically a Window in the working directory.

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Then, the modules can be called in the following way (or via ad-hoc aliases) : For Windows : Manager %ProCAST20091%\bin\manager.exe MeshCAST %ProCAST20091%\bin\meshcast PreCAST %ProCAST20091%\bin\precast prefix DataCAST %ProCAST20091%\bin\datacast prefix ProCAST %ProCAST20091%\bin\procast prefix ViewCAST %ProCAST20091%\bin\viewcast prefix For Unix (tcsh, csh) : Manager $ProCAST20091/bin/manager.exe MeshCAST $ProCAST20091/bin/meshcast PreCAST $ProCAST20091/bin/precast prefix DataCAST $ProCAST20091/bin/datacast prefix ProCAST $ProCAST20091/bin/procast prefix ViewCAST $ProCAST20091/bin/viewcast prefix The Volume mesher of MeshCAST can be called in batch mode with the following command : On Windows : %ProCAST20091%\bin\meshcast -batch prefix.sm Flag On Unix (tcsh, csh) : $ProCAST20091/bin/meshcast -batch prefix.sm Flag "Flag" is an integer value defining : 0 : no layer 1 : partial layer 2 : full layer

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ADVANCED MODULE CALLS

Advanced modules, such as the Parallel solver of ProCAST, the Advanced Porosity module, the CAFE module or the Inverse solver, can now be called from the manager. To do so, firstly, the Manager should be configured in the following way (in the "Installation Settings" window.

In the "Preferences" tab, one can select which "modules" should be activated (under "Modules display") in the Manager :

By default, none is activated.

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"Advanced Porosity module" will activate the possibility to launch and visualize Advanced Porosity calculations (see the "Advanced Porosity Calculations" chapter for more details). "Inverse module" will activate the possibility to launch inverse calculations form the Manager (see the "Inverse modeling" chapter for more details). "CAFE Module" will activate the possibility to launch an visualize CAFE calculations (see the "CAFE-3D" chapter for more details). "ProCAST Parallel" button (in the "Parallel" tab) will activate the possibility to launch the parallel solver (see the "Parallel Solver" chapter for more details). When these modules are activated in the "Preferences", the "ProCAST" window has the following appearance (more details about the functionnalities in the corresponding chapters) :

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RUN L IST

The "Run List" allows to launch automatically several calculations in a row, as well as to "chain" different calculations (such as a ProCAST thermal calculation followed by an Advanced Porosity calculation). This allows also to launch calculations in batch mode.

When the "Run List" menu is selected the Manager window appears as follows :

If it is create a "Run List" from cases in the same directory, one should check that the desired case name is specified in the bottom window, then the desired solver should be selected in the left window (Available Solvers) and the "Add button" should be pressed. The corresponding run will appear in the right window

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(Solvers to be run). Then, one can add as many runs as desired (see example hereafter where the Case1 and Case2 are launch sequentially).

In the following example, the ProCAST thermal calculation (including DataCAST) is automatically followed by the "Advanced Porosity" run.

If the cases to be run are not all in the same directory, one should first select the Solver to be run (in the left window) and then press the "Folder" button (above the "Add" button). This is opening a browser, where one can select the desired directory and the desired case to be run. Once the "Open" button of the browser is pressed, the corresponding line in the right window is added. With this method, one can run sequentially a serie of calculation which are located in different directories. It is also possible to remove an entry from the right list, by selecting it and pressing the "Remove" button. Once the list is ready, the "Run Computations" button can be pressed. This will automatically launch the calculations. Otherwise, it is also possible to save the "Batch file", with the "Create Batch File" button. This file will automatically store the batch file in the working directory.

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One can also edit the batch file or run it with the corresponding buttons. In these two cases a browser will open automatically, to select the desired file.

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SOFTWARE CONFIGURATION

The software can be configured in the "Installation Settings" window :

Preferences tab The Preferences can defined, such as the Default directory which will appear every time the Manager is launched, the preferred Text editor can be configured.

The Option "Use the 64Bits executables" shall be used on 64 bits machines (e.g. Windows 64). This allows to use automatically the 64 bits executables of the

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solver and of MeshCAST. If this option is not activated, the 32 bits executables will be used. The access to the "Advanced modules" (Advanced Porosity, Inverse, CAFE and HCS) can be configured in this window (see the "Advanced module calls" section for more details). ViewCAST File format compatibility ViewCAST allows a full compatibility between UNIX and Windows results. This means that it is possible to visualize on a Windows machine, results which have been calculated on a Unix machine, or vice-versa. To do so, one should "Activate the swap mode", as shown below.

Then, the user can select the desired default mode between the two above choices. This default mode will be used when the "ViewCAST" button will be pressed. However, it is still possible to use the other mode (i.e. Swap format), by making a right click on the "ViewCAST" button. Then, one can chose between the "No swap format" (which means that ViewCAST and the ProCAST run were performed on the same platform) or the "Swap format" (which means that ViewCAST and the ProCAST run were performed on a different platform).

FlexLM manager : LMtools It is possible to open the FlexLM Manager (LMtools), by clicking on the corresponding button in the "Preferences" tab of the "Installation settings".

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This will work only if FlexLM is installed in the "standard" directory. Parallel tab The Parallel Tab allows to define the DMP settings (see the "Parallel Solver" chapter for more details).

Installation tab In the "Installation" tab, one can check that the environment variable ProCAST20091 is well configured. It should point towards the v2009.1 directory, above the "bin", "dat" and "lib" directories.

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The "Command window Launch Option" check box (in the bottom of this Installation Settings window" allows to activate the Command windows when PreCAST and ViewCAST are launched. This mode should be activated in case of problems in order to see the possible error messages which may occur. In normal situation, this mode should be deactivated. The "DOS Path Converter" (on Windows only) can be useful to convert "long directory names" into short "DOS" ones. In ViewCAST, the time is displayed at the bottom of the screen. By default, the time is shown in seconds. However, in the case of large casting modeling, it may be useful to see the time in hours:min:sec, whereas for high pressure die casting, milliseconds are preferred. The default settings can be set in the file "manager.tcl", which is located in the "bin" directory of the installation. At about 30 lines from the top of the file, there is the following lines :

### Viewcast ### global viewcastOption set viewcastOption "-T1"

The viewcastOption variable is controlling the time display as follows :

set viewcastOption "-T1" (display in seconds) set viewcastOption "-T2" (display in hours:min:sec ) set viewcastOption "-T3" (display in milliseconds)

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CUSTOMIZED INSTALLATION

In some cases, the software is installed in a centralized location of the company. In previous versions, it was necessary the set the installation directory of the software with Read/Write access rights, in order to allow the access to the databases and to the status files. From version 2004.1, ProCAST allows to install the software in a Read only location and to customize the location of the files which have to be modified by the user (databases, status files, preferences). To do so, two optional Environment variables are available : ProCAST20091_DB for the location of the databases. ProCAST20091_USER for the status files and preferences. If a user, or a group of users, would like to have the databases in a different location then the software installation, one should copy the "db" directory in the desired location (e.g. /my_db_location/db). Then, the ProCAST20091_DB environment variable should be set (manually) to the /my_db_location directory. In the same way, if a user would like to set it own preferences and status files, one should copy the "pref" and "statpro" directories in the desired location (e.g. /my_pref_location/pref and /my_pref_location/statpro). Then, the ProCAST20091_USER environment variable should be set (manually) to the /my_pref_location directory. Please note that the "Preferences" directory is containing preferences of the Manager, as well as the User customized icons of MeshCAST.

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FLEX LM

The software is locked using the FlexLM tool. For "Node locked" licenses, the following procedure can be used (for floating licenses, please refer to the general FlexLM documentation). The following is valid for Windows only. For Unix, please refer to the FlexLM documentation. In order to activate your license, a license file should be requested to ESI. The first step is to identify the machine on which the software has to run. To do so, run the "FlexLM License Manager", by a double click on the corresponding icon in the "PAM-SYSTEM" directory which is on your desktop.

This will open the following panel. Go to the second tab "System Settings" (1) and send this panel to your local distributor. You can also transform this information in a text file, using the "Save HOSTID Info to a File" button (2).

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Then, the licence file which is received from ESI should be called "pam_lmd.lic" (usually, it is called "*****.cry" and you should rename it to "pam_lmd.lic" - previously it was called "license.dat"). Then, the "pam_lmd.lic" file should be placed in the C:\flexlm directory. When one of the following modules (PreCAST, ProCAST or ViewCAST) is called for the first time, the following screen will be prompted :

Please select "Specify the License File" and press "Next>".

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The location of the "pam_lmd.lic" file should be specified. The "Browse" button could be used to find the "C:\flexlm\pam_lmd.lic" file :

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Once the "C:\flexlm\pam_lmd.lic" file is specified, the "Next>" button can be pressed in order to finish the FlexLM installation.

When the "Finish" button is pressed, the software is unlocked and all the modules can be used.

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GETTING STARTED

SOFTWARE LAUNCH

Launch - Windows platform When the software is installed on Windows, a directory named PAM-SYSTEM is automatically installed on the Desktop of the computer. Inside this directory, a "ProCAST 2009.1 Manager" icon is present.

To launch the software, double click on this icon and the ProCAST Manager will start.

Launch - UNIX / Linux Platforms On UNIX / Linux platforms, the ProCAST Manager is launched by typing the command "cast" in a Console window.

ProCAST 2009.1 Manager Both on Windows and on UNIX-Linux, the ProCAST 2009.1 Manager has the following appearance.

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The "on-line help" can be opened with the "Help" button (1). The working directory should be set with the browse tools (2) . The "Case" name (or prefix) should be defined (3). The different modules can be called with the upper buttons (4). The software is ready to be used.

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PROBLEM SET -UP

In order to get started, a very simple thermal problem will be set-up, step by step. To do so, a very simple mesh located in the installation directory will be used. Please note that the meshing, described in the MeshCAST manual will be addressed in this section (please refer to the MeshCAST manual for more details). The mesh can be found in the following directory : On Windows : %ProCAST20050%\Test\Geometry\Test.mesh On Unix / Linux : $ProCAST20050/Test/Geometry/Test.mesh

Software launch This "Test.mesh" files should be copied in the desired working directory (C:\Temp\Start in the following example). Then, the software manager should be launched (see previous section) and one should browse to the working directory and set the Case name (prefix) to "Test".

Pre-processing launch When the "PreCAST" button is pressed (in the upper black band), the pre-processing module opens and the mesh ("Test.mesh" file) is automatically loaded.

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A window with some information about the loaded model (number of domains, of nodes and elements, as well as the model size) appears. Any click on the menus will automatically close this window. The geometry can be rotated interactively

with the mouse. The icon can be pressed in order to view the geometry in "Solid" mode.

Materials menu The first operation to perform is to assign material properties to the two domains. The first domain should be selected (1) and the desired material properties should be selected in the database (2). An "H13-steel" is selected in this case. Then the "Assign" button should be pressed in order to assign the selected material properties to the given material domain (3). The material property assignment should be repeated for the second material domain (let's select the "AL-7%Si-0.3%Mg-A356" alloy. Finally, the material type ("Mold" for the first domain and "Casting" for the second domain) should be specified (4). This is done with a right click in the "Type" column.

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Interface menu In the interface menu, one should create the interfaces between the different material domains and assign the desired interface heat transfer coefficients. The type of interface should be specified. To do so, one should click once on "EQUIV" (1), which will change into "COINC" (for coincident interface). The "Apply" button (2), which is turning orange should be pressed to accept the coincident interface type. A message will appear on the screen, which should be acknowledged. The desired interface heat transfer coefficient should be selected in the database (3) and assigned to the corresponding interface (4).

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Boundary Conditions menu The cooling of the outside of the mold with the air, as well as the top surface of the casting should be defined in the "Boundary Conditions" menu. The type of boundary condition should be selected with the "Add" button (1). The "Heat" type should be selected in the list which is appearing. Then, this "Heat" boundary condition appears in the BC-Type column (2). A "Heat" boundary condition allows to define a heat transfer coefficient between the model and the ambient air, as well as the air temperature. The corresponding values are selected in the database (3) and the "Assign" button is pressed (4) to link the Heat boundary condition to the database values. The database entry number is then indicated in the "DB entry" column (5). This boundary condition should be then applied to the model. To do so, the "Select all" icon should be pressed (6) and all the model is colored in red (7), showing that all outside surfaces were selected. Finally, the "Store" button, which was turned to yellow, should be pressed in order to save the selection (8).

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Process menu The gravity should be defined in the "Process menu". To do so, click on the menu "Process" and select the "Gravity" sub-menu. This will open the "Gravity" panel. A gravity in the -Z direction is set and the panel is closed with the "Close" button.

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Initial Conditions menu The initial temperature of both material domains should be specified in the "Initial Conditions" menu. Each domain should be selected (1) and the initial temperature should be entered in the field in (2).

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Run Parameters Menu Finally, the calculations parameters should be specified in the "Run Parameters" menu. In this example, all the default values can be used. One could just modify the value of TSTOP (in the "General/Standard" tab) to 500°C (in order to stop the calculation when all the temperature are below 500°C).

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Save and Exit As the set-up of the model is finished, one can save and exit. In the "File" menu, one can select the "Exit" sub-menu. The software will ask whether one would like to save the model before exit. Select "Yes" and the software will first save the model and then exit PreCAST. The pre-processing stage is finished and one is ready to launch the calculation.

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CALCULATION

The calculation can now be launched in the Manager. To do so, the "ProCAST" button should be pressed (1), which will open the confirmation window for the run. The "Execute DataCAST first" should be activated (2) and then one can confirm the launch of the solver by pressing the "Run" button (3).

On Windows, a Command window will open and the DataCAST and ProCAST are automatically launched. A PAUSE message is displayed when the calculation is finished.

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The progress of the calculation can be monitored by pressing on the "Status" button of the Manager (top right button). The following window displays all the information about the current situation of the calculation.

Once the calculation is finished, or anytime during the calculation, one can view the results in the post-processor ViewCAST.

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RESULTS DISPLAY

To launch the post-processor, the button "ViewCAST" should be activated in the Manager. Once the ViewCAST window is opened, one can interactively rotate the mouse (with a left click in the graphics area (1)). The material domains to be displayed can be selected with the icon (2). The result to be displayed (i.e. Temperature, Fraction of Solid, ...) should be selected in the "Contour" menu (3). In order to display a snapshot, the icon (4) should be active. Then, one can display the different timesteps with the tape player (5), either as an animation or as a step-by-step display. The scale can be changed by a click on the scale values (6).

Slices through the model can be obtained with the Slice icon (1). When no slices are defined, it will automatically open the slice definition window (2). Then, one should select the "Add ->" button and the "XYZ Plane" sub-menu, which will open the slice selection panel (3). When the desired slice is selected, the Apply button should be pressed and the slice will be displayed. One can select more than one slice by repeating the "Add ->" operation. Finally, one can show the different timesteps with the Tape player (4).

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Time evolutions can also be shown with the "XY Plot" menu. The desired field (e.g. Temperature) should be selected and the desired locations to be plotted should be defined (e.g. with the "Interval" sub-menu (a value of 50 nodes interval was selected in the figure hereafter).

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To Quit ViewCAST, the File/Exit menu should be used. The software is asking whether you want to store the last view. If it is stored, the current position and orientation of the model on the screen, as well as the material selection, will be retrieved at the next launch of the post-processor.

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PRE-PROCESSING INTRODUCTION

To start the Pre-processor, the "PreCAST" button should be used. If a mesh file (case.mesh) or a "d.dat" file (cased.dat) is present, the case will be automatically opened.

If there is no case present in the working directory, then the browse window will open so that the user can select the desired input files (see the Geometry import section). When the case is loaded, a window appears with some information about the model, such as the number of materials, the number of nodes and elements, as well as the model size. Then, the pre-processor is ready to set-up a case.

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The top bar menu is divided in 9 menus which allow to perform all the operations to set-up a case :

• File • Geometry • Materials • Interface • Boundary Conditions • Process • Initial Conditions • Run Parameters • Inverse • Help

First the model should be opened or saved in the File menu. It allows also to quit the Pre-processor.

Then, in the Geometry Menu, symmetries can be defined, as well as the virtual mold characteristics. Moreover, some features of the FEM mesh can be checked, such as negative Jacobians, or the volume of each domain.

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In the Material menu, the characteristics of each domain (or each material) can be defined. In addition to the material properties, one can specify the type of the domain (casting, mold, filter, foam, ...), as well as if it will be empty or not at the beginning of the calculation (for mold filling).

The Interface menu has no sub-menus. It opens the window which allows to define the interactions between the different materials, such as heat transfers. The Boundary condition menu allows to define all the interactions between the different materials and the outside world (i.e. on the outside surfaces of the model), such as external cooling, velocities at the surface of the model for flow calculations, displacements or constraints for stress calculations, etc...

The Process menu gives access to the definition of the gravity, as well as the definition of the motion of the different domains or enclosures.

The initial temperatures of each materials are defined in the Initial Conditions menu.

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The Run Parameters menu, as well as the Help menu have no sub-menus. All the calculation parameters are defined in the Run Parameters window. The on-line Help can be access from the Help menu. Below the menus, icons allows to perform a number of operations linked to the display of the model on the screen. These icons are described in the Geometry manipulation section.

The next sections are presenting the set-up of a case, according to the following flow chart.

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GEOMETRY IMPORT

When PreCAST is started from the Manager, it is automatically reading a mesh or a d.dat file (if they are present in the working directory, with the selected prefix). The priority is first a "d.dat" and then a ".mesh" file. If there is no mesh file or d.dat file present in the working directory with the corresponding prefix, the pre-processor opens with the browser window.

Then the user has the choice of the input format, through the following filter :

The Pre-processor is able to read PreCAST input files (*d.dat), also called "Restart" files, or meshes coming from MeshCAST (*.mesh), from PATRAN (*.out) or I-DEAS (*.unv).

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The reading of multiple meshes (for non-coincident meshes or for radiation calculation) is described in the "Advanced features" section of the Pre-processor.

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THERMAL

Thermal model The Thermal module allows to perform a heat flow calculation, by solving the Fourier heat conduction equation, including the latent heat release during solidification. The typical results which can be obtained are the following :

• Temperature distribution • Fraction of solid evolution • Heat flux and thermal gradients • Solidification time • Hot spots • Porosity prediction

Flow chart This section describes the set-up of a thermal case. It is also the opportunity to introduce the general work flow of the pre-processor, as well as some aspects which may be used by different modules (e.g. symmetry).

Each step described in the above flow chart is described in the following sections.

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Geometry assignments

Once the geometry is loaded, the following operations can be performed on the geometry :

Symmetries can be defined at this stage (see the "Thermal/Radiation" section for more details). The definition of the Virtual mold is also done at this level. (see the "Virtual Mold" section for more details). In the "Check Geom" menu, the following features are accessible :

Neg-Jac (negative Jacobian) and Neg-Area correspond to problems in the mesh. These buttons allow to locate where these problems are in the mesh in order to give indication where to modify the mesh in MeshCAST. Volumes gives access to the volume of each material domain, whereas Min-Max indicates the dimensions of the model.

Materials assignment

Once the model is loaded (see the "Geometry import" section), the first operation is to define the different materials with their properties and attributes. This is performed in the Material/Assign menu.

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On the right of the window, two frames are shown. The top one contains the material list (or domain list), whereas the bottom one corresponds to the material database.

When one clicks on the different materials in the material list, the corresponding

domains are highlighted (in the picture below, the hidden mode with mesh was selected - see the "Geometry manipulation" section for the other display modes).

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In the lower frame ("Material database" list), the list of all available material properties in the material database is displayed. To manage the database entries, please refer the "Databases" sections. The {T} or {F}which are indicated before the material name are telling wheter material properties are present in this material for Thermal only calculations (T) or for Thermal and Fluid flow calculations {F}. If a {*} appears, it means that the material properties definition is uncomplete and that this material entry can not be used for a calculation at this stage.

In the top frame ("Domain list"), all the domains (or materials) present in the mesh are listed. When a mesh is loaded, it appears as follows :

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Then, one should assign a Material to each domain, to define the type of each domain and to specify whether the domain is empty or not at the beginning of the calculation. To assign Materials, (1) one should select the desired domain in the upper list, (2) select the desired material in the material database list, and (3) click on the Assign button. This should be repeated for each domain.

Then, the "Type" of each material should be defined. To do so, make a right click on the "CASTING" word and the available list of possible selection will appear :

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Mold : the mold material should be set to "Mold". This will be used for cycling calculation (in die casting) in order to allow the calculation of the heating of a die during cycling (i.e. the temperature of the mold domains will not be reset to the initial temperature at the beginning of each cycle). Casting : the casting material should be set to "Casting". This setting is necessary in particular for all the domains where fluid flow will occur. For a cycling calculation, the casting domains initial temperatures will be reset at the beginning of each cycle. Filter : filter domains should be set with the "Filter" type (see the "Filters" section for more details). Foam : for lost foam calculations, the domains where the foam is present at the beginning of the calculation should be set to "Foam". Of course, during the filling, the casting material will replace the foam, as it burns. Insulation : this type has no specific effect on the solver. It will correspond to a "Mold" type of material. At this moment, this is for information purposes. Exothermic : this will activate the Exothermic properties of the sleeve (if they are defined in the corresponding material properties). If the material properties are containing the exothermic information, but the "Exothermic" type is not activated, the exothermic model will not be activated (see the "Exothermic" section for more details). Core : a core type material should be defined in the case of cycling, where cores are placed into the mold at each cycle. This means that unlike mold materials, the initial temperature of the cores will be reset at the beginning of each cycle. Reservoir : a Reservoir type material is a domain where the free surface will always be perpendicular to the gravity. This allows to simplify the free surface computation and it is especially useful in the case of tundish modeling. The "RESERVOIR" domains should have an "EQUIV" interface with the other CASTING materials.

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Please note that if there is more than one RESERVOIR domain, they should all touch each other and they should be all full at the beginning. Otherwise, problems may be encountered. If one want to empty the reservoir, no special BC should be specified. If one would like to keep the reservoir full, a pressure BC should be set at the surface of the reservoir. Finally the user has to specify which domains are empty at the beginning of the calculation (for mold filling calculations). One should make a left click on the "No" to turn it to "Yes" (which means that Yes the domain is empty). On additional click returns to No. Of course, more than one domain may be empty (if the casting is made out of several mesh domains).

When one makes a right click on the material name in the upper list, the lower list is pointing on this particular material. This is very useful if one wants to see the material properties of this material.

Interfaces assignment

Once the Materials are defined, one should define the Interfaces, with the Interface menu.

As for the Material window, two frames appear on the right of the window. The top one contains the list of all the possible interfaces, whereas the lower one shows the Interface database. To manage the database entries, please refer the "Databases" sections.

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Firstly, one should define the type of interfaces in the upper right window :

On the left, the "Material Pair" are shown. "1 and 3" means that there is an interface between material 1 and material 3. By default, the Type of the interface is set to "COINC". By clicking on the "COINC" text, one can toggle between "COINC", "NCOINC" and "EQUIV". When a mesh is generated with MeshCAST (or with most common mesh generator), the elements which are on either side of an interface (i.e. adjacent elements which belongs to two different domains) are sharing the same nodes. This is called a coincident mesh. EQUIV option

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When two domains are part of the same entity (i.e. they both belong to the casting with the same material properties, but they were meshed separately for technical reasons), one will set an "equivalenced" interface between them (EQUIV). It means that there will be a continuum between the two domains, with a continuous temperature profile across the interface, as well as continuous velocity field. In such a case, the nodes at the interface (shown in orange in the figure below) are shared by the elements on both sides. This EQUIV option can also be used if one has different materials in the two domains, but the materials are welded together (i.e. with a total bounding between the two materials).

COINC option At an interface between two different materials, such as the casting and the mold, there is usually a temperature drop. In this case, the nodes at the interface should be doubled (for a coincident interface), in order to distinct temperature on each side of the interface. As during the mesh generation, there is one node at the interface, it is necessary at this stage to duplicate all the interface nodes (as shown in green in the figure below). This duplication operation is performed when "COINC" is selected (for "coincident nodes"). The interface, which is shown in yellow in the figure below has in fact a zero thickness.

NCOINC option It is also possible to generate a non-coincident mesh (i.e. where the elements on both sides of the interface are not matching, which means that they are not sharing the same nodes), by adding different meshes together (see the "Advanced features" section for more details on non-coincident meshes). In this case, one has to specify that the interface is non-coincident, with the "NCOINC" option.

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When one toggles between the different options, the interface appears in red and green. It is thus possible to well identify whether it corresponds well to the desired

interface (see figure below, which was obtained in hidden mesh mode )

An other way to view the desired interfaces is to click on the "Material Pair" and the material on both sides will be highlighted in red and green respectively - the first material in the list is in red and the second one in green (see figure below,

which was obtained in hidden mesh mode )

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Once the desired selections (between COINC, EQUIV and NCOINC) are done for each possible interface, the STORE button (which is highlighted in orange) should be pressed.

Then the pre-processor will automatically create the double nodes and a message will appear to confirm that the number of nodes of the model has increased.

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As it is now possible in version 2009.1 to go from EQUIV to COINC and vice-versa, the user should be careful that as nodes were duplicated or removed, some boundary condition assignments may be corrupted, as well as the extracted initial conditions. Thus, in this case, they should be re-assigned. Once the types of interfaces are defined, one has to apply the corresponding heat transfer coefficients (for COINC and NCOINC only, as nothing as to be specified for EQUIV). To assign Interface heat transfer coefficients, (1) one should select the desired Material Pair in the upper list, (2) select the desired interface heat transfer coefficient in the interface database list, and (3) click on the Assign button. This should be repeated for each coincident or non-coincident interface.

For non-coincident meshes, it is possible to have access to the non-coincident tolerances with a right click on the NCOINC label. A window will open with the two tolerances.

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Boundary conditions assignment

After the definition of the interfaces, the Boundary conditions should be specified. This is done in the "Boundary Conditions" menu.

Three types of boundary conditions can be applied : • Surface boundary conditions ("Assign Surface"), which correspond to all the

conditions applied to the outside of the model or the outside of a given material domain. This is the most commonly used type of boundary conditions.

• Volume conditions ("Assign Volume"), which corresponds to conditions which are applied in a whole volume (e.g. volumetric heat or mass source).

• Boundary conditions assigned to Enclosures ("Assign Enclosure") in case of radiation problem (see the "Radiation" section for more details).

Assign Surface The principles of Boundary conditions definition are described in the following figure.

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Firstly, the desired boundary conditions should be "Added" (1) in the upper list (2). With the "Add ->" button, one has the following choices :

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The boundary conditions corresponding to Thermal problems are "Symmetry", "Periodic", "Temperature" and "Heat". Then the "location" where the boundary condition should be applied on the geometry should be specified. The selection tools (3) allow to "paint" the desired area on the geometry (4). The values to be assigned to the boundary conditions should be selected in the database (5) and then they are assigned to the corresponding boundary condition (6). See the "boundary conditions database" section for more details about the different type of boundary conditions, as well as the database management. It is possible to have a quick access to the database entries in the following way. When one makes a right click on the boundary condition entry in the upper list (2), the lower list is pointing on this particular boundary condition entry in the lower list (5). The "Selection tools" allow to "Select", "Deselect", "Propagate", "Clip", "Copy" and "Paste" faces or nodes on the geometry.

For some boundary conditions, such as "Heat" or "Symmetry", faces of the Finite Element Mesh are selected. For other boundary conditions, such as "Temperature", "Velocity", ... the boundary conditions are applied on nodes. The choice between faces or nodes is automatic.

Selection of individual faces or nodes.

Deselection of individual faces or nodes.

Select all.

Deselect all.

Select and propagate. All the faces or nodes which have an angle with the neighbors smaller than the specified propagation angle will be selected.

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Deselect and propagate. All the faces or nodes which have an angle with the neighbors smaller than the specified propagation angle will be deselected.

Definition of the propagation angle.

Select remainder. The remaining faces or nodes which have not yet been selected are selected.

Select interface. For "Heat" boundary conditions, the selections are applied on external faces only. However, for cycling, one would like sometimes to apply a Heat BC on faces which lie at interfaces. This allows to select those interfaces automatically. In this case, the following panel is opened. It is proposing the list off all active materials. One could select one or more material and all the faces of the selected materials which are lying on an interface will be selected.

Button to clip a model. This allows to perform a selection inside a model, where is it not accessible from the outside.

Button to "Backtrack" the clip.

Copy of selection. All the nodes or faces which are applied on the geometry for the active boundary condition will be copied in the memory.

Paste of selection. The copied selections (above button) can be pasted on a different boundary condition (i.e. on the active boundary condition when the Paste

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button is pressed). Please note that one can not copy the node selection of a Temperature BC to a Heat BC (as faces are expected).

Assign Volume In the "Assign Volume" menu, the following entities can be assigned :

Volumetric Heat corresponds to a "heat source" in the entire volume (see the "Boundary Conditions Database" section for more details). Surface Heat allows to specify how the free surface inside a given material domain is cooling down. It is possible to assign a "Heat" boundary condition to the free surface inside the domain. With this, it is possible to assign a convective heat transfer coefficient and an external temperature which will drive the cooling condition of the free surface itself. For instance, this could be important to take into account the cooling of the free surface of a swimming pool. Please note that it is not possible to activate the radiation model with view factors on a free surface. Momentum Source corresponds to a force term on the liquid (momentum force) in the entire volume (see the "Boundary Conditions Database" section for more details). Mass Source corresponds to a different way of applying an inlet of metal in the case of filling (see the "Boundary Conditions Database" section for more details). Filter Heat allows to define the interface heat transfer coefficient between the liquid metal and the filter material. Thus, the cooling of the hot liquid, when passing through an initially cold filter can be modeled using a "Filter heat". The interface heat transfer coefficient (which is the same as the one defined in the "Interfaces assignment" section) is applied to the entire filter domain.

Assign Enclosure In the case of radiation problems with View Factors, the ambiance or the furnace can be modeled with an enclosure. See the "Pre-Processing/Radiation" secton for more details. This menu is not used for Thermal problems without "View Factor radiation".

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Process conditions assignment

For Thermal problems (as well as for flow), the gravity vector should be defined in the "Process" menu.

Gravity For Thermal only problems, it is important to define the gravity direction for the calculation o of the porosity (using the POROS=1 model). The gravity is defined in the following panel. For standard problem, a constant gravity (1) is defined. The three components of the gravity are defined in (2). If one clicks on the X, or the Y, or the Z letter, automatically, the gravity vector is set in the X-, Y- or Z- direction. With two clicks, the negative direction will be set.

The "Rotate" is used only for Fluid flow problem (see the "Fluid Flow & Filling" section for more details).

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Assign Volume This option is used to specify a translation, a rotation or a revolution to the material domains. As this is mainly used in the case of Radiation problems, please look for more details in the "Pre-processing/Radiation" section.

Assign Enclosure This option is used only for radiation problems (see the "Pre-processing/Radiation" section for more details.

Initial conditions assignment

The initial temperature of each material should be defined in the initial condition menu.

The initial temperature can be defined either as a Constant value throughout the material domain, or as an Extracted temperature field coming from a previous calculation. In the case of "Constant", the list of all the Material domains is displayed and one can enter the initial temperature (in the lower white field) for each one.

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The "Extract" functionnality is described in the "Extract/Results extraction" section.

Run parameters assignment

The following Run Parameters should be specified :

The thermal module should be activated with THERMAL = 1 or 2. The storage frequency of the thermal results (TFREQ) should be specified, as well as the activation of the porosity model (POROS) . Please refer to the "Thermal Run Parameters" section for the full description of all the Run Parameters.

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FLUID FLOW & FILLING

Fluid flow model The fluid flow module allows to perform mold filling calculation (free surface) as well as fluid flow computation, by the resolution of the Navier-Stokes equation. The typical results which can be obtained are the following :

• Filling behavior • Free surface evolution • Natural and forced convection currents • Dynamic pressure of the liquid • Entrapped gas • Filter behavior

Flow chart This section describes the additional set-up necessary for fluid flow and mold filling. For the set-up of a thermal case, please refer to the "Thermal" section of the Pre-processor.

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Materials menu Concerning the material assignments, the only requirement is that the domains in which fluid flow calculation will be performed are defined as "Casting" domains (or "Filter" or "Foam" - see the "Advanced features" section for more details). Then, one should define whether the corresponding domain is Empty or not (in the case of mold filling). One can change from No to Yes and vice-versa by clicking on the text directly.

Moreover, the material properties of the fluid material should have the flow properties (e.g. viscosity). This can be checked in the Material database list. The Material name should be preceded by an {F} (for Fluid properties).

Interface menu Concerning the interfaces, nothing special should be done concerning the fluid flow. One can however notice that if the casting (i.e. the flow domain) is non-coincident with the mold domain(s), one will need to set a zero velocity boundary condition all around the casting domain (in order to prevent "leaks"). See the "Advanced features" section for more details on non-coincident meshes.

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Boundary conditions menu Concerning the boundary condition assignments, one has to specify the velocity, pressure, wall and/or inlet BC. See the "boundary conditions database" section for more details about the different type of boundary conditions, as well as the database management. See the "Thermal/Boundary Conditions Assignment" section for more details about how to assign boundary conditions. Please note that when a filling-flow calculation is performed on a model where there is no mold, it is necessary to set a zero-velocity boundary condition around the whole mesh (i.e. at all the location where a mold would be in contact with the casting). A zero velocity boundary condition can also be replaced by a WALL boundary condition, which has the same effect.

Process menu For fluid flow problems, the gravity has to be defined (see the "Thermal/Process Conditions Assignment" section for more details).

Initial conditions menu Nothing should be specified in this menu for fluid flow problems.

Run parameters menu The following Run Parameters should be specified :

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The fluid flow module should be activated with FLOW = 1 or 3, as well as the free surface model (FREESF) for mold filling and the gas model (GAS). The storage frequency of the fluid flow results (VFREQ) should be specified. Then, information about the reference pressure (PREF) and pressure driven inlet (PINLET), about the final fill fraction (LVSURF) and the filling parameter (WSHEAR, WALLF) shall be defined. Please refer to the "Flow Run Parameters" section for the full description of all the Run Parameters.

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RADIATION

Radiation model The radiation module allows to perform complex radiative problems (e.g. investment casting), with the calculation of the shadowing effects (view factor calculations). The typical results which can be obtained are the following :

• Effect of radiative heat transfer • Shadowing effect

Radiation can be either treated as a simple radiative flux (described in the "Thermal/Boundary conditions" section), or with a complex radiation algorithm which takes into account reflexions, obstructions and shadowing effects. The set-up of a case with such complex radiation (called hereafter "Radiation with view factors") is explained in this section. As Radiation with view factors involves the calculation of the interaction of the components (casting and mold) with the environment (furnace, castshop, ...), it is necessary to include the environment into the model. This is done with an "Enclosure". If the casting is put into a furnace, the Enclosure is the furnace itself (or the inner skin of the furnace). However, it the casting (and mold) is sitting on the floor of the castshop, one should set an "artificial" enclosure which will surround the casting and which will have the same effect as the environment. An enclosure can be either a solid (represented by a solid 3-D FEM mesh, as the casting, mold, etc...), or by a closed surface (represented by a closed FEM surface mesh). The figure below shows a casting within a solid enclosure (for symmetry reasons, only a sector is modeled).

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The figure below presents a casting within a surface enclosure shown in grey (for symmetry reasons, only half of the geometry is modeled)

Flow chart This section describes the additional set-up necessary for radiation calculations. For the set-up of a thermal case, please refer to the "Thermal" section of the Pre-processor.

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File/Multiple meshes menu When a model contains an enclosure (i.e. a surface mesh which will act as an enclosure), there are two ways to load the corresponding meshes : a) the enclosure is built into MeshCAST, together with the solid mesh. In this case, the enclosure should be "tagged" as an enclosure. b) the enclosure is built separately in MeshCAST, as a conventional surface mesh (without and "enclosure tag"). Then, the solid mesh and surfaces meshes should be loaded into PreCAST using the "File/Multiple meshes" menu. Please note that in previous versions, the surface meshes of the enclosures had to be "tagged" as enclosures. This is not anymore needed.

Geometry/Symmetry menu Firstly the symmetries (if any) should be defined. ProCAST is able to deal with symmetry implying one mirror, two orthogonal mirrors, a single rotation of n sectors and a combination of them. In order to illustrate the different possibility of symmetry, consider the simple but explicit example of two concentric cylinders (the inside cylinder is the casting and the outside cylinder is a solid enclosure). The full geometry is shown in the figure hereafter.

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The full geometry of the two concentric cylinders.

The following figures illustrate the different possibility of simplification by symmetry. • One mirror (M1)

Two examples of simplified geometry by one mirror.

• Two orthogonal mirrors (M1 and M2)

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Two examples of simplified geometry by two orthogonal mirrors.

• A simple rotation of n sectors (R)

A simplified geometry by a rotation of 8 sectors.

• A rotation of n sectors (R) associated with a mirror (M1)

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Two examples of simplified geometry by a rotation (left: 8 sectors, right: 4 sectors) and

one mirror. • A rotation of n sectors (R) associated with two orthogonal mirrors (M1 and

M2)

A simplified geometry by a rotation with 4 sectors and two orthogonal mirrors.

The symmetries are defined in the Geometry/Symmetry menu :

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In case of a rotation, the axis of rotation should be defined by the coordinates of two points and the number of sectors. Then, the "Rotational" check box should be checked. One should be careful that the mesh should be defined so that the selected number of sectors will not create overlaps of the mesh (i.e. to specify 7 sectors for a mesh which corresponds to a sector of 60°). For mirror symmetries, each plane of symmetry should be defined by the coordinates of three points (which should not be co-linear). Then the "Mirror-1" and "Mirror-2" (if applicable) check box should be checked. If two mirror symmetry are used, one should be careful to make sure that the two planes are orthogonal. In the case of mirror symmetry with a rotation, the axis of rotation should be either perpendicular or parallel to the mirror plane(s). In case of parallel plane(s), the axis of rotation should be within the mirror plane(s). Then, the "Apply" button should be used to validate the symmetry definition. To disable a symmetry, just uncheck the corresponding check box. The "Get Co-ord" button allows to pick nodes of the FEM mesh for an interactive definition of the mirror planes or rotational axis. To use it, first click in the X coordinate box of the point which should be defined interactively, then click on "Get Co-ord" and finally, click on the desired node on the geometry. The corresponding coordinates will fill automatically the corresponding fields. Repeat it for the other points. Please note that one should click very close to the desired node (otherwise, it may be possible that a node "behind" is selected).

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Check of the symmetry planes When a symmetry plane is used for a Radiation calculation (and/or for a Stress calculation), it is very important that all the nodes of the symmetry plane are exactly lying on the right plane. When the symmetry planes are defined in the "Geometry/Symmetry" menu (see above), it is creating automatically the corresponding "Symmetry" Boundary condition (in the "Boundary Condition/Assign Surface" Menu). However, if some nodes are not lying exactly on the symmetry plane, this boundary condition could be either empty or some nodes (and thus elements) will be missing. In the following figure, such a case is shown :

This is due to the fact that three nodes are not exactly on the plane as shown on the following figure (one node is inside and two are outside the plane).

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If the nodes are not too much outside the symmetry plane, PreCAST is able to move automatically those nodes in order to put them back onto the symmetry plane. When the "Symmetry" selection is stored, PreCAST is determining how many symmetry planes are found (maximum 3) and then it is asked whether the node alignment should be checked or not.

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If the nodes have a small offset and if the movements of these nodes is not corrupting the adjacent mesh (e.g. by creating negative jacobians), the operation will be successful and the following message (The symmetry node alignment check is OK) will be displayed.

If the nodes have a too large offset with respect to the symmetry plane or if the mesh is becoming corrupted (negative jacobians) during the node alignment operation, the following message will be displayed.

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In such case, the mesh should be changed in the mesh generator and the model set-up should be started again.

Materials and Interface menu Nothing specific should be defined at the level of the Materials and Interface menus. The complex radiation method should be set in the "Boundary conditions" and "Process" menus.

Boundary conditions menu When the ambiance or the furnace is modeled with an enclosure, one should specify the temperature and the emissivity of the enclosure in the "Assign Enclosure" menu.

The enclosure can be divided in different sets (1) (in order to apply different temperatures and/or emissivities). One can Add new sets (2). Then, using the selections tools (3) (see the "Pre-processing/Thermal" section for the full

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description of the selection tools), the desired surfaces of the enclosure can be "painted" (4) and stored (5). Finally, the desired temperature and emissivity can be selected in the database (6) and assigned (7). Please note that one should assign to each set both a Temperature entry and an Emissivity entry. In order to compute well the View Factors of the enclosure, one should make sure that the surfaces of the enclosure (i.e the triangles or the quadrangles) are well oriented (i.e. the surfaces are pointing inwards). To do so, the following icons are available next to the selection tools :

View icon : Viewing of the face orientation

Reverse icon : Reversal of the face orientations

Align icon : Automatic alignment of the face orientations To view the face orientations, one should first select the desired "Enclosure set" and then press the "View" icon. The arrows are drawn for the selected set as shown in the figure hereafter.

If all the arrows are pointing outwards, the "Reverse" icon allows to reverse the orientation of all arrows.

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If only a few arrows are pointing in the wrong direction, one should use the "Align" icon in order to have all the arrows pointing in the same direction. Then, one may need to use the "Reverse" icon to point the arrows inwards.

Process menu The process menu allows to define the motion (if any) of the enclosure (Assign Enclosure) with respect to the casting or of material domains (Assign Volume). Moreover, it allows to define the gravity vector (see the "Thermal/Process Conditions Assignment" section for more details). When "Assign Enclosure" is opened, the following panel appears on the upper right corner of the window. Each enclosure set is displayed and three database entries are possible. The first column corresponds to a "Translation", the second one to "Rotation" and the third one to "Revolution". If a "*" appears, it means that no motion is defined for this set. Otherwise, the number indicates the corresponding database entry.

In the case of "Assign Volume", the same type of panel appears, but instead of the enclosure sets, the different material domains are listed. Again in this case, it is possible to specify a Translation, a Rotation or a Revolution. Any combination of the three is possible, however, please note that the user should check that there is no conflict between these motions and prevent any inter-penetration of the different materials and/or enclosures.

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On the bottom right, the motion database (Process database) appear (see the "Process Database" section for more details).


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The radiation module is automatically activated when Heat Boundary conditions with View Factors ON are set. Thus, no specific Run Parameter should be activated at this stage. There is however three Run parameters which are important to set if the enclosure is moving. In this case, the update of the view factors will be triggered by the VFTIME or VFDISP parameters. If VFDISP is activated, the Enclosure ID on which the motion will be recorded should be specified. Please refer to the "Radiation Run Parameters" section for the full description of all the Run Parameters.

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STRESS

Stress models The stress module allows to perform a thermo-mechanical calculation. The typical results which can be obtained are the following :

• Stress distribution • Deformations (elastic and plastic) • Displacements • Gap formation • Elastic springback • Die fatigue • Hot tears • Cracks

In order to address these different aspects, six different stress models are available.

• Linear Elastic • Elasto-plastic • Elasto-viscoplastic • Visco-elastic • Rigid • Vacant

These different models are presented in the Databases section.

Flow chart This section describes the additional set-up necessary for stress calculations. For the set-up of a thermal case, please refer to the "Thermal" section of the Pre-processor.

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Materials menu The stress properties should be assigned in the Materials/Stress menu.

This is opening the following window. Firstly, each domain should be selected (1). Then, the desired properties should be chosen in the database list (2) and then the "Assign" button (3) should be pressed in order to link the material with the corresponding stress properties. The stress properties, as well as the different stress models are described in the "Stress database" section.

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Interface menu Nothing specific should be defined at the level of the interfaces.

Boundary conditions menu The user can specify three types of stress boundary conditions, as shown in the figure below.

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The specification of the displacements is very important in order to guarantee that the model will not rotate or move in an unexpected fashion, under the effect of stresses. The figure below is summarizing typical displacement constraints.

One should be careful not to over constrain the model with too many displacements boundary conditions. If this is the case, this may induce artificial stresses locally, as shown in the figure hereafter.

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One should note that a symmetry is also inducing displacement constraints as shown in the figure below.

It is necessary to specify displacements on the casting domain when the mold is set to "Vacant". However, when the mold is set to "Rigid", it is not necessary to specify displacements on the mold, except if one wants to model the Elastic spring-back when the mold is opened. In the case of die casting, it is recommended to set a zero vertical displacement at all the top and bottom points of the upper and lower dies (black triangles on the figure below), as well as one lateral zero displacement on each side of each die (blue triangle on the figure below).

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One should be aware that the application of only a "Surface load" on the top die (as shown below) is not enough.

This can be explained with the following sketch.. In the left case (blue), only two loads are applied to the part. This part is not constraint and it can move in any direction. In order to make sure that the part will not move, one has to apply in addition the appropriate zero displacements (right case in green). In the center case (orange), the displacement constraints are not sufficient and the part could rotate around the bottom right point.

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Finally, "Point load" can be applied locally to model the effect of a local force.

Symmetries Symmetries can be used for stress calculations. However, one should be very careful to have meshes which are exactly matching the symmetry plane. If this is not the case, it will create artificial constraints which will degrade the quality of the results as well as the convergence of the calculation. See the "Pre-processing/Radiation/Check of the symmetry planes" section for more details about how to check the symmetry planes.

Process Initial conditions menu Nothing should be specified in these menus for stress problems.


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The stress module should be activated with STRESS = 1. The storage frequency of the stress results (SFREQ), as well as the calculation frequency of the stresses (SCALC) should also be specified. Please refer to the "Stress Run Parameters" section for the full description of all the Run Parameters. In addition, when a Stress calculation is performed, one should set PIPEFS = 0. This allows to prevent an unexpected effect of the piping on the stress calculation.

Advanced stress features Elastic Springback The stress module of ProCAST allows to simulate the Elastic Springback occurring when a mold is opened. In the figure below (left picture), the mold in blue is closed and it induces some stresses on the "T-bar". When the mold is opened (right picture), the corresponding mold resistance is removed and the

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stresses are relaxed. As the elastic strain is released, the shape of the part is changing (on the right picture, both the part and the mold are represented, although the mold is not anymore present).

To model the Elastic Springback effect, the user just needs to define a function for the interface heat transfer coefficient (at all the interfaces which will not be anymore in contact when the mold opens). One should define a zero interface heat transfer coefficient when the mold opens and automatically, the mechanical effect of the mold will be removed in the model. However, if one want to continue to simulate the cooling of the casting, while in the air, the user should not forget to set a Heat boundary condition on the casting surface (and eventually on the inside mold surface) with a non-zero value from the opening time (the technique is the same as the one used in cycling calculations).

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DATABASES

Material Database

All the material properties are stored in Databases. This section describes the database containing the material properties for Thermal and flow calculations. The Database containing stress properties is described in the "Databases / Stress Database" section. Moreover, the "Thermodynamic" databases are described in the "Databases / Thermodynamic databases" section. In the Material Assignment menu (see "Material assignments"), the content of the material database is shown (see below). Above the material list, the database management buttons are present : Read : the database entry can be read and modified (if the user has the appropriate rights) Add : a new entry can be created Copy : an existing entry can be copied in order to create a new entry Del : an exisiting entry can be deleted Sort : the list of materials is sorted by alphabeti cal order Search : a search on the material name can be done

When an existing material is opened (with the READ button), a window appears with the following content :

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Firstly, the material name, the user, as well as the creation date of the material is shown. Then, the material properties are organized in different tabs, with a hierarchical structure :

Composition Thermal

Conductivity Density Specific Heat Enthalpy Fraction Solid Latent heat Liquidus-Solidus Exothermic

Fluid Viscosity Surface Tension Permeability Filter

Comments The yellow tabs indicate that values are defined for the corresponding properties. The white tab shows the active one. Once the "Thermal" or "Fluid" tab is selected, a second level of tabs becomes active (and so on). The figure below shows the definition of the thermal conductivity :

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The above figure shows the standard panel for material properties definition. Firstly, the user has to define whether the material property is defined by a

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Constant or by a Table (function of temperature), by clicking on the corresponding radio button. When a Constant is selected, the user can choose the units and enter the constant material property in the white field below "Enter". When a Table is selected, the user can input the temperature-dependant property in the white field on the bottom left of the screen. Each time a new line is filled, the graph on the right is updated. In this case, the units for the temperature and the property can be selected. Above the table, the buttons allow to erase the whole table, erase only the selected line, import or export the table. For imports, the table should be in the form of a text file, with X and Y values on the same line, separated by at least a blank. The number of lines should not exceed 100. The Export format is the same. If a "Table" is defined and the user decides to switch to a "Constant" (or vice-versa), a warning will be prompted saying that the table will be lost. A confirmation will then be asked to the user. Of course, the data will be totally lost only when the material is "Stored". All the properties which can be defined as temperature-dependant are organized in the same way. The only thing which changes is the hierarchy of tabs, as shown below for the Fluid/Viscosity/Carreau-Yasuda/Zero Viscosity definition.

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Beside these properties, some of them are defined only by constants, such as the latent heat, the liquidus and solidus temperature or the filter properties. In this case, only the corresponding constant(s) should be entered (see figure below).

The following section "Material Properties" describes the different properties and when it should be defined.

Material Properties

Good material properties are the best base for a good simulation. Properties could be found in several locations, such as litterature, material suppliers, universities, web, ... www.matweb.com is material properties website which contains many useful data. www.matdata.net is a search engine for material properties. An other way to obtain material properties is through the Thermodynamic Databases which are embedded into ProCAST (see the "Thermodynamic Databases" section for more details).

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Thermal problems No phase change For thermal problems (with or without solidification), the minimum data which are required are the following (typically for mold materials) :

Thermal conductivity Specific heat Density

These properties can be either constant or temperature dependant. With phase change (solidification) When solidification is present (i.e. for casting materials), one should define in addition the following properties :

Fraction of solid Latent heat Liquidus and Solidus temperatures

The fraction of solid curve must be temperature-dependant. It should start at 0.0 at high temperature and increase to 1.0 towards the low temperatures. The fraction of solid should be a strictly descending curve and it should be strictly defined between 0.0 and 1.0. If it is not the case, a warning will be issued. If there is a isothermal transformation (e.g. eutectic plateau), it should be "spread" over an interval of one degree. The latent heat, liquidus and solidus temperatures are defined by constants. Please note that the liquidus and solidus temperatures should be consistent with the fraction of solid curve (no consistency checks are performed). The liquidus and solidus temperatures are used for the porosity models and for the calculation of the permeability of the mushy zone in the case of flow calculations. ProCAST offers an alternative in the definition of the phase change. Instead of defining the specific heat, and the latent heat, one can define the corresponding enthalpy curve. The enthalpy as a function of temperature, H(T), is defined as follows :

where cp(T) is the specific heat as a function of temperature, L is the latent heat and fs is the fraction of solid. As there are two ways of defining the phase change, the software is automatically detecting if there is a conflict in order to have either :

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specific heat Latent heat

or enthalpy

If this is the case, the following message is displayed :

and the user has to select which definition is preferred. In previous versions (v4.x.x and v3.x.x), there was no check to prevent both definitions. Thus, if a model which was created in a previous versions is loaded into PreCAST v2009.1, the following warning will be displayed (during the load in PreCAST) :

The user will need to resolve the conflict, by selecting which data are to be kept (i.e. either enthalpy or specific heat/latent heat) for each material which has this duplicate definition. Density The density is used in thermal calculation (it multiplies the specific heat, the enthalpy and the latent heat), as well as in fluid flow calculations and in porosity calculations. Please refer to the "Porosity models" section for more details about the density definition.

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Fluid flow problems For fluid flow problems, it is mandatory to define the viscosity. Then, optionnal definitions are available, such as "Surface Tension", "Permeability" and "Filter". Viscosity Several viscosity models are available in ProCAST :

Newtonian Carreau-Yasuda Power-cutoff

The Carreau-Yasuda model corresponds to Non-Newtonian flow, where the viscosity depends upon the shear rate (see the equation below) :

with :

strain rate

zero strain rate viscosity

infinite strain rate viscosity

phase shift n Power law coefficient a Yasuda coefficient

The above parameters can be defined in the database (as constants or as function of temperature) as follows :

The Power-cutoff is used in the case of Thixocasting. Surface tension This option is not described as it has not been validated at this stage. One can say that in conventional casting processes, the surface tension effects are certainly negligible in comparison to the simplifications made in the free surface algorithms.

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Permeability For a casting material, the permeability is defined by a Karman-Cozeny model, modified by Beckermann at low fraction of solid. The user has also the ability to define its own permeability table, as a function of temperature. In this case, a high permeability corresponds to a "free flow", whereas a low value corresponds to "no flow". For "casting" materials, the permeability is applied only in between the solidus and the liquidus temperatures. For mold materials (in the case of lost foam), a permeability should be defined. In this case, one can define a constant or a temperature dependant permeability. For Filter materials, if the Permeability is defined, it will override the default permeability calculated from the Filter tab.

Filter Filters are characterized by the following properties :

Void fraction Surface area Pressure Drop

The void fraction (Fv) corresponds to the amount of "porosity" or void inside the filter. This value is dimensionless [-]. The definition of this value is mandatory in all cases. The Surface area (Sa) corresponds to the amount of "interface" between the filter material and the air (when the filter is empty) per unit volume (see example below). This value is used for the calculation of the thermal exchange between the filter and the liquid metal going through, as well as for the automatic permeability calculation. The units are the reversed of a distance (e.g. [1/m]). The definition of this value is mandatory in all cases.

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The Permeability of the filter (i.e. its resistance to the flow) can be calculated in three different ways.

a) Automatic permeability calculation From the Void Fraction (Fv) and the Surface Area (Sa) definitions, the permeability can be automatically computed (based upon Karman-Cozeny), according to the following relationship :

This mode is activated if the "Pressure Drop" and "Permeability" tabs are not defined.

b) Pressure drop calculation If the "Pressure Drop" tab is defined, then, the permeability is calculated, using the following values (coming from simple experiments) :

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and the following equation :

where v, ∆P and ∆x are measured values which can be made in a simple experiment (or provided by the Filter supplier). Please note that the Flow rate, v, corresponds to the velocity used in the experiment and not the velocity of your casting model. If both the "Pressure Drop" and "Permeability" tabs are defined, the "Permeability" values are ignored (and replaced by the ones obtained from the above equation).

c) Specified permeability It is also possible to define a given permeability value in the "Permeability tab". In this case, the "Void fraction" is not used for the automatic Karman-Cozeny relationship. See the "Filters" section for more details about the settings of cases with Filters.

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Thermodynamic Databases

Material properties, such as the enthalpy curve and the solidification path (i.e. the fraction of solid curve versus temperature), density, viscosity and thermal conductivity can be computed automatically from thermodynamic databases. ProCAST has an automatic link with thermodynamic databases to calculate these properties. It is thus possible to compute the enthalpy curve, the fraction of solid curve, the density, the viscosity and the thermal conductivity, based upon the chemical composition, for the following systems and the following alloying elements :

CompuTherm LLC databases Al database: Ag Al B C Cr Cu Fe Ge Hf Mg Mn Ni Sc Si Sn Sr Ti V Zn Zr Fe database: Al B C Co Cr Cu Fe Mg Mn Mo N Nb Ni P S Si Ti V W Ni database: Al B C Co Cr Fe Hf Mo N Nb Ni Re Si Ta Ti W Zr Ti database: Al B C Cr Cu Fe H Mo N Nb Ni O Si Sn Ta Ti V Zr Mg database: Ag Al Ca Ce Cu Fe Gd Li Mg Mn Nd Sc Si Sr Y Zn Zr Cu database: Al B C Cr Fe Mn Ni P Pb Si Sn Ti Zn The other alloying elements which are not present in this list are not available in the database and will have no effect on the computed material properties. More details about composition limitations are given in the Database limitations section. To activate the thermodynamic database, one should go in the "Composition" tab of the material properties window.

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Then the Base alloy (i.e. Al, Fe, Ni, Ti or Mg) should be entered, as well as each alloying element with its concentration (in weight percent). Once the chemical composition is entered, the "Apply->" button is pressed and the "Scheil" or "Lever" option is selected to start the computation of the fraction of solid and of the enthalpy.

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"Scheil" and "Lever" correspond to two different microsegregation models. In the case of "Lever", the Lever Rule is applied, which corresponds to a complete mixing of the solute in the solid (i.e. very good diffusion in the solid). On the other hand, the Scheil model corresponds to no diffusion at all in the solid phase (both model consider complete mixing or infinite diffusion in the liquid). The "Back Diffusion" model allows for some diffusion in the solid and corresponds thus to a situation in between the Lever Rule and Scheil. When the "Back Diffusion" model is used, an average cooling rate (corresponding to a representative cooling rate of the casting to be modeled) should be specified in order to determine the amount of back diffusion.

Warning Please note that the cooling rate should not be set below 0.01 K/s. If a lower value is needed, please use the Lever Rule model. For iron and carbon steel, the Lever rule is still recommended. The main difference between the three models is the shape of the fraction of solid curve at the end of solidification, as well as the solidus temperature (see figure below).

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The following figure is showing the influence of the different models on the fraction of solid curve for an A356 alloy (Al-Si7%-Mg0.3%). The curves labeled 0.1 K/s and 1.0 K/s correspond to the "Back Diffusion" model with these cooling rates. For such alloy, the Lever Rule model will correspond to low cooling rates (below 0.01 K/s), whereas the Scheil model will correspond to high cooling rates (above 20 K/s). One can see that the back diffusion has a quite important effect on the solidus temperature.

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On the following alloy (Mar-M 200 Hf), the difference in the solidus temperature between the Scheil model and the Lever rule is 550 degrees !

It is recommended to use the "Back Diffusion" model with a representative cooling rate. However, when this is not known, it is recommended, for most alloys. to use the Scheil model, except for low alloy steels where the diffusion in the solid is very fast. In the example above, when the Scheil button is selected, the following curves appear :

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One could see the fraction of solid curve, as well as the fractions of the different phases as a function of temperature. In the same time, automatically, the fraction of solid curve, the liquidus and solidus temperatures, the enthalpy curve, the density, the viscosity and the thermal conductivity are stored in the database, as shown hereafter (of course the value are finally stored only when the "Store" button is pressed, before exiting the database).

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Thermal conductivity

Density

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Enthalpy

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Fraction of solid

Liquidus-Solidus

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Viscosity

Please note that when a thermodynamic database is used, as the enthalpy is calculated, the specific heat and the latent heat should not be defined (as they are contained in the enthalpy). During the Thermodynamic database calculation, a file named "prefix.phs" is created. It contains for each temperature the phase fractions, as well as the composition of each phase. This information is not needed for a ProCAST calculation, but it can be interesting for other purposes (e.g. growth kinetics calculations).

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For some chemical composition, it may happen that the software which extracts the data from the Thermodynamic database is not able to find the right set of stable phases at low temperature.

Usually, this does not affect the determination of properties of interest (which are more near the solidification range). Thus, it is possible to use the calculated values as such. If such situation occurs, one should check the calculated data in order to be sure that it covers at least the temperature range of interest. In very few cases, it is possible that the density calculation does not give relevant results, as shown in the figure hereafter. In this case, these result should not be used (or the wrong values should be erased).

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As a general rule, if the results are not realistic, it is advised to suppress (i.e. ignore) the elements which are present in very low concentrations. This is especially true for traces of Sulfur (S) and Phosphorus (P) in steels, which are sometimes "corrupting" the results.

Calculation of Stress Properties

Beside the thermal properties, it is possible to calculate automatically some Stress properties. At this stage, the Young's modulus, the Poisson's ratio and the Thermal expansion coefficient can be calculated based upon the phases obtained from the thermodynamic databases. For Al alloys, the Yield Strength can also be calculated (this can be done only if the Back Diffusion model is selected). When the Properties calculation is started in PreCAST with either the Scheil or the Lever model, the following window appears :

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The user has the choice of either not calculate the Stress properties, to create a new entry in the Stress database or to substitute/Add the data to an existing entry. If a new entry is created the user has to specify its name (without spaces). If the user would like to substitute or add the calculated data to an existing entry of the stress database, one should select the desired entry with the Browse button. Once these choices are made, the computation can be started (of both the thermal and stress properties) with the "Compute" button. Please note that the other Stress properties (i.e. hardening, viscoplastic,...) can not be calculated at this stage (for Al only, the Yield stress can be calculated). Thus these properties will remain empty. The following figures are showing examples of computed Stress data from an A356 alloy.

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Young's modulus

Poisson's ratio

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Thermal expansion coefficient

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Yield Stress (for Al systems only - available only with the "Back Diffusion"

model)

The Yield Stress can be calculated for Al systems only (it is calculated only when the Back Diffusion model is activated). Moreover, the Yield Stress calculation is taking into account the effect of the microstructure (mainly the SDAS) through the cooling rate. The following figure is showing the calculated Yield Stress of the A356 alloy, for different cooling rates :

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One can see that the effect is very strong as it can change by about 100% between low and high cooling rates.

Databases limitations

The Computherm databases can be used for the following elements and in the following ranges. More information can be obtained on the www.computherm.com web site. The recommended composition ranges mentioned hereafter are not strict limits. These are ranges which were extensively tested. The Computherm manual (from Computherm LCC) is added in the Software installation (in the dat/manuals/PDF directory). This manual describes for each alloying system the phases which are calculated, the limitations as well as the validations which have been made.

Al database Developed for Al-rich alloys such as commercial casting and wrought alloys. Tested with more than 40 commercial Al alloys.

20 Components : Major alloy elements: Al, Cu, Fe, Mg, Mn, Si, Zn Minor alloy elements: Ag, B, C, Cr, Ge, Hf, Ni, Sc, Sn, Sr, Ti, V, Zr

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Major phases: Liquid, Fcc_A1(Al), Diamond_A4(Si), Al5Cu2Mg8Si6,

Al8FeMg3Si6, Eps, Sigma-(Al,Cu,Zn)2Mg, T-(Al,Cu,Zn)49Mg32,

Al20Cu2Mn3, Al23CuFe4, Al7Cu2Fe, S-Al2CuMg, TAO(t), a-AlFeSi,

b-AlFeSi, AL15_FeMn3Si2(a-AlMnSi), AlMnSi-Beta, AlCu_Theta(q),

Al13Fe4, AlMg_Beta, Al11Mn4, Al12Mn, Al4Mn, AL6_FeMn,

Al3Ni1, AlSr4, Mg2Si,Al3Zr, Al3Sc_x Recommended composition range (in wt%): Al 80 ~ 100 Cu 0 ~ 5.5 Fe 0 ~ 1.0 Mg 0 ~ 7.6 Mn 0 ~ 1.2 Si 0 ~ 17.5 Zn 0 ~ 8.1 other 0 ~ 0.5

Fe database Developed for Fe-rich alloys.

19 Components: Al, B, C, Co, Cr, Cu, Fe, Mg, Mn, Mo, N, Nb, Ni, P, S, Si, Ti, V, W. 59 Phases: Liquid, BCC_A2 (ferrite), HCP_A3, FCC_A1(austenite), TCP phases, Carbides, and so on. Recommended Composition Limits (wt%): Fe > 50 Ni < 31 Cr < 27 Co, Mo < 10 V, W < 7 C, Cu, Mn, Nb, Si, Ti < 4 Al, Mg, N < 0.5 P, S < 0.05 It was observed that alloy elements which are present is very small quantities (such as P and S) may cause problems in the phase determination. As these elements do not affect significantly the material properties (although it may have important effects in other fields), it is recommended to remove these elements for the computation.

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Mg database

Developed for commercial Mg-rich alloys 17 components: Mg, Ag, Al, Ca, Ce, Cu, Fe, Gd, Li, Mn, Nd, Sc, Si, Sr, Y, Zn, Zr Contains more than 285 phases. Recommended composition range (in wt%): Mg > 75 Al, Ca, Li, Mn, Si, Zn < 10 (but not in combination Ca+Mn, Ca+Zn, Mn+Si or Si+Zn) Ag, Ce, Gd, nd, Sc, Sr, Y, Zr, Fe, Cu < 1 Many element combinations can be used beyond these limits, but it may lead to problems.

Ni database Developed for commercial Ni-rich alloys.

17 Components: Al, B, C, Co, Cr, Fe, Hf, Mo, N, Nb, Ni, Re, Si, Ta, Ti, W, and Zr. 63 Phases: Liquid, Fcc_A1(g), L12_Fcc(g¢), TCP phas es, Carbides, and so on. Recommended Composition Limits (wt%): Ni > 50 Al, Co, Cr, Fe < 22 Mo, Re, W < 12 Hf, Nb, Ta, Ti < 5 B, C, N, Si, Zr < 0.5

Ti database Developed for commercial Ti-rich alloys such as alpha, alpha+beta, and beta alloys.

18 Components: Al, B, C, Cr, Cu, Fe, H, Mo, N, Nb, Ni, O, Si, Sn, Ta, Ti, V and Zr 108 Phases: Liquid, BCC_A2(b), HCP_A3(a), DO19_Ti3A l(a2), Laves, and so on. Recommended Composition Limits (wt%): Ti > 75 Al, V < 11 Mo, Nb, Ta, Zr < 8

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Cr, Sn < 5 Cu, Fe, Ni < 3 B, C, H, N, O, Si < 0.5

Cu database Developed for commercial Cu-rich alloys.

14 Components: Major alloy elements: Cr Fe Ni P Si Sn Zn Minor alloy elements: Al B C Mn Pb Ti 180 Phases are calculated. Recommended Composition Limits (wt%): Cu > 50 Al < 3 Cr, Fe, Mn < 10 Ni < 35 Sn < 14 Zn < 45 Si < 5 Pb < 1 B, C, Ti < 0.5

Please note that Pb is a very "delicate" allowing element (i.e. it is very difficult to predict accurately the phases formed in the presence of Lead) and its addition may lead to odd results. This is a known problems of the Computherm database and it is not linked ProCAST itself. If odd results are obtained, the amount of Pb should be reduced for the calculation (or the Computherm database should not be used). The Pb limit in the release notes of Computherm is 5%, however, it was observered that this limit is too high and it does not work in most cases above 1%.

Influence of alloying elements

The goal of this section is to illustrate the influence of alloying elements on properties and to show why properties obtain with thermodynamic databases may differ from experimental data. Example 1 : Al alloy Example 2 : Ni alloys

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Al alloy

An AlSi9Cu3Fe will be considered to illustrate the effect of alloying element on the fraction of solid curve (as well as on the liquidus and solidus lines). The usual average chemical composition of such alloy is the following :

When the Scheil model is used, with the above composition, 10 phases are found (in addition to the liquid phase) :

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Starting from AlSi9Cu3Mg0.3, the other alloying elements are added progressively. The effect on the solid fraction curve is shown in the following figures (please note that the Temperature scale is changing from one graph to the next one):

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AlSi9Cu3Mg0.3

AlSi9Cu3Mg0.3Fe1.3

(the effect of Fe is mainly visible at the liquidus)

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AlSi9Cu3Mg0.3Fe1.3Mn0.55Ni0.55Zn1.2

(Mn, Ni and Zn are mainly affecting the second half of the curve)

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AlSi9Cu3Mg0.3Fe1.3Mn0.55Ni0.55Zn1.2Cr0.15

(Cr is rising the liquidus temperature from 612 to 640°C)

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AlSi9Cu3Mg0.3Fe1.3Mn0.55Ni0.55Zn1.2Cr0.15Ti0.15

(When Ti is added, the Al3Ti phase appears, with a very high liquidus temperature above 760°C)

The following figure are showing the solid fraction curves for all the alloys together.

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In order to see the effect near the liquidus, the same figure is shown, with a different vertical scale. Only the first 5% are shown.

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One can see very well on this latter figure the effect of Ti. Ti is added in order to create this Al3Ti phase which is stable at very high temperature, which is acting as inocculant. The amount of this phase is very small (around 0.5%). The above example is showing that one should be careful with the use of Thermodynamic databases. In this case, for instance, it would be advisable to ignore the Ti for the thermodynamic computation, in order to avoid this "artificially" high liquidus temperature. This explains also why there are differences observed between literature values (measurements) and computed values for liquidus and solidus temperature. This is due to the fact that such values are measured usually by Thermoanalysis and that small amount of solid (like the few percents due to Fe, Cr and Ti near the liquidus temperature) can not be detected. One should note that the usual literature value of the liquidus for this alloy is 588°C which corresponds to a computed value of about 5% of fraction of solid. The measurement of the solidus temperature is even more difficult and thus, it is normal to observe differences.

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Ni alloys

Usually, alloy composition is given with a range around the nominal value. The following example is illustrating the effect of small composition changes within this range on the value of the liquidus temperature. The following table is showing the composition of three typical Ni alloys, with the Low, Nom and High compositions.

All these compositions were computed using the Computherm thermodynamic database of ProCAST. One can see that taking the extreme compositions at the limit of the range can lead to differences in the liquidus temperature of +/- 30-40°C.

This has to be taken into account when comparing experimental values with computed ones, as well as during the real process, as composition fluctuations can affect significantly the solidification conditions and thus the defects which may appear.

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Interface Database

The "Interface" database contains two types of entries :

Interface Die Combo

"Interface" corresponds to "standard" interface heat transfer coefficients between two different domains, where a "coincident" or "non-coincident" interface has been defined (not applicable in case of perfect contact - EQUIV). "Die Combo" is a specific entry to define a "composite" type of heat transfer in the case of die casting. It allows to define automatically the sequence of closed and opened dies.

Interface For the definition of the Interface heat transfer coefficient, the following panel is opened.

The structure of the above panel is described hereafter (see the numbers in the panel below). Firstly, the type of the database entry is shown on the top of the panel (1). Then, the entry can be labeled with a Keyword (2) which will help to recognize it's content for later use. If a constant heat transfer coefficient is to be defined, it's value should be entered in the corresponding field (3). Then the units can be defined (4). The available choice of units is proposed when one clicks on the unit box. If it is desired to define a "Temperature-" and/or a "Time-"dependant

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heat transfer coefficient, the corresponding table can be defined in the "Temperature" or "Time" buttons (5) (for more details about the definition of tables, please refer to the "Boundary Conditions Database" section). It is also possible to specify that the interface heat transfer coefficient will be defined by a User Function (6). Finally, the data are saved with the "Store" button (7).

If the interface heat transfer coefficient is non-constant, the value defined in (3) and the table(s) defined in (5) are all multiplied to get the final value (at a given temperature and a given time). It is allowed to define only a table without a constant (in this case, it is like if the constant is equal to 1). If a User function is specified, neither a constant value, nor a table can be defined.

Die Combo The "Die Combo" definition is used only in the case of die casting, to handle automatically the sequence of closed and opened dies (see the "Cycling" section for more details). The "Die Combo" database entry corresponds to the following panel.

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It allows to define : a) the interface heat transfer coefficient (when the die is closed) in the "Constant" field and/or as a Temperature-dependant table ("Temperature" button). b) when the die opens, the interface heat transfer coefficient between the die and the air is defined by a heat transfer coefficient (Air Coeff) and by an ambient temperature (Air Temp). c) if there is a Spray cooling stage, it can be defined by the corresponding heat transfer coefficient (Spray Coeff) and the Spray temperature (Spray Temp). The check-box "Attached until Ejection" will tell whether the switch between the interface heat transfer and the air cooling will be done when the dies opens or upon ejection of the part. The time at which the mold is opened, closed and when the spraying is starting and finishing can be defined either for each Die Combo entry (to have different values for each interface), in the above panel, and/or in the "Run parameters", in the "Cycles" tab, as shown below.

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The values define in the Run Parameters will apply to all the Die Combo interfaces where no values are specified in the Die Combo panel (i.e. if all the values are set to 0.).

Boundary Conditions Database

The "Boundary Conditions" database contains the following types of entries in the "Assign Surface" menu :

Temperature Heat Velocity Pressure Inlet Turbulence Vent Inject Displacement Point load Surface load

in the "Assign Volume" menu :

Volumetric Heat Momentum Source Mass Source

and in the "Assign Enclosure" menu :

Emissivity

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Temperature "Temperature" allows to specify (or impose) a temperature at a given point. It is especially used to specify inlet temperatures in filling calculations. The following panel corresponds to the "Temperature" database entry.

As most of the panels of the Boundary Conditions database have the same structure, the principles will be described for this one only. Firstly, the type of the database entry is shown on the top of the panel (1). Then, the entry can be labeled with a Keyword (2) which will help to recognize it's content for later use. If a constant value of temperature is to be defined, it's value should be entered in the corresponding field (3). Then the units can be defined (4). The available choice of units is proposed when one clicks on the unit box. If it is desired to define a "Time-"dependant Temperature, the corresponding table can be defined in the"Time" button (5). Finally, the data are saved with the "Store" button (6).

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The following figure shows the choice of available units (when one clicks on the unit box).

In order to define a Time-dependant function, one should click on the "Time" button (see 2 in the figure below). This automatically opens a table, as well as a graph. The values of the table can be entered in (3). It is possible to manage the table (4), with "Erase" operations, as well as "Import" or "Export". For the import, the data should be stored in a text file, with the X and Y values on the same line. One can have up to 100 lines (i.e. 100 points). The Export will also create an text file. For both the Import and the Export, it is possible to Browse in order to find the right location of the imported or exported file. Finally, when the table is well defined, one should SAVE it (5), before Storing (6) the database entry.

Heat The "Heat" boundary condition allows to define the heat transfer between the outside faces of a given domain and the outside world (air, water, ...). The following panel is available for Heat database entry definition.

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The following equation shows the three possible contributions to the "Heat" boundary condition (all the contributions are added, although they may not be all active in the same time or in the same cases).

The first term corresponds to a specified flux. It can be used if a given heat flux was measured for instance. The second term corresponds to Convective cooling. This is the most common definition of the cooling of an external face. It is defined by a heat transfer coefficient with the ambiance and by an external temperature (of the ambiance). The third term is used at high temperature, when radiation becomes important. In this case, the transfer is proportional to the Stefan-Bolzmann constant and the emissivity and the difference of the fourth power of the temperatures (surface temperature and ambiance temperature). The above equation contains the four values which are shown in the panel below (1), such as the "Film Coeff", the "Emissivity", the "Ambient Temp" and the "Heat Flux". These values can be also "Time" and/or "Temperature" dependant (2). In this case, the value of the constant (if any) is multiplied by the corresponding table(s). It is also possible to define the different parameters by the corresponding "User Functions" (3).

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In the case of "Complex" radiation calculations, one should include "View Factors" (see the "Radiation" section for more details). In order to active the "Radiation" model, the "View Factor" button (see item 4 in the figure above) should be turned ON.

Velocity The definition of the velocity is made in the following panel. In this case, the three components of the velocity vector should be defined. If a Time- or a Pressure-dependant velocity is set, each component of the vector will be multiplied by the corresponding table(s). If a gate should be active until a given filling fraction is reached, the "Fill Limit" slider can be used for that purpose. This Fill limit has not the same effect as the Run parameter LVSURF (see the "Run parameters" section for more details). LVSURF allows to stop the filling, but more important it allows to switch off the Fluid flow solver when the filling is finished. On the other hand, the Fill limit defined in this boundary condition should be used if multiple gates are present. It allows to switch off automatically one gate when a given fill fraction is reached an the other gate will continue until LVSURF is reached. Although it is possible to define a Pressure-dependant velocity, one should be very careful in the use of such capability, as the pressure solution is very sensitive.

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When an inlet velocity is set to fill a casting, there are situations where the user would like to know which value of velocity should be set in order to achieve a given filling time. To do so, a "Velocity calculator" is available.

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To use the velocity calculator, the following operations should be done (see the numbers in the upper figure). Firstly, one should "Add" a new velocity boundary condition (1) and assign the corresponding nodes on the geometry. Then, open the "Velocity" boundary condition entry (2) and click on "Velocity calculator" (3). The "Calculator" window will appear (4) and one should select all the domains which correspond to the casting (5) - please note that the selected volumes should be set as EMPTY, otherwise, the volume taken into account for the calculation will be zero. In the above example, the casting is made of four empty domains. Then, the user has to select whether he wants to compute the inlet velocity magnitude or the Filling time (as a function of the other one) with the corresponding radio button (6). In the case where the Fill time should be calculated, the user has to enter the inlet velocity (7) - if it is specified in the BC entry, this value will be automatically used. The Inlet area is automatically taken as the one corresponding the boundary selection on the model. However, if this area is different, the user can change it directly in the corresponding field (7). When the "Calculate" button is pressed (8), the Fill time is automatically calculated (9). If the inlet velocity is defined by a time function, the calculated filling time will take it into account. If a Fill limit is set in the velocity BC, it will be taken into account in the filling time calculation. When the inlet velocity is calculated (based upon the inlet surface and the filling time, the computed value should then be transferred "manually" in the velocity BC panel.

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One should be aware that the velocity calculator will give accurate results if all the nodes on the inlet surface are selected. If only a few nodes are selected, the inlet surface will "overflow" to the neighboring elements and the filling time will be shorter than the one specified. In order to prevent that, it is advised to design a small additional volume, corresponding to the jet of liquid entering the casting.

Pressure The pressure is defined in the following panel, which has the same principles as the "Temperature" panel described above.

Inlet Inlet boundary conditions are used to specify in the same time an "equivalent" inlet velocity together with an inlet temperature. The inlet Flow rate can be time dependant.

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Please note that the direction of the equivalent inlet velocity vector is taken as the average of the normals over all the nodes of the inlet. One should be careful if nodes at edges of the geometry are selected as it will have an influence on the inlet velocity direction.

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The Fill time calculator can be used as described in the "velocity BC" section (see above). In this case, the user has the choice to compute either the Flow rate or the Fill time (as function of the other value). If the Flow rate is defined by a time function, it is taken into account in the Fill time computation. As the density is needed to compute a Flow rate in mass per unit time (e.g. kg/s), the user has to specify a temperature at which the density is evaluated. This temperature should correspond to the inlet temperature (if this temperature is specified in the Inlet BC panel, it is automatically transferred to the calculator).

Turbulence In the case of a Turbulent model, one can specify the "Turbulent" state at the entry of the liquid in the calculation domain.

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Vent If the "Gas" model is activated, the air can escape through vents. Vents are applied on nodes of the casting domains. Each vent is represented by an "equivalent tube" by which the air can escape. Thus, a vent is described by the diameter and the length of the "equivalent tube", as well as a roughness and the exit pressure.

Inject

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In the case of low pressure die casting (lpdc), it is possible to model the liquid bath of metal and to apply a pressure on it (in order to drive the metal in the mold) via injected air. The inject BC allows to specify the amount of injected air. Please note that this method may be delicate to converge.

Displacement In the case of stress calculations, the displacement of the model should be constraint. The Displacement BC allows to define these constraints. Please note that if a field is not filled, the displacement is not constraint in this direction (e.g. it is possible to specify only a "0" in the x-field which will mean that the node can not move in the X-direction, but it is free to move in the Y and Z-directions.

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Point Load For stress calculations, it is possible to apply a load (or a force) at a given location. The three components of the load should be defined.

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Surface Load In the case of stress calculations, one can define a load applied on a given surface. In this case, it corresponds to a pressure. The direction of the load is specified by the three components of the load vector.

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Volumetric Heat In some thermal problem, it may be necessary to define the generation of heat inside a given material (e.g. to model the effect of an electrical resistance). In this case, the thermal power which is generated per unit volume should be defined. This heat source will be applied on the entire specified material.

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Momentum Source In the case of flow problems, one would like to model a source of momentum in a given material. This could be the case to take into account electromagnetic forces or the effect of a propeller. In this case, the momentum force vector should be defined. Please note that this force will be applied in the whole specified material.

Mass Source In the case of filling calculations, one would like to define the amount of metal which enters into the material with a Mass source (instead of a velocity or an inlet BC). In this case, one can specify that a given amount of metal (Flow rate) is "appearing" at the given location (X, Y and Z coordinates) at the specified temperature. The metal will "appear" with a zero velocity.

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Emissivity For radiation calculations, the emissivity of the mold, the casting top surface, the furnace or the enclosure should be specified. The emissivity should be defined between zero and one.

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Process Database

It is possible to define Translations, rotations and revolutions of domains. This is used especially for radiation calculations with view factors (where the furnace is moving with respect to the part, or vice-versa. The following panels allow to define these data.

Translation The translation of a given material domain or of an enclosure is defined with the following panel. The translation can be defined in three different ways : x(t) - Translation vector or position (i.e. position vs time) v(t) - Translation velocity as a function of time (i.e. velocity vs time) v(x) - Translation velocity as a function of position (i.e. velocity vs position) x(t) - Position vs Time The position of the domain is defined as a function of time. This position is relative to the original position at step 0. The translation vector is defined by X, Y and Z which is multiplied by the Time function (in order to have the domain moving, it is necessary to define a time function. Otherwise, the domain will remain fixed - no motion). When x(t) is defined, it is possible to define the translation vector with user functions.

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v(t) - Velocity vs Time The velocity of the domain vs time can be defined with the panel hereafter. The direction of the velocity vector is defined by the U, V and W components. This velocity vector can be either constant or it can be multiplied by a Time function. When v(t) is used, the software is transforming it in x(t) automatically in order to have a translation position which is independant from the timestep.

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v(x) - Velocity vs Position The velocity of the domain vs Position can be defined with the panel hereafter. The direction of the velocity vector is defined by the U, V and W components (it should be a "unit vector"). This velocity vector can be either constant or it can be multiplied by a "Distance" function. The "Distance" is the relative distance with respect to the initial location of the domain which moves. When v(x) is used, it is mandatory to have a non-zero velocity for the initial position (i.e. the zero position). Please note that it is also mandatory to have always non-zero velocities defined (i.e. the velocity should never be zero).

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Rotation The following panel allows to define the rotation of a material domain or an enclosure. The axis of rotation should be defined by two points.

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The rotation is defined in the "Time" button, which opens the following panel, for the definition of the angle as a function of time.

Revolution The "Rotation" definition is used when less than one turn is done during the entire process. When one has several turns, the "Revolution" definition is used. In this case, the axis of revolution should be defined by two points.

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The "speed" of revolution can be defined either as a constant or as a function of time, with the following panel.

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Stress Database

To access the Stress database, one should to in the Material/Stress menu

Then, the list of available materials (stress properties) is shown in a window in the lower right corner (as for the standard material database. The database can be managed in the same way with the "Read", "Add", "Copy" and "Del" capabilities.

When a new stress database entry is created, the following window appears.

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The first thing to do is to select the desired model among the five following options :

Vacant Rigid Linear-Elastic Elasto-Plastic Elasto-ViscoPlastic

"Vacant" is used to specify that the domain will not participate to the stress calculation. Thus, no stress and no strain will be calculated and the domain will not participate to the contact algorithm (i.e. the domain will not create any resistance to the neighboring domains). No properties should be defined for a Vacant domain. No stress calculation will be done in a "Rigid" domain, however, the domain will participate to the contact algorithm (i.e. the neighboring domains will not be allowed to penetrate in the Rigid ones). No properties should be defined for a Rigid domain. For the three other models, the following data are required :

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All the properties can be defined as Constants or as Temperature dependant tables. The standard input panel is used as for the material database (see the "Material Database" section for more details) :

The three models, as well as the meaning of the corresponding properties, are described in the "Stress Models and Properties" section. Warning For stress calculations, the thermal material properties must include the phase change (i.e. fraction of solid curve). Otherwise, no stresses will be calculated in

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this material (as the fraction of solid will not be defined, it will be considered as "zero" and no stress will be calculated). For more advanced calculations, it is possible to define mechanical properties which are not only temperature dependant, but also a function of the microstructure and/or the defects (such as porosity). For more details, please refer to the "Stress properties depending upon microstructure" chapter.

Stress Models and Properties

Warning Before defining the stress properties, one should be aware of the following. For stress calculations, the thermal material properties must include the phase change (i.e. fraction of solid curve). Otherwise, no stresses will be calculated in this material (as the fraction of solid will not be defined, it will be considered as "zero" and no stress will be calculated). The three stress models available in ProCAST can be summarized in the following figure.

Linear Elastic model The Elastic model is mainly characterized by the Young's modulus. It corresponds to the slope of the initial part of the stress-strain curve.

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Beside the Young's modulus, one should define the Poisson's Ratio and the Thermal Expansion coefficients. The value of the Poisson's ratio is usually around 0.3 for metals.

The thermal expansion can be defined by two different ways :

"Thermal Strain" "Secant" thermal expansion coefficient

In the case a Strain curve as a function of Temperature is measured, one can directly input such a curve in the "Thermal Expansion/Strain" tab.

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However, in the equation (see above), it is the "Secant" thermal expansion coefficient which is used. Thus, one can define "Secant" thermal expansion coefficient directly.

The figure above shows how to transform a measured "Strain curve" (shown in blue) in a Secant thermal expansion coefficient. To do so, one needs to define a

Reference Temperature (Tref), shown in the above figure as To, which corresponds to a zero strain. The "Secant" thermal expansion coefficient at

temperature T2 corresponds to the slope S2 of the line between a zero strain (To)

and the strain at the temperature T2. In the case of a constant Thermal Expansion coefficient, the strain curve is a straight line and the coefficient corresponds to the slope of this line. One does NOT need to define a reference temperature in the case of a Constant coefficient.

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The Reference Temperature is defined in the lower part of the "Secant" panel (see above).

Elasto-Plastic model For the Elasto-Plastic model, the properties described above for the Elastic model (i.e. the Young's modulus, the Poisson's ratio and the Thermal Expansion coefficients) should also be defined. In addition, one should define the Yield stress and the Hardening coefficient.

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The Yield stress corresponds to the stress at which plastic deformation starts. It can be temperature dependant.

The hardening coefficient corresponds to the slope of the stress-strain curve in the plastic range. Four different models of hardening are available in ProCAST :

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Linear hardening is defined as follows :

whereas Non-linear hardening is defined as :

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The Hardening can also be defined freely in an ASCII file where one can enter any "digitized" curve. More information about this possibility is in the "Digitized Hardening" section. In order to take into account for the "Kinematic" non-isotropic hardening behavior (Bauschinger effect), the Amstrong-Frederick model is available :

x is called the back stress. It corresponds to the "movement" of the center of the Yield surface. Isotropic and Kinematic models can be used either individually or together.

Elasto-ViscoPlastic model For the Elasto-ViscoPlastic model, the properties described above for both the Elastic model (i.e. the Young's modulus, the Poisson's ratio and the Thermal

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Expansion coefficients) and the Elasto-Plastic model (i.e. the Young's modulus and the Hardening coefficient) should also be defined.

In order to account for the visco-plasticity, three models are available : a) Perzyna b) Norton c) Strain Hardening Creep Perzyna model This model allows to describe the secondary (steady-state) creep with threshold.

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Norton model This model allows to describe the secondary (steady-state) creep with no threshold.

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As there is no threshold value, the data for the Yield Stress and the Hardening will be ignored.

Strain Hardening Creep model This model allows to describe both the primary (strain hardening) creep and secondary (steady-state) creep regimes with a possible threshold.

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For the three models, one have (for the plastic model) :

or

Moreover, the value of the normalization stress ( σ* ) is defined by the user (usually a value of 1 is recommended, in the same unit system as the measured stresses). One should note that the value of η and n will depend upon the selected value for σ*. Further details on the Perzyna law can be found in : "Numerical Modelling in Materials Science and Engineering", M. Bellet, M. Rappaz and M. Deville, Spinger, 2003, pp. 306-310. The principles of the determination of plastic and visco-plastic properties from experimental measurements are described in the "Viscoplastic properties determination" section. Some advices about the viscoplastic properties are written in the "Viscoplastic properties recommendations" section.

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Finally, one should however notice that in most cases, the use of an elastic-plastic model gives very realistic results, without the burden of finding appropriate data for the visco-plastic behavior.

Stress properties depending upon microstructure For more advanced calculations, it is possible to define mechanical properties which are not only temperature dependant, but also a function of the microstructure and/or the defects (such as porosity). For more details, please refer to the "Stress properties depending upon microstructure" chapter.

Annealing During a stress calculations, at high temperature, the plastic deformation is not contributing to the hardening. The stress solver was modified in order to ignore the contribution of the plastic deformation to the hardening, above a critical temperature (called "Annealing temperature"). As a result, only the plastic deformation which has occured below the "Annealing temperature" will contribute to the hardening. The Annealing temperature is defined in the Stress properties panel, as shown below. The Annealing model will be activated if a value is specified in this tab.

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During a heat treatment, when a part is heated up from a low temperature to a temperatue above the crititcal Annealing Temperature, the "pre-existing" plastic deformation contribution to the hardening will be "erased" (which means that when the part will be further cooled down below the Annealing temperature, the hardening will take into account only the plastic deformation contribution which start to be accumulated as soon as the temperature is below the Annealing temperature). Please note that the "Plastic strain" (which can be viewed in the post-processing) will be the result of the accumulation of all the plastic deformation, below and above the Annealing temperature (without reset). The Annealing model can be used with both the Elasto-Plastic or the Elasto-ViscoPlastic models.

Temperature-dependant stress data The three graphs hereafter are showing how it is recommended to define the Elastic Young's modulus, the Yield stress and the Hardening coefficient (in the case of Linear Hardening), over the whole temperature range. These recommendations will allow the best compromise between the physics and the convergence of the stress solver. Please note that the definition of these parameters in the mushy zone will influence the hot tearing indicator prediction.

The value of the Young's modulus in the mushy zone (below a fraction of solid of 20%) should be set as a constant value corresponding to the value of fs = 20%. Usually, this corresponds to values between 50 and 500 MPa.

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Please note that the Youngs's modulus can be automatically calculated in PreCAST as function of the chemical composition, using the thermodynamic databases.

The value of the Yield stress in the mushy zone (below a fraction of solid of 50%) should be set as a constant value corresponding to 5-10 MPa. One should not set values below 5 MPa.

If no data are available, the Hardening (in case of linear hardening) can be set to about 1/20 of the Young's modulus. In all cases, the Hardening should be set to 0 MPa for fraction of solid smaller than 50%.

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Remark : If a tensile test is made on a sample which will be fully mushy at a given time, a non-zero value of the Hardening should be set for fraction of solid below 50%. However, this case is never occurring in usual casting processes. Concerning the Poisson's ratio, if a value of 0.5 is set, it is automatically changed in the software to 0.48. Together with these data, the corresponding Run parameters are recommended (see the "Stress Run Parameters" section for more details) : CRITFS = 0.5 CONVS = 0.01 (for more accuracy, it is advised to use a smaller value like 0.001) PENALTY = 0.01 AVEPEN = 0.1 mm (for large casting, this value can be increased) SCALC = 5

Digitized Hardening

Instead of defining the Hardening either as Linear or with a Powerlaw, it is possible to enter in an ASCII file digitized hardening curves (i.e. the plastic part of tensile test curves at different temperatures). To activate this mode, one should select the "Table" tab in the "Hardening" tab :

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Then, the number of tables specified in the ASCII file should be set (i.e. the number of different temperatures at which a curve is digitized - two in the example below). The corresponding ASCII file should be called : *ssN.dat (e.g. : prefixssN.dat), where N is the domain number, and it should have the following structure :

STRESS_UNIT 4 CURVE 1 POINTS 4 TEMPERATURE 1 293. 0. 8.1159e+01 0.02 1.7684e+02 0.03 2.2671e+02 0.04 2.8462e+02 CURVE 2 POINTS 3 TEMPERATURE 1 823. 0. 9.838 0.01 3.89105e+01 0.05 4.73871e+01

The stress units are defined first (the unit code corresponds to the one of the ProCAST d.dat file - e.g. 4 corresponds to MPa). Then, the number of the curve should be specified, followed by the number of points in the curve. The temperature at which the curve is defined (with the unit code before it - e.g. 1 corresponds to degrees Kelvin, 2 to Centigrade and 3 to Fahrenheit), followed by the curve itself (strain - stress). Please note that only the plastic part of the curve (i.e. the hardening) is defined by the tables. This means that each curve should start by a zero strain (this is mandatory) and that the corresponding stress value is the Yield stress at this temperature. Thus, the Yield stress defined in the "Yield Stress" tab in PreCAST will not be used in the case of Tables (the values will be ignored). Each curve can have a different number of points. Above the last point, the Stress is extrapolated as a constant (i.e. perfect plasticity). Remark : Each domain (of the mesh) for which we would like to use the digitized hardening should have its corresponding prefixssN.dat file. This means that if it should be used in domains 2, 5 and 8, one should duplicate three times the same file with the names prefixss2.dat, prefixss5.dat and prefixss8.dat.

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Plastic and Viscoplastic properties determination

In order to determine the plastic and viscoplastic properties (σo, H, η, n) at different temperatures, including the transition, two methods are suggested (for the Perzyna model with linear hardening) :

• Tensile test method • Creep test method

Tensile test method In the "tensile test method", one should perform controlled tensile tests. These tensile tests should be performed for different temperatures using various strain rates. To do so, the tensile test should be done at constant RAM speed (in order to pull at specified strain rates). The stress and strain should be recorded during these tests. This is usually obtained with a Gleeble machine. The figure below shows the results of such measurements : at low temperature (T1 - green curve), the curve is independent from the strain rate. Thus, the behavior is elastic-plastic. At high temperature (T3 - red curves), one can see that the stress level is depending upon the strain rate and that there is no hardening (viscoplasticity only), as the curve is horizontal at a given stress level. At

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"intermediate" temperature (T2 - blue curves), one has both plasticity (with hardening) and viscoplasticity (as the curve depends upon the strain rate).

Low Temperature At low temperature (usually T1 < Tm/3), the tensile test curve is independent from the strain rate. This means that different tests made at different RAM speeds are giving the same curve (see the green curve in the figure below). From this curve, one can get the Yield stress (σo) and the Hardening coefficient (H). The value of the viscous parameter (η) should be set to zero in order to "disable" the viscoplasticity. The Power (n) can be set to any value as it will not be used.

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High Temperature At high temperature (usually T3 > Tm/2), the tensile test curve is dependent from the strain rate and the stress level is constant (no hardening) after the transition stage (see the red curves in the figure below). As there is no hardening, the value of H should be set to zero. Therefore the threshold (σy) is equal to the Yield stress σo.

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In order to obtain the viscoplastic parameters (η and n), one should first determine

the value of the Yield stress (σo), which can be equal to zero. To do so, one should perform a tensile test at the lowest possible strain rate (possibly zero !) and see the value of the stress on the plateau. If this value is very low, one can

consider that the Yield stress (σo) is zero. In order to determine this value, one can also make loading-unloading tests, with increasing loads until plastic deformation is obtained.

Then, for each measured tensile test curve, the value of (σ- σY)/σ* (which is the

stress level of the plateau minus the Flow stress, σY, which is equal to σo in this

case, as H = 0) and dε/dt should be plotted in a log-log graph. The value of η and n can be deduced from this graph (see below).

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Intermediate Temperature At intermediate temperature (usually Tm/3 < T3 < Tm/2), the tensile test curve is dependent from the strain rate and the stress level is not constant (hardening) after the transition stage (see the blue curves in the figure below). The hardening (H) corresponds to the slope of the curves (after the transition stage). In this model, the hardening is the same for all strain rates. In order to obtain the viscoplastic parameters (η and n), one should first determine

the value of the Yield stress (σo), which can be equal to zero. To do so, one should perform a tensile test at the lowest possible strain rate (possibly zero !) and see the value of the stress zero plastic strain. If this value is very low, one can

consider that the Yield stress (σo) is zero. In order to determine this value, one can also make loading-unloading tests, with increasing loads until plastic deformation is obtained.

Then, for each measured tensile test curve, the value of (σ- σY)/σ* (which is the

extrapolated stress level at zero strain minus the Flow stress, σY. In this case, σY

is equal to σo, as εpl = 0 - because the extrapolation is performed a zero strain)

and dε/dt should be plotted in a log-log graph. The value of η and n can be deduced from this graph (see previous figure).

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Creep test method In the "creep test method", one should perform controlled creep tests (plastic deformation as a function of time for a given fixed load). The creep tests should be performed for different temperatures using various loads (stress). The figure below shows the results of such measurements : at low temperature (T1 - green curves), the curves are independent from time (plateau). Thus, the behavior is elastic-plastic. At high temperature (T3 - red curves), one can see that the plastic strain is increasing linearly with time (viscoplasticity only). At "intermediate" temperature (T2 - blue curves), one has both plasticity (with hardening) and viscoplasticity.

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Low Temperature At low temperature (usually T1 < Tm/3), the following curves are measured at different loads.

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From these curves, one can get the Yield stress (σo) and the Hardening coefficient (H). To do so, the values (shown in the graph below) of ε and σ (at the different loads) should be plotted in a σ-ε graph. A linear or Power Law Hardening can be fitted on those points.

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Beside the above, the value of the viscous parameter (η) should be set to zero in order to "disable" the viscoplasticity. The Power (n) can be set to any value as it will not be used. High Temperature At high temperature (usually T3 > Tm/2), the slope of each curve represents the strain rate, dε/dt (see the red curves in the figure below).

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In order to obtain the viscoplastic parameters (η and n), one should first determine

the value of the Yield stress (σo), which can be equal to zero. To do so, one should perform a creep test at decreasing loads. The Yield stress is reached when there is no more plastic strain. If this value is very low, one can consider that the

Yield stress (σo) is zero. Then, for each measured creep curve (shown above), the value of strain rate

(dε/dt) should be plotted as a function of (σ- σY)/σ* (which is the stress level of

the plateau minus the Flow stress, σY, which is equal to σo in this case, as H = 0) in a log-log graph (see below). The value of η and n can be deduced from this graph (see below).

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Beside the above values, as there is no hardening, the value of H should be set to zero. Therefore the threshold (σy) is equal to the Yield stress σo. Intermediate Temperature At intermediate temperature (usually Tm/3 < T3 < Tm/2), the creep test curves are dependent from both the load (stress level) and time (see the blue curves in the figure below).

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From these curves, one can get the Yield stress (σo) and the Hardening coefficient (H) as described above in the "Low Temperature" section. To do so, the values (shown in the graph below) of ε and σ (at the different loads) should be plotted in a σ-ε graph. A linear or Power Law Hardening can be fitted on those points. In order to obtain the viscoplastic parameters (η and n), one should first determine

the value of the Yield stress (σo), which can be equal to zero. To do so, one should perform a creep test at decreasing loads. The Yield stress is reached when there is no more plastic strain. If this value is very low, one can consider that the

Yield stress (σo) is zero. Then, for each measured creep curve (see blue curves in the zoom below), the values of the INITIAL strain rate (dε/dt) should be plotted as a function of (σ-

σY)/σ* (which is the load, σi, minus the Flow stress, σY. In this case, σY is

equal to σo, as εpl = 0 - because the extrapolation is performed at time=0, where the strain is zero) in a log-log graph (as described in the "High Temperature" section).

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Viscoplastic properties recommendations

The Perzyna model is defined as follows (see the "Stress Models and Properties" section for more details) :

If we express the stress as a function of the strain rate when

we have the following :

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The second term of the right hand side can be called the "Viscoplastic stress"

( ). Thus, we have :

with

If we perform a "numerical isothermal tensile test" at various strain rate, one gets the following curves. The first graph is with a zero hardening, whereas the second graph is with hardening.

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One can well see how the "Viscoplastic stress" is increasing with the strain rate. As the "Viscoplastic stress" is a function of the inverse power of the "Power" term "p", it is very sensitive to this parameter. Thus, the combination of the "Power" term and the "Viscous parameter" term should lead to consistent values of the "Viscoplastic stress", and that at each temperature. The following figures are showing the temperature dependence of the Viscous parameter and of the Power for an A356 Aluminium alloy. Please note that the Viscous parameter is displayed in a logarithmic scale.

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Based upon the Viscous parameter and of the Power of the above graphs, the "Viscoplastic stress" has been calculated for different strain rates, as shown hereafter.

One can see on the above graph that the "Viscoplastic stress" is higher at intermediate temperature, however, when this "Viscoplastic stress" is normalized by the Yield Stress (see next figure)

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it becomes clear that the viscoplasticity is negligible at low temperature and is significant at high temperature.

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When viscoplastic properties are determined for a new material, it is strongly advised to compute and plot (in Excel for instance) the "Viscoplastic stress", as well as the "Normalized Viscoplastic stress", at the different temperature and for different strain rates. This will allow to make sure that the curves are consistent (e.g. the curves should normally not cross each other) and that the order of magnitudes are right. The following section is showing how the "Viscoplastic stress" can change a lot with a "small change" of the Viscous parameter and/or the Power.

Important Remark about the tabulation of the Viscous Parameter The Viscous Parameter is varying across many orders of magnitude (from 1e36 at low temperature down to 1e6 at high temperature - 30 orders of magnitude). This is why it is displayed in a logarithmic scale. The following figure is showing the same curves as the previous section, but all grouped together.

In ProCAST, all the properties defined by tables are linearly interpolated. In the case of the Viscous parameter, as the values are changing over so many orders of magnitude, the linear interpolation is not anymore appropriate if the curve is defined by too few points. In the next example, the properties (corresponding to the A356 alloy of the above figure) between 300 and 500°C are defined only by two points. Thus, the software

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will make a linear interpolation of the Viscous Parameter and the Power between these two temperature. The following figures are showing the "interpolated" values of the calculated "Viscoplastic Stress" at 320, 400 and 480°C (see red dots). This is showing that this linear interpolation is not appropriate and leads to "wrong" values of the "Viscoplastic Stress" (especially at 480°C).

Calculated values of the "Viscoplastic Stress" and of the "Normalized Viscoplastic

Stress" at 320°C, based upon linearly interpolated values of the Viscous Parameter and the Power between 300 and 500°C.

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Calculated values of the "Viscoplastic Stress" and of the "Normalized Viscoplastic

Stress" at 400°C, based upon linearly interpolated values of the Viscous Parameter and the Power between 300 and 500°C.

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Calculated values of the "Viscoplastic Stress" and of the "Normalized Viscoplastic Stress" at 480°C, based upon linearly interpolated values of the Viscous Parameter and

the Power between 300 and 500°C. In order to prevent such odd behavior, one should make sure that the Viscous Parameter and the Power are tabulated with enough points (for instance with a 20°C interval).

Visco-elasticity

Waxes used in investment casting are polymers which exhibit viscoelastic behavior. As the calculation of deformations of waxes may be important for such processes, viscoelastic models were introduced in ProCAST. This section describes briefly the models which are implemented in the software, followed by a short description of the different inputs, in relationship with the above mentioned models.

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For the Stress material properties definition, select the Visco-elastic properties.

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The Elastic properties (Young's Modulus, Poisson's Ratio and Thermal Expansion), the instantaneous properties should be defined as a standard elastic material. The specific data for the visco-elastic properties should be defined in the "Shear Modulus" tab.

First, the Williams-Landell-Ferry(WLF) constants (see equation above) are defined in the first "Constant" tab.

Second, the relaxation shear moduli table should be defined in the second tab (see equation above).

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Otherwise, all the other conditions (e.g. displacement BC and Run parameters) should be defined in a standard way.

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EXTRACT AND MAPPING

Three different functionalities, which can be coupled together, are presented in this chapter : • Extraction of results from a previous calculation as initial conditions for a new

calculation • Removal of domains in order to run a new calculation with less domains than a

previous run • Addition of new domains, coming from a different calculation, to an existing

case Examples illustrating the potential of combining together these functionalities are then presented. Please note that all the functionalities described in this chapter can be used as well with the Scalar and the DMP versions.

Important remarks about new files created by the Extract and Delete/Add operations Please note that when an Extract is performed (even of temperature only), the prefix.ini file which is created is necessary to run the case, together with the d.dat and p.dat files. This is especially important when input files must be transferred to a third party (or to the Support), not to forget to provide the .ini file too. When a "Delete" and/or and "Add" domain(s) is performed, PreCAST is keeping track of the correspondence between the nodes and elements of the initial and final models. This information is stored in the prefix.nnc and prefix.enc files. This information is used only when an Extract (of Temperature, FVOL, Stress and/or Porosity results) from the original model is performed. If the extracted information seems to be totally mixed up, check that these files are existing. One should note that if a model (named "model_B") was created by an Add or Delete of "model_A" and then a "model_C" is created as an exact copy of "model_B", a special care should be taken if it is desired to Extract results in "model_C" coming either from "model_A" or "model_B" : Extraction in "model_C" of results from "model_A" : the "model_B.nnc" and "model_B.enc" files should be copied in the "model_C" directory as "model_C.nnc" and "model_C.enc" before the Extract operation Extraction in "modelC" of results from "model_B" : there should be no *.nnc and *.enc files present (as there is no change of mesh between these two cases).

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One should note that if a model (named "model_B") was created by an Add or Delete of "model_A" and then a "model_C" was created by an Add or Delete of "model_B" ("cascade Delete/Add operation"), a special care should also be taken if it is desired to Extract results in "model_C" coming either from "model_A" or "model_B" : Extraction in "model_C" of results from "model_A" : one should make sure that the *.nnc and *.enc files are well present in the "model_B" and "model_C" directories respectively. Then, the extraction will work well as such. Extraction in "model_C" of results from "model_B" : if this is the desired operation, it is required that before the Add/Delete operation of "model_C", from "model_B", the "model_B.nnc" and "model_B.enc" files must be removed (or renamed). This will suppress the "link" between model_B and "model_A", thus allowing the Extract from "model_B" to "model_C". In any case, it is strongly advised to isolate each case in a separate directory and to well document the "parents" and "child" in the "Delete/Add" operations.

Warnings It is not possible to optimize a mesh which is the result of a "Delete/Add" operation if an "Extract" has been made. This will mess up the node and element numbering and thus the Extract information. It is not possible to change the "nature" of the interfaces (EQUIV/COINC/NCOINC) in a mesh which is the result of a "Delete/Add" operation if an "Extract" has been made. This will mess up the node and element numbering and thus the Extract information.

Results extraction

The Results extraction allows to use results from a previous calculation as initial conditions for a new calculation. It is possible to extract the following results :

• Temperature • Stress fields • Free surface information (FVOL) • Porosity

The Stress fields correspond to the 6 components of the stress tensor, the plastic strain and the displacements (thus the deformed geometry is also extracted). The Free surface information corresponds to the value of FVOL. This means that the locations which are full and which are empty will be extracted. When a thermal only calculation is following an extract of a partial filling, it is necessary

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to activate POROS = 1. This is due to a fact that in a thermal only calculation with POROS = 0, the FVOL values are not stored. Thus, the extract of FVOL would be lost. If an Extract is performed, the temperature is extracted in all cases, whereas the extraction of the Stress fields and free surface information is optional. One should note that in version 2009.0 the Microstructure results are not extracted. To extract results, the following procedure should be used (see next figure).

The above window appears when the "Initial Conditions/Extract" menu (1) is called. The list of the available domains appears on the top right of the screen. First the desired domain(s )which will correspond to the same extraction (i.e. results extracted from the same case and at the same timestep) should be selected (2) - more than one domain can be selected at the same time. A simple click on the domain name is selecting it (and is highlighting it in red). An additional click on a selected domain will unselect it. Then, the "Extract" button should be pressed (3), which will open the "Extract panel" (4). The case from which the results should be extracted must be selected with the "Browse" button (4). The file "prefixt.unf" should be selected (to select the case named "prefix"). Then the desired timestep of the extraction should be specified (5). In all cases, the temperature are extracted. The user can select in addition the Free surface information (FVOL),

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the Stress fields and/or the Porosity. Finally, the "Apply" button (6) will confirm the extract definition. Once the Extract is confirmed (with the Apply button), the extracted temperature can be displayed on one or more domains. To do so, select the desired domain(s) and press on the "Display" button. The temperature will be displayed as shown in the following figure. Please note that the scale can not be changed in this view.

When an Extract is made, a file called "prefix.ini" is automatically created by PreCAST. It contains all the restart information for Temperature, FVOL, Stress fields and Porosity. This file needs to be present together with the d.dat and p.dat files and is used by DataCAST. Once DataCAST is run, this file is not anymore needed in the working directory. When input files must be transferred to a third party (or to the Support), do not to forget to provide the .ini file too. When an Extract of FVOL, of Stress Fields and/or of Porosity are defined, the Run Parameter INILEV is automatically set to -1 in the p.dat file. The calculation will however start at the step 0 (see the "General Run Parameters" section for more details). If a "pre-defined" set of Run Parameters is selected, automatically, the value of INILEV will be set to -1. Warning When an Extract is performed with an original case having time functions, one should be careful that the time zero of the extracted calculation is not anymore the

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same as the original one. Thus, the time functions have to be shifted in the second calculation, with respect to the first one. Examples illustrating the possiblities offered by the Extraction of the free surface information and the Stress Fields are described in the "Extract examples" section.

Results mapping

The results mapping is working exactly in the same way as the "Extract" (see the "Results extraction" section for more details). The only difference is that one should select the "Mapping" button instead of the "Extract" one. All the rest of the procedure is identical.

The principle of the mapping is the following for fields defined at nodes (like Temperature, FVOL or porosity) : for each node of the target mesh, the corresponding element of the source mesh is searched. Then, the value of the target node is interpolated from the values of the vertices of the source element. A special care should be taken if the target node is outside the source mesh. If the mismatch is small (i.e. a fraction of the average size of the neighboring element of the outside node), the value is calculated as an interpolation of the nodes of the closest face of the source mesh from the target node. If the target node is outside the source mesh with a larger mismatch, the average of the neighboring target nodes which have already been calculated is propagated

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to the node. This allows to take care of situation where the target mesh has an extra volume (like an added riser or a removed cooling channel) with respect to the source mesh, with reasonable mapping values. When multiple domains mapping is performed, the mapping is done between the same "Material Type" of domains (i.e. MOLD, CASTING, CORE, ...). If the source calculation has a CORE and then it is transformed in CASTING in the target calculation, there will be no mapping between the CORE temperature of the source calculation and the CASTING temperature of the target calculation. This volume will be considered as a hole and the propagation described above will be applied (if it is desired to map the CORE temperature onto the CASTING volume, one should change the CORE to CASTING type of this domain and run "datacast -u" before doing the Mapping). Warning The mesh from which the results will be extracted must be in tetrahedra only (it is not allowed to have hex or wedges). However the target mesh (i.e. the mesh on which the mapping will be applied) can have any type of elements. The two following images are showing the result of a mapping of an HPDC casting from a coarse mesh (left) to a fine mesh (right).

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One can see that the match between the two meshes is very good. The quality of the mapping is as good when going from a fine mesh to a coarse one.

Domain removal

When a mesh contains several domains, it is possible in PreCAST to remove one or more domains from this mesh. This can be useful in two kinds of situations : • When one domain of the original mesh is not anymore interesting for the

calculation (e.g. when several scenario are done based upon the same mesh). • When a mold must be removed at the mold knock-out or a gate is cut. To remove/delete one or more domains, use the "Geometry -> Delete/Add Materials" menu.

This is opening a Delete/Add panel on the right of your screen. Select the domain(s) to be deleted (by toggling between No and Yes).

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Then press the "Delete" button and the corresponding domain(s) will be removed.

The main advantage of this "Delete" procedure, with respect to doing it in the Mesh Generator is that the set-up of the case is remaining after the delete operation (at least all the features which are applied to the remaining domains). Thus, it is only necessary to complement the set-up by the missing or new features and the calculation can be run again. Remark 1 Please note that when a Domain is "Delete", the Run parameters are automatically reset (even if a p.dat file was present in the working directory). It is thus necessary to redefine the Run parameters after a "Delete". Remark 2 In the case of stress extraction with domain(s) removal, one should make sure that all the remaining domain(s) are well defined as "CASTING". For instance, if the original model has a CASTING, a MOLD and a CORE and only the MOLD has to be deleted first (i.e. to run a stress calculation with the CASTING and the

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CORE), the CORE must be switched to CASTING (ignore the Warning message saying that two different materials are assigned to the different CASTING domains) in order to have a successful Extract. This is due to the "renumbering" algorithm applied to the Extract which is currently made only on the CASTING domains.

Domain addition

With the "Domain addition" functionality, it is possible to Add one or more domain(s) to an existing mesh or case. It is also possible to add an Enclosure. To illustrate that, one shall take the example of an HPDC case where we will add the outer mold to the model. As it can be shown in the next figure, only the "inner mold" is taken into account in this first model.

The goal is now to "Add" the "Outer mold" to this model. This outer mold has been mesh separately as shown in the next figure. Please note that of course, the coordinate system of the two meshes should coincide.

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In order to Add this "outer mold", the following steps should be performed : Load the original model (without outer mold) in PreCAST. Go in the "Geometry -> Delete/Add Materials" menu and press on the "Add" button.

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A Browser will open. Select the right filter (d.dat or .mesh file) and browse the desired mesh of the outer mold. Select it and press the "Open" button. This will open the "Second model" window, as shown hereafter.

The list of available domain(s) in the second model is displayed. Select the desired domain(s), by toggling No into Yes and press the "Move up" button. The selected domain(s) will be added to the "First model" list as well as in the Graphical window (see next figure).

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Then, the material properties and boundary conditions corresponding to this new added domain(s) should be specified. In particular, one should not forget to create the non-coincident interfaces between this new domain(s) and the one of the first original model (see figure hereafter).

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As we can see on the following figure, the inner and outer molds are well taken into account in this new model.

Remarks It is possible to use the "Add" functionality to add an enclosure to an existing case (where the enclosure would not been present already). Please note that when a Domain is "Added", the Run parameters are automatically reset (even if a p.dat file was present in the working directory). It is thus necessary to redefine the Run parameters after an "Add".

Extract examples

This section is giving a few examples of the different possibilities offered by the extended Extractions possibilities :

• Mold removal and gate cutting • Stress calculation on a partially filled casting

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• Cycling and shot sleeve in HPDC • Filling in multiple stages

Mold Removal and Gate Cutting

This Extract procedure, including the possibility to "Delete" domains and to extract stress information can be used in a very powerful way to address the Mold removal (or mold knock-out) and the Gate Cutting effect on the final casting shape during a Thermal-Stress calculation. The following example is showing a very simple case where the casting (and gating) is first solidified in a Rigid mold (the mold can be as well elastic-plastic). Then the mold is opened and thus the shape of the casting can change due to the fact that the mold constraints are disappearing. Later on, the gate is removed, allowing the part to take its final shape. This can be done now in three stages in the following way.

Calculation 1 (solidification and cooling in the mold) : The initial calculation should be set as usual. The casting and the gating should be defined as distinct domains, inside the mold (see next figure).

The stress calculation should be activated in the casting and gating (it is optional in the mold). Then the calculation should be run until the time of the mold opening (mold knock-out).

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Calculation 2 (removal of the mold and further cooling) : Once the calculation 1 is finished, the following procedure should be applied in order to simulate the mold knock-out :

• Copy the d.dat and the p.dat files of Calculation 1 in a new directory corresponding to Calculation 2.

• Go in the "Geometry -> Delete/Add Materials and delete the Mold domain(s). One can see that the set-up on the remaining domains is still present (the p.dat file however has been reset and will need to be reconfigured)

• As the mold is not anymore present, the appropriate displacement BC should be set on the casting/gating geometry, in order to make sure that the geometry is well constrained.

• The cooling conditions (Heat BC) should be set on the outside of the casting/gating geometry.

• The Temperature and Stress results of the last timestep of Calculation 1 (corresponding to the time of the mold knock-out) should be extracted for the casting and gating.

• The ad-hoc Run parameters should be defined. • The calculation should be run until the time at which the gating is

removed.

Calculation 3 (gate cutting and cooling down to room temperature) : Once the calculation 2 is finished, the following procedure should be applied in order to simulate the gate cutting :

• Copy the d.dat and the p.dat files of Calculation 2 in a new directory corresponding to Calculation 3.

• Go in the "Geometry -> Delete/Add Materials and delete the Gate domain(s). One can see that the set-up on the remaining domain(s) is still present (the p.dat file however has been reset and will need to be reconfigured)

• As the gate is not anymore present, the appropriate displacement BC should be set on the casting geometry, in order to make sure that the geometry is well constrained.

• The cooling conditions (Heat BC) should be set on the outside of the casting geometry (i.e. at the faces corresponding to the former gate/casting interface).

• The Temperature and Stress results of the last timestep of Calculation 2 (corresponding to the time of the gate cutting) should be extracted for the casting.

• The ad-hoc Run parameters should be defined. • The calculation should be run until room temperature.

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The following figures are showing the results of these three calculations. The first set of pictures shows the results without an increased deformation, whereas the second set is showing the same results, with a deformation magnitude of 10. In both sets, the total displacement is shown (with the same scale for all figures), allowing to well see the effect of the mold knock-out and the gate cutting on the shape of the casting.

View of the total displacement (same scale for all the figures, from 0 to 18 mm) at different stages of the casting process : 1. Initial geometry (calculation 1), 2. Just

before mold knock-out (calculation 1), 3. Just after mold knock-out (calculation 2), 4. Just before gate cutting (calculation 2), 5. Just after gate cutting (calculation 3), 6. Room temperature (calculation 3). The pictures are taken with a "Displacement

magnitude" of 0 (no visible deformation of the geometry).

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View of the total displacement (same scale for all the figures, from 0 to 18 mm) at different stages of the casting process : 1. Initial geometry (calculation 1), 2. Just

before mold knock-out (calculation 1), 3. Just after mold knock-out (calculation 2), 4. Just before gate cutting (calculation 2), 5. Just after gate cutting (calculation 3), 6. Room temperature (calculation 3). The pictures are taken with a "Displacement

magnitude" of 10 (increased deformation).

Stress calculation on a partially filled casting

Quite often in Investment or gravity casting, the cavity is not completely filled (i.e. the pouring cup is only partially filled). If one wants to perform a stress calculation on such partially filled casting, but without having to perform the stress calculation during the filling, it is possible to do so with the extraction of the Free surface information.

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Moreover, the stress calculation can be continued after the mold removal (mold knock-out). The different stages are the following (illustrated by a very simple test geometry) :

Calculation 1 (filling) : Filling + Thermal calculation, with the usual set-up and LVSURF = 0.70 (to stop the filling at 70%) The calculation can be stopped just after the end of the filling.

Calculation 2 (stress calculation during the solidification) : The d.dat and p.dat files of the Calculation 1 are copied (in a new directory) and loaded in PreCAST. The following set-up should be done :

• In the Materials menu, the casting domain should be set as full (EMPTY NO).

• The stress material properties should be set. • The displacement BC should be set (if needed). • The filling BC can be removed. • The Temperature and the FVOL should be extracted from the

Calculation 1, at the step corresponding to the end of the filling. • The Run parameters for a Thermal + Stress calculation should be

defined.

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The following figure is showing the result of the stress calculation (the total displacements are shown, with a "Displacement magnitude" of 20).

Calculation 3 (stress calculation after mold knock-out) : The d.dat and p.dat files of the Calculation 2 are copied (in a new directory) and loaded in PreCAST. The following set-up should be done :

• In the Geometry menu, go in the "Delete/Add Materials". • Select the mold (specify "Yes" in the right column). • Press the "Delete" button (the mold will disappear from the

graphics window). • Set the appropriate cooling BC (Heat) around the casting. • Set the appropriate displacement BC on the casting • Extract the temperature, the FVOL and the stress data of the last

timestep of Calculation 2 above. • Set the appropriate Run parameters

The following figure is showing the results just before and just after the mold knock-out.

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The following figure is showing the temperature and casting shapes just after the mold knock-out (step 0 of calculation 3) and at the end of the cooling (last step of calculation 3).

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Cycling and shot sleeve in HPDC

This example is showing how it is possible to add a shot sleeve to an existing HPDC case and to use the mold temperature after cycling as initial conditions for the shot sleeve calculation. The procedure to do that is the following. Please note that on this simple example, it may look not optimum to use this procedure to achieve this goal, however, if the mold is very complex and leads to many interface definitions, this can be quite powerful. Moreover, this could allow a quite easy change of shot piston geometry without remeshing the mold and without redefining all the mold properties, boundary conditions and interfaces in PreCAST.

Calculation 1 (cycling without the shot piston) : The calculation should be defined as usual in PreCAST on the following geometry. The cycling conditions should be set.

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The above figure is showing the temperature contour during the last cycle, whereas the following figure shows the temperature evolutions along the 5 calculated cycles.

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Calculation 2 (Filling and Solidification with the shot piston) : In order to add the shot piston to the calculation 1 above and to use the mold temperature at the end of the last cycle of calculation 1, the following procedure should be applied. 1. Copy the d.dat file of Calculation 1 in a new directory (Calculation 2). 2. Load this d.dat file into PreCAST and remove the casting domain (using the Geometry -> Delete/Add Materials menu). The geometry will appear like the following figure.

3. In the "Geometry -> Delete/Add Materials" menu, select "Add" and Browse in the directory where the mesh containing the casting and the shot piston is located. Please note that this can be either in a mesh file (*.mesh) or in a data file (*d.dat).

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4. Open this second file and a new window called "Second model" will open below the "First model window" (see hereafter). The list of all available domains of he second model is shown in the "Second model" window.

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5. Select the domains (Materials) that you want to import from the Second model to the First one (by toggling No to Yes) and then press the "Move up" button (left window above). 6. The selected domains of the Second model are automatically imported in the First model (see right window above). 7. Now that the geometry is complete, all the missing assignments should be made. The first one is the Material properties assignment (see below).

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8. If the "Added" geometry was coming from a mesh file, some interfaces may need to be created. If the "Added" geometry was coming from a d.dat file, the already present interfaces will be imported as well and thus do not need to be created again.

9. Between the original model (of Calculation 1) and the imported domains (coming from Calculation 2), it is necessary to create "Non-coincident" interfaces. It is recalled that if temperature dependant interface heat transfer coefficient will be used, the Master must be the casting.

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10. As we would like to use the temperature of the mold at the end of the last cycle, we should extract it from Calculation 1. To do so, select all the mold domains (which will be highlighted in red) and click on "Extract". A window will open, which allows to Browse the Calculation 1 case and to specify the timestep corresponding to the end of the last cycle.

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11. When the Browsed model is selected (select the prefixt.unf file), the Open button can be pressed, in order to execute the extraction. 12. When the "Display" button is pressed, the extracted temperature can be viewed.

13. Finally, the Run parameters should be configured as usual. The next three figures are showing the results of the calculation. The first figure shows the initial step with the extracted temperature of the mold.

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Important Remark As described at point 9) above, at interfaces between the original domains of Calculation 1 and the imported (added) domains of Calculation 2, there must be a "Non-coincident" (NCOINC) interface. It is not possible to have an "Equivalent" (EQUIV) between original and imported domains. This is why the in the above example, the "Casting" domain had to be Deleted and then re-imported from Calculation 2, together with the shot sleeve.

Filling in multiple stages

In the case of large castings, sometimes, the filling is done is several stages. As the time between two filling sequences may be significant, it is now possible to run a "thermal only" calculation in between these fillings. This is saving a lot of CPU time. The procedure to do that is the following.

Calculation 1 (first stage filling) : Set-up the first stage filling as usual (in the following example, the initial filling corresponds to a bottom filling). The value of LVSURF should be set 1. Run the calculation until a few steps beyond the filling percentage corresponding to this first stage filling

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Calculation 2 (thermal only calculation in between the two filling stages) : The d.dat and p.dat files of the Calculation 1 are copied (in a new directory) and loaded in PreCAST. The following set-up should be done :

• In the Materials menu, the casting domain should be kept as empty (EMPTY YES).

• Suppress the inlet BC. • Extract the temperature and the FVOL from the last step of the

Calculation 1. • Change the Run Parameters for a Thermal only calculation (i.e.

disable the flow - FLOW = 0). • Make sure that POROS is equal to 1. • Run the calculation until a few steps after the time corresponding to

the beginning of the second filling stage.

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The above figure is showing the cooling in between the two filling stages. As it is a Thermal only calculation, it can be done with large timesteps (much larger than when the flow is activated).

Calculation 3 (second stage filling) : The d.dat and p.dat files of the Calculation 2 are copied (in a new directory) and loaded in PreCAST. The following set-up should be done :

• In the Materials menu, the casting domain should be kept as empty (EMPTY YES).

• Add a new inlet BC (top filling in the present example). Please note that the inlet temperature can be different from the previous one.

• Extract the temperature and the FVOL from the last step of the Calculation 2.

• Change the Run Parameters for a Filling calculation (i.e. reactivate the flow - FLOW = 1).

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RUN PARAMETERS

This section contains the comprehensive description of all Run parameters. The ones shown in blue are either new or have been modified or further described, with respect to previous versions. The different categories of Run Parameters are organized in Tabs. The first Tab layer (1) corresponds to the different modules of ProCAST. For each modules, the Run Parameters are divided in a "Standard" tab (2), with the most often used parameters and one or two "Advanced" tabs (2) with less often used Run Parameters. The values are then defined in (3).

The values of the Run Parameters are stored in a file named "prefixp.dat" (often called the "p.dat" file). The Run Parameters can thus be changed either in the PreCAST interface, or directly "by hand" in the "p.dat" file (see example below).

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The default values are not anymore specified in the manual, as they are set in the "default_p.dat" file (see the "Pre-defined Run Parameters" section for more details).

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General Run Parameters

The Run Parameters which are used by any module are grouped in the "General" tab. It is also possible to defined the units which will be used for the display of the results (it will not affect the results themselves).

The Run Parameters of the "General/Advanced" tab are usually not changed from the default values, except in very specific cases. It corresponds mainly to the parameters of the different general solver algorithms.

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General

AVEPROP specifies the method to be used in calculating the properties for each element. ProCAST will calculate the properties at each Gauss point or you may specify that the properties be calculated only at the element center and that this value will be used as an average for the whole element. This averaging reduces, somewhat, the finite element integration time required. This averaging does not apply to the specific heat or enthalpy calculations. Choose from: 0 to calculate at each point, or 1 to use the average

CGSQ specifies the Conjugate Gradient Squared solver flag. The values specified in this parameter may be added together. This allows you to "build" a customized solver approach for your simulation. Choose from:

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0 = Use the default iterative solver ( TDMA ), 1 = Use the CGSQ solver on the U momentum equation, 2 = Use the CGSQ solver on the V momentum equation, 4 = Use the CGSQ solver on the W momentum equation, 16 = Use the CGSQ solver on the energy equation, 64 = Use the CGSQ solver on the turbulence intensity equation, 128 = Use the CGSQ solver on the turbulence dissipation equation, or 512 = Use the CGSQ solver on the density equation for compressible flow

CONVTOL specifies the convergence tolerance which will be used in conjunction with the default non-symmetric iterative solver. Enter a floating (real) value.

DIAG specifies the diagonal preconditioning flag for the symmetric solver. Choose from: 0 = use partial Cholesky preconditioning for everything, 8 = use diagonal preconditioning for pressure, 16 = use diagonal preconditioning for energy, and 16384 = use diagonal preconditioning for radiosity

DT specifies the initial time step size. Setting DT to zero when INILEV > 0 will cause ProCAST to use the DT at step INILEV. Enter a floating (real) value. The default is 1.0000e-03. Select the units of time from: {sec | min}

DTMAX specifies the maximum time step size. Enter a floating (real) value. Select the units of time from: {sec | min} The maximum timestep size can be set as a time-dependant table :

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The time table is stored in the d.dat file. The value which appears in the DTMAX field, as well as in the p.dat file should be zero in order to activate the table. If one would like to deactivate the table, a non-zero value should be set. Please note that if the value of DTMAX is reduced at a given time (e.g. reduction from 5 to 1 s. at 50 s.) the timestep may be reduced only after about 55 s. (as the previous timestep may have been at 49.9 s. and thus the next timestep will still be done with DTMAX = 5 s.).

DTMAXFILL specifies the maximum time step size which will be used during the filling stage only. Once the filling is finished, the DTMAX value will be used. If DTMAXFILL is not defined (i.e. it is set to zero), the value of DTMAX will be used for the whole calculation. Enter a floating (real) value. Select the units of time from: {sec | min} The value of DTMAXFILL can also be defined as a time-dependant table. See DTMAX above for more details.

INILEV specifies the initial time level. When an analysis is first started, INILEV should be equal to zero. When you are resuming an analysis, INILEV should be set to the time step from which you would like to continue. Note: You must have results for that time step. If a larger value than the last stored step is specified, the last stored timestep will be used. The last complete step corresponding to TFREQ, VFREQ and SFREQ will be selected and the calculation will be restarted with this last time step. It is assumed that MFREQ=TFREQ.

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When an Extract of "FVOL" or of "STRESS" results are performed, the value of INILEV must be set to -1 (and the calculation will start at step 0) (see the "Extract/Results extraction" section for more details). Enter an integer value.

LUFAC specifies the preconditioning parameter for the CGSQ solver. This parameter may speed-up calculations of large models Choose from: 0 to use diagonal preconditioning, or 1 to use partial LU factorization preconditioning

NEWTONR turns on the NEWTON Raphson technique for the energy equation. Choose from: 0 to turn off the Newton Raphson technique, 1 to turn the Newton Raphson technique on, or 2 to turn on the Newton Raphson technique and use bsplines The default is 0. Option 2 results in using b-splines instead of linear line segments in the representation of the thermal properties. It is suggested that all thermal input data be smoothed before attempting to use b-splines. Enter an integer value.

NPRFR specifies the printout frequency. This controls the time step interval at which results are output to the prefixp.out file. Enter an integer value.

NRSTAR specifies the number of allowable restarts before the entire run is abandoned. A restart occurs when the maximum number of corrections is reached. If too many restarts are taking place, it could indicate problems with the model setup. Enter an integer value.

NSTEP specifies the number of time steps to take in the current run and is used in conjunction with TFINAL. ProCAST will terminate the run when it reaches this limit or the TFINAL value, whichever occurs first. Enter an integer value.

PRNLEV specifies the level of nodal results to be printed out. The values specified in this parameter may be added together. This allows you to collect combinations of nodal information in a single run. Choose from: 0 = no printout, 1 = nodal velocities,

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8 = nodal pressures, 16 = nodal temperatures, 64 = nodal turbulence intensities, 128 = nodal turbulence dissipation rates, 1024 = nodal displacements, 8192 = surface heat fluxes, and 32768 = nodal magnetic potentials

SDEBUG specifies the level of solution debugging messages to be captured. These messages are written to the p.out file. Choose from: 0 to capture no solution debugging messages, or 1 to obtain information concerning, solver performance, time step control, and the free surface model

TENDFILL specifies the delay after the end of the filling at which to terminate a ProCAST analysis. If this parameter is zero, this parameter will not be active. If one wants to stop the calculation right after the end of the filling, one should set a small value, different from 0. Enter a floating (real) value. Select the units of time from: {sec | min}

TFINAL specifies the simulated time at which to terminate a ProCAST analysis. If this parameter is zero, the run will be stopped by the TSTOP or NSTEP parameter. If NSTEP and TSTOP and TFINAL parameters are set, the simulation will be terminated based upon which parameter is reached first. Enter a floating (real) value. Select the units of time from: {sec | min}

TSTOP specifies the temperature at which to terminate a ProCAST analysis (i.e. when all the temperatures at all nodes are below the TSTOP temperature). If this parameter is zero, the run will be stopped by the TFINAL or NSTEP parameter. If NSTEP and TSTOP and TFINAL parameters are set, the simulation will be terminated based upon which parameter is reached first. Enter a floating (real) value. Select the units of Temperature from: {C | K | F}

TMODR specifies the time step modification factor for restarts. If MAXCOR correction steps are taken without convergence, the time step is multiplied by TMODR. Therefore, this number should be less than 1. Enter a floating (real) value.

TMODS

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specifies the time step modification factor for normal stepping. If the number of correction steps is less than or equal to NCORL, the subsequent time step is multiplied by TMODS. If the number of correction steps is greater than or equal to NCORU, the subsequent time step is divided by TMODS. Enter a floating (real) value.

Units

PUNITS specifies the pressure units to be used in the outputs. Choose from: {N/m**2 | Pa | KPa | MPa | bar | dyne/cm**2 | atm | psia | Ksi | lb/ft**2}

QUNITS specifies the heat flux units to be used in the outputs. Choose from: { W/m**2 | cal/cm**2/sec | cal/mm**2/sec | Btu/ft**2/sec | Btu/in**2/sec | cal/cm**2/min | cal/mm**2/min | Btu/ft**2/min | Btu/in**2/min}

TCUNITS specifies the thermocouple units to be used in the outputs and is only used for inverse modeling. Choose from: {C | F | R | K}

TUNITS specifies the temperature units to be used in the outputs. Choose from: {C | F | R | K}

VUNITS specifies the velocity units to be used in the outputs. Choose from: {m/sec | cm/sec | mm/sec | ft/sec | in /sec | m/min | cm/min | mm/min | ft/min | in/min} The choice of the units does not have any effect on the calculated results.

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Thermal Run Parameters

The Thermal model activation, the Temperature results storage frequency, as well as the Porosity model and parameters are the main parameters to be defined in this tab.

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Thermal

CINIT Reserved for future use.

CLUMP specifies the capacitance matrix lumping factor. Enter: 0 to use consistent matrix, or 1 to use diagonal matrix

CONVT specifies the convergence criterion for temperature. A value of around one degree is generally appropriate. Values larger than the mushy (liquidus--solidus) zone range are not recommended. Enter a floating (real) value. Select the units of temperature from: {C | F | R | K}

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DRAINFS For LPDC, it is possible to "drain" the remaining liquid in the inlet sprue region which is still liquid when the pressure is released. DRAINFS corresponds to the critical solid fraction below which the metal is drained. This means that all the metal which has a solid fraction below DRAINFS which is connected to the pressure or inlet boundary condition location will be drained (i.e the metal will be removed). This value should be used in conjunction with DRAINTIME. Enter a floating (real) value between 0 and 1. This Run parameter has to be added manually in the p.dat file. The default value is 0.7.

DRAINTIME For LPDC, it is possible to "drain" the remaining liquid in the inlet sprue region which is still liquid when the pressure is released. The value of DRAINTIME corresponds to the time at which the pressure is released and thus the time at which draining will occur. The unit code of time should be specified before the time (e.g. 1 for seconds). This value should be used in conjunction with DRAINFS. Enter a floating (real) value after the unit code of time (e.g. DRAINTIME 1 25.). This Run parameter has to be added manually in the p.dat file.

FEEDLEN "Feeding length" (distance), at which macroporosity can occur, beyond the MACROFS isosurface. Enter a floating (real) value.

GATEFEED allows to specify whether liquid can be fed at the ingate or not. In the case of injection (i.e. hpdc or lpdc), the shrinkage at the gate is compensated by the liquid pushed by the piston (for hpdc). On the other hand, in gravity casting, there is no feeding at the top of the risers and piping will occur. GATEFEED=1 tells the software to activate the feeding at the ingate, thus leading to no piping at this location. GATEFEED=1 will automatically activate the "Active feeding" where inlet velocities or pressures are set (see the "Active Feeding" section for more details). Enter an integer value.

GATEFS GATEFS allows to control the critical fraction of solid above which there is no more feeding during the third stage pressure in HPDC (see the "Active Feeding" section for more details). This Run Parameter has to be added or modified manually in the p.dat file (it does not appear in PreCAST). A higher value of GATEFS will involve less porosity. Enter a value between zero and one. The default value is 0.95.

GATENODE GATENODE is an alternative to GATEFEED. When a gate feeding should be applied, but there is no external surface of the model where an inlet surface or a pressure can be applied. This is the case for instance when a shot piston is

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modeled. In such case, one can define a location in the volume where this gate feeding is applied (typically in the middle of the biscuit). In order to define this location, the corresponding node number should be specified. In such case, no pressure or inlet velocity BC needs to be specified. To find the desired node number, it is advised to use the "pick" selection in ViewCAST (Run DataCAST first) (see the "Active Feeding" section for more details). Enter an integer value.

LINSRC specifies the source term linearization parameter for micromodels. This parameter may be used in conjunction with micromodels that control the evolution of the solid fraction and thus the release of latent heat. The default value of zero indicates that the heat generation will only appear in the right hand side source term. A value of one will give some contribution to the diagonal terms of the left hand side matrix. This improves numerical stability, but does require that the LHS be factored, which would normally happen anyway. Enter: 0 = no linearization, or 1 = for linearization of the source term

MACROFS Parameter for the macroporosity calculation. It sets the limiting fraction of solid between the macroporosity and the microporosity formation. The value should be set between 0 and 1. Enter a floating (real) value.

MOBILE The mobility limit, MOBILE, determines the critical liquid fraction at which the fluid is no longer able to flow. When considering the development of pipes in risers, higher mobility limits will produce deeper pipes. MOBILE will also control the motion of pistons in shot sleeve (HPDC). The piston will not move anymore when the higher solid fraction of an element in contact with the piston is higher than (1-MOBILE). Enter a floating (real) value.

MOLDRIG The rigidity of the mold has an influence on the amount of porosity in the case of expanding alloys. If the mold is totally rigid, the casting can not expand and thus the alloy expansion will be "available" for the "refill" of the existing porosity. On the other hand, if the mold is very soft (or weak), the casting will expand and thus there will be no "refill" of the porosity (of course, the reality is more complex as the solid shell is thick enough it will act as a "rigid" mold, even if the sand mold is weak. In order to take the mold rigidity into account, the Run Parameter MOLDRIG is used (see the "Cast Iron Porosity model" section for more details). MOLDRIG

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should be defined by a value between 0 and 1. All the net expansion is multiplied by MOLDRIG. Thus, with MOLDRIG=1, corresponding to a rigid mole, the expansion will be fully accounted. On the other hand, no expansion will be taken into account if MOLDRIG=0. The expansion will be compensated by the mold movement because the mold is too weak to hold the expansion in this case. For real situations, the value of MOLDRIG should be set somewhere between 0 and 1 depending upon the casting processes. The default value is 1.

PIPEFS Parameter for the piping calculation (during a porosity calculation). It sets the limiting fraction of solid for piping formation. The value should be set between 0 and 1. In order to disable the porosity calculation, one should set POROS = 0. However, this may still lead to some piping calculation. In order to disable also the piping, one should set in addition PIPEFS = 0. For stress calculations, PIPEFS must be set to 0. This is needed in order to prevent the unexepected influence of the pipe on the stress calculation. One should note that if in the physical sitution, piping must occur, this will be taken into account in the calculation as "macropores" when PIPEFS = 0. Enter a floating (real) value.

POROS specifies the porosity calculations to be performed (see the porosity models description). Choose from: 0 for no porosity calculation, 1 - most advanced porosity model 4 - evolution of the POROS=8 model, which allows to handle multiple free surfaces 8 - old porosity model from version 3.2.0 In order to disable the porosity calculation, one should set POROS = 0. However, this may still lead to some piping calculation. In order to disable also the piping, one should set in addition PIPEFS = 0.

QFREQ specifies the time step interval for writing heat flux data to the unformatted results file. This parameter can be used to reduce the size of the prefixq.unf file. Heat flux results may not be of interest to everyone, so it may be desirable to minimize the size of this file. Enter an integer value.

TFREQ specifies the time step interval for writing temperature data to the unformatted results file. This parameter can be used to reduce the size of the prefixt.unf file, which can become quite large for problems with many nodes and time steps. Note that it is only possible to restart a run from one of the time steps that was written out.

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Enter an integer value.

THERMAL specifies the thermal analysis to be performed. Choose from: 0 for no thermal analysis. Solve flow equations alone, 1 to perform thermal analysis, using temperature as the primary variable, or 2 to perform thermal analysis, using enthalpy as the primary variable

TRELAX specifies the temperature relaxation parameter. This is used for computing the initial guess for the temperature field in the predictor step. TRELAX should be greater than or equal to zero and less than or equal to one. Enter a floating (real) value.

USERHO specifies the how the density in the mushy zone is calculated. Choose from: 0 - automatic density calculation, by extrapolation of the densities at liquidus and solidus, weighted by the fraction of solid. 1 - the density table, which is defined in the database is used.

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Cycling Run Parameters

When cycling is modeled, one should define the corresponding Run Parameters in this tab (number of cycle and cycling time). In addition, when "Die Combo" interface definitions are used, additional parameters should be set.

CYCLEF CYCLEF allows to perform a filling calculation at the last cycle. This means that the N-1 cycles are run with a thermal only calculation and for the last cycle (N) a filling-thermal calculation is performed.

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The casting should be set as empty and the inlet boundary conditions (thermal and velocity/inlet) should be defined (these will be applied only during the last cycle and will be ignored during the first N-1 thermal cycles). When CYCLEF is ON, FLOW should be set to 9 (instead of 3). Please note that if a value of 1 is used for FLOW, the flow (i.e. natural convection) will be activated during all cycles (and the filling will be applied only to the last one). Although this is possible, this is not really useful and it is thus not advised to do so. Enter an integer value. CYCLEF OFF corresponds to a value of 0 (default), whereas a value of 1 corresponds to ON.

NCYCLE specifies the number of casting cycles to be simulated in a continuous mode. This parameter is used along with TCYCLE. Both NCYCLE and TCYCLE must be set. This parameter is typically used in die casting and permanent mold problems. Enter an integer value.

TCYCLE specifies the time of casting cycle to be simulated in a continuous mode (duration of a cycle). This parameter is used along with NCYCLE. Both NCYCLE and TCYCLE must be set. Enter a floating (real) value. Select the units of time from: {sec | min}

TOPEN specifies the time at which the mold opens, during one casting cycle. This is used in conjunction with the "Die Combo" interface definition. Enter a floating (real) value. Select the units of time from: {sec | min}

TEJECT specifies the time at which the part is ejected from the mold, during one casting cycle. This is used in conjunction with the "Die Combo" interface definition. Enter a floating (real) value. Select the units of time from: {sec | min}

TBSPRAY specifies the time of the beginning of the spray sequence, during one casting cycle. This is used in conjunction with the "Die Combo" interface definition. Enter a floating (real) value. Select the units of time from: {sec | min}

TESPRAY specifies the time of the end of the spray sequence, during one casting cycle. This is used in conjunction with the "Die Combo" interface definition. Enter a floating (real) value. Select the units of time from: {sec | min}

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TCLOSE specifies the time at which the mold closes (before the start of the next filling), during one casting cycle. This is used in conjunction with the "Die Combo" interface definition. Enter a floating (real) value. Select the units of time from: {sec | min}

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Radiation Run Parameters

When a calculation with Radiation, including View Factors is run, the following parameters should be defined. If the "View factor OFF" option is selected, it is not needed to define these Run parameters.

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ANGTOL specifies the angle tolerance to be used with VFLIM. Radiation faces which are grouped using VFLIM tolerance are further differentiated by their solid angle. Enter a floating (real) value.

ENCLID specifies an enclosure identification number. This parameter is used in combination with VFDISP for updating view factors by a displacement interval. ENCLID indicates which enclosure set is to be tracked, in case all the enclosure elements are not moving at the same rate. Enter an integer value.

EPTOL specifies the emissive power tolerance to be used with VFLIM. Radiation faces which are grouped using VFLIM tolerance are further differentiated by their solid angle. Enter a floating (real) value.

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RDEBUG specifies the user debug parameter for printing detailed view factor information. Various combinations of these files may be obtained by adding together these numbers. For example, RDEBUG = 7 gives all three files. Note that these files can be quite large, especially the prefix.vf. Enter an integer value based upon the following: 1 for face to face view factors after symmetrization, in the prefix.vf file, 2 for face to group view factors after symmetrization, in the prepfix.view file (necessary to see FACE TO GROUP in ViewCAST), or 4 for row sum errors before symmetrization, in the prefix.serr file (necessary to see ROW SUM ERRORS in ViewCAST

RFREQ specifies the radiation update frequency. This provides a mechanism for recomputing the radiosities at some time step interval other than one. This is particularly useful if you are performing a filling transient along with the view factor radiation model. In this case, the time step size may be small due to the filling whereas the mold temperature may not be changing very rapidly. You can save some computational time by recomputing the radiosities at every tenth step, for example. Enter an integer value.

TRI2QUAD specifies the option to group or not triangles into quadrangles for the radiation view factor calculation. When TRI2QUAD is set to 1, adjacent triangles are grouped in order to obtain quadrangles (providing the angle between the triangles is not too large). This has the effect of reducing the number of radiative face (by about 50%) which is cutting down the CPU time significantly (by about 75%).

VFDISP specifies the displacement interval for updating view factors in the radiation model if there are moving relative surfaces. This is used in conjunction with ENCLID and will be used in preference to VFTIME if both are specified. Enter a floating (real) value. Choose the units of length from: {m | cm | mm | ft | in}. The default is m.

VFLIM specifies the view factor limit. This parameter is used to agglomerate faces in the view factor calculations. This reduces the size of the radiosity matrix and speeds up the radiation calculations.

VFLIM can be set to a fraction between zero and one. If one face occupies less than this fraction of the total view space, as seen from another face, the first face is combined with some others. A value of 0.01 is a good starting point. Enter a floating (real) value.

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VFTIME specifies the time interval for updating view factors in the radiation model if there are moving relative surfaces. Enter a floating (real) value. Choose the units of time from: {sec | min}. The default is sec.

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Flow Run Parameters

When fluid flow and/or filling models are activated, the "Flow" Run Parameters should be defined. The main parameters are present in the "Standard" tab. In the "Advanced 1" tab, one should mainly define the WSHEAR and the WALLF parameters. In most cases, all the other parameters can remain as the default values.

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ADVECTW specifies the weighting of advection velocities and controls the degree of non-linearity of the momentum equations. ADVECTW can take on values between zero and one. Velocities at the last time step are used as the advecting velocities if a value of zero is used. Velocities at the current time step are used as the advecting velocities if a value of one is used. Numerical experience has shown that the accuracy of natural circulation flows can be enhanced by using a factor of 0.5. For most filling analyses, a value of zero works fine and requires much less computational time. Enter a floating (real) value.

COLDSHUT Disable the cold shut algorithm detection. If a "cold shut switch off" flag is activated (which is stopping the calculation) for an undesired reason, it is possible to disable this detection (and restart the calculation), by setting COLDSHUT = 0. The default value is 1. A cold shut will happen if for any given node in the fluid domain there is no valid connection all the way to the inlets. This path can be

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broken by 2 conditions: - solid fraction is above 1-MOBILE - FVOL < 0.5 (this can be due to a physical boundary, e.g. if there are two separate fluid cavities, or a bad mesh) The second condition may happen if the mesh has an anomaly, like for instance if an element is connected to the neighbors only through edges and not through at least one face. If this situation occurs, even for an isothermal case, the "cold shut switch off" will happen right at the beginning of the calculation. COMPRES specifies whether this is an incompressible flow problem or a compressible flow problem. Choose from: 0 to specify an incompressible flow problem, or 1 to specify a compressible flow problem

CONVV specifies the convergence criterion for velocity. The value given here is a fraction of the maximum velocity calculated at each step. Generally, .05 or 5% is appropriate. Enter a floating (real) value.

COUPLED specifies whether the energy and fluid solutions should be coupled or decoupled within a time step. When the analysis is decoupled, the momentum and pressure equations are solved repeatedly until convergence. Subsequently, the energy equation is solved until convergence, assuming the flow field is fixed. With a coupled analysis, the energy equation is solved in the same loop with momentum and pressure. Both the momentum and temperature convergence criteria have to be met to terminate the loop. This method is more accurate, but usually takes more computational time. Choose from: 0 to decouple energy and fluid solutions within a time step, or 1 to fully couple energy and fluid solutions within a timestep

COURANT specifies the courant limit on time step size. This parameter is only used for filling problems. If COURANT is set to 1.0, the time step will be adjusted so that the fluid will advance no more than one element length. This is a fairly severe limit on time step size, but will give the most accurate results for filling transients. Acceptable results can usually be obtained with values around 100. Enter a floating (real) value.

DETACHTOP allows to have a better treatment of the detachment of liquid which is in contact with horizontal top walls (like "roofs"). A value of 1 allows a better detachment of such liquid regions, however it takes some more CPU time. This Run parameter should be added/changed manually in the p.dat file.

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EDGE This Run parameter is not anymore available (however it should be set to 0 if present in the p.out file)

ENDFILL Sometimes, the user may not be interested by the filling of the last percents (e.g. the end of the filling of a riser or an overflow). If ENDFILL = 0.98, once 98% will be reached, the remaining 2% will be filled in one timestep.

FFREQ specifies the flow update frequency. This provides a mechanism for re-computing the velocities at some time step interval other than one. This might come into play if you were solving a conjugate heat transfer problem where the velocity field is changing on a longer time scale than the temperatures. This option is not appropriate for free surface problems. Enter an integer value.

FGROUP The mass balance correction algorithm at the free surface in the case of multiple free surface (e.g. multiple inlets) is governed by FGROUP. With FGROUP = 0, the free surface is considered as a single entity and the mass balance correction is performed globally on the whole free surface. This algorithm is not working very well in the case of multiple free surface (e.g. with multiple inlets). In order to obtain a well balanced filling in the case of multiple inlets one should activate a more sophisticated algorithm with FGROUP=2. FGROUP = 2 is the default value for both the Scalar and the DMP solvers (please note that FGROUP = 1 is not anymore recommended). Enter an integer value. Default value : 2.

FLOW controls the use of fluid equations. Choose from: 0 do not solve fluid equations, 1 to solve fluid equations, 3 to solve fluid equations during filling, but switch over to thermal only analysis when the LVSURF fill limit is reached and NCYCLE = 1, 9 to solve fluid equations during filling, but switch over to thermal only analysis when the LVSURF fill limit is reached and NCYCLE > 1. FLOW must be set to 9 when CYCLEF is activated (see the "Cycling Run Parameters" sectoin for more details). The default is 0 if there are no "Casting" materials. If "Casting" materials exist, the default is 1.

FLOWDEL specifies the delay time between the end of fill and a switch to a thermal only, in the case of FLOW = 3 simulation. This option is used in conjunction with velocity boundary conditions with active fill limits. The time delay corresponds to the time

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for the fluid to completely settle down in the casting before the thermal only phase begins. Enter a floating (real) value. Select the units of time from: {sec | min} The default is sec.

FREESF specifies the free surface model number to be used. Choose from: 0 = no free surface model activated 1 = use the momentum dominated movement of free surface, rapid filling model, 2 = use the gravity dominated movement of free surface, slow filling model.

FREESFBAL In the case of large horizontal free surfaces (e.g. bottom filling of large ingots, filling of a "swimming pool"), the free surface may be not as calm as it should be. In order to stabilize the free surface (and to avoid unexpected waves), the calculation of the mass balance of partially filled elements at the free surface was refined. This can be activated with FREESFBAL = 2. This should be activated only for gravity filling with large horizontal free surfaces and not in other cases. The Run parameter FREESFBAL should be added manually in the p.dat file. 0 = default value (no special treatment of the partially filled elements) 2 = improved algorithm for the calculation of the mass balance of partially filled elements at the free surface (to be added manually in the p.dat file)

FREESFOPT The filling algorithm (in the case of FREESF = 1) was significantly improved in version 2006.0. From now on, three filling algorithms are available : FREESFOPT = 0 : it corresponds to the filling algorithm of version 2005.0. It is less precise than the two other algorithms, however it is the most robust algorithm. FREESFOPT = 1 and 2 corresponds to two improved filling algorithms. The difference between these two algorithm is the "numerical balance" between the mass conservation contribution to the free surface and the momentum contribution. With FREESFOPT = 1, the mass conservation contribution is more important than the momentum contribution. This algorithm is more robust, but may lead to slightly less precise results. With FREESFOPT = 2, the momentum contribution is predominant over the mass conservation contribution. This model is supposed to be the most precise, however it is more sensitive to the quality of the mesh. In order to have good results with FREESFOPT = 2, the mesh should be well adapted to the local free surface (e.g. one should have enough nodes in the stream of the liquid in the case of a thin jet of liquid). This means that the FREESFOPT = 2 algorithm is less robust as the 1 (or the 0). As a conclusion, it is strongly advised to use FREESFOPT = 1 in most cases. If more precision is required, the mesh should be refined and well tuned so that FREESFOPT = 2 could be used. The FREESFOPT = 0 option is provided for backwards compatibility purposes, however, it is not advised to be used. The default value is 1.

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GAS specifies whether or not to consider the trapped gas effects. If the option to consider trapped gas effects is chosen, trapped gas effects will be considered even when the model contains no vents, gas injection, or gas diffusion through the mold. When features normally found in a gas problem (vents, injection, or gas diffusion through the mold ) are present in a model, GAS will be set automatically. Choose from: 0 to not consider trapped gas effects, or 1 to consider trapped gas effects

HEAD_ON specifies the approach to be used when calculating gravitational term in the momentum equation for flow problems without free surfaces. Choose from: 0 = calculate as rho - rho_ref, or 1 = calculate as rho * g

HIVISC specifies different solution methods for viscosity in the flow problem. Choose from: 0 = normal flow problem, 1= high viscous flow problem. To be used when the Reynolds number is less the one. This method only works for viscosity less than 104 poise. In this case, the advection terms are neglected, symmetric solvers are employed on the momentum equations, and large degrees of pressure relaxation are utilized, or 2 = very high viscous flow problem. To be used when the Reynolds number is less the one. This method is always preferred. In this case, the advection terms are neglected and momentum effect on implicitly included within a Poisson pressure equation. This option usually allows for much larger time steps than HIVISC = 1

JUNCTION JUNCTION is activating different algorithm for the calculation of the "metal front tracking" and metal movement during the filling. This allows to track where the particles and impurities are most likely to be accumulated and to view the flow junction lines. As this algorithm is taking an amount of CPU time which may not be negligible, by default this calculation is not activated (JUNCTION = 0). To activate it, one should set JUNCTION to 1, 2, 3, 4, 11, 12, 13 or 14 in the p.dat file (this Run parameter should be added manually in the p.dat file). For the description of the meaning of the different values, see the "Results analysis/Fluid Front Tracking" section for more details. Enter an integer value of 0, 1, 2, 3, 4, 11, 12, 13 or 14 (default : 0).

LVSURF provides a way to switch from the filling transient to a mode where advection is due to buoyancy and shrinkage. LVSURF turns all inlets off. It is assumed thereafter that the free surface is perpendicular to the gravity vector. This allows

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the time step to increase significantly. The number represents the fraction of the total casting volume which is to be filled before changing modes. Enter a floating (real) value.

MLDUPDT specifies the material properties update frequency (in the mold only). For large casting (when a mold is present), it the calculation can be slightly speed-up by reducing the frequency of update of the material properites (reducing the number of matrix operations). The integer which is specified after corresponds to the update frequency. By default the value is 1. See the "Large Ingot filling" section for more details. Enter an integer value.

MLUMP specifies the mass matrix lumping factor. Choose from: 0.0 to use a consistent matrix, or 1.0 to use a diagonal matrix

NNEWTON specifies whether the flow is newtonian or non-newtonian. Choose from: 0 to indicate Newtonian flow, or 1 to indicate non-newtonian flow, where viscosity is a function of shear rate

PENETRATE Flag to activate the algorithm of inter-penetrating meshes (with a value of 1). This is used especially for the modeling of a shot piston in hpdc. Enter an integer value.

PFREQ specifies the "Particle tracing" launch frequency in the solver. Particles are launched at each node of the inlet (defined by a velocity BC, an inlet pressure BC or an Inlet BC), every PFREQ steps. A value of 50 is recommended (see "Display parameters" for the description of Particle tracing) Enter an integer value.

PINLET specifies a pressure driven inflow. Setting PINLET to 1 indicates that all the pressure boundary conditions are also inflow boundary conditions. Use of this option allows one to avoid using thin filled regions at the inlets of pressure driven problems. It allows for filling of metal without having an initial layer of fluid. Enter an integer value of 0 (off) or 1 (on).

PLIMIT specifies the pressure cutoff limit. You can use this parameter to turn off an inlet velocity when the back pressure exceeds the given value. This is useful particularly in cases where cold shuts are occurring. Otherwise, the program will

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keep trying to force more mass into the fluid region, even though there is no place for it to go, and the pressure will continue to rise. Enter a floating (real) value. Choose the pressure units from: {N/m**2 | Pa | KPa | MPa | bar | dyne/cm**2 | atm | psia | Ksi | lb/ft**2}

PREF specifies the pressure which is to be subtracted from any boundary condition pressure in order to convert an absolute pressure into a gauge pressure. This parameter comes into play when: (1) there is trapped gas, (2) a pressure boundary condition drives the flow, (3) there are vents, and/or (4) there is gas injected. For example, if the pressure boundary condition drives the flow at a gauge of 1 atmosphere, the boundary condition is set to 2 atm. PREF should be set to 1 atm. Enter a floating (real) value. Choose the pressure units from: {N/m**2 | Pa | KPa | MPa | bar | dyne/cm**2 | atm | psia | Ksi | lb/ft**2}

PRELAX specifies the pressure relaxation factor. PRELAX, to have an effect, should be greater than zero and less than one. If it is left to the default value of one, ProCAST will automatically compute an appropriate relaxation factor. Enter a floating (real) value.

RELVEL For centrifugal casting, the fluid flow should be solved in a Relative velocity reference frame (i.e. in a rotating velocity reference frame). Thus, for centrifugal casting cases, one should set RELVEL to 1. This Run parameter should be added manually in the p.dat file (it does not appear in PreCAST). 0 = standard case - no centrifugal (default value) 1 = activation of the relative velocity reference frame - to be used for centrifugal casting. Enter an integer value.

TILT For Tilt pouring problems, one should activate the "Tilt" mode, by setting TILT to 1. This improves the appearance of undesired sticking in the pouring cup. This Run parameter should be added manually in the p.dat file (it does not appear in PreCAST). 0 = standard filling mode (default value) 1 = activation of the Tilt mode Enter an integer value.

TOFRSF2 TOFRSF2 allows to switch the filling algorithm from FREESF = 1 to FREESF = 2 automatically when the specified fill fraction is reached. This option should be used for Large ingot filling (see the "Large Ingot filling" section for more details). The fill fraction for the transition should be specified as a real value (e.g.

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"TOFRSF2 0.01" corresponds to a transition at 1% of filling). Please note that FREESF should be set to 1 when TOFRSF2 is used. Enter an real value.

TOPFILL TOPFILL is used for the top filling of large ingots (see the "Large Ingot filling" section for more details). TOPFILL should be used in conjuction with a mass source. 0 = deactivated (default value) 1 = activated

TPROF This parameter defines the type of algorithms which are used to calculate the temperature in the case of advection along a mold wall (i.e. in the case of fluid flow along a wall). The two following situations are considered : a) In order to account for thermal boundary layers at the mold wall (in the case of fluid flow), the temperature of the nodes which are close to the wall (like Node C in the figure below) can be computed in two different ways. The temperature of Node C is a function of the temperature of the nodes backwards (i.e. Nodes A and B which are behind - look at the direction of the flow indicated by the green arrows). The temperature of Node C can be either a linear interpolation between the temperatures of Nodes A and B (corresponding to T0 in the figure below). This is the case with TPROF = 0. In order to better account for the thermal boundary layer (corresponding to the red temperature profile in the figure below), the temperature of Node C will be taken as T1 (which is larger than T0 and thus closer to the temperature of Node A). This is the case with TPROF = 1. It is highly recommended to use TPROF = 1 which is much closer to the reality, especially when the mesh is coarse. This algorithm is valid for all liquid nodes which are in the elements next to the wall, but are not themselves on the wall.

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b) Beside the algorithm described above, one should also compute the temperature of the wall nodes which are just beyond the free surface (see Node D in the figure below which is in the air at time t1 and which is at the free surface at time t2). The green arrows are showing the direction of the velocity. When TPROF = 0, the temperature of Node D is taken as the one of the closest node, which may be either a core or wall node, (e.g. the one of Node C in the example of the figure below). When TPROF = 2, the temperature of Node D is taken as the closest surface node (i.e. node B). This algorithm is active only for the wall nodes which are at the free surface.

As a consequence, the free surface temperature at the mold wall will be "colder" in the case of TPROF = 2 than with TPROF = 0. One should also be aware that when TPROF=2 is used, the TPROF=1 algorithm described above in a) will be deactivated. In order to have both algorithms active, one should use TPROF = 3. The default value is TPROF = 1.

TSOFF This parameter specifies the time at which to switch off the flow solution. For example, TSOFF 1 42, indicates that the flow solution will be turned off 42 seconds into the simulation. If a cyclic analysis is being performed, then the flow solution will be turned off 42 seconds into each cycle. Choose from: 0 = turns this option off, or a real value sets the time Enter a floating (real) value. Choose the time units from: {sec | min}.

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VFREQ specifies the time step interval for writing velocity and pressure results to the unformatted files. This parameter can be used to reduce the size of these results files, which can become quite large for problems with many nodes and time steps. Note that it is only possible to restart a run from one of the time steps that was written. Only the steps that are written can be viewed with post-processing. Enter an integer value.

VPROF This parameter indicates that a flow boundary layer profile is used at the wall for the momentum equation with advection. This has been found to reduce false diffusion errors, although it is not very useful with WSHEAR=2. Choose from: 0 = do not use boundary layer profile, or 1 = use boundary layer profile Enter an integer value.

WALLF WALLF is used to compute the velocity of the free surface at the mold wall (not used away from the free surface). In order to compute the velocity of the free surface at the mold wall, one takes the core velocity of the closest core node (i.e. closest node in the volume). The surface velocity at the free surface is equal to the core velocity of this closest node multiplied by WALLF. This algorithm is applied for any value of WSHEAR. A value of 0.99 corresponds to more slip along the wall, whereas a value of 0.8 will act as if the mold surface is rougher (more friction). It is advised to use a value of 0.8 for sand gravity casting and LPDC casting, a value of 0.9 for gravity die casting and a value of 0.99 for high pressure die casting (HPDC). The default value is 0.9.

WSHEAR The WSHEAR algorithm (wall shear) allows to take into account a velocity boundary layer along mold wall. It allows to have non-zero velocities at the mold walls, which is more representative of the reality (slip of the liquid along walls). This is valid at all liquid-mold interfaces and not only at the free surface (whereas the WALLF algorithm is valid only at the free surface). Physically, the velocity at a mold wall is zero (in the figure below, the velocity of Node B should be zero, represented by the green dot). However, a velocity boundary layer (see the red velocity profile) is present and the velocity close from the wall is very quickly not zero anymore. As the mesh size is most of the time larger (or much larger) than the velocity boundary layer thickness, the wall velocity is computed in order to reflect the velocity just away from the wall (the velocity will correspond to v1 shown with the blue dot in the figure below).

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When WSHEAR = 0, the velocities at the mold wall are always zero. With WSHEAR = 1 or 2, the velocities at the mold walls are computed in order to account for the boundary layer. The difference between WSHEAR 1 and 2 corresponds to laminar or turbulent boundary layers (please note that the thickness of the boundary layer is influenced by the viscosity of the alloy). The figure below is showing a zoom on the boundary layer with the wall velocities corresponding to different values of WSHEAR.

For HPDC and Gravity casting, a value of WSHEAR = 2 is recommended (however, for large gravity casting a value of WSHEAR = 0 should be used). For LPDC, a value of WSHEAR = 0 must be used.

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Turbulence Run Parameters

CMU specifies the proportionality constant used in the turbulent viscosity equation. Enter a floating (real) value.

CONE specifies the proportionality constant used in the production of turbulent energy dissipation. Enter a floating (real) value.

CTWO specifies the proportionality constant used in the destruction of turbulent energy dissipation. Enter a floating (real) value.

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KAPPA specifies the Von Karman's constant, usually taken as 0.4 Enter a floating (real) value.

SIGMAE specifies the diffusivity modifier used in the turbulent energy dissipation transport equation. Enter a floating (real) value.

SIGMAK specifies the diffusivity modifier used in the turbulent kinetic energy transport equation. Enter a floating (real) value.

TBRELAX specifies the turbulence relaxation parameter. Enter a floating (real) value.

TURB specifies whether the turbulent flow model is turned on or off. A model started with TURB = 1 can be restarted at a later time with TURB = 0. This allows laminar conditions to be considered during mushy or natural circulation flows. Once TURB has been set to zero, the turbulence model can not be restarted at a later time. Setting TURB to one for a flow problem which has no turbulence boundary conditions assigned is OK; the software will automatically define them. Enter: 0 to turn the turbulent flow model off, or 1 to turn the turbulent flow model on

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Stress Run Parameters

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AVEPEN AVEPEN corresponds to the "Average Penetration". This corresponds to the maximum average penetration which is allowed during the calculation. During the calculation, the PENALTY is automatically changed in order that the penetration is not larger than AVEPEN. The goal is to have the lowest possible PENALTY number to speed-up convergence, and AVEPEN allows to set the upper limit. The default value of AVEPEN is 0.1 mm. For large casting, it is advised to increase the value of AVEPEN for faster convergence.

CLAYERS CLAYERS operates in conjunction with GLOAD = 1. CLAYERS controls the number of layers of nodes, starting from the wall, that have a zero displacement constraint applied while the nodal fraction solid is less than CRITFS. If CLAYERS = 1, for example, then once the wall nodes have solidified (fs >= CRITFS), there will be no more zero displacement constraints applied automatically to the casting. (Displacement BCs applied by the user will still be

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active.) By contrast, if GLOAD = 0, then all the unsolidified nodes of the casting will be constrained, which limits the effect of gravitational load. Default value : 3

CRACK The cracking indicator model is activated with CRACK = 1 or 3. By default, the value of CRACK is set to zero. This Run parameter is not available in the Run Parameters menu and it should be added manually in the p.dat file. CRACK = 1 activates the cracking model, without feedback on the stress properties CRACK = 3 activates the cracking model, with a feedback on the stress properties. In this case, the hardening properties are changed, according to the cracking model.

CRITFS This corresponds to the critical fraction of solid where the stress calculation starts. By default, it is set to 0.5 (i.e. 50% fraction of solid). This critical value is also used for the computation of the hot tearing.

CONVS specifies the convergence criterion for the stress calculation. Enter a floating (real) value.

CYCL_ALGM During a stress calculation, together with cycling, "CYCLE_ALGM=2" is resetting the original mesh at the beginning of each cycle. In such case, the deformation is still accumulated. This method may prevent the creation of highly distorted elements, (i.e. Negative Jacobians) during successive cycles, due to too high accumulated distortions. If the calculation is able to go through the first cycle, the calculation of the other cycles should be then possible without problems. However, in the post-processing, we will still be able to see a mesh which is distorting more and more along the cycles. The default value is 1, which correspond to no special action and thus no re-alignment. Enter an integer value (default : 1).

GAPMOD specifies the treatment of the interface heat transfer coefficient. With a value of 1, the interface heat transfer coefficient is automatically modified to account for the air gap formation (an additional thermal resistance is computed as a function of the gap width, taking into account conduction and radiation through the air or vacuum). With a value of 0, the interface heat transfer coefficient which is defined in PreCAST will not be modified during the calculation.

GLOAD In the case of stress calculations, one should make sure that the casting is always in contact with the mold in the direction of the gravity. Moreover, especially for large heavy casting, it is better to take into account the casting weight on the mold. The Run Parameter GLOAD allows to take these two effects into account :

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GLOAD = 1 : in order to take into account the casting weight, the static pressure head is calculated and applied as an internal boundary conditions in the mushy zone (on the isosurface corresponding to the solid fraction defined by the Run Parameter GLOADFS - default value .8). This option is useful only for heavy castings. See the description of CLAYERS which is active in the case of GLOAD = 1. GLOAD = 2 : In order to guarantee that the casting is always in contact with the mold, in the direction of gravity, GLOAD should be set to 2. The algorithm will find the smallest gap in the direction of gravity between the casting and mold, and then move the casting down by that amount. Once the casting is in contact or penetrates the mold, this algorithm is deactivated. It is strongly advised to set GLOAD = 2 in all cases where the casting is not fully surrounded by a mold. GLOAD = 3 : activation of both models 1 and 2 described above. Remark : Please note that even with a casting weighing several tons, the pressure on the mold will be only a few MPa, to be compared with thermally induced stresses which can go for instance up to a few hundreds MPa. This Run parameter has to be added manually in the p.dat file. Default value : 0

GLOADFS As described above for GLOAD = 1, the static pressure of the casting is applied on the GLOADFS isosurface. If GLOADFS < CRITFS then, GLOADFS is automatically set to CRITFS. Default value : 0.8

LOADSCL When a load is applied in non-linear problem, it has to be applied incrementaly (within a timestep). LOADSCL is the number of increments for this loading. The higher the value of LOADSCL, the more accurate is the result (and the higher is the CPU time). This has to be used mainly for structure analysis type of problems (e.g. tensile test). For usual casting, as the loading is progressive (due to gradual temperature changes), it is not necessary to apply such increments. The default value of LOADSCL is 1. This value has to be added manually in the p.dat file.

PENALTY PENALTY controls the level of "penetration" allowed by the "contact algorithm". As the displacements are computed numerically at interfaces, there is always some penetration between two bodies (as long as they are touching). High values of PENALTY means that the allowed penetration is very small and this leads to a more difficult convergence of the algorithm. Small values of the PENALTY allows to have more penetration (which means a more easy convergence). The default value for Penalty is 1, but for thin sections, it could be advised to set it to 0.01. During the calculation, the PENALTY is automatically changed in order to optimize the CPU time and in order to be within the AVEPEN limit. When a calculation is restarted, it is advised to set the PENALTY to zero. In this case, the last PENALTY which was used in the calculation will be automatically

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set. If a non-zero value is defined, it will be used for the restart step. One should note that if the PENALTY was decreased during the calculation, to leave the default value may lead to a very long convergence at the restart step. Thus, it is strongly advised to set it to zero for a restart. The PENALTY at each stress timestep is indicated in the p.out file.

PENMOD Parameter which allows to scale the penalty number according to the local properties. With PENMOD = 1, the local contact penalty number is scaled according to the Young's modulus. Thus, in the mushy zone where this value is quite low, the penalty number will also scale down. The penalty value of the p.dat file will be used at Room temperature. Then, at high temperature, it will be scaled according to Youngs modulus. This results in a better balance between the contact force and the strength of the material to sustain it at all temperature. With PENMOD = 1, it allows to increase the global penalty number from the 1.e-2 (standard usual value) to 0.1 or even 1.0. With PENMOD = 0, the standard model, with a global PENALTY number is used. In such case PENALTY should be set to 1e-2 to 1e-3. Enter an integer value (Default value : 0).

SCALC specifies the time step interval the stress calculation is performed. It is thus possible to perform the stress calculation only every 10 thermal steps. SCALC and SFREQ are independent values and one will not affect the other. Enter an integer value.

SFREQ specifies the time step interval for writing stress results to the unformatted files. This parameter can be used to reduce the size of these files, which can become quite large for problems with many nodes and time steps. Note that it is only possible to restart a run from one of the time steps that was written. SCALC and SFREQ are independent values and one will not affect the other. One should however be careful that SFREQ is a multiple of SCALC. Enter an integer value.

STRESS specifies whether the stress calculation is turned on or off. Enter: 0 to turn the stress calculation off, or 1 to turn the stress calculation on

VACUUM When GAPMOD = 1, the interface heat transfer coefficient depends upon the gap width. With VACUUM = 0, air conduction is taken into account (i.e. a heat resistance corresponding to heat conduction through air is taken into account). With VACUUM = 1, no heat conduction is taken into account. In both cases, radiative transfer through the interface is taken into account (when there is a gap).

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This Run parameter should be added manually in the p.dat file.

Micro Run Parameters

EQNMAX First nucleation parameter of the dendritic primary phase. Maximum density of nuclei of the Gaussian distribution. EQSTD Second nucleation parameter of the dendritic primary phase. Standard deviation of the Gaussian distribution.

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EQUNDER Third nucleation parameter of the dendritic primary phase. Average undercooling of the Gaussian distribution. EUNUCL First nucleation parameter of the eutectic phase. Nucleation factor. EUPOWER Second nucleation parameter of the eutectic phase. Nucleation exponent. EUGROW Eutectic growth kinetics constant. FADING In the case of SGI, the melt is treated with Magnesium. Depending upon the volume of the melt (in ladle) or the type of treatment (e.g. "in mold" treatment), the Mg content can decrease with time (Fading effect), which will affect the graphite nodules. This is leading to a decrease of the expansion. The FADING Run parameter allows to calibrate the Fading effect. A value of 1 corresponds to a maximum Fading (i.e. the expansion potential disappears totally after about 20 minutes). With a value of 0, no Fading is occurring (i.e. we have always the same expansion potential). Between 0 and 1, we will have a reduced Fading effect (i.e. the smaller the value of FADING, the longer the expansion will be occurring). See the "Microstructures/Iron and Steel/Iron and Steel models" section for more details). FADING should be defined between 0 and 1. Default value : 1.0 GRAPHITE In the micro model for cast iron, the amount of "graphitisation" can be adjusted with the GRAPHITE Run parameter. A value of 1 corresponds to a maximum of graphitisation, whereas a value of 0 corresponds to no graphitisation. The larger the value of GRAPHITE, the larger the expansion of the cast iron will be. See the "Microstructures/Iron and Steel/Iron and Steel models" section and the "Cast Iron Porosity model" section for more details). GRAPHITE should be defined between 0 and 1. Default value : 1.0 MGTREAT For SGI, the graphite formation tends to diminish as the interval between the inocculation and the beginning of the solidification increases. This is accounted in the SGI micro model by the "fading" model (see the "Microstructures/Iron and Steel/Iron and Steel models" section and the "Cast Iron Porosity model" section for more details). In order to have an accurate "fading" model, it is necessary to account for the right amount of time between the inocculation and the beginning of the solidification. The value of MGTREAT corresponds to the time between the inocculation and the beginning of the calculation (which corresponds to the beginning of the filling or when the mold is full). Default value : 0 seconds.

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MICCPL The Microstructure model can be run in "Coupled" or "Uncoupled" modes (see the "Microstructures/Case set-up and Results" section for more details). This is activated in the Micro Run parameter panel by the button on the right of the MICRO Run parameter. This choice corresponds to the MICCPL Run parameter in the p.dat file. MICCPL = 0 (default value) corresponds to the "Uncoupled" mode. MICCPL = 1 corresponds to the "Coupled" mode. MICRO Activation of the microstructure module. The module is activated with a value of 1. PERGROW Pre-factor of the Growth kinetics of the pearlite. The default value is 0.0168. This value can be changed in order to calibrate the calculated amount of perlite (respectively of ferrite) with experimental observations. If the value is decreased, the amount of pearlite will also decrease, as the growth kinetics will be slower. Please note that the pearlite/ferrite fractions also depend upon the nodule count. Thus, it is advised to first calibrate the nodule count (EUNUCL, EUPOWER and EUGROW) first and then to calibrate PERGROW (together with PERNUCL). Default value : 0.0168 PERNUCL Nucleation parameter of the pearlite.Pre-factor of the Nucleation model of the pearlite. The default value is 5e6. This value can be changed in order to calibrate the calculated amount of perlite (respectively of ferrite) with experimental observations. If the value is decreased, the amount of pearlite will also decrease, as the number of pearlite nodules will be lower. Please note that the pearlite/ferrite fractions also depend upon the nodule count. Thus, it is advised to first calibrate the nodule count (EUNUCL, EUPOWER and EUGROW) first and then to calibrate PERNUCL (together with PERGROW). Default value : 5e6 See the "Microstructures" chapter for more details about the models. It is possible to select the default values for a given system with the "Select Default Values" button.

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The default values correspond to the following table :

Default value of PERGROW : 0.0168 Default value of PERNUCL : 5e6

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Pre-defined Run Parameters

ProCAST allows to define "Pre-defined sets" of Run Parameters in the Preferences.

When one clicks on the "Select Pre-defined Set" button, a list of the available sets are displayed. Then, the user has to select the desired one. In the case below, six sets are available, among ten possible sets.

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The values contained in the Pre-defined sets correspond to the Recommended Run Parameters for each process. It is thus strongly advised to use these pre-defined sets or to customize them according to your specific processes (see below). The configuration of the Pre-defined sets can be easily performed by the user. One should just save the a "d.dat" file, with the desired Run Parameters in the "dat/pref" directory of the installation, under the name "predefined_x_p.dat", where x is a number between 1 and 10 (see below).

The label which appears in the Run Parameter window above should be included in the predefined file as follows (TITLE line) :

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Moreover, in the "dat/pref" directory, there is also a file named "default_p.dat". This file contains the "default" values of the Run Parameters which will appear when a new case is created. The user can change the content of this file (which has exactly the same structure as a normal p.dat file) at his convenience.

Run Parameters Recommendations

ProCAST provides the access to many Run parameters, in order to allow the treatment of all kind of situations. However, for an everyday use, only a few Run parameters have to be set or modified. This section is presenting the most "popular" Run Parameters that should be set, with proposed values, for each main family of processes. These parameters recommendations may be slightly different from previous versions, as the solver algorithms have been modified. These recommended Run parameters correspond to the one which are pre-defined in the "Pre-defined Run Parameters" window. It is thus advised to activate the "pre-defined" set corresponding to the process and then to set the appropriate stopping criteria.

For all processes

Stopping criteria (it is advisable to set a stopping criterion in order to limit the CPU time and avoid unnecessary storage of results) TFINAL TSTOP

Porosity POROS = 1 (this model is now recommended for all processes) MACROFS = 0.7 FEEDLEN = X (The value FEEDLEN depends upon the size of the mushy zone and thus, the size of the casting. A value ranging from a few millimeters to a few centimeters is recommended. This should be calibrated with experiments. A value of 0 is not advised as this will produce a uniform microporosity throughout the part, beside the macroshrinkage)

Gravity casting Timestep handling

DT = 1e-3 DTMAXFILL = 1e-1 DTMAX = 0.5 - 5 (depending upon the size of the model and thus the solidification time)

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Porosity PIPEFS = 0.3 GATEFEED = 0

Filling WSHEAR = 2 FREESFOPT = 1 WALLF = 0.8 LVSURF = 0.98

High pressure die casting (HPDC) Timestep handling

DT = 1e-6 to 1e-4 (it depends upon the initial velocity of the first stage) DTMAXFILL = 1e-2 DTMAX = 0.2 - 1 (depending upon the size of the model and thus the solidification time)


Filling WSHEAR = 2 FREESFOPT = 1 WALLF = 0.99 LVSURF = 1.0 PINLET = 1 for a pressure filling or PINLET = 0 for a velocity/inlet filling

Low pressure die casting (LPDC) Timestep handling

DT = 1e-3 DTMAXFILL = 1e-2 (it is important to limit the timestep during the filling of an LPDC part. A value of 1e-2 is recommended for filling time of about 5-20 s.). DTMAX = 0.2 - 1 (depending upon the size of the model and thus the solidification time)


Filling WSHEAR = 0 (never use WSHEAR = 2 for LPDC) FREESFOPT = 1 WALLF = 0.8 LVSURF = 1.0 PINLET = 1 for a pressure filling or PINLET = 0 for a velocity/inlet filling

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Tilt casting Timestep handling



Filling WSHEAR = 2 FREESFOPT = 1 WALLF = 0.8 TILT = 1 DETACHTOP = 1

Centrifugal casting Timestep handling



Filling WSHEAR = 2 FREESFOPT = 1 WALLF = 0.8 RELVEL = 1

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POROSITY MODELS

The different porosity models available in ProCAST are summarized hereafter. Then, a full description of each model is provided.

POROS = 1 The POROS = 1 model corresponds to the latest porosity model of ProCAST. It accounts for coupled micro and macroporosity, as well as pipe shrinkage. It can be applied to both gravity casting and injection (either hpdc or lpdc). This model can be used with or without flow calculations.

POROS = 4 The POROS = 4 model corresponds to the same model as POROS=8 (see below), with the additional treatment of multiple free surfaces for piping. This model can be used with or without flow calculations.

POROS = 8

The POROS = 8 model corresponds to the porosity model which was available in version 3.2.0 of ProCAST (using the POROS=1 Run Parameter of v3.2.0). Although this model is less sophisticated than the current POROS = 1 model, it was kept in this version for the users who have calibrated the model to their casting and who obtained good results in the past. The only difference between the current POROS=8 model and the one available in version 3.2.0 is the method used to compute liquid pockets. Thus, this may lead to slight differences between the versions. This model can be used with or without flow calculations. One should notice that even if POROS = 0 is set, piping will be still calculated and displayed. In order to disable the piping calculation (in the case of a THERMAL only calculation), one should set FREESF to zero.

To disable the porosity and piping calculations

In order to disable the porosity calculation, one should set POROS = 0. However, this may still lead to some piping calculation. In order to disable also the piping, one should set in addition PIPEFS = 0.

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POROS=1

Parameters of the model

POROS 1 (porosity model) MACROFS 0.7 (critical fs for porosity formation) PIPEFS 0.3 (critical fs for piping formation) USERHO 1 (flag to set the density model) FEEDLEN 1 5.0e-3 (critical feeding length)

It is necessary to define the gravity vector in order to have meaningful results with POROS=1.

Model

When a casting solidifies, pockets of liquid are created, surrounded by a mushy zone and then a solid shell. Automatically, the casting is divided into "regions" within which the fraction of solid is lower than one or that are bounded by walls (or symmetry planes). As solidification proceeds and depending upon the complexity of the geometry, the number of "regions" may increase with time. A region can thus be split in more regions. A region can disappear when all nodes have completely solidified.

When a "region" is cooling down, if the density is increasing with decreasing temperature (the usual case for most alloys), some shrinkage occurs. At each timestep, the accumulated shrinkage occurring at all the nodes which have a solid

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fraction equal to or lower than MACROFS, plus those nodes between the MACROFS and MACROFS + FEEDLEN isosurfaces, is computed. This shrinkage is then distributed according to the following scenarios: a) Find the highest point of the region that is on a free surface and has a fraction of solid lower than PIPEFS. In this case, piping occurs and the free surface of the casting (usually the riser) goes down by the amount corresponding to the shrinkage (For display purposes, in the pipe, the shrinkage porosity value is set to 1 and FVOL is set to a value below 0.5, so that it will exhibit piping, i.e. "empty nodes").

b) Find the highest point of the region that is on a free surface and has a fraction of solid higher than PIPEFS. In this case, macroshrinkage occurs at that point. This will also correspond to piping (same result as a) above). However, instead of showing an empty volume, it will have a "Shrinkage porosity" value of 1. (For display purposes, in the macroshrinkage, the shrinkage porosity value is set to 1 and FVOL is set to a value above 0.5, so that it will not exhibit piping, i.e. "empty nodes", but shrinkage).

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c) No nodes of the "region" are on a free surface with a fraction solid lower than PIPEFS. In this case, no more piping can occur and macroshrinkage in the bulk of the casting will appear. The macroporosity will appear at the highest most liquid point of the region (e.g. if there is a pocket of liquid which is surrounded by a mushy zone, itself surrounded by a solid shell, the macroporosity will start at the highest point of the liquid pocket). (For display purposes, in the macroporosity region, the shrinkage porosity value is set to any value and FVOL is set to a value above 0.5, so that it will not exhibit piping, i.e. "empty nodes", but shrinkage).

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During the same time, microporosity is computed in the following way: a) microporosity can appear only in the zone where the fraction of solid is in between MACROFS and 1. b) within this zone, two situations may occur : b1) there is still some mushy zone (or liquid) below MACROFS. In this case, microporosity can occur only at a distance higher than the value of FEEDLEN from the MACROFS isosurface (Zone A in the figure below). This means that, if high gradients are present, the distance between the MACROFS and solidus isosurface is smaller than FEEDLEN, no microporosity occurs (Zone B in the figure below). The amount of microporosity is equal to the density change between the local fraction of solid and 1. b2) there is no more mushy zone below MACROFS. In this case, the FEEDLEN parameter is not active anymore and there could be microporosity in the whole region between MACROFS and 1. This is due to the fact that as there is no more "open liquid" to feed the shrinkage, local microporosity has to occur in order to compensate the local shrinkage. The amount of microporosity is equal to the density change between the local fraction of solid and 1.

c) on the other hand, if FEEDLEN=0, the amount of microporosity is the same throughout the part (except where there is macroporosity). In this case, the amount of microporosity is everywhere equal to the density change between Fs=MACROFS and Fs=1. d) if FEEDLEN is set to a very large value (larger than the casting side), the region between MACROFS+FEEDLEN is not existing anymore. Thus, no microporosity is created until the whole pocket is above MACROFS (i.e. no

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microporosity created according to b1) above). Then, microporosity can start to occur, according to b2) above. The amount of porosity is displayed in ViewCAST under the "Shrinkage porosity" Contour. The unit is volume fraction [-]. In general, values which are higher than 0.01 can be considered as macroporosity, whereas regions with a value lower than 0.01 correspond to dispersed microporosity. Symmetry planes are taken into account in the liquid pocket calculation (i.e. symmetry planes "close" the pockets, even if there is liquid at the symmetry wall. See the "Density definition" section for more details about how to define the density. See the "Active feeding" section for more details about feeding from the piston or the ingate in the case of hpdc and lpdc.

POROS=4


POROS 4 (porosity model) MACROFS 0.7 (critical fs for porosity formation)

Model This model is based upon the same algorithm as the POROS=8 model (see below). In addition, multiple piping can be considered. This means that piping occurs at the highest free surface of each region. Thus, one can have piping at the top of risers which are at different levels (this was not the case in version 3.2.0 and thus does not occur with POROS=8) See the "Density definition" section for more details about how to define the density.

POROS=8


POROS 8 (porosity model) MACROFS 0.7 (critical fs for porosity formation)

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In version 3.2.0, this Run parameters was called MO BILE (MOBILE still exists in version 2004.0 for other pu rposes. Thus, it should not be used anymore for porosity se ttings).

Model When the casting solidifies, pockets of liquid are created, surrounded by a mushy zone and then a solid shell. As soon as a pocket of liquid is surrounded by a zone which has a solid fraction higher than MACROFS, the density of each node inside the pocket (from fs=1 to fs=MACROFS) is recorded (as a "critical density"). Then, the amount of porosity of each of these nodes is equal to the density variation between this "critical density" and the density of the solid. Piping is occurring at the highest free surface of the model. Thus, if there are two separate regions with risers at different heights, only the highest one will exhibit piping, even if the lower one is in an isolated region. POROS=4 corrects this situation (see above). Symmetry planes are taken into account in the liquid pocket calculation (i.e. symmetry planes are "closing" the pockets, even if there is liquid at the symmetry wall. The amount of porosity is displayed in ViewCAST under the "Shrinkage porosity" Contour. The unit is volume fraction [-]. See the "Density definition" section for more details about how to define the density.

Density definition

For most alloys, the density at the liquidus is lower than the density at the solidus, thus leading to porosity. By default, the porosity module of ProCAST is using the density curve in the mushy zone which is defined in the material database (see the green curve in the Graph A below). However, if this density change in the mushy zone is not well known, it is possible to automatically calculate the density in the mushy zone, as an average of the liquid and solid densities, weighted by the fraction of solid. The density of the liquid and of the solid is calculated as a function of temperature, by extrapolating the density slopes at the liquidus and solidus respectively.

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The user has the possibility to activate this automatic density computation with the Run parameter USERHO. If USERHO is set to 0 (instead of 1 which is the default value), the density curve which is defined in the material properties, between the solidus and liquidus, will be ignored and the automatic density computation will be activated. (Please note that in version 4.x.x, the default value was 0). This is valid for all the Porosity models (POROS = 1, 4, 8).

Active Feeding

In the case of injection (e.g. high or low pressure die casting), for a while, the shrinkage is compensated by the piston in the case of hpdc and by the liquid bath for lpdc, thus leading to no piping. ProCAST can account for such "active feeding", by setting the Run parameter GATEFEED=1. In this case, no piping will occur, but liquid will feed the ingate, as long as the fraction of solid is lower than GATEFS (i.e. there is feeding in all regions which are within the same GAFEFS isosurface as the gate). The gate is defined as being the region where in inlet velocity is applied, or where a pressure is applied (or where GATENODE is applied).

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One should note that the porosity level will NOT depend upon the value of the pressure. The Active feeding is there only to compensate for the shrinkage of the region in contact with the piston, as long as the fraction of solid is lower then GATEFS (i.e. within the same GATEFS isosurface as the gate). This does not correspond fully to a real third stage pressure, however, the value of GATEFS could be adjusted with pressure if desired). For HPDC and LPDC, it is advised to set PIPEFS = 0.0 in order to prevent piping at the top of the casting, if the gate is closing too early. The active feeding is valid only with the POROS = 1 model. In the case of a thermal only calculation (for HPDC or LPDC), one should set a Pressure boundary condition at the ingate (in order to activate the active feeding) and one should disable the FLOW run parameter (as normally a Pressure BC would automatically switch ON the flow solver). Of course, GATEFEED should also be set to 1 in this case. In order to activate GATEFEED, one should apply a pressure of inlet velocity BC on external faces. There are cases where there are no external faces on which to apply these boundary conditions. This happens in the case of a filling with a shot piston. To account with such situation, one can apply instead a "Gate feeding" condition on an inside location of the casting (defined by its node number). In general, it is advised to select a node inside the final biscuit, which will remain liquid during most of the casting process. To define this node number, the GATENODE Run Parameter should be specified, followed by the node number. In order to find the node number corresponding to the desired location, it is advised to use the "pick" capability of ViewCAST. This can be done before the run of the case, just after DataCAST. Warning : In the case of a thermal only calculation, a Pressure BC should be set at the ingate in order to switch ON the active feeding. In such a case, the Pre-processor automatically is activating the flow solver (FLOW=3). As a consequence, one should set FLOW=0 manually in the d.dat file in order to deactivate the flow solver (but the porosity calculation will be performed with active feeding).

Cast Iron Porosity model

Instead of shrinking during solidification, some alloys do also exhibit some expansion. The most well known material which exhibits this behavior is the Nodular Cast Iron, also called Spheroidal Graphite Iron (SGI). Grey Iron may also exhibit such behavior. The volume change as a function of temperature is shown in the figure hereafter for different cast irons.

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POROS = 1 model in case of expansion In order to account for such expansion, the POROS=1 model was adapted in the way describe hereafter. In the "pockets" of liquid and mushy zone which have a solid fraction lower than MACROFS (+FEEDLEN), the integral of the density change at each timestep is performed. In the case of expanding material, some location will expand and some will shrink. If the total density change corresponds to a net shrinkage, the "regular" model applies (i.e. this macroshrinkage will occur as the highest most liquid point). If it corresponds to a net expansion, two scenario may occur : a) Find the highest point of the region that is on a free surface and has a fraction

of solid lower than PIPEFS. In this case, the free surface of the casting (usually in the riser) will go up by the amount corresponding to the net expansion.

b) Find the highest point of the region that is on a free surface and has a fraction

of solid higher than PIPEFS. The amount of expansion is applied proportionally to all of the nodes in the region that have pre-existing porosity (thus, the macroporosity which appeared earlier, when there was a net shrinkage, will be "refilled"). For example, if the amount of expansion is enough to "refill" 50% of the total porosity in the region, then the porosity of each node is reduced by 50%.

c) No nodes of the "region" are on a free surface with a fraction solid lower than

PIPEFS. The expansion is distributed to all the nodes in the region as described in b).

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At the same time, microporosity is computed in the following way: a) Microporosity can appear or disappear (partially or fully) only in the zone

where the fraction of solid is in between MACROFS (+FEEDLEN) and 1. b) Within this zone, two situations may occur: b1) There is still some mushy zone (or liquid) below MACROFS. In this case,

microporosity can occur or disappear (partially or fully) only at a distance greater than the value of FEEDLEN from the MACROFS isosurface (Zone A). This means that, if high gradients are present, the distance between the MACROFS and solidus isosurface is smaller than FEEDLEN, no microporosity occurs or disappears (Zone B). The amount of microporosity formation or disappearance is equal to the density change between the local fraction of solid and 1.

b2) There is no more mushy zone below MACROFS. In this case, the FEEDLEN parameter is not active anymore and there could be microporosity in the whole region between MACROFS and 1 for shrinkage. This is due to the fact that as there is no more "open liquid" to feed the shrinkage, local microporosity has to occur in order to compensate the local shrinkage. The amount of microporosity is equal to the density change between the local fraction of solid and 1. If the density change between the local fraction of solid and 1 is positive (expansion), there is no microporosity formation. The already formed micro porosity can be refilled partially or fully during expansion depending on the degree of the density change.

c) On the other hand, if FEEDLEN=0, the amount of microporosity is the same

throughout the part (except where there is macroporosity). In this case, the amount of microporosity is everywhere equal to the density change between Fs=MACROFS and Fs=1. Again if the density change between the fs=MACROFS and fs=1 is positive (expansion), there is no microporosity formation. The already formed micro porosity can be refilled partially or fully during expansion depending on the degree of the density change.

d) If FEEDLEN is set to a very large value (larger than the casting size), the

region between MACROFS+FEEDLEN is not existing anymore. Thus, no microporosity is created or refilled until the whole pocket is above MACROFS (i.e. no microporosity created or refilled according to b1) above). Then, microporosity can start to occur or disappear, according to b2) above.

Mold rigidity The rigidity of the mold has an influence on the amount of porosity in the case of expanding alloys. If the mold is totally rigid, the casting can not expand and thus the alloy expansion will be "available" for the "refill" of the existing porosity. On the other hand, if the mold is very soft (or weak), the casting will expand and thus there will be no "refill" of the porosity (of course, the reality is more complex as the solid shell is thick enough it will act as a "rigid" mold, even if the sand mold is weak.

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In order to take the mold rigidity into account, the Run Parameter MOLDRIG is introduced. MOLDRIG should be defined by a value between 0 and 1. All the net expansion is multiplied by MOLDRIG. Thus, with MOLDRIG=1, corresponding to a rigid mole, the expansion will be fully accounted. On the other hand, no expansion will be taken into account if MOLDRIG=0. The expansion will be compensated by the mold movement because the mold is too weak to hold the expansion in this case. For real situations, the value of MOLDRIG should be set somewhere between 0 and 1 depending upon the casting processes. MOLDRIG should be added in the "Thermal Run Parameters" tab. The default value is 1. Density curve For expanding materials, the density defined in PreCAST should be not anymore monotonic. The density can increase (locally) with increasing temperature.

One should note that such density curve will not be obtained when the material properties are computed with the Computherm database. This is because the expansion is depending upon the microstructure which itself depends upon the cooling rate (see next section). Thus, such curve should be defined manually by the user, based upon experiments.

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Coupled Microstructure - Porosity calculation When a microstructure calculation is performed in the case of SGI, the density is automatically calculated at each location (i.e. each node) of the casting and this local density is used "on-line" in the porosity calculation (POROS = 1 model only). The following figures are showing the solidification of a simple SGI casting calculated with the MICRO model. The corresponding cooling curves and densities (calculated by the micro model) are also shown. One can well see that depending upon the cooling rate, one can have full expansion to full shrinkage, with intermediate behavior in between.

Microstructures and Porosity calculated with the Microstructure module of ProCAST (top) with the corresponding Cooling curves and computed density curves (bottom) (SGI

with 3.54% C, 2.46% Si, 0.14% Mn, 0.29% Cu, 0.05% Mg, 0.019% P, 0.007% S)

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The above example is showing the advantage of using a coupled Microstructure - Porosity calculation. If the Microstructure module is not available, one should use the density curve which corresponds to the "closest" average cooling rate. The density will be influenced by the Graphite treatment (with Magnesium), as well as by the level of graphitisation. For the graphite treatment, the influence of the time between the treatment and the solidification is taken into account (fading effect - FADING and MGTREAT). The more we wait between the treatment and the casting, the least graphitisation will occur and thus the least amount of expansion will happen (thus leading to more porosity). The level of graphitisation, controlled by the Run parameter GRAPHITE, will have an influence on the amount of expansion and thus on the porosity. Please refer to the "Microstructures/Iron and Steel/Iron and Steel models" section of the manual for the description of the influence of GRAPHITE, FADING and MGTREAT on the densities and thus on the porosity.

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Example The figures hereafter are showing an example of an expanding alloy. One can see very well that the level of the metal in the left riser (which has an insulating sleeve) is first going down (overall shrinkage) and then it is going back up (overall expansion).

The following figure is showing an enlargement on the riser where the liquid level is going down and then up.

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VIRTUAL MOLD

ProCAST offers the capability of modeling a mold without meshing it, with the Virtual Mold option. This is especially useful in the case of large sand casting. It can also be used in permanent mold casting, if one is mainly interested in the filling behavior. When a Virtual mold is used, one should define the dimension of the mold (which is an orthogonal box, aligned with X, Y and Z, the material properties of the mold and the interface heat transfer coefficient between the different part of the casting and the mold. The Virtual mold model considers that the thermal diffusion is occurring in the mold, according to "half diffusion distances". Thus, the model calculates for each face of the casting what is the half diffusion distance. This distance is either the one between the face and the limit of the mold or half the distance between the face and an other face in front. At the limit of the mold, an adiabatic boundary condition (i.e. no flux) is considered. Thus, it is advised to defined a "box" which is large enough, in order not to "saturate" the virtual mold. A good start for the Virtual Mold definition is to look at the minimum and maximum size of the model in the "Geometry/Check Geom/Min-Max" menu.

Then, one should open the "Geometry/Virtual Mold" menu, to get the following :

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The size of the Virtual Mold box can be defined in the following fields. One has the possibility to define automatically the virtual mold box size, using the "Default Size" button. One should first select on the right, whether the virtual mold box should be 1, 2, 3, 4 or 5 times larger than the part, in the X, Y and Z directions respectively. For small components, it is advised to use a virtual mold 5 times the component size. For large castings, a virtual mold with a size of 2 o r 3 times the component size will be enough. In case there is any doubt, it is advisable to take a large virtual mold rather than the reverse, in order to avoid saturation.

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Please note that one should NOT use the real size of the mold for the Virtual mold computation. As the model considers that there is no cooling of the sides of the virtual mold, the box should be large enough in order to avoid satuaration of the mold (and thus too slow cooling). The size of the Mold box can be visualized with the "Show Mold" button (in the case of the figure hereafter, the virtual mold of a size 1 time larger than the component was selected, for viewing purposes).

When the Mold size is good, one can "compute" the Virtual Mold, using the "Compute Mold" button. Please note that the computation may take sometime, depending upon the size (i.e. the number of surface elements) of the model. The computation time is independent upon the size of the mold box itself (in the case of the figure hereafter, the virtual mold of a size 1 time larger than the component was selected, for viewing purposes).

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Once the Virtual Mold is computed, the "Thermal depth" can be visualized with the "Show Depth" button. The color scale can be changed with the "Set Scale" button, which opens the following panel :

Finally, if needed, it is possible to erase the Virtual mold, using the "Remove Mold" button. Before setting a Virtual mold, a few precautions should be taken : When a virtual mold is used in conjunction with a symmetry, it is mandatory to set first the symmetry and then to generate the virtual mold. Otherwise, the symmetry of the virtual mold will not be applied.

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If the mesh is made out of several material domains, it is mandatory to define first the interfaces between the different domains and then to generate the Virtual mold. If interfaces are changes after the Virtual mold creation, it will be destroyed. Once the Virtual Mold is generated, it appears in the Material list in the Material properties assignment. One should assign the desired material properties to this Virtual mold domain.

In the same way, the interfaces between the Virtual Mold and the different material domains are automatically generated. These are labeled "Virtual". One should assign an interface heat transfer coefficient to each "Virtual" interface.

Finally, in the case of filling/flow computation with a Virtual mold, it is mandatory to set a zero velocity (or a WALL BC) on all the casting nodes (except the inlet nodes).

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FILTERS

If Filters are present in the process, they can be modeled. Firstly, the filter should be meshed as a separate material domain, as shown hereafter.

Once the model is loaded, a Filter material should be assigned to the corresponding material domain (see the "Databases/Material Properties" section for the description of the filter properties definition).

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Then, the "FILTER" type should be assigned to this material domain. In the Interface menu, the interfaces between the casting and the filter material (on both sides) should be kept as "EQUIV" (i.e. no interface should be created between the casting material and the filter).

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Finally, the interface heat transfer coefficient between the liquid metal (casting material) and the filter material can be defined in the "Boundary Conditions/Assign Volume/Filter Heat" menu. The list of the Filter materials is shown, as well as the interface heat transfer coefficient database, ready for an assignment.

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EXOTHERMIC

Exothermic sleeved can be modeled in ProCAST, with the appropriate heat generation. Firstly the exothermic sleeve should be meshed as a separate material domain. Then, the corresponding material properties should be assigned and the "EXOTHERMIC" type should be defined (if the EXOTHERMIC type is not defined, the exothermic energy, as defined hereafter will not be released) :

The material properties of the Exothermic sleeve must be defined as follows :

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The "standard" properties (thermal conductivity, density and specific heat) should be defined as usual (1) for the sleeve material. In addition, the exothermic properties should be defined in the "Exothermic" tab (2). The Exothermic energy (3) corresponds to the amount of energy which is generated during the burning of the sleeve. The Ignition Temperature (3) corresponds to the temperature at which the exothermic reaction is initiated. The "burning kinetics" is defined in the table (4-5), as a fraction of burning, which is a function of time. Once the exothermic reaction is started (i.e. when the temperature is going above the ignition temperature), the exothermic energy will be released according to the burnt fraction.

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CYCLING

ProCAST allows to model the cycling sequence in the case of die casting (i.e. to account for the heating of the die mold during the first cycles of casting). The figure below shows the principles of cycling, as well as the different sequences.

In order to model cycling, one should be able to take into account the fact that when the mold is closed, there is an interface heat transfer between the casting and the mold and when the mold is opened, one should consider a cooling of the die and of the casting with the ambiance. One should thus switch between an interface heat transfer coefficient and two "Heat" boundary conditions.

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The above diagrams are showing in green the interface heat transfer coefficients as a function of time for both the interface between the casting and the fixed die (solid green line) and between the casting and the mobile die (dashed green line). One could see that the interface heat transfer coefficient goes to zero when the casting and the mold are not anymore in contact. On the reverse, as soon as the mold opens, a "Heat" boundary condition should be set (the red curve on the above figure corresponds to the heat transfer coefficient and the dashed blue curve corresponds to the ambient (or external) temperature. One could see on the above figure that during the spray sequence, the heat transfer coefficient increases and the spray temperature is also taken into account. When the die is closed, before the next filling, the interface heat transfer coefficient between the dies is again activated and the interfaces between the casting and the die(s) are set to zero. One should note that the Pre-defined Run parameters for HPDC-cycling are not designed in order to peform a Porosity calculation during the cycling calculation. If this is desired, one should set to :

POROS 1 PIPEFS 0.

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GATEFEED 1 Then, a pressure BC should be set at the ingate in order to trigger Gate feeding. It is possible to perform a cycling calculation (thermal only) which is automatically followed by a filling-thermal calculation during the last cycle. To do so, the CYCLEF Run Parameter should be set to ON (or to 1 in the p.dat file) (see the "Cycling Run Parameters" sectoin for more details).

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LOST FOAM

ProCAST provides the capability to model "lost foam" casting or "evaporative pattern" casting. The cavity is filled with foam and is surrounded by a sand mold. During the filling, the hot liquid metal is heating up the foam which is burning, leaving the space for the liquid metal. In the Lost Foam process, the filling is controlled by the rate of burning of the foam, as well as the escape of the gas through the ingate or through the permeable sand mold. The set-up of a Lost Foam case should be done as follows. Firstly, the geometry should contain at least three components : a part of the downsprue which is empty, the cavity filled with the foam and a sand mold (see figure below).

The following figure shows how the materials should be set. The downsprue should be assigned with the casting material and it should be set as EMPTY=YES. The cavity, which is filled with foam should be assigned with a "Foam" material (EMPTY=NO) and the mold should be set with a sand material (EMPTY=NO).

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There are no special requirements for the material properties definition of the casting material. For the Foam material, the thermal conductivity, the density, the specific heat and the latent heat (of burning) of the foam should be specified. Moreover, under Tsolidus and Tliquidus, one should specify the temperature at which the foam starts and ends to burn respectively. One should note that the burning kinetics (and thus the filling rate) is influenced by the density, the specific heat, the latent heat and the burning temperature. The larger these values, the slower the burning kinetics will be. This is due to the fact that the foam should be heated up by the liquid metal and that if these quantities are larger the amount of heat required to burn the foam will be larger and thus it will take more time. For the sand, in addition to the usual thermal properties, it is necessary to define it's permeability (in the "Fluid/Permeability" tab). Typical values range from 1e-6 to 1e-7 cm**2. The interface between the casting material and the foam material should be set as "EQUIV" (i.e. no interface), whereas the other interfaces should be set as "COINC".

In addition the usual "Heat" boundary condition (to cool down the outside of the mold) and the inlet Temperature, one should set two Pressure BC. One for the top of the down sprue (on the whole surface) and the other for the outside of the mold. It is recommended to set a value of 1 atm. on the outside of the mold and a value slightly larger (e.g. 1.05 atm) on the top of the downsprue.

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The Run Parameters should be configured as a regular Gravity filling problem with an inlet pressure. Additional Run parameters should be set in the p.dat file for Lost Foam :

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FOAMHTC 0.02 FOAMHTCMAX 0.25 BURNZONE 1.0 GASFRAC 0.1 DIAG 262144 These parameters are regulating the rate of transfer of heat between the liquid metal and the foam. When the liquid metal front is at a distance of "BURNZONE" from the foam, the "interface heat transfer" between them is equal to the value of FOAMHTC/BURNZONE. This heat transfer is increasing as the liquid get closer from the foam. When the liquid is "touching" the foam, a maximum heat transfer coefficient (equal to FOAMHTCMAX) is set. FOAMHTC and FOAMHTCMAX are defined in the p.dat file in CGS units and BURNZONE is in "cm". BURNZONE corresponds to the "usual" distance between the foam and the liquid metal. One should be careful that the mesh size must be finer than the value of BURNZONE. One should note that the burning kinetics will change when the value of BURNZONE is changed (as the interface heat transfer coefficient is equal to FOAMHTC divided by BURNZONE). As the rate of heat transfer between the foam and the liquid metal is not well known, it may be needed to calibrate the filling time with the values of FOAMHTC and FOAMHTCMAX. To shorten the filling time, one should increase these values. The value of GASFRAC corresponds to the fraction of the foam which is transformed into gas (during the burning). The rest is mainly transformed in liquid traces. A value of 0.1 (10%) is recommended. In order to allow for smooth Restarts, the Run Parameter DIAG should be set to 262144. This setting is not necessary if no Restart is performed.

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THIXO CASTING

ProCAST has a dedicated model for thixo casting (or semi-solid casting). When a semi-solid material is injected in a mold cavity, it's viscosity is depending upon the shear rate (as well as the shear rate which was encountered by the metal previously during the injection). When the shear rate is high, the solidifying dendrites are broken and the fluidity is increasing (i.e. the viscosity is decreasing). In order to account for such a behavior, a specific "Power cut-off" model was designed. In order to set-up a Thixo casting case, one should define the appropriate material properties of the casting material and define an additional simple input file (prefixg0.dat). In the Material properties definition, all the thermal properties should be defined as usual. In the Fluid tab, the Viscosity should be defined with the "Power-Cutoff" tab.

The values of the "Zero viscosity", the "K Factor" and the "Power", which can be Temperature dependant, should be calibrated with experiments. Please note that the value of n should be negative (in order to have a decreasing viscosity with an increasing shear rate).

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The principle of the Thixo casting model is to divide the mesh in different regions. For each region, it is possible to define the critical "cut-off" value of the shear rate

. This definition is done in a small input file named prefixg0.dat. The format of this ASCII file is the following (one line per domain of the mesh) : Domain_number critical_shear_rate The following example shows a g0.dat file for a case with 4 domains. One should note that domain 2 is the mould and a dummy value (of 1) should be set. The units of this critical cut-off shear rate is [s].

The principle for the definition of the critical cut-off shear rates is described hereafter. It is based upon the fact that dendrites are broken in locations where the shear rate is high and then, even if the shear rate is decreasing afterwards (in an opened cavity), the viscosity will not increase anymore (as the dendrites have been broken). This means that the viscosity in a cavity which is following a gate will remain at a rather low level, corresponding to the shear rate of that gate. One can illustrate this principle with the following figure.

In domain 3, the viscosity of the semi-solid material is about the one which corresponds to the shear rate that was encountered in the gate (i.e. domain 2). Thus, one should set a "cut-off" value in domain 3 which corresponds to the mean shear rate of domain 2. In the same way, the "cut-off" value of domain 5 should

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correspond to the shear rate encountered in domain 4 (which should be a higher value than domain 2 as the section is smaller). In domains 1, 2 and 4, it is not necessary to set a cut-off value (the default value of 1 can be used), as the effective shear rates will correspond well to the reality. To determine the shear rate in a gate, one can view the "Non-Newtonian Shear Rate" in ViewCAST.

Finally, in order to activate the Power cutoff model, the two following Run parameters should be set : HIVISC = 2 NNEWTON = 2

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CENTRIFUGAL CASTING

The centrifugal casting model of ProCAST is designed for vertical centrifugal casting only. The inlet should be centered, with inlet velocities parallel to the rotation axis. Starting from version 2006.0, centrifugal casting cases should be set-up in the following way. Only the CASTING domains should be set with a revolution velocity (i.e. not the mold materials). This must be defined in the "Process/Assign Volume" menu, with a "Revolution". The Run Parameter RELVEL should be set to 1. This Run parameter is activating the resolution of the fluid equations in a "Relative velocity reference frame" to handle the rotation. The rest of the set-up should be done as for a standard gravity casting (i.e. WSHEAR = 2, WALLF = 0.8, FREESFOPT = 1 (or 2)). When a Centrifugal casting case is run with the RELVEL algorithm (relative rotational frame), the velocity vectors are including the rotational component. As a consequence, it is not convenient to view these velocities. In order to view the velocity vectors as if the observer would be attached to the rotating casting, one should calculate the "Relative velocities" with the "Action/Relative velocity" menu :

This will create a set of relative velocity files, named prefixru.unf, prefixrv.unf and prefixrw.unf. In order to view these results, it is necessary to change manually the name of these files to prefixu.unf, prefixv.unf and prefixw.unf (which will substitute the existing velocity files having the same names - of course, it is advised to save these files before this substitution, especially if a restart is planned). In future version, it will be possible to automatically view both type of results. The figure below is showing the "standard" velocity vectors (including the rotational component).

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The figure hereafter is showing the same result as above, but with the relative velocities.

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On the figure below, a zoom on one branch of the above geometry is shown. On the left, the "standard" velocities (including the rotational component) are shown, whereas on the right, the "relative velocities" are displayed.

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LARGE INGOT FILLING

Large ingot filling needs some special treatment. This is due to the fact that the filling times are usually very long on one side, and on the other side, rather high velocities are leading to quite small timesteps. As a result, the computing times are often quite long. In order to reduce as much as possible the CPU time, the following procedures are proposed.

Top Filling The recommended procedure for Top filled ingot is the following : A "Mass source" should be set at the bottom of the casting cavity, with the appropriate amount of inlet metal and the desired inlet temperature. The coordinate of the mass source should be approximately the bottom of the ingot, but it may be a few millimeters or centimeters above. Then, the Run parameter TOPFILL = 1 should be added manually in the p.dat file, together with FREESF = 2. To Deactivate this Top filling mode, TOPFILL should be set to 0. This setting will have the effect that, instead of having a point mass source (as usual), the incoming mass will be evenly distributed just below the whole free surface (which is moving upwards). This will have the advantage of not having a large velocity at the mass source location, which will require the use of small timesteps.

Bottom Filling The case of Bottom filling is more complicated as one needs to fill first the downsprue(s) and then to bring the hot metal from the bottom. In order to do so, one should set the Run Parameter TOFRSF2 followed by a fill fraction (e.g. TOFRSF2 0.01), together with FREESF = 1. The filling will start in FREESF = 1 mode (i.e the normal filling mode). When the critical fill fraction defined by TOFRSF2 is reached, the calculation will switch automatically from FREESF = 1 to FREESF = 2 for the rest of the filling. However, the hot metal will well be brought at the bottom of the ingot through the downsprue(s). The TOFRSF2 Run parameter should be added manually in the p.dat file. The switch to FREESF = 2 will allow larger timesteps and thus it will reduce the CPU time. One should however be aware that if the downsprue diameter is rather small the velocities can be quite large (as well as at the exit of the downsprue on

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the casting) and this will limit the size of the timestep, thus leading to important CPU times.

General rules MLDUPDT When a mold is present, it is possible to reduce slightly the CPU time by updating the material properties in the mold every N step. To do that the MLDUPDT Run parameter should be added manually in the p.dat file, followed by an integer. This number corresponds to the material properties update frequency. A value of 50 may be recommended. The MLDUPDT Run parameter should be added manually in the p.dat file. Boundary Layers When large castings are modeled, the mesh size becomes very large with respect to the thermal gradients, especially in the early stages of cooling. In order to have appropriate answers (i.e. more accurate temperatures), it is advised to generate a few layers (of a few mm in thickness) inside the casting, as well as inside the mold.

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MULTIPLE MESHES AND NON -COINCIDENT MESHES

ProCAST has the capability to handle non-coincident meshes (see figure below).

If the different domains are meshed separately, they can be loaded in PreCAST using the "File/Multiple Meshes" menu.

Then, a window opens, which allows to load the different meshes.

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Once the meshes are loaded, the set-up of the case in PreCAST should be done as for conventional meshes, except for the definition of the interfaces (see figure below). Firstly, all the non-coincident interfaces, where at least one element is coincident on each side, are automatically listed in the interface list. One should change the "Type" from EQUIV to NOCOIN (1). Then, for the non-coincident interfaces which are not listed, one should "create" manually these interfaces, with the Add button (2). This will open the"Add Interface Pair" window, where the material numbers of each side can be defined (3). The "Master-Slave" concept is used in the calculation of the heat transfer across the non-coincident interface. It is advised to set the casting as the Master and the mold as the Slave (although it does have only a minor importance on the accuracy of the results). Then, one should check the "Non-coincident Interface" button (4). Once all the interfaces are

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defined, one can "Apply" the whole selection (5), which will create the appropriate interfaces.

When a non-coincident interface is defined, it is possible to change the default tolerances used for the detection of the nodes on the opposite side. To do so, one should make a right click on the NCOINC label and the following window will appear :

The "In-plane Tolerance" corresponds to the maximum distance between the two surfaces in order to have a contact (distance normal to the plane of the interface). The "Perimeter Tolerance" corresponds to the maximum distance around an element of the master surface where a node of the slave surface can be found.

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By default, the In-plane and Perimeter tolerances are taken as a fraction of the smallest edge of the whole mesh. Thus, if the mesh has a quite heterogeneous mesh size, these tolerances may be too small (and thus, there will be "no contact" and thus no heat transfer at these non-coincident interfaces). If such a case occurs, one can change (i.e. increase) these tolerances. One should however be careful not to use too large tolerances so that nodes beyond the opposite surface will be taken into account. A good tolerance value should be about half of the mesh size of the corresponding surface.

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GEOMETRY MANIPULATION

The geometry can be manipulated and can be displayed with different modes, using the following icons.

Manual rotation of the model (it opens the Rotate window). Otherwise, the model can be rotated interactively with the mouse at any time (as long as the Center or Drag icon is not activated). If the model is rotated interactively with the mouse, while the "Shift" key is pressed in the same time, the model is rotating along the axis perpendicular to the screen (the mouse should be rotated horizontally).

Restore the X-Y orientation of the model (Z-axis perpendicular to the screen)

Interactive zoom (the model is enlarged when the cursor is moved towards the bottom of the screen and it is reduced when the cursor is moved towards the top of the screen)

Auto-scale (automatic scaling of the model so that it fits into the graphics window)

Center of the model (the location of the model which is selected will move to the center of the screen)

Drag of the model (interactive move of the model on the screen)

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Material (or domain) selection

Wire frame display mode

Hidden wire frame display mode

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Hidden display mode with the mesh

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Shaded display mode

Activation of the enclosure viewing (for radiation models)

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MESH OPTIMIZATION

The speed of a FEM calculation depends upon the structure of the mathematical matrices which have to be solved. This depends upon the way the FEM mesh is numbered (i.e. which nodes belong to which element and vice-versa). It is possible to optimize the FEM mesh numbering in order to minimize the CPU time. This was done previously in MeshCAST. However, as the addition of interfaces is creating new nodes, it was necessary to know already in MeshCAST which interfaces had to be created. In order to simplify this operation, it is now possible to optimize the mesh in PreCAST, just before SAVING a case. This will take automatically into account the created interfaces and will thus guarantee that the mesh is optimum. As the optimization operation may be rather long for large meshes, it is not done by default at every save of the model. In order to activate the optimization, one should set it in the "File" menu :

This optimization will be done before exiting PreCAST (it is not performed with a "Save" or "Save as" operation, but in this case a warning is displayed upon Exit). One should note that if an optimized model is loaded again in PreCAST, it is not necessary to optimize it again, as long as the interface settings are not changed. In the case of initial conditions EXTRACTion (i.e. extract of initial temperatures from a previous calculation), one should NOT optimize the mesh anymore as this will renumber the mesh and thus the extracted temperatures will be scrambled.

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USER FUNCTIONS

ProCAST allows the use of User Functions. User Functions can be used to define boundary conditions in a very flexible way, such as combined time, temperature and/or space dependant heat transfer coefficients. Please note that the User functions usage requires the corresponding license (not included in the base package). Three categories of Functions are available in ProCAST : • User Functions to define a given condition, instead of a constant or a table • External Functions which can be called from the User Functions, in order to

get the values of some fields at any node. • External Computation Function which can be called during the execution of

the calculation (e.g. for coupling with external softwares).

User Functions description Currently, the following User Functions are available : • Interface BC : interface heat transfer coefficient • Heat BC : external heat transfer coefficient • Heat BC : external temperature • Heat BC : emissivity • Heat BC : heat flux • Imposed velocity (X, Y and Z components) • Solid transport velocity (X, Y and Z components) • Translation vector (X, Y and Z components) • Mass source position (X, Y and Z components) • Mass source flow rate Each of these functions have the following arguments : • Time • Local temperature • Local fraction of solid • Local coordinates • Material number • Boundary condition ID This allows to define conditions as a function of any of the above arguments (e.g. a time- and space-dependant interface heat transfer coefficient).

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In addition, "external functions" allow to get the value of the main fields (e.g. temperature, fraction of solid, velocities, ...) at any location of the model. This allows to define for instance a heat transfer coefficient as a function of a "control temperature", corresponding to a given location, somewhere else ("remote control"). User Function Templates are available in the next section.

External Functions description From any User Function, it is possible to get the value of some fields (e.g. Temperature, fraction of solid, velocity) at any node, specified by its node number. To do so, the following functions are available : • usertemp1(node#) for temperature • userfs1(node#) for the fraction of solid • uservx1(node#) for the X-component of the velocity • uservy1(node#) for the Y-component of the velocity • uservz1(node#) for the Z-component of the velocity In addition, it is possible to get the node number by giving the coordinates, using the following function : • nodNum (xin, yin, zin, domain#, xout, yout, zout) where xin, yin and zin are the coordinates specified by the user, xout, yout and zout the coordinates of the closest nodes which corresponds to the returned node number. domain# is the domain number in which the search node should be found.

External Computation Function description Beside User Functions for the definition of flexible conditions, ProCAST is providing an "External User Function", which is called at the following times : • at the beginning of the calculation • at the beginning of each timestep • at the end of each timestep • at the end of the calculation This allows to perform a number of operations, as defined by the user, at these different moments. As for the User Functions, the "internal functions" allow to retrieve the values of the main fields (e.g. temperature, fraction of solid, velocities, ...) at any location of the model. Such External calls can be used for instance to couple ProCAST with other softwares. The Template of the External Function is available in the next section.

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If the "externalcompute.c" function is to be used alone (i.e. with no other user functions), it will not be called automatically (as it is designed to work in conjunction with other user functions). In such situation, one should activate (in PreCAST) a "dummy" user function (like a Heat BC) and set a constant value (like 0) and assign it to any location of the mesh. This "dummy" user function will not have any effect on the calculation results, however, it will have the effect to activate the "externalcompute.c" call.

Language and Compiler All the User Functions and External Functions should be written in C language, based upon the provided Templates. In order to be able to use User Functions, a C compiler and linker should be available on the machine. Specific compiler and linker are needed (only the compiler/linker which have been used for the creation of the executables are guaranteed to work with the software). There is no guarantee that the software will work with other compilers/linkers. Windows (32 bits) On Windows, the compiler and linker of the Microsoft Visual C++ 6.0 package has been used to create the executables. An "reduced" version of this compiler and linker, called "Microsoft Visual C++ 2008 Express Edition" is available for free on the web (information valid in January 2009). It can be downloaded from the following link and then installed : Microsoft Express Edition download Site : http://www.microsoft.com/express/download If this link is not anymore valid, search in the Microsoft official site. In order to use "Microsoft Visual C++ 2008 Express Edition", one should "manually" set the following : In the ProCAST20091/bin directory of the installation, the "procastRun.BAT" should be manually modified. At about 10 lines from the top of the file, there is a line for the tool kit variables initialisation : @call "C:\Program Files (x86)\Microsoft Visual Stud io 8\VC\vcvarsall.bat" %2 The line shown above should be changed as : @call "C:\Program Files (x86)\Microsoft Visual Stud io 9.0 \VC\vcvarsall.bat" %2

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Windows (64 bits) On Windows, the compiler and linker of the Microsoft Visual C++ 6.0 package has been used to create the executables. An "reduced" version of this compiler and linker, called "Microsoft Visual C++ 2008 Express Edition", together with "Windows SDK for Windows Server 2008" and ".NET Framework 3.5", are available for free on the web (information valid in January 2009). They can be downloaded from the following link and then installed : Microsoft Express Edition download Site : http://www.microsoft.com/express/download Windows SDK for Windows Server 2008 and .NET Framework 3.5 http://www.microsoft.com/downloads/details.aspx?Fam ilyID=e

6e1c3df-a74f-4207-8586-711ebe331cdc&displaylang=en If these links are not anymore valid, search in the Microsoft official site. In order to use "Microsoft Visual C++ 2008 Express Edition", one should "manually" set the following : In the ProCAST20091/bin directory of the installation, the "procastRun.BAT" should be manually modified. At about 10 lines from the top of the file, there is a line for the tool kit variables initialisation : @call "C:\Program Files (x86)\Microsoft Visual Stud io 8\VC\vcvarsall.bat" %2 The line shown above should be changed as : @call "C:\Program Files (x86)\Microsoft Visual Stud io 9.0 \VC\vcvarsall.bat" %2 Then, in the file :

C:\Program Files (x86)\Microsoft Visual Studio 9.0\VC\vcvarsall.bat

the :amd64 block should be changed from :

:amd64 if not exist "%~dp0bin\ amd64\ vcvars amd64.bat" goto missing call "%~dp0bin\ amd64\ vcvarsamd64.bat" goto :eof

to :

:amd64 if not exist "%~dp0bin\vcvars64.bat" goto missing call "%~dp0bin\vcvars64.bat"

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goto :eof Linux Intel C compiler (icc), version 9.1

Use of User Functions Once the User Functions are defined (i.e. programmed), they should be placed in the current working directory (i.e. next to the standard input files). Please note that the user functions should be renamed : prefix_userfunction.c (e.g. : prefix_convehtransfer.c). If it not renamed, it will not be compiled and linked automatically by the launch script. Then, when the "procast" executable is launched (either from the Manager, or "manually" in a Command window), the User Functions are automatically compiled and linked. A local DLL is created, as well as a local executable. Then, this executable is automatically launched and the calculation starts. This DLL and local executables are automatically deleted at the end of the execution (if the calculation is stopped manually or if it crashes, these files will remain in the local directory). If only the external user function "externalcompute.c" is used in a given calculation, without any other user function, one should set manually in the p.dat file the Run Parameter "USER 1", in order to make such that this function is well called by the solver (this is not necessary when there are any other user function active in the case).

Units ProCAST allows to define the inputs with almost any kind of units. In order to define which units should be taken into account into the software, two possibilities are provided to the user. 1. Default units can be specified in an installation file (either the main central

installation or in the local user preference file (see the "customized installation" section for more details). These units will be used in all the cases run by the user. This ASCII file is called "UserFunctions_units.dat" and is located in the "dat/pref" directory.

2. Specific units can be used for a given case. These specific units should be specified in a text file in the local execution directory. This ASCII file is called "prefix_units.dat".

In both cases, the same units should be used in all the User Functions of the same case.

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The files "UserFunctions_units.dat" or "prefix_units.dat" have exactly the same format as follows :

time 1 length 1 temperature 2 velocity 1 heatflux 1 heattransfercoefficient 1 massflowrate 1 thermalconductivity 1

Each type of variable available in user functions are mentioned in the above list. Then, a unit code is following (as an integer value). The above values correspond to the default units (set at the installation) used by the user routines of the ProCAST solver (SI Units and degree Celsius). One can change these units, with a text editor, using the following nomenclature (corresponding to the standard unit codes of ProCAST, used in the d.dat file) :

temperature

1 = Kelvin 2 = Celsius 3 = Fahrenheit

length 1 = m 2 = cm 3 = mm 4 = ft 5 = in

velocity 1 = m/s 2 = cm/s 3 = mm/s 4 = ft/s 5 = in/s 6 = m/min 7 = cm/min 8 = ft/min 8 = in/min

time 1 = sec 2 = min

heatflux 1 = W/m2 2 = cal/cm2/sec 3 = cal/mm2/sec 4 = Btu/ft2/sec 5 = Btu/in2/sec

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6 = cal/cm2/min 7 = Btu/ft2/min 8 = Btu/in2/min

heattransfercoefficient 1 = W/m2/K 2 = cal/cm2/C/sec 3 = cal/mm2/C/sec 4 = Btu/ft2/F/sec 5 = Btu/in2/F/sec 6 = cal/cm2/C/min 7 = Btu/ft2/F/min 8 = Btu/in2/F/min

massflowrate

1 = Kg/sec 2 = g/sec 3 = lb/sec 4 = Kg/min 5 = g/min 6 = lb/min

thermalconductivity

1 = W/m/K 2 = cal/cm/C/sec 3 = cal/mm/C/sec 4 = Btu/ft/F/sec 5 = Btu/in/F/sec 6 = cal/cm/C/min 7 = Btu/ft/F/min 8 = Btu/in/F/min

User Functions Templates

The following section is presenting the templates of all the User and External Functions. The meaning of the arguments are described in the comments of the functions. • External heat transfer coefficient Function (convehtransfer.c) • External temperature Function (texternal.c) • Emissivity Function (emissivity.c) • Heat flux Function (heatflux.c) • Interface heat transfer coefficient Function (interhtransfer.c) • Mass Source Flow Rate Function (masssourceflowrate.c) • X-component Mass Source Vector Function (xmasssource.c) - same for Y and

Z • X-component Translation Vector Function (xtranslation.c) - same for Y and Z • X-component Imposed Velocity Vector Function (vximposed.c) - same for Y

and Z

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• X-component Solid Transport Velocity Vector Function (vxsolidtransport.c) - same for Y and Z

• External Function (externalcompute.c)

External heat transfer coefficient Function

This function is called : convehtransfer.c It is used to define a convective heat transfer coefficient on the outside of a domain, to be used in conjunction with an external temperature. #include <stdio.h> #include <stdlib.h>

#define real double

#ifdef WIN32 #define EXPORT _declspec(dllexport) EXPORT real func_convehtransfer(char*, int, real, r eal, real, real, real, real, int); #else real func_convehtransfer(char*, int, real, real, re al, real, real, real, int); #endif

extern real usertemp1(int); extern real userfs1(int); extern real uservx1(int); extern real uservy1(int); extern real uservz1(int); extern int nodNum (real,real,real,int,real*,real*,r eal* );

/* * convective heat transfer coefficient (applied on external surfaces) */

real func_convehtransfer( char prefix[], /* case name */ int dimension, /* 2 = 2D ; 3 = 3D */ real temp, /* current temperature */ real fs, /* current fraction of solid */ real time, /* current time */ real x_coor, /* local coordinates: x */ real y_coor, /* local coordinates: y */ real z_coor, /* local coordinates: z */ int numBC) /* boundary condition ID num ber */ { /* ------------- Do not change anything above this line ------------- * * ------------- Program your function below this l ine ------------- */

/* ------------ Do not forget to remove the call to exit ------------ * * ------------ hereafter before running the calcul ation ------------ */ printf("---> exit in C user function convehtrans fer <---\n");

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exit(1);

External temperature Function

This function is called : texternal.c It is used to define an external temperature on the outside of a domain, to be used in conjunction with a convective heat transfer. #include <stdio.h> #include <stdlib.h>

#define real double

#ifdef WIN32 #define EXPORT _declspec(dllexport) EXPORT real func_texternal(char*, int, real, real, real, real, real, real, int); #else real func_texternal(char*, int, real, real, real, r eal, real, real, int); #endif


/* * ambient temperature (applied on external surf aces) */

real func_texternal( char prefix[], /* case name */ int dimension, /* 2 = 2D ; 3 = 3D */ real temp, /* current temperature */ real fs, /* current fraction of solid */ real time, /* current time */ real x_coor, /* local coordinates: x */ real y_coor, /* local coordinates: y */ real z_coor, /* local coordinates: z */ int numBC) /* boundary condition ID num ber */ { /* ------------- Do not change anything above this line ------------- * * ------------- Program your function below this l ine ------------- */

/* ------------ Do not forget to remove the call to exit ------------ * * ------------ hereafter before running the calcul ation ------------ */

printf("---> exit in C user function texternal < ---\n"); exit(1);

return 0;

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}

Emissivity Function

This function is called : emissivity.c It is used to define an emissivity on the outside of a domain. #include <stdio.h> #include <stdlib.h>

#define real double

#ifdef WIN32 #define EXPORT _declspec(dllexport) EXPORT real func_emissivity(char*, int, real, real, real, real, real, real, int); #else real func_emissivity(char*, int, real, real, real, real, real, real, int); #endif


/* * emissivity coefficient (applied on external s urfaces) */

real func_emissivity( char prefix[], /* case name */ int dimension, /* 2 = 2D ; 3 = 3D */ real temp, /* current temperature */ real fs, /* current fraction of solid */ real time, /* current time */ real x_coor, /* local coordinates: x */ real y_coor, /* local coordinates: y */ real z_coor, /* local coordinates: z */ int numBC) /* boundary condition ID num ber */ { /* ------------- Do not change anything above this line ------------- * * ------------- Program your function below this l ine ------------- */


printf("---> exit in C user function emissivity <---\n"); exit(1);

return 0; }

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Heat flux Function

This function is called : heatflux.c It is used to define a heat flux on the outside of a domain. #include <stdio.h> #include <stdlib.h>

#define real double

#ifdef WIN32 #define EXPORT _declspec(dllexport) EXPORT real func_heatflux(char*, int, real, real, r eal, real, real, real, int); #else real func_heatflux(char*, int, real, real, real, re al, real, real, int); #endif


/* * heat flux coefficient (applied on external su rfaces) */ real func_heatflux( char prefix[], /* case name */ int dimension, /* 2 = 2D ; 3 = 3D */ real temp, /* current temperature */ real fs, /* current fraction of solid */ real time, /* current time */ real x_coor, /* local coordinates: x */ real y_coor, /* local coordinates: y */ real z_coor, /* local coordinates: z */ int numBC) /* boundary condition ID num ber */ { /* ------------- Do not change anything above this line ------------- * * ------------- Program your function below this l ine ------------- */


printf("---> exit in C user function heatflux <- --\n"); exit(1);

return 0; }

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Interface heat transfer coefficient Function

This function is called : interhtransfer.c It is used to define an interface heat transfer coefficient between two domains. This function can also be used for the definition of the gap properties (if one wants to use something else than air or vacuum). See the "Tips&Traps/Gaps in Stress models" section for more details. #include <stdio.h> #include <stdlib.h> #include "common_dll.h"

#define real double

#ifdef WIN32 #define EXPORT _declspec(dllexport) EXPORT real func_interhtransfer(char*, int, real, r eal, real, real, real, real, int); #else real func_interhtransfer(char*, int, real, real, re al, real, real, real, int); #endif


/* * interface heat transfer coefficient */

real func_interhtransfer( char prefix[], /* case name */ int dimension, /* 2 = 2D ; 3 = 3D */ real temp, /* current temperature */ real fs, /* current fraction of solid */ real time, /* current time */ real x_coor, /* local coordinates: x */ real y_coor, /* local coordinates: y */ real z_coor, /* local coordinates: z */ int numBC) /* boundary ID number */ { /* ------------- Do not change anything above this line ------------- * * ------------- Program your function below this l ine ------------- */


printf("---> exit in C user function interhtrans fer <---\n"); exit(1);

return 0; }

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Mass Source Flow Rate Function

This function is called : masssourceflowrate.c It is used to define a variable flow rate of a mass source. #include <stdio.h> #include <stdlib.h>

#define real double

#ifdef WIN32 #define EXPORT _declspec(dllexport) EXPORT real func_masssourceflowrate(char*, int, rea l, real, real, real, int); #else real func_masssourceflowrate(char*, int, real, real , real, real, int); #endif

extern real usertemp1(int); extern real userfs1(int); extern real uservx1(int); extern real uservy1(int); extern real uservz1(int); extern int nodNum (real,real,real,int,real* ,real* , real* );

/* * mass source flow rate coefficient */

real func_masssourceflowrate( char prefix[], /* case name */ int dimension, /* 2 = 2D ; 3 = 3D */ real time, /* current time */ real x_coor, /* local coordinates: x */ real y_coor, /* local coordinates: y */ real z_coor, /* local coordinates: z */ int numMat) /* number of the domain */ { /* ------------- Do not change anything above this line ------------- * * ------------- Program your function below this l ine ------------- */


printf("---> exit in C user function masssourcef lowrate <---\n"); exit(1);

return 0; }

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Mass Source Vector Function

This function is called : xmasssource.c (same for ymasssource.c and zmasssource.c) It is used to define the X-component of the location of a mass source. #include <stdio.h> #include <stdlib.h>

#define real double

#ifdef WIN32 #define EXPORT _declspec(dllexport) EXPORT real func_xmasssource(char*, int, real, int) ; #else real func_xmasssource(char*, int, real, int); #endif


/* * masssource vector of a domain : x - component */

real func_xmasssource( char prefix[], /* case name */ int dimension, /* 2 = 2D ; 3 = 3D */ real time, /* current time */ int numMat) /* number of the domain */ { /* ------------- Do not change anything above this line ------------- * * ------------- Program your function below this l ine ------------- */


printf("---> exit in C user function xmasssource <---\n"); exit(1);

return 0; }

Translation Vector Function

This function is called : xtranslation.c (same for ytranslation.c and ztranslation.c) It is used to define the X-component of the translation of a domain.

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#include <stdio.h> #include <stdlib.h>

#define real double

#ifdef WIN32 #define EXPORT _declspec(dllexport) EXPORT real func_xtranslation(char*, int, real, int ); #else real func_xtranslation(char*, int, real, int); #endif


/* * translation vector of a domain : x - componen t */

real func_xtranslation( char prefix[], /* case name */ int dimension, /* 2 = 2D ; 3 = 3D */ real time, /* current time */ int numMat) /* number of the domain */ { /* ------------- Do not change anything above this line ------------- * * ------------- Program your function below this l ine ------------- */


printf("---> exit in C user function xtranslatio n <---\n"); exit(1);

return 0; }

Imposed Velocity Vector Function

This function is called : vximposed.c (same for vyimposed.c and vzimposed.c) It is used to define the X-component of an imposed velocity BC. #include <stdio.h> #include <stdlib.h>

#define real double

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#ifdef WIN32 #define EXPORT _declspec(dllexport) EXPORT real func_vximposed(char*, int, real, real, real, real, real, real, int); #else real func_vximposed(char*, int, real, real, real, r eal, real, real, int); #endif



real func_vximposed( char prefix[], /* case name */ int dimension, /* 2 = 2D ; 3 = 3D */ real temp, /* current temperature */ real fs, /* current fraction of solid */ real time, /* current time */ real x_coor, /* local coordinates: x */ real y_coor, /* local coordinates: y */ real z_coor, /* local coordinates: z */ int numBC) /* number of boundary condit ion */ { /* ------------- Do not change anything above this line ------------- * * ------------- Program your function below this l ine ------------- */


printf("---> exit in C user function vximposed < ---\n"); exit(1);

return 0; }

Solid Transport Velocity Vector Function

This function is called : vxsolidtransport.c (same for vysolidtransport.c and vzsolidtransport.c) It is used to define the X-component of transport velocity of a solid. #include <stdio.h> #include <stdlib.h>

#define real double

#ifdef WIN32 #define EXPORT _declspec(dllexport) EXPORT real func_vxsolidtransport(char*, int, real, real, real, real, real, real, int); #else

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real func_vxsolidtransport(char*, int, real, real, real, real, real, real, int); #endif



real func_vxsolidtransport( char prefix[], /* case name */ int dimension, /* 2 = 2D ; 3 = 3D */ real temp, /* current temperature */ real fs, /* current fraction of solid */ real time, /* current time */ real x_coor, /* local coordinates: x */ real y_coor, /* local coordinates: y */ real z_coor, /* local coordinates: z */ int numBC) /* number of boundary condit ion */ { /* ------------- Do not change anything above this line ------------- * * ------------- Program your function below this l ine ------------- */


printf("---> exit in C user function vxsolidtran sport <---\n"); exit(1);

return 0; }

External Function

This function is called : externalcompute.c This function is called at the start of the calculation, at the start of each timestep, at the end of each timestep and at the end of the calculation. Many parameters are available in this function (see the "extern" declarations). These parameters can also be used in the other user functions (e.g. interhtransfer.c), as shown at the end of this section. If the "externalcompute.c" function is to be used alone (i.e. with no other user functions), it will not be called automatically (as it is designed to work in conjunction with other user functions). In such situation, one should activate (in PreCAST) a "dummy" user function (like a Heat BC) and set a constant value (like 0) and assign it to any location of the mesh. This "dummy" user function will not have any effect on the calculation results, however, it will have the effect to activate the "externalcompute.c" call.

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#include <stdio.h> #include <stdlib.h>

#define real double

#ifdef WIN #define EXPORT _declspec(dllexport) EXPORT void func_externalcompute(char*,int,int,real ); EXPORT int tnodecontrol; EXPORT int vnodecontrol;

#else void func_externalcompute(char*,int,int,real); int tnodecontrol; int vnodecontrol; #endif

#ifdef MP extern real usertemp1Global(int); extern real userfs1Global(int); extern real uservx1Global(int); extern real uservy1Global(int); extern real uservz1Global(int); extern int nodNumGlobal (real,real,real,int,real* , real* , real* ); #else /* These functions return numbers and not indices * / extern int userget_nbnodes_casting (); /* number of

nodes in the CASTING domains */ extern int userget_nbnodes_castmold (); /* number of

nodes in the CASTING + MOLD domains */ extern int userget_nbelems_castmold (); /* number of

elements in the CASTING + MOLD domains */ extern int user_nb_ithnode_inelem (int,int); /* Connectivity

of the elements */ /* 1st argument

: number of the node in the element */ /* 2nd argument

: element number */ extern int user_getelemtype(int); /* element type

(eg : 2 for tetrahedra, */ /* 3 for wedge

and 1 for hexahedra) */ extern int user_getmaterialnb(int); /* Domain number

*/ /* These functions take node numbers as arguments * / /* the index 1 corresponds to the beginning of the timestep */ /* the index 2 corresponds to the end of the timest ep */ extern real usertemp1(int); /* Temperatur e */ extern real usertemp2(int); extern real userfs1(int); /* Solid frac tion */ extern real userfs2(int); extern real uservx1(int); /* X-velocity component */ extern real uservy1(int); /* Y-velocity component */ extern real uservz1(int); /* Z-velocity component */ extern real uservx2(int); extern real uservy2(int); extern real uservz2(int); extern real userx1(int); /* X-coordina te, including

deformations */ extern real usery1(int); /* Y-coordina te, including

deformations */

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extern real userz1(int); /* Z-coordina te, including deformations */

extern real user_hottear(int); /* Hot tearin g indicator */ extern real user_coldcrack(int); /* Crack indi cator */ extern real uservf_s1(int); /* Microporos ity */ extern real uservf_s2(int); extern real userf_vol1(int); /* FVOL */ extern real userf_vol2(int); extern real userjct1 (int); /* Junction * / extern real userjct2 (int); extern real userfatigue1 (int); /* Fatigue in dicator */ extern real userpnode1 (int); /* Liquid pre ssure */ extern real userpnode2 (int); /* These functions take element numbers as argument s */ extern real user3dstress_xx(int); /* SigmaXX st ress */ extern real user3dstress_yy(int); /* SigmaYY st ress */ extern real user3dstress_zz(int); /* SigmaZZ st ress */ extern real user3dstress_xy(int); /* SigmaXY st ress */ extern real user3dstress_yz(int); /* SigmaYZ st ress */ extern real user3dstress_xz(int); /* SigmaXZ st ress */ extern real usereff_plstrain(int); /* Plastic st rain */ extern real userel_vol(int); /* Volume of the FE element, including

deformation */

extern int nodNum (real,real,real,int,real* ,real* , real* ); #endif

/* * function called at the beginning, the end of the calculation * and at the beginning of each timestep * loop = 0 : function is called at the start of the computation * loop = 1 : function is called at the start of the current timestep * loop = 2 : function is called at the end of t he current timestep * loop = 3 : function is called at the end of t he computation * */

void func_externalcompute( char prefix[], /* case name */ int loop, /* loop value : 0/1/2/3 */ int timestep, /* current timestep */ real time) /* current time */

{ if ( loop == 0 ) { tnodecontrol = 0; vnodecontrol = 0; } /* ------------- Do not change anything above this line ------------- * * ------------- Program your function below this l ine ------------- */

return; }

Example of external parameters used in interhtransfer.c (the same approach can be used in any user function) In this example, the interface heat transfer coefficient is taken as a function of the liquid pressure. To do so, the "extern" declaration of the liquid pressure should be

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copied from the upper "externalcompute.c" function (see red line below). Then, this value can be used in the user function (see the blue lines). #include <stdio.h> #include <stdlib.h> #include "common_dll.h"

#define real double

#ifdef WIN32 #define EXPORT _declspec(dllexport) EXPORT real func_interhtransfer(char*, int, real, r eal, real, real, real, real, int); #else real func_interhtransfer(char*, int, real, real, re al, real, real, real, int); #endif


extern real userpnode1 (int); /* Liquid pre ssure */


real func_interhtransfer( char prefix[], /* case name */ int dimension, /* 2 = 2D ; 3 = 3D */ real temp, /* current temperature */ real fs, /* current fraction of solid */ real time, /* current time */ real x_coor, /* local coordinates: x */ real y_coor, /* local coordinates: y */ real z_coor, /* local coordinates: z */ int numBC) /* boundary ID number */ { /* ------------- Do not change anything above this line ------------- * * ------------- Program your function below this l ine ------------- */

real hcoeff; real local_pressure; int local_node_number;

local_node_number = 100 ; local_pressure = userpnode1 (local_node_number) ;

hcoeff = local_pressure / 100. ;

return hcoeff; }

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BATCH PRE-PROCESSING

PreCAST is having a scripting language which allows to perform a complete case set-up in batch. This method is very convenient to automatize repetitive set-up or to apply the same set-up to different meshes. Batch pre-processing is also used when running Optimization calculations.

Introduction

Most of the Pre-processing operations which are performed in PreCAST can be defined in a script (PRS script). A script corresponding to a simple set-up is shown hereafter :

*GENERAL *END_GENERAL *SEQUENTIAL *MATERIALS_ASSIGN_MATERIAL 1 Al_AlSi7Mg03-A356 *MATERIALS_ASSIGN_TYPE 1 CASTING *BC_ADD Heat *BC_ASSIGN 1 Air_cooling *SURF_SELECT_ALL 1 *BC_STORE 1 CURRENT *GRAVITY_VECTOR 0.000000e+000 -9.800000e+000 0.000000e+000 *INITIAL_CONDITIONS_CONSTANT 1 700.00 *RUN_PARAMS_PREDEFINED Gravity_Thermal *END_SEQUENTIAL *FINAL *END_FINAL

The principle of such script is that it follows the operations and the menu (or button) names used in PreCAST. All the available commands are described in the "Script language" section. A script can be used either to perform a whole set-up, starting from a mesh file, or to perform a partial set-up, starting from a d.dat file. It is also possible to modify a set-up (as it is done when a d.dat file is loaded and a few items are modified - e.g. to change only a boundary condition).

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The PRS script can be created in a User interface (see the "PRS User interface" section for more details). To Run PreCAST in batch mode, use the "PreCAST Batch" command :

or launch it in a Command window. The Command to be launched is the following : Command to modify an existing d.dat file :

.../bin/precast.exe –batch prefix script.prs

Command to create a new d.dat file from a mesh file :

.../bin/precast.exe -mesh_file –batch prefix script .prs

PRS User Interface

The PRS script can be created interactively with a specific User interface. This interface can be called by the Manager with a right click on the "PreCAST" button and the selection of "PreCAST Script Editor (PRS)" menu.

The "PreCAST Script Editor (PRS)" menu is opening this PRS Editor with the following display.

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The principle is that the user is setting his case in the same way as it is done in the "Standard PreCAST", and each time an operation is performed, the corresponding line are added to the PRS Script in the bottom window.

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As an example, the assignment of materials is shown in the figure above, whereas the definition of interfaces is presented in the next figure.

For the Bourndary conditions, the operations are done in the same way as in the "Standard PreCAST" interface. The corresponding lines in the PRS script are shown hereafter.

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The main difficulty in Batch pre-processing is the definition of the locations (sets of elements or nodes) where Boundary conditions should be applied. The selections like "Select All", "Deselect All", "Select Remaining" can be used very easily. For more specific selctions, "Box" selections can be defined. To do so, the "Parametric selection" menu (on the top right) should be used. Then the user can select the "Box" or "Rotated_box" mode and the box can be defined interactively and labeled with a user defined name (to be used to the selection will be called).

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The different operations to specify a "Box" selection are shown in the figure above.

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The "Box" selection is working in the following way : • Select "Box" • Specify a name for the selection • Select nodes interactively on the screen (either single nodes with the left

mouse button or inside a Rubber band box with the right mouse button). You are allowed to rotate and zoom the part to select/deselect any node.

• When the "OK" button is pressed, the dimensions (i.e. the coordinates) of the correponding box will be written in the script.

The dimensions of the "Box" are taken as the min and max values of the coordinates of the selected nodes along the X, Y and Z axis. This means that the box coordinates are not depending upon the orientation of the model when the nodes are selected. The "Rotated_Box" selection is working in the following way : • Select "Rotated_Box" • Specify a name for the selection • Select nodes interactively on the screen with at least one Rubber band box

(with the right mouse button). • When the "OK" button is pressed, the dimensions (i.e. the coordinates) of the

correponding box will be written in the script. The dimensions of the "Rotated_box" are defined as follow : the box will have one face parallel to the plane of the screen (called X'-Y') at the time of the capture of the last Rubber Band box selection. The size of the box within this plane (X'-Y') will be the size of the last Rubber Band box selection which was made. The "depth" of the box (i.e. Zmin' and Zmax' in the direction Z', perpendicular to the plane (X'-Y')) is given by the selected nodes. If this depth is not appropriate, one can select or deselect nodes before pressing the "OK" button. In order to better visualize the extent of the box (i.e. the selected nodes), it is advised to set the "non-hidden" mode of the display. The following figure is showing the operations to be done in order to "Add" a new BC (1), to select a pre-defined "Box" (2), to Store the selection (3) and to Assign the desired BC entry of the database (4).

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Finally, "Default Run Parameters" can be assigned

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and specific Run Parameters can be set/modified. To do so, one should check the corresponding check-box (1) and set the desired value (2). Then, before changing tab, the "Store" button should be pressed (3) in order to write the corresponding lines in the script.

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Beside the interactive creation of the PRS script described above, it is also possible to create script lines using the *GENERAL, *SEQUENTIAL or *FINAL menus in the Script Editor Window. Then, the different keywords are available.

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Finally, the four buttons allow to do the following operations : save save the PRS script at any time during the pre-processing process (the script is saved anyhow at the end of the session). Please note that the "PRS PreCAST Script editor interface" is not creating or modifying the d.dat file. It is only creating a PRS file. update when lines are written manually in the script editor, the "update" button allows to store them in the Editor (not saved yet in the file) indent The indent button allows to indent the different commands for a better viewing (it has no effect on the running of the script) quit Closes the script editor window. The window can be opened again with the "prs" icon on the right of the icon bar.

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Script language

Most of the pre-processing operations can be controlled by a script ("prefix.prs" ASCII file). This section summarizes the commands which are available. The general philosophy is to have command names that resemble the menus of PreCAST. The different commands are specified using keyword lines. A keyword always start with a *. Spaces are allowed on a line before the keyword and a $ character corresponds to commenting out of the keyword. Keyword lines are often followed by data lines, which contain the parameters necessary to process the above keyword. Data lines cannot be commented out but will be ignored if the corresponding keyword line is commented out. Blank lines are also allowed in the script file. Warnings Forgetting the star before a keyword name leads to ignored the corresponding command. The script is case sensitive. The commands are grouped in three different categories : • GENERAL COMMANDS • SEQUENTIAL COMMANDS • FINAL COMMANDS

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Each of these categories should start by the corresponding keyword (*GENERAL, *SEQUENTIAL and *FINAL) and finish by *END_GENERAL, *END_SEQUENTIAL and *END_FINAL. The PRS script can be created in a User interface (see the "PRS User interface" section for more details). Remark This is a first version of the commands (ProCAST 2009.0). It is possible that some commands may change in the near future in order to be more powerful and efficient.

GENERAL COMMANDS

*GENERAL This keyword should only be defined once per script file together with a *END_GENERAL counterpart. It encloses the commands that are handled before the actual preprocessing session starts.

*VERSION version_number This keyword defines version of the software used to create the PRS script (e.g. 2009.1)

*SELECTION_TOLERANCE Tolerance This keyword defines the tolerance for deciding whether or not a surface node is part of a given geometrical selection.

*SELECTION_GEOMETRY Type name parameters This command defines a geometrical selection. The only available geometry at this point is a box (type Box) where the parameters are the coordinates (in 3D) of diagonal corners of the box (brick built on the coordinate axes). In this, 6 parameters are specified : x1, y1, z1 and x2, y2, z2. The “General_brick” selection is also available and defined by 4 points (see separate schema). The “Perpendicular_interface_brick” is computed from the normal to equivalent interface between domain n1 and n2 (input n2 = -1 afro a free surface or a non equivalent interface) as numbered when this selection is used for the first time. The node closest to the first point is used as a reference. Finally, a length along this axis must be entered. Two directions are input to describe the section of the box. These directions are projected on the local tangent plane. The selection “Rotated_box” is defined by giving 4 points : the origin and three ends for a set of vectors on which a box can be built.. The “General_cylinder” selection takes 8 parameters : first are the three coordinates of the center point, then the three components of the axis and finally the half-height and the radius of the cylinder.

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The “Perpendicular_interface_cylinder” selection has an axis normal to the equivalent interface between n1 and n2, given as first input (if n2 = -1, free surfaces or non equivalent interfaces are considered). A point is then input and the axis will be determined as the normal to the surface at the surface node closest to this point. Finally, the half-height and the radius of the cylinder must be input. *CHECK_OVERLAP Param This commands will activate the check of overlap in combo selections. Param can take the following values : none (no output), console (warning messages on the console), full (warnings, dump total overlap value to file, dump overlap.lck).

*CHECK_DEGENERATE_SELECTION Nb This command activates the degenerate selection (a selection that will select nodes but no element faces, such as a thin row of nodes) checker for geometry selections. If Nb is 0, a degenerate selection is emptied. For any other value, a lock file is dumped.

*CHANGE_DOMAIN_NUMBER Nb name nb_p Sets the domain number to Nb for elements with a domain number nb_p that have all their nodes inside the geometrical selection named "name". If nb_p is negative, only the selection criterion will be respected (i.e. all domains are considered) . When batch preprocessing starts from a mesh file, any domain number may be assigned to an element (renumbering may occur in PreCast if the added domain number is more than just greater than the maximum pre-existing domain number). When preprocessing starts with a d.dat file, only a pre-existing domain number may be assigned to elements (in fact, a non pre-existing number may be assigned for a transient state but is forbidden for actually running a calculation).

*OPTIMIZE_MESH flag Depending upon whether flag is “on” or “off”, the mesh will be optimized upon saving the d.dat file. If this keyword is omitted, no optimization takes place. *SYMMETRY_ROTATION values (6) Nb This keyword activates or modifies the symmetry rotation definition. The six values are the coordinates of the two end points of the axis and are to be given first. The last input is the number of sectors.

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*SYMMETRY_MIRROR_1 values (9) This keyword activates or modifies the first mirror symmetry. The 9 values are the coordinates of the three points defining the mirror plane.

*SYMMETRY_MIRROR_2 values (9) This keyword activates or modifies the second mirror symmetry. The 9 values are the coordinates of the three points defining the mirror plane.

SEQUENTIAL COMMANDS

*SEQUENTIAL This keyword should only be defined once per script file together with a *END_SEQUENTIAL counterpart at the end of the block. The commands within this block are processed in the order they appear.

*MATERIALS_ASSIGN_TYPE Nb type Nb is the number of the material Type is a string describing the type : MOLD, CASTING, FILTER, FOAM, INSULATION, EXOTHERMIC, RESERVOIR

*MATERIALS_ASSIGN_EMPTY Nb type Nb is the number of the material. Type is a string describing whether the material is empty or not : FILLED, EMPTY

*MATERIALS_ASSIGN_MATERIAL Nb name Nb is the number of the material in the mesh. Name is a string containing the name of the material in the database (can be any name in the materials db)

*MATDB_MODIFY Name type Values This will modify the material db entry with name name. The only available type of modifications at this stage is cst_density (modifies constant values of the density) and temptbl_density (modifies the temperature table definition of the density without affecting units,…). For modification of the exothermic properties, the following types have been added : tbl_burntfrac (modifes the burnt fraction vs. time table), cst_ignit (modifies ignition temperature) and cst_exotherm (modifies

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exothermic energy). For thermal conductivity, cst_conductivity and temptbl_conductivity are now available. For specific heat, cst_specificheat and temptbl_specificheat can be used. For the enthalpy vs. temperature table, temptbl_enthalpy is available. For the solid fraction vs. temperature table, temptbl_solidfraction is available. For the latent heat cst_latentheat is available. For the solidus and liquidus, cst_solidus and cs_liquidus are available. For the Newtonian viscosity as a function of temperature, cst_newtonviscosity and temptbl_newtonviscosity are available. For the surface tension, cst_surfacetension and temptbl_surfacetension are available. For permeability, solidfractbl_permeability and cst_permeability are available.

*MATERIALS_ASSIGN_STRESS Nb name Nb is the number of the material in the mesh Name is a string containing the name of the material in the stress database (can be any name in the stress db).

*STRESSDB_MODIFY Name type Values This will modify the stress db entry with name name. The only available type of modifications at this stage is cst_yieldstr (modifies constant values of the yield stress) and temptbl_yieldstr (modifies the temperature table definition of the yield stress without affecting units,…). For Young’s modulus, cst_youngsmod and

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temptbl_youngsmod are available. For Poisson’s ratio, cst_poissonsratio and temptbl_poissonsratio are available. For the secant definition of thermal expansion, tref_secantthermalexp, temptbl_secantthermalexp and cst_secantthermalexp are available. For a strain-based definition of thermal expansion temptbl_strainthermalexp is available. For the plastic modulus of an isotropic linear hardening law, cst_plasticmod and temptbl_plasticmod are available. To modify the annealing temperature, cst_annealingtemp can be used.

*DELETE_MATERIAL Nb Deletes the material number Nb from the geometry in the d.dat file. This will not work if enclosures are present. Warning : any prior modification of the p.dat file by the script will be erased by this command.

*GRAVITY_VECTOR gx gy gz gx gy and gy are the components of the gravity vector and they should be

expressed in m s-2

. Rotation of the gravity vector cannot be defined from the script.

*INTERFACE_ASSIGN_TYPE Nb type Nb is the number of the material pair Type is a string describing the type : equivalent, coincident, non coincident.

*INTERFACE_ASSIGN_HEAT_TRANSFER Nb type Nb is the number of the material pair Type is the name of an interface heat transfer condition in the db.

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*INTERFDB_MODIFY Name type Values This will modify the intf db entry with name name. The available types of modification at this stage are die_combo (modifies constant values of the values in a die combo condition : constant h, air coeff and temp, spay coeff and temp, attached 1 or 0, mold open, mold close, spray start, spray end), cst_standard, timetbl_standard and temptbl_standard. The keyword die_combo becomes cst_diecombo and temptbl_diecombo was added. *INITIAL_CONDITIONS_CONSTANT Nb temperature Nb is the number of the material and temperature is the corresponding initial temperature, which must be given in °C. The extract of boundary conditions cannot be scripted using this command.

*BC_ADD Type Type is a string corresponding to the type of boundary condition to be added to the list of BC : Symmetry, Periodic, Accordion, Temp, Heat, Vel, Pres, Inlet, Wall, Vent, Inj, Tur, Rot, , Displacement, PtLd, SrfLd, CurrentDensity, Voltage, MagPotential, Nucleation. Note that if a BC is added and no selection or db entry is assigned to it, it will not appear in the final d.dat file. The number of the newly created BC is equal to the last BC list number +1.

*BC_DELETE Nb Deletes the bc with number Nb

*SURF_SELECT_ALL Nb Selects the entire surface after highlighting boundary condition number Nb.

*SURF_DESELECT_ALL Nb Deselects the entire surface after highlighting boundary condition number Nb.

*SURF_SELECT_GEOM Nb name Selects the surface nodes corresponding to the criterion defined in selection geometry with name "name". This selection will be made active for bc of number Nb in the list. If Nb is set equal to 0, the nodal selection operation is performed only.

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*SURF_RESELECT_GEOM Nb name Nb_ext Selects the surface nodes previously selected for bc number Nb and retains only those inside selection named "name". The nodes that were previously selected but are out of the selection called name are assigned to boundary condition number Nb_ext.

*SURF_DESELECT_GEOM Nb name Selects the surface node corresponding to the criterion defined in selection geometry with name name. This selection will be made active for bc of number Nb in the list. If Nb is set equal to 0, the nodal selection operation is performed only.

*SURF_SELECT_REMAINING Nb Selects the remaining surface after highlighting boundary condition number Nb.

*SELECTION_COMBO Name Selection keywords This sores the result of combined selection operation and the combo selection is named name. As many selection keywords as desired can be used and the block should be terminated with and *END_SEL_COMBO keyword. These commands may not be nested however. Selection combos can only be used for selection of surface nodes.

*SURF_SELECT_COMB Nb name Highlits bc number Nb and selects the area defined by the selection combo named name (CURRENT for the active combo).

*SURF_SELECT_COPY Nb_i Nb_t This command copies and stores the selection from bc number Nb_i to bc number Nb_t

*BC_ASSIGN Nb name Nb is the number of the bc in the list and name is the name of the bc in the bc db. If "last" is used instead of name, the last bc of the db will be assigned.

*BC_STORE Nb selection_name The command stores a surface selection into the bc that has number Nb in the bc list. Selection name is either CURRENT for the active selection or the name of a combo selection. Only CÙRRENT is available at this stage. N.B: After saving, the list of BC will be rearranged so that the number of a given bc may change number from one preprocessing session to another.

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*BCDB_MODIFY Name type Values This will modify the bc db entry with name name. Two available types of modifications at this stage are cst_velocity (modifies constant values of the velocity), cst_hcoeff(constant value of convective heat transfer coefficient) and cst_temperature (modifies constant value of the temperature). It is now possible to modify tables for heat transfer coefficients using the types timetbl_hcoeff or temptbl_hcoeff. The number of points in the new table should be specified as the first value. Only the values in the table and number of points can be altered by this command. The other parameters (type of function, units,…) must have been defined previously.

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*BCDB_ADD Name type Values This will create the bc db entry with name name ("default" as name will use an automatic numbering scheme). The only available types of new bc at this stage are cst_velocity (creates a constant velocity bc) and cst_temperature.

*BCDB_DELETE Name This will delete the bc db entry with name name. If "Name" does not exist, no deletion is performed

*RUN_PARAMS_PREDEFINED Name This command will apply the predefined set of run parameters with name name.

*VIRTUAL_MOLD_CREATE Nb This command will create a virtual mold with size Nb x default size.

*PROCDB_MODIFY Name type Values This will modify the proc db entry with name name. The available types of modifications are : cst_axis (specify 6 values : 3 coordinates for the first point of the axis then 3 for the second point; cst_revol (specify the number of revolutions per unit time), cst_uvw : specify the uvw vector used in solid transport and translation condition, tbl_uvw : specifiy (starting with the number of points) the table given in solid transport or translation entry, tbl_rotation : specify the rotation angle vs. time table, tbl_revolution : specify the revolution rate table. The other parameters (type of function, units,…) must have been defined previously. *PROC_ASSIGN No name No is the number of the volume in the list and name is the name of the proc db entry. If “last” is used instead of name, the last bc of the db will be assigned.

FINAL COMMANDS

*FINAL This keyword should only be defined once per script file together with a *END_FINAL counterpart at the end of the block. The commands within this block are processed after saving the p.dat and d.dat file obtained in the sequential session.

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*RUN_PARAM_STRING String String is a line of the p.dat file as it would be added by hand. If a line corresponding to the chosen run parameter exists in the p.dat file, it will be replaced by String. If the corresponding run parameter is not present in the p.dat file, String will be added at the end.

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RUN OF THE CALCULATION SOLVER

Once the problem is set-up in PreCAST, two operations should be performed in order to run the solver :

• Run DataCAST • Run ProCAST

DataCAST DataCAST converts the input data stored in ASCII in the prefixd.dat file into binary data ready for the solver. DataCAST also cleans any previously existing result files and prepare the new ones. This means that when DataCAST is run, all results will be erased. Some error checking is also performed in DataCAST. DataCAST is called with the DataCAST button of the Software manager. When DataCAST is finished, one should press Return to close the corresponding command window (see the Module calls section of the Software Manager chapter for more details). See the "DataCAST -u" option at the end of this section.

ProCAST ProCAST is running the solver. No message is displayed by ProCAST, except if the solver is stopping for an unexpected reason. ProCAST is called with the ProCAST button of the Software manager. When ProCAST is finished, one should press Return to close the corresponding command window (see the Module calls section of the Software Manager chapter for more details).

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Status During the calculation, the status of the model can be monitored. To do so, use the "Status" button of the Manager (see the Module calls section of the Software Manager chapter for more details). The prefix of the case to be monitored should be present in the "Case" field and when the Status button is pressed, a window with the calculation status is displayed :

The status information is stored in the software installation directory (in the dat/stat directory), under the name prefix.stat. This means that the status of any calculation is available at any time, by any user who is using the same software installation. As a consequence, if two calculations with the same prefix are run in the same time, there will be a conflict and the status will be once the one of calculation A and once of calculation B. Such a conflict however has no influence at all on the calculations themselves.

Batch calculations It is possible to run several calculations sequentially in batch mode. To do so, a simple script should be written and launch in a Command window, as shown in the example hereafter (for Windows) :

cd calculations_A cd case_1 %ProCAST20091%\bin\procast case_1 cd .. cd case_2 %ProCAST20091%\bin\procast case_2 cd .. cd .. cd calculations_B cd case_3 %ProCAST20091%\bin\procast case_3 cd .. cd ..

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DataCAST -u option It is possible to run a calculation until a given step (e.g. step 500) with given settings and then to continue the calculation with different settings (e.g. if one would like to test different heat transfer coefficients from step 500). To do so, run the calculation as usual until step 500. Then, in order to prevent any error, copy the results in a safe place (as if a wrong operation is performed with DataCAST, all the results files will be erased). Load the d.dat file in PreCAST and make the desired changes (e.g. change a heat transfer coefficient). Change the Run parameter INILEV to 500 and set DT = 0 (so that the last stored timestep will be used as the first one of the restart) and exit PreCAST. Then, in order to update the calculation binary files, DataCAST has to be run. However, in order to prevent DataCAST to erase the existing result files, it is necessary to activate the -u option.

To use the "-u" option of DataCAST, the corresponding check box should be activated (see figure above). One could also launch it from a Command window with the following syntax :

datacast prefix -u Then, the solver ProCAST can be launched and the calculation will be continued from the step 500, with the new settings. Please note that it is not necessary to run DataCAST if only the Run Parameters are changed (i.e. only the content of the p.dat file is changed).

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TROUBLESHOOTING

During the execution of the solver, information are stored in the prefixp.out file. In case of problem, it may be useful to check the convergence of the solver in this file. At each timestep, a number of information are printed in the p.out file. The most important ones (hereafter in the case of a thermal only calculation) are the step number (1), the timestep (2), the fraction which has already solidified (3) and the iterations (4). If a calculation seems not to run well, it can be useful to look at the evolution of the timesteps, during the course of the calculation. If the timestep is significantly reduced, it means that the convergence of the calculation is poor. In addition, the number of iterations per timesteps (i.e. the number of line shown in (4) in the figure below, "T" indicating the resolution of the Thermal model) is a good indication of the quality of the convergence. The least number of iterations, the better the convergence.

In the case of a mold filling calculation, the prefixp.out file is looking like the following figure. One can check that the "free surface model" is well activated (1), that the model is filling with the filling percentage (2). The iterations (3) for the Thermal model ("T"), for the pressure solver ("P") and for the three components of the velocity ("U", "V" and "W") are shown. When more than 5-10 iterations are necessary, one can anticipate a convergence problem. Finally, the memory used by the calculation (for the current timestep) is shown (4).

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One of the Run Parameter is COURANT. This parameter is limiting the timestep in order to prevent the free surface to advance more than N elements during one timestep. When the mesh has a large number of elements and when the elements are small, this limitation may be quite drastic for small COURANT values. When this limit is reached, the following message appears in the prefixp.out file :

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The Run Parameter LVSURF allows to switch off the filling calculation when the casting fill fraction has reached the LVSURF value. A message is printed in the prefixp.out file to acknowledge this switch.

The fluid flow model will still be solved until the next stored timestep and then it will be switched off (see figure below). The calculation will then continue with a thermal only calculation (and stress if activated).

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When the calculation is not converging, the following message is printed in the prefixp.out file and the calculation of the given timestep is restarted with a reduced timestep. This can happen a few times during the calculation and one should not worry about it (typically, if the inlet velocity is suddenly increased, the timestep may be too large and it should be reduced through this mechanism). However, if the calculation does not converge several consecutive times, it may indicate a problem in the problem set-up or in the input data (non relevant material properties for instance).

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RESULTS VIEWING INTRODUCTION

Once the calculation is performed, the results can be viewed with the ProCAST post-processor, called ViewCAST. ViewCAST can be called from the Manager as follows :

The following results can be visualized in the post-processor :

• snapshot (or maps) • slices (or cuts) • scan of slices • x-ray views • evolutions

Depending upon the type of calculation which was performed, the following entities (or variables) can be viewed (raw results) : • Scalar fields :

• Temperature • Fraction of solid

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• Heat flux magnitude • Velocity magnitude • Pressure • Stresses • Strains and displacements • ...

• Vector fields :

• Velocities • Heat fluxes

This chapter is describing how these results can be viewed. In the Result analysis chapter, the display of more entities, such as porosity, solidification time, secondary arm spacings, etc... will be described. The export of the calculated results, to be used in other softwares are described in the Results Exports chapter. Once ViewCAST is started, if the prefix of the case is well defined, the case is automatically loaded in the post-processor and the initial temperature field is displayed :

The background of the screen can be switched from black to white in the "Parameters/Reverse Video" menu :

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The screen is divided in different zones : 1. Display zone 2. Scale zone 3. Information zone 4. Menus 5. Icons 6. Tape player The post-processor is "driven" by the Menus, the icons and the Tape player :

Firstly, the case should be opened in the File menu (if it is not opened automatically when the ViewCAST is launched from the Manager). Then, the field (scalar) to be displayed (e.g. Temperature) is selected in the Contour menu. In the case of vectors, the desired field is selected in the Vector menu - see the Field selection section for more details. The times (or steps) to be displayed are selected in the Steps menu, whereas all the parameters to configure the display (e.g. symmetry, cut-off values, type of display, ...) are defined in the Parameters menu - see the Display parameters section for more details. Then, the Picture menu allows to select the type of display (i.e. snapshot, slice, scan slices or cut-off view) - see the Display types section for more details.

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Once these selections are made, the display is activated with the Tape player, either as individual pictures or frame, or as animations (see the Tape Player section for more details). The X-Y Plots menu allows to draw curves (time evolutions) of the different fields (see the Curves section). The Actions menu allows to calculate some parameters from the raw results (such as SDAS, isochrons, Niyama, etc...) - see the Results analysis chapter for more details. Please note that the Actions and X-Y Plots menus are replacing the former module PostCAST (version 400 and before), as well as the File/Export menu.

The Geometry manipulation, as well as the different viewing modes is described in the Geometry manipulation section. To File/Exit menu allows to quit the post-processing session. Upon Exit, the user is asked whether he would like to keep the information about the current orientation of the model as well as the definition of the material display (i.e. which materials are active and in which mode) for the next launch of the post-processor.

GIF/AVI capture All the pictures which are displayed in ViewCAST can be captured as GIF/AVI

files or GIF/AVI animations. To do so, the icon should be used, which opens the following window

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The file name can be specified and one can browse in the desired directory (by default it is stored in the working directory and the file name corresponds to the case prefix) - the suffix (.gif or .mpg) is optional. One has to select between a Still picture or an Animated picture and to select between the GIF or the AVI format. It is also possible to activate the Reverse Video (with the "Reverse Video" check box) in order to have a white background. Then the picture is stored when the "Apply" button is pressed. For an animation, it will start to store the animation when the Forward button of the Tape player is activated. The "Cancel" button allows to exit without any action. If the filename is already existing, the following prompt window is shown :

One has the choice between "Append" (i.e. to append or add the picture to the previous one(s)), to "Overwrite" (i.e. to replace the existing file by this one) or "Cancel" to abort the capture operation. The AVI files are compressed using a "Motion jpeg" compressor. It has been observed that with old versions of Powerpoint, such "Motion jpeg" files were not recognized, unless they are renamed as prefix.mpg (instead of prefix.avi).

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When an animation is stored in the GIF format, it can be interrupted at any time (and the GIF animation will be stored until the interruption). However, it is not possible to interrupt an animation when an AVI file is created. If the animation is interrupted before the end, the AVI file will not be created. Thus, one has to specify the starting and ending steps before the creation of an AVI animation.

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FIELD SELECTION

The entities to be displayed have to be selected in either the Contour or the Vector menu. Contour corresponds to scalar variables, such as Temperature, Fraction of solid, Heat flux intensity, Pressure, Velocity magnitude, Principal stress, X-displacement, etc... Vector corresponds to vector variables, such as Velocities or Heat fluxes. It is possible to display either one Contour or one Vector field at a time, or to superimpose one Contour field, with one Vector field.

Contour The Contour menu is divided according to the different models which can be activated in the ProCAST solvers. The different "Contour" fields which are available are shown hereafter

One should note that the "Solidification Time" corresponds to elapsed time between the liquidus and the solidus temperatures. The Shrinkage Porosity is only calculated in the Run Parameter POROS is set to a non-zero value.

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As the stresses (i.e. the stress tensor) are calculated at Gauss points in the solver, it is necessary to compute in the post-processing the different stress entities that can be viewed (e.g. Effective stress, Principal Stress, Sigma X, ...). As these calculations can be rather long, it is possible to compute all the desired one in one shot, with the "Prepare Stress Results" option. In this case, the following panel appears :

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The stress result files which are present and up-to-date are shown in Green. The ones which are not present are shown in Red. If there are files which are present but not up-to-date (i.e. these files are older than the latest computed stress results by the solver), they appear in Orange. In this panel, it is possible to select all the desired stress results to be computed and to press "Apply" to start the computation. The results which are in green will not be recomputed (unless the "Overwrite Existing Files" is checked). Remarks on the Stress results • The "Average Normal Stress" corresponds to the average of the normal stresses

along the X, Y and Z planes. This does not correspond to a stress normal to an external surface (thus it is possible that the Average Normal Stress is not zero on a casting surface).

• The "Displacement -> Plane" option corresponds to the difference (between the initial timestep and the selected timestep) of distance between a User specified plane and a given point (the distance is taken normal to the plane).

• When Stress results are to be viewed from a CD-ROM (on Windows only), the calculated stress results (e.g. Principal Stress 1) can not be stored on the CD (as it is Read-only). Thus, when the directory where the case is located is in Read-only mode, automatically, the stress results are created and stored in a local file on the PC and are automatically used (even in a latter post-processing

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session). These results are stored in a directory named : C:\Documents and Settings\USER\Local Settings\Temp\Prefix . One should just be careful that if two cases having the same prefix are visualized from a CD, the data will be overwritten.

Please note that the fields which are shown in the menus correspond only to the available result files in the working directory. For instance, if results are computed in the "Action" menu - such as Niyama (see the Result analysis chapter for more details), the corresponding item will be added in the menu.

Additional Contours Since version 2007.0, it is possible to have new customized contours in the Additional sub-menu.

These contours corresponds to prefix.usf files. The Fluid Front Tracking results (see the "Results analysis/Fluid Front Tracking" section for more details) are stored in such file and are thus accessible in this "Additional" sub-menu.

Vector Vector results, such as Heat Flux and Fluid velocity can be selected in the Vector menu.

It is possible to view both vectors and contours, if desired. In this case, the vectors will be displayed in white (respectively black). If vectors only are shown, the color of the vector can be set in the Parameters menu (see the Display Parameters section for more details) to the vector magnitude, to the temperature or the pressure. In order to shown the vectors only, the Contour/None option should be selected.

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DISPLAY TYPES

The type of display can be selected either with the following icons

or with the Picture Menu

Snapshot - 3D view of the selected field (e.g. Temperature), displayed on the surface of the selected domains. For filling the free surface is viewed in 3D. This mode can be accessed directly with the F5 key.

Slice - 2D cuts (shown within the 3D model). One or several slices can be selected, either along the X, Y and/or Z planes or along any plane. This mode can be accessed directly with the F6 key.

Scan - Scan of 2D slices along either the X, Y or Z axis. This mode can be accessed directly with the F7 key.

CutOff - X-Ray view of the inside of a model. The model is made partially transparent (according to a criterion such as above a given temperature) in order to see features which are inside the model, such as pockets of liquid, surrounded by a solid shell (which is made transparent). This mode can be accessed directly with the F8 key. The selected mode can be viewed by a red square around the corresponding icon.

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Examples of Snapshots (during filling and after), of slice and CutOff (X-Ray) view

Example of Scan slices

Each Display type, except Snapshot, has ad-hoc settings (available in the Parameters menu), as described hereafter (Slice Data, Scan Data and Scan Data).

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Slice definition For Slice Data definition (see figure below) : 1. Select "Slice Data" in the Parameters menu 2. Select "Add" and then XYZ Plane (for orthogonal slices). This will open the

slice selection window (3) 3. Select the X, Y or Z plane and then define the location of the plane with the

slider 4. The plane is shown on the model

5. Press "Apply", the corresponding selection will appear in the list (6) and the

slice will be displayed.

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It is possible to use the Tape Player at this stage to see this slice over the timesteps, either as single pictures or as animations.

As shown in the figure below, several slices can be selected. Moreover, the slice characteristics can be stored in a file (file named "prefix.clip" in the local directory) with the "Store" button and can be retrieved in a later session with the "Read" button. The "Delete" button allows to delete the selected slice. The Show "Yes"/"No" toggle allows to activate or deactivate slices, without deleting them.

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In the following case, two slices are activated, as shown in the frame above.

When one slice only is activated, one can draw this slice with or without the Background (using the "Display Background" button.

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With "Display Background : None", only the slice is shown (upper right). With "Display Background -", the slice is shown together with the background (upper left). With the "Display Background +", the foreground is shown, up to the slice (lower left). When the model is rotated (for instance around a vertical axis in the above example), the background becomes the foreground and vice-versa. This option is not available with more than one slice. With the "Add->" button, it is also possible to select "Any Plane" :

In this case, the following window opens. One should define the slice plane by the coordinates of three points. To select interactively the points on the mesh, the "Get Co-ord" button can be used (to select the point which is highlighted in red). Once the three points are selected, it is possible to move this plane along its normal, with a given Offset.

It is also possible to rotate this plane with the "Rotate" button. In this case, the following window allows to define the rotation axis, as well as the angle of rotation.

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Finally, the "Copy Plane" is used to copy a plane which was already defined in order to modify its characteristics. This is especially useful when one would like to define several parallel planes which are not in the X, Y or Z directions. One will define one plane with the standard Anyplane definition procedure and then, one will copy this plane and offset it to the appropriate value. This can be repeated for the other parallel planes.

Scan definition The definition of the Scan parameters is done in the Parameters/Scan Data menu, which opens the following window :

The Scan direction is selected, as well as the number of planes (or slices) which will be shown. The largest dimension of the model in the selected direction is divided by the number of planes. Then, the display and the scan through the planes is activated with the Tape Player. Beside this slice mode, it is possible at any time to slice interactively the model, using the "Scan" slider (see figure below).

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Cut-off definition The Cut-off (or X-Ray) parameters are defined in the Parameters/CutOff Data menu, which opens the following window :

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The Cut-off parameters are defined by two values (e.g. two temperatures). Then the user has to select among five different display possibilities : • Above Red : only the zones which are above the upper value (in red) are

shown • Below Blue : only the zones which are below the lower value (in blue) are

shown • Inbetween Bounds : only the zones which are in between the upper and the

lower values are shown • Outside Bounds : only the zones which are below the lower value and above

the upper value are shown • Isosurfaces : the isosurfaces corresponding to the two values are shown The figure hereafter is illustrating these different possibilities.

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Shrinkage and Advanced Porosity display When the Shrinkage Porosity or Advanced Porosity contours are selected for the

first time, automatically, the "cut-off" mode is activated, with the definition "above 0.01" (which corresponds to a porosity value higher than 1%). Of course, it is always possible to go back to the normal snapshot mode, by clicking on the

snapshot icon .

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DISPLAY PARAMETERS

Firstly, the timesteps to be viewed should be defined in the "Steps" menu, which opens the following window :

The user can choose between Steps and Time increments. In blue, the available minimum and maximum values are shown. The time values are always indicated in seconds. If the selected Step increment is smaller than the available stored one, it will take the first available step for the display. If ViewCAST is launched during a calculation, the "Update" button allows to "refresh" the available steps and to view what has been calculated between the launch of ViewCAST and the current instant. One can also set "ViewCAST" such that the update is made in a "continuous" mode during the calculation (this is useful when ViewCAST is launched while the ProCAST calculation is still running). To do so, the "Setup" button (of the above screen) should be pressed and the Update interval can be specified (please note that if it is intended to leave the ViewCAST session opened for a few hours, it is advisable to set an Update interval not too small, as this will load the CPU) :

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The Display parameters are defined in the Parameters menu :

Reverse Video By default, the background of the screen is black. It can be reversed to white with the Reverse Video option.

Free Surface To visualize a mold filling four options are available to view the free surface (i.e. the surface between the liquid metal and the air) :

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The option "Free Surface (Foreground)" is used to view the free surface even when it is hidden by the liquid or the rest of the casting. One can see in the upper figure hereafter (Back face) the free surface in the ingate. If we rotate the casting (lower figures), the free surface is behind. If the Free Surface is ON, we do not see it. If the Free Surface is set as "Foreground", one can see it although it is behind. Of course, one can also see ONLY the free surface.

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The "Foreground" option can be quite useful to view entrapped gas pockets (which are fully surrounded by liquid).

Enclosure In the case of a radiation problem with an enclosure (this is valid only for surface enclosures as solid ones are considered as materials) the display mode of the enclosure can be selected among six choices : Invisible, Wireframe, Hidden, Solid, Translucent or Shade :

The following figure shows an example of a shaded enclosure.

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Feature Angle When the geometry is displayed in Wireframe, one can tune the "density" of lines. In the following example, a Feature Angle of 10 and 60 degrees has been used.

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Vector settings When vectors are selected, it is possible to color them according to the vector magnitude or according to Temperature or Pressure. By default, the color is White. When the "Parameters/Vector Settings" menu is called, the following panels opens.

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One can choose between an automatic vector length or a manual vector length. It is also possible to define a Unique vector length (i.e. all the vectors will be displayed with the same length, regardless of the vector magnitude (except if it is zero). When vectors are shown together with a Contour Plot (i.e. a scalar variable such as Temperature), it is not possible to color the vectors. The vectors can be plotted with or without the arrow at the tip of the vector.

Displacement Mag. In the case of Stress calculations, the display of the deformations can be artificially increased in order to better view them. The real displacements are multiplied by the "Displacement Magnitude" value.

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Slice Data, Scan Data, CutOff Data These options are described in the "Display types" section.

Titles Titles (text), arrows and cirlces can be added to the graphics, using the Parameters/Titles menu, which opens the following window :

Then, one can "Add ->" either a String (text), an Arrow or a Circle. When a String is selected, the text has to be typed in the corresponding field and then the text should be placed with the mouse. When an Arrow is selected, it should be located with the mouse. The first click should be at the starting point of the line and the second click should correspond to the end of the arrow. For circle, the two opposite corners of the square enclosing the desired circle should be defined. To delete an item, click on the desired one (in the left grey zone), which will highlight it in red and then press the Delete button. All the information of this panel can be Stored in an ASCII file and retrieved (with the Read button) for later use.

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Symmetry For cases which have been calculated with symmetry, it is possible to "reconstruct" the full geometry, using the symmetry menu :

The figure below illustrate a mirror symmetry. For more details about the definition of the symmetries, please refer to the Radiation section of the Pre-processing chapter.

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Display Foam In the case of a lost foam calculation, one can display or not the foam with this toggle menu.

Display Pipe In case of porosity, if piping or macroshrinkage occurs, the corresponding volumes will be shown as empty. However, in the visualization of the "Shrinkage porosity", it may be useful to view together the porosity and the pipe shrinkage. To do so, the "Display Pipe" OFF mode will allow to see the empty regions as "Shrinkage porosity" with a value of 1 (i.e. 100% void). This mode is only applicable for the Contour "Shrinkage porosity" and will not affect the viewing of the other fields, such as the Temperature, Fraction of solid, ...

Particle tracing The particle tracing allows to follow streamlines during the filling. The particle traces are calculated during the filling calculation (as it is needed to have access to all the timesteps, which is not the case during the post-processing). To do so, "virtual particles" are launched at each inlet node (defined by a velocity BC, an

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inlet pressure BC or an Inlet BC) at given intervals specified by PFREQ (see "Flow Run Parameters"). This means that it is not possible to compute particle traces in the case of tilt casting or casting with a filled reservoir of material (as there are no inlet boundary conditions where particles could be launched). Moreover, if the inlet is applied to a few nodes only, the number of traces is not very significant. This will be improved in future versions with more sophisticated means to launch particles. To view the Particle traces, activate "Particle Tracking" in the "Parameters" menu. The traces can be viewed either alone or together with any contour or vectors. One should note that the traces are always displayed in the foreground of a contour plot (no hidden view of the traces). In order to allow the viewing of successive batches of particles, the "tail" of the traces are erased, as the traces are progressing, leaving the place to new traces.

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Depending upon the geometry and the mesh size, it is possible that one or two particles are going out of the model. Please note that this does not harm the other results.

Tilt In case of a tilt pouring calculation, it is possible to disable the viewing of the model rotation. By default, the display of the rotation is active.

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Display Undeformed

In a Stress calculation, it is possible to superimpose the Undeformed geometry (in wireframe mode) to the deformed geometry. The extent of the part deformation can be adjusted with the "Displacement Mag." option. If the wireframe has "too many lines", it is possible to adjust that with the "Feature Angle" option.

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Scale The scale can be modified by a direct click on the scale itself (1). Then, the Scale settings panel opens (2).

The scale can be defined either automatically, or semi-automatically, via the "Min-Max" or "Semi-Auto" settings. It is also possible to change each value independently (with the Manual field), by clicking on each value to be changed.

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For the temperature scale, if there is a material where the solidification range is defined (i.e. a casting material), there is also the possibility to select automatically the Solidus-Liquidus interval (Tsol-Tliq). In the same line, when the Temperature is displayed, the Solidus and Liquidus temperatures are indicated on the color scale :

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It is possible to deactivate this display by unchecking the "Display Tsol-Tliq" in the above window. When a scale was defined other than "Automatically", the minimum and maximum values are stored for each field (the storage is done upon exit of the model if the "Store the last view and Exit" option is selected. When the model is loaded the next time, these settings will be automatically retrieved. The values are indicated in the "Stored" field (the values can not be modified interactively, use the Min-Max fields above). The values are stored in a local file called prefix.scale (this file can be copied in an other case if one wants to use the same values for this new model). Finally, the color scale can be change, by clicking on the color map itself. The following panel opens and the colors can be changed. It is also possible to store and load a different color scale.

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One should note that the scale and the color map is stored in memory for each field (e.g. temperature, fraction of solid, velocity magnitude, ...). Thus, if the scale is changed for the display of temperature and then fraction of solid is shown, when the temperature field is displayed again, the modified scale is kept.

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TAPE PLAYER

To activate the display, the Tape Player must be used. This allows to display either individual pictures or animations.

As for a Tape recorder, the Tape Player has the following functions.

Displays the first define time or time-step (Goto first)

Plays the animation backwards (Rewind)

Displays the previous step (Step back)

Pause (stops the animation)

Display the next step (Step forward)

Plays the animation forwards (forward)

Display the last define time or time-step (Goto end) The definition of the first and last times or time-steps, as well as the time or time-step increment between two frames is made in the Steps menu (see the Display parameters section for more details).

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CURVES

Curves can be viewed in ViewCAST, using the X-Y Plots menu. This allows to visualize time evolutions of the calculated fields, such as Temperature, pressure, velocity, etc... Please note that these capabilities are replacing the former PostCAST module.

Three types of selections are available : • Interval - selection of the curves every N nodes • Nodes - selection node by node • External - loading of a set of external curves (e.g. measurements)

Interval When Interval is selected, the user has to specify the Nodal interval. This means that curves will be selected every N nodes (1, 501, 1001, 1501, ...). Only the nodes of the materials which are active (as Solid) will be selected.

In addition, the user can select the Units which will be used for the display of the curves. When the Apply button is pressed, the curves are read in the files and displayed.

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Nodes When "Nodes" is selected, the following node selection window appears :

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The node numbers can be entered manually, or an interactive selection can be

made with the button.

In addition, the user can select the Units which will be used for the display of the curves. When the Apply button is pressed, the curves are read in the files and displayed. The node numbers (as well as the defined scale) can be stored (Export) and retrieved (Import) in a file. To do so, the "File" button should be pressed and the following window is opening :

In the case of an Export, the file name should be specified and it will be stored in the working directory. For Import, one can "Browse" the desired file. The format of the Export file is the following : -1 0 3.56 10. 1550. 0 10 30 100

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234 The first line contains the scale. As the scale is optional, the line should start by a "-1" and should be followed by xmin, xmax, ymin, ymax. Then, there is a "0" or a "1" to specify whether the Y-scale is defined automatically of not. A value of "0" means that the specified ymin and ymax are taken into account, whereas a value of "1" means that the Y-scale is set automatically. Then, the list of the nodes should be specified. Finally, a file named "prefix.tt" is created when the curves are displayed, with the x and y coordinates of the displayed curves. These data can be then either viewed together with other results (see the External section below) or exported to spreadsheets (e.g. Excel).

External When curves are selected with the Nodes mode (see above), the displayed curves are stored in the same time in a text file named "prefix.tt". The fist line of the file (see below) contains the number of time-steps (132), the number of stored curved (3) and the corresponding node numbers (567, 9587 and 23129). Then, each line contains the time and the field values for each curve.

Any file which as the above format can be loaded and displayed in ViewCAST with this External option :

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The desired files should be selected with the Browse. Please note that if the format should be as described above, the name of the file is free. Once this selection is accepted with the Apply button, the selected curves will be displayed in the same time as the ones selected with the Nodes option.

X-Y Plot settings The display of the X-Y plots can be tuned in the X-Y Plot settings window. For the settings of the time scale, the calculated minimum and maximum values are shown in blue (1). The vertical scale can be adjusted automatically with the "Auto" check box (2).

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GEOMETRY MANIPULATION

The geometry can be manipulated with the following icons :

Opens the Rotate definition window (see below)

Restores the original orientation of the model (with the Z-axis perpendicular to the screen)

Interactive zoom (zoom up when the mouse is move towards the bottom of the screen)

Auto-scale (or zoom out)

Interactive center of the model (the location which is clicked is moved towards the center of the screen)

Interactive drag of the model

Rotation When the Rotate icons is activated, the following Rotate window is opened :

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With the X, Y and Z sliders, the rotation can be prepared. Exact angles can be manually entered in the fields on the right. The rotation will be applied only when the "Rotate" button is pressed. If the "Rotate" button is pressed again, a new rotation (with the same values) is applied again. The "Reset" button resets all the sliders to zero. By default, rotation are with positive angles. If one clicks on the "+" sign, it becomes negative (for negative rotation).

Automatic Rotation in the X-direction , in the Y-direction and n the

Z-direction can be activated, as well as a standard isometric view . When the left mouse key is used, the model is oriented with the X, respectively Y and Z, axis perpendicular to the screen, pointing outwards, whereas the opposite orientation (pointing inwards) can be obtained with a right mouse key click. Finally, the X, Y and Z keys can be used to rotate the model by 10° around the x, y and z axis respectively. When the <ctrl> key is pressed in the same time, the rotation direction is reversed. When the <shift> key is pressed in the same time, the rotation is by 30° instead of 10°.

Interactive Rotation At any time, the model can be rotated interactively with the mouse. The left mouse key should be pressed and the model is rotated when the mouse is moved. The center of rotation corresponds to the center of the screen (green arrow). If the "Shift" key is pressed during the rotation, the model will rotate around an axis which is perpendicular to the screen and located in the center of the screen (green cross). The rotation is activated upon the horizontal motion of the mouse (while the left mouse key is pressed).

Zoom

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Beside the zoom icon (which allows to increase or decrease the size of the model), the F2 and F3 keys can be used to increase, respectively decrease the size of the model (zoom in and zoom out). Moreover, with the center mouse key, it is possible to zoom interactively a specific zone of the model with a rubber band box. Once the center key is pressed, it defines one corner of the rubber band box and the opposite corner is defined by the movement of the mouse until the key is released. Then, the zoomed model is automatically displayed. It is possible to zoom the model several time using this

technique. To zoom out, use the Auto-scale icon .

Stored Views It is possible to store 6 different views in the "Parameters/Store View" menu. The views are containing the orientation of the model as well as the material selection.

When a small arrow is following the View-X, it means that a view is stored already. To store a view in a View-X which is available, just click on the Parameters/StoreView/View-X. To retrieve (or Restore) a given view, use the

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"Restore" option (one can also use the Ctrl-... key where ... is the number of the view (1 to 6)). With the "Replace" option, the current view will replace the one which was previously stored. The "Reset view" (or Ctrl+0) will automatically reset the orientation of the model in the isometric view with the gravity pointing downwards. These views are stored in a file named prefix.lv (only if the option "Store the last View and Exit" is selected upon exit of ViewCAST). Please note that in View-1, it is always the last view which is active on the screen upon exit which is stored (which will replace any previously stored one). Please note that this *.lv file is not compatible with versions before 2006.0.

Material selection

The Material selection icon opens the Material selection window, which allows to define which material are display as well as the type of display.

The list of the all the available materials is displayed. On the right, the colored columns allow to specify the display attribute of each material, according to the following nomenclature :

• SO : Solid (displays the selected field values - e.g. Temperature) • IN : Invisible (hide the selected material) • WI : Wireframe (displays the selected material with wireframe

only) • HM : Hidden mesh (displays the FEM mesh in hidden mode) • SH : Shaded material • TR : Transparent material

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For each material, one should click in the desired column and a "X" will be displayed. To define all the materials with the same selection, one could click on the label (e.g. click on "IN" will make all the materials invisible). Finally, when the apply button is selected, the display will be updated with the corresponding selections.

Explode materials In the Materials selection window, there is the "Explode Materials" button, which opens the following window. For each material, it is possible to define an offset for its display. If some materials have no interface between them (EQUIV), they will be considered in the same group and they can not be exploded separately.

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When the Apply button is pressed, the corresponding offsets are applied, leading to a picture as follows :

Display node and element numbers The node numbers of the surface of the mesh can be viewed with the "Ctrl-N" keys. When "Shift-Ctrl-N" keys are pressed, a small window is opening :

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One can enter a node or an element number. By pressing the "Node" button, all the elements which are connected to the specified node are displayed :

If the "Element" button is pressed, the nodes which belong to this element are listed :

Pick option

The icon allows to pick a location on the geometry and display the node number, the node coordinates as well as the field value (e.g. Temperature, velocity magnitude, ...).

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One should first click on the icon (which becomes outlined in red) and then click on any point on the surface of the model. The information are displayed in a yellow frame.

In the case of Stress models (i.e. deformed models), the displayed coordinates will depend upon the "Displacement Magnitude" which is set. In order to have the real deformed coordinate, one should set a Displacement Magnitude to 1 (with a value of 0, it will correspond to the initial location of the mesh at the beginning of the calculation). The Pick option is also available in PreCAST :

ViewCAST exit Upon Exit of ViewCAST, a message is asking to the user whether he would like to keep the Last View. If Yes is answered, a file named "prefix.lv" will be stored

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in the working directory. This file is containing the model orientation, zoom and position, as well as the material selections.

These settings will be used for the next ViewCAST launch's.

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RESULTS ANALYSIS CRITERION FUNCTIONS

ViewCAST allows to process the results which are calculated in the solver in order to built criterion functions or metallurgical results (Remark : this corresponds to the functionalities which were present in PostCAST in previous releases). The Actions menu give access to these functionalities.

R G L calculation RGL is a generic menu which allows to calculate the solidification rate "R", the cooling rate "L" and the gradients "G", as well as any combination of those. The solidification rate corresponds to the velocity of a given isotherm (e.g. the liquidus isotherm). Thus, the user has to specify at which temperature he would like to calculate the solidification rate (see "R,G Temp" in the figure below). One can notice that it is allowed to calculate the velocity of any isotherm for other purposes than a solidification rate. The cooling rate is calculated as a linear interpolation between two temperatures (e.g. between the liquidus temperature and 10°C above). Thus, the user has to specify these two temperatures (see "L Upper Temp" and "L Lower Temp" in the figure below). The gradient (magnitude) is also calculated at a given temperature, which should be specified by the user (and which corresponds to the same temperature as the one used for the solidification rate) - see "R,G Temp" in the figure below. When the RGL menu is activated, the following window opens :

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Firstly, the user has to choose between two methods to calculate the solidification rate. In Method 1, when each node reaches the specified temperature, a point is located along the temperature gradient some distance away and the time that it takes for the isotherm to reach that point is determined. R is then calculated as that distance divided by the difference in time. In Method 2, R is calculated as the cooling rate divided by the temperature gradient. Method 1 takes longer to compute, but it does not depend on the cooling rate. The results obtained by Method 2 are affected by the temperature levels used to calculate L. Four options are available for the calculation of the thermal gradient. One can either compute the "Total" gradient (i.e. all components of the gradient) or in either the X, Y or Z directions. Please note that the gradient is calculated at each node, when the "R,G Temp" is reached. This means that the gradient corresponds to a different time at each node.

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Then, the user has the possibility to combine the R, G and L variables together to obtain a criterion function (called Mapping factor). To do so, the coefficients a, b, c and d should be specified

and the Mapping factor "M" will be calculated as :

If the following parameters are used :

a = 1.0 b = 0.0 c = 1.0 d = -0.5

the Mapping factor "M" corresponds to the Nyiama criterion :

For the calculation of the Nyiama criterion, suggested values are :

• L Upper Temp = Tliquidus + 2 • L Lower Temp = Tsolidus • R,G Temp = Tsolidus + 0.1 * (Tliquidus - Tsolid us)

Finally, the units (length and temperature) used in the RGL calculation, as well as the output format (*m.unf, Patran or I-DEAS) should be defined. When the *m.unf output format is used, the Mapping Factors (M), the cooling rates (L), the temperature gradient (G) and the Isotherm velocity (R) can be selected for visualization in the Contour Menu.

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Feeding length The Feeding length provides the capability to calculate the distance between the solidus and some user defined critical temperature which represents some fraction solid beyond which feeding is impaired. This distance is then compared with a "critical feeding length," which is a simple linear function of the hydrostatic pressure. If the feeding distance exceeds the critical length, then porosity would be likely. The Feeding length was designed for the cases of directional solidification (such as DS or SX casting). Thus, it is not guaranteed that the Feeding length will work well in other cases. The critical Feeding Length is calculated as :

These constants A and B should be calibrated with experiments. The solidus temperature should be entered in the "Solidus" field (see below) and the temperature corresponding to a critical solid fraction (at which feeding is not anymore possible - typically 60-80%) should be entered in the "Critical" field.

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Please note that as the hydrostatic pressure is used in the Feeding length calculation, the gravity vector should be defined in PreCAST (but it is not necessary to run fluid flow). If a thermal only calculation was run and the gravity was not defined in PreCAST before the run of the calculation, it is still possible to load the case again in PreCAST, to set the gravity vector, to save the case and to exit. Then, "DataCAST -u" should be used (see the "Solver" chapter for more details on DataCAST -u, as well as the special care which should be taken in the use of this capability in order not to scratch the results). Then, the units used in the calculation, as well as the output format have to be selected. Once the Apply button is pressed, the Feeding length is calculated. It can then be viewed in the Contour Menu.

Isochrons An Isochron is corresponding to the elapsed time from the beginning of the calculation until a specific temperature is reached. The Isochrons can be calculated in the Actions / Isochron menu.

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In order to select the desired temperatures, two possibilities are available : "Semi Auto" and "Specify Temps". In Semi Auto, the user can select 15 temperatures (to calculate 15 isochrons plots) by specifying the starting temperature, as well as a "delta" increment between the temperatures (then the units and the output format should also be specified).

With the "Specify Temps" mode, the user can select any temperature (up to 15 isochrons). Again, the output format and the units should be selected.

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Once the Apply button is pressed, the Isochrons are calculated. They can then be viewed in the Contour Menu.

Alpha case "Alpha case" is formed as the result of reaction between liquid Ti metal and the

mold wall, leading to the formation of TiO2.

Alpha case corresponds to the thickness of the TiO2 layer at the surface of the Ti alloy casting in contact with the ceramic shell mold, in investment casting. This thickness depends upon the cooling rate, the casting geometry and the amount of oxygen at the mold/casting interface.

The alpha case thickness (tα) is calculated with the following equation :

where :

Do is the Diffusion Coefficient of oxygen in the liquid Ti alloy (m2/s) Q is the Activation Energy (J/molK)

co is the Surface Concentration of oxygen (wt %)

c∞ is the Bulk Concentration (wt %) c* is the Limit Concentration (wt %)

tα is the Alpha case thickness (m)

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The above parameters, as well as the output format, should be specified in the

following window. Please note that the Bulk Concentration (c∞) must be smaller than the Limit Concentration (c*).

Once the Apply button is pressed, the Alpha case is calculated. It can then be viewed in the Contour Menu.

SDAS (secondary dendrite arm spacing)

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The secondary dendrite arm spacing (also called SDAS or λ2 ) can be calculated

according to the following equations, where tf is the local solidification time and M a constant which depends upon the alloy properties.

The SDAS is calculated in ViewCAST according to the following parameters.

Tstart and Tend are the temperatures which are used to compute the local solidification time. Usually Tstart corresponds to the liquidus temperature, whereas Tend should be the temperature just above (e.g. 1 degree above) the first eutectic transformation. The Exponent corresponds to the power 1/3 in the above equation (it is thus recommended to set the Exponent to 0.33333) and M is the coarsening constant according to the above equation (which is alloy dependant).

The units for M should be [microns3/sec].

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For an Al-7%Si-0.3%Mg (A356), the coarsening constant M is equal to 680

[microns3/sec].

For an Al-2%Cu, the coarsening constant M is equal to 1400 [microns3/sec].

For an Fe-0.09%C (Low carbon steel), the coarsening constant M is equal to

29250 [microns3/sec].

For an Fe-0.6%C (Cast iron), the coarsening constant M is equal to 6050

[microns3/sec].

For an Fe-10%Ni (Stainless steel), the coarsening constant M is equal to 20600

[microns3/sec].

Once the Apply button is pressed, the SDAS is calculated. It can then be viewed in the Contour Menu.

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POROSITY

To analyse the porosity in a casting, several options are available :

• Temperature field with the cut-off option • Fraction of solid field with the cut-off option • Shrinkage porosity field • Niyama criteria for critical cooling rates • Specific RGL criteria

Temperature field and Fraction of solid field The porosity being primarily due to enclosed pockets of liquid, one can well observe them by looking at the Temperature or Solid fraction fields in cut-off mode (in order to visualize inside the casting during the solidification). For temperatures, it is recommended to select a cut-off value above the solidus temperature, whereas cut-off values of solid fractions below 70% shall be used.

Porosity When POROS > 0 is used, one can visualize the Contour called "Shrinkage porosity". Values corresponding to a level below 0.01 shall be considered as microporosity (to be viewed best with slices) and values above 0.01 are considered as macroporosity (to be viewed best with cut-off mode). See the "Porosity models" section for more details.

Niyama See the Criterion Functions section for more details.

Specific RGL criteria One has the possibility to define a customized criterion function, with the RGL option (see the Criterion Functions section for more details).

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FATIGUE LIFE INDICATOR

In the case of die casting, when a stress calculation is run, ProCAST calculates automatically the fatigue life in the dies. The model is based upon a "strain-driven" approach and a power law relationship, which corresponds to low cycle fatigue. During the calculation, the accumulated plastic strain (if any) is recorded at each location of the die. Then, the life of the die is calculated as a power law of this plastic strain. If this life is shorter than the previously calculated life at this given location, this latter value is stored. If there is no plastic strain, then, the elastic strain is recorded and the life of the die is calculated with an other power law relationship. Again, if the computed life is shorter as the previously calculated (at this same location), this latter value will be used. The parameters of the model correspond to measured values for a typical die alloy (H13 steel), published by the Society of Automotive Engineers. One should note that the values are measured at room temperature and thus, the effect of temperature is only taken into account through the temperature-dependant stress properties (i.e. Youngs modulus, Yield stress, Hardening, ...). Thus, one should consider that ProCAST calculates a "Fatigue life INDICATOR" and that it does not correspond to absolute values of number of cycles. No data are required for this model and it can be used as an indicator for different steel grades generally used for molds. One should notice that it should be mainly used to compare different designs with the same mold material (e.g. to compare the effect of cooling channels or of cycling time). One should not compare the influence of different steels on the "Fatigue life indicator".

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HOT TEARING INDICATOR

During a stress calculation, ProCAST calculates the susceptibility to hot tearing. The hot tearing indicator allows to model cracks which are forming during the solidification (i.e. it corresponds to openings in between dendrites which are not yet totally solidified and which are opening because of a tensile stress). Hot tearing are formed only above the solidus temperature. The hot tearing indicator is a "strain-driven" model based upon the total strain which occurs during the solidification. The model is computing the elastic and the plastic strain at a given node when the fraction of solid is between CRITFS (usually 50%) and 99%. There is no parameter for this model (except CRITFS which is a general stress Run Parameter). As the amount of plastic strain will strongly depend upon the stress properties in the mushy zone, the hot tearing indicator should be used to compare different designs with the same alloy. One should not compare hot tearing indicator levels for different alloys.

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CRACKING INDICATOR

The "Cracking indicator" model of ProCAST corresponds to cracking occurring after completion of solidification. The model is based upon the "modified Gurson" model. It corresponds to a plastic strain driven model. The cracking indicator model couples the stress calculation with the porosity calculation. It is valid with any porosity model. The cracking indicator is corresponding to a void fraction indicator (i.e. it calculates the amount of voids created by cracks, which have nucleated and grown under the influence of stresses). Plastic strain (and plastic strain only) will allow cracks to nucleate and grow (thus to create "crack void fraction"). The presence of porosity will increase the amount of crack nucleation and growth. All the plastic strain is taken into account (including the one forming in the mushy zone). There is no inputs needed for that model. One should note that the constants which are in the modified Gurson model, are not temperature dependant (as there is no indication in the literature about how these values should change with temperature). However, the temperature dependency is taken into account in one way by the stress material properties and thus the plastic strain (e.g. there will be less plastic strain at low temperature). This model is an "Indicator" which can be used for any material. The value of the scale of the indicator will strongly depend upon the material and the stress data. Thus, one should not compare two different materials, but one should use it to compare the same material in different situation (i.e. different cooling conditions, different stress state, different porosity level). This model corresponds to a "damage" model, which couples for the first time stress calculation with defects in the casting (i.e porosity). This model is very new and should be used with care as there is very little experience in this field at this stage. However, it could be very interesting to see the effect of design decisions on the level of damage (e.g. a reduced cooling will change the amount of porosity and/or change the amount of stress and thus, it will change the amount of cracks which may appear). The cracking model is activated with the Run Parameter CRACK = 1 or 3. The default value is 0. See the "Stress Run Parameters" for more details.

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FRECKLES INDICATOR

The "Freckles indicator" of ProCAST is based upon a local Rayleigh Number calculation. The algorithm is described in "Development of a Freckle Predictor via Rayleigh-Number method for Single-Crystal Nickel-Based Superalloy Castings", by C. Beckermann, J.P. Gu and W. Boettinger, Metallurgical and Materials Transactions A, Vol. 31A. To activate this model, the casting material properties should have been created in PreCAST with the Thermodynamic databases (see the "Thermodynamic Databases" section for more details), using the Ni database. When the properties are calculated, a file named "prefixls.dat" is created. This file (which contains the liquid solute concentrations) should be present in the working directory in order to be able to calculate the Freckles indicator. Moreover, the Run Parameter FRECK with a value of 1 should be added manually in the p.dat file. Freckles will occur only if the liquid density inside the mushy zone is decreasing with decreasing temperatures. In order to predict whether an alloy will have freckles, one can look at the liquid density in the prefix_rho.dat file (created by PreCAST when the material properties are created with Computherm). The liquid density is the last column of the prefix_rho.dat file. If the liquid density in the mushy zone is not decreasing (for decreasing temperatures), it is useless to run a Freckle calculation.

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FLUID FRONT TRACKING

During a filling calculation, ProCAST can calculate different indicators which allows to better quantify the filling pattern. Four different models (called "Junction models") are available :

• JUNCTION = 1 (or 11) : Front tracking indicator "Free surface cumulated volume" which corresponds to the local free surface area multiplied by the travelled distance (volume units). Particularly useful to quantify the amount of carbon inclusions in a lost foam process.

• JUNCTION = 2 (or 12) : Front tracking indicator "Free surface time exposure" which corresponds to the local free surface area multiplied by time (surface * time units) and can be used to quantify the amount of oxides transported by the free surface.

• JUNCTION = 3 (or 13) : Material age (time units) • JUNCTION = 4 (or 14) : Flow length (length units)

Each of these models is described hereafter. These values are calculated in the solver and are then transported by subsequent fluid movement. As these values are obtained by the resolution of an additional transport equation, it was observed that the additional CPU time can be significant (up to 20%). Thus, a simplified option is also proposed (where the additional CPU time is significantly reduced, but with of course less precise results). The simplified option can be activated with JUNCTION values of 11, 12, 13 and 14 respectively. To activate the calculation of the Fluid Front Tracking, the Run Parameter "JUNCTION" should be added manually to the p.dat file, with a value of 1, 2, 3, 4, 11, 12, 13 or 14 respectively (see the "Run Parameters/Flow" section for more details). The JUNCTION results can be viewed in VisualCAST in the FLUID section and in ViewCAST in the "Contour/Additional/Fluid Front Tracking" sub-menu (see the "Results viewing/Field Selection" section for more details).

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JUNCTION = 1 (or 11) - "Free surface cumulated volume" The Fluid Front Tracking indicator "Free surface cumulated volume" has the units of [cm3]. The principle of calculation of this indicator is the following : • At each point of the free surface, the displacement of the free surface during one

timestep, multiplied by the free surface area is calculated. This value is cumulated with the value of the previous timestep. In addition, this value is transported with the free surface and with the fluid flow.

• When two free surfaces are meeting, both values are added. • When there is no more free surface at a given location, the value of the Front

tracking indicator can still be transported by the fluid movement (during the filling - and after if FLOW = 1).

This indicator allows to identify the locations where oxides and impurities trapped at the free surface are most likely to end-up as well as to study the flow junctions. The following figures are showing the Front Tracking indicator "Free surface cumulated volume" for the same geometry cast with 4 different gravity orientations (and thus 4 different filling patterns). In each case, the gravity is pointing downwards.

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The top figure shows the values during the filling, whereas the bottom figure shows the results near the end of the filling.

Remarks • This Fluid Front Tracking is a qualitative INDICATOR only (not a quantitative

value).

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• For the Lost Foam, this value corresponds somehow to the amount of foam which was burnt in contact with this free surface. It is thus an indication of the potential defects which occur during lost foam burning.

• The numerical diffusion is slightly "diluting" the values of the indicator behind the free surface, instead of remaining a "sharp" value at the free surface.

• This algorithm can not be used for centrifugal casting (as a Relative rotating coordinate system is used).

JUNCTION = 2 (or 12) - "Free surface time exposure" The Fluid Front Tracking indicator "Free surface time exposure" has the units of [cm2*s]. The principle of calculation of this indicator is the following : • At each point of the free surface, the free surface area multiplied by the time.

This value is cumulated with the value of the previous timestep. In addition, this value is transported with the free surface and with the fluid flow.

• When two free surfaces are meeting, both values are added. • When there is no more free surface at a given location, the value of the Front

tracking indicator can still be transported by the fluid movement (during the filling - and after if FLOW = 1).

This indicator allows to identify the amount of oxides formed at the free surface and where they are most likely to end-up as well as to study the flow junctions. The following figures are showing the Front Tracking indicator "Free surface time exposure" for the same geometry cast with 4 different gravity orientations (and thus 4 different filling patterns). In each case, the gravity is pointing downwards.

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Remarks • This Fluid Front Tracking is a qualitative INDICATOR only (not a quantitative

value). • For alloys which are oxidizing (like Al), it corresponds somehow to the time

exposure during which oxidation can occur.

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• The numerical diffusion is slightly "diluting" the values of the indicator behind the free surface, instead of remaining a "sharp" value at the free surface.

• This algorithm can not be used for centrifugal casting (as a Relative rotating coordinate system is used).

JUNCTION = 3 (or 13) - "Material age" The "Material age" has the units of [s]. It corresponds to age of the material between its entry in the system (i.e. the inlet) to the given location. This information is available at every point of the liquid (not only at the free surface). This value is not cumulated upon junction of two fronts. Please note that a similar information can be calculated in the VisualCAST post-processing (in the "Results -> Create New Particles..." menu.) However, in this case, it will be done only on the stored timesteps instead of all the timesteps. The following figures are showing the "Material Age" for the same geometry cast with 4 different gravity orientations (and thus 4 different filling patterns). In each case, the gravity is pointing downwards.


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JUNCTION = 4 (or 14) - "Flow length" The "Flow length" has the units of [cm]. It corresponds to "travelled" distance of the material between its entry in the system (i.e. the inlet) to the given location. This information is available at every point of the liquid (not only at the free surface). This value is not cumulated upon junction of two fronts. Please note that a similar information can be calculated in the VisualCAST post-processing (in the "Results -> Create New Particles..." menu.) However, in this case, it will be done only on the stored timesteps instead of all the timesteps. The following figures are showing the "Material Age" for the same geometry cast with 4 different gravity orientations (and thus 4 different filling patterns). In each case, the gravity is pointing downwards.

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RESULTS EXPORTS INTRODUCTION

Different kind of calculated results can be exported in ViewCAST. The File/Export menu should be used for this purpose.

The results can be exported either in Patran or I-DEAS format, except the Stress results which can be exported in an ASCII format.

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GEOMETRY

When the File/Export/Geometry menu is selected, the following window opens

Firstly, the format of the output file should be selected (1). Then, as Patran or I-DEAS files do not contain the unit information, it is necessary to specify in which units it is desired to export the geometry information (2). In the case of stress calculations, as the geometry is deforming, one can choose to export the deformed geometry at a given timestep (3). It is also possible to export the geometry with the "reversed displacements" (4). This latter option is useful if one would like to run a stress model with a "negative" distortion in order to see whether the final shape will correspond to one of the original drawing. In this case, one should export the model in the d.dat format.

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RADIATION FACES

For a radiation model, the radiation faces can be exported in the Patran or I-DEAS formats. One should also specify the units which will be used in the exported file.

Radiation faces correspond to a "surface mesh" or radiative faces, like an enclosure.

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TEMPERATURE

For the export of Temperatures, three options are available for the selection of the time-steps to be exported, as shown in the menu below.

Interval With the Interval option, one can export temperatures according to the steps which are defined in the Steps menu (only the Steps selection will be used and not the Time selection) :

Then the format of the exported file (Patran or I-DEAS) and the units should be selected.

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Specify Steps Any step to be exported can be selected with the "Specify Steps" option. The selected time-steps should be entered in the following list :

The above window allows also to select the format of the export (Patran or I-DEAS), as well as the units. The data are exported when the Apply button is pressed.

Select Steps The "Select Steps" option allows to choose the desired steps in the list of the available timesteps :

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The selected steps are highlighted in red. The above window allows also to select the format of the export (Patran or I-DEAS), as well as the units. The data are exported when the Apply button is pressed. The clear button allows to clear all the selections. Once the data are exported, a log file with the exported steps is created. This file is named prefixt.log :

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HEAT FLUX

The heat flux can be exported in exactly the same way as the temperature - see the "Results Exports / Temperature" section for more details.

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DISPLACEMENTS

The displacements can be exported in exactly the same way as the temperature - see the "Results Exports / Temperature" section for more details. In order to Export the geometry with "reversed" displacements, please refer to the "Results Exports / Geometry" section for more details.

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STRESS

Two different Stress export capabilities are available in ProCAST : 1. Simple Export 2. Advanced Export (to be re-imported in other mechanical software) Both formats are described hereafter. The Advanced export allows to export stress results directly in Sysweld or Abaqus format. A generic ascii format allows also to export to any other Mechanical software.

Simple Export The stress results can be exported in exactly the same way as the temperature - see the "Results Exports / Temperature" section for more details. The only difference is that the stress results are exported in a "Neutral" ASCII file format in order to be imported in any stress software.

The format of this "Neutral file" is the following : Loop on the Timesteps Timestep Number_of_nodes Loop on the Number_of_nodes node_number, x, y, z, s1, s2, s3, s4, s5, s6 End_loop End_loop where x, y and z are the node coordinates and s1 to s6 are the six components of the stress tensor at the node.

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As ProCAST is calculating the stress data at the Gauss points, these values are interpolated at the nodes.

Advanced Export The Advanced Export is achieved in PreCAST (although the calculation is already done), in two stages : a) The stress results should be first "Extracted" (see the "Results extraction" section for more details). b) The Extracted stress results can then be Exported in Sysweld, Abaqus or Generic formats. Stress Extract The stress results should be "Extracted" first (in the "initial conditions/Extract" menu). It is mandatory to extract ALL the domains. If you would like to extract only a limited number of domains, you should first "Delete" the undesired domains (with the "Geometry/Delete-Add Materials" menu) and then proceed with the Extract. If only one stress calculation was performed (i.e. no chaining with Extracts), one should make an extract of the own results of the case. This means that in the "Browse", one should select the case itself (which is currently loaded in PreCAST). It is of course also possible to extract results from a different case.

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Stress Export Once the Extract is performed, the Export can be done (in the "File/Export" menu).

The available formats are "Systus/Sysweld" (*.ASC for the mesh and *.SSF for the stress results), Abaqus (*.inp for the mesh and *.asf for the stress results) and a Generic ASCII format (*.gmf for the mesh and *.gsf for the stress resutls). You should select the desired format and press the Store button. Generic Format The mesh file (prefix.gmf) has the following format :

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The stress export file (prefix.gsf) has the following format :

The following figure is a zoom of the above one.

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Abaqus Format See the next section (Abaqus Import). Sysweld Format See the next section (Sysweld Import).

Abaqus Import

Once the Mesh and stress data have been exported from ProCAST, the two files prefix.inp and prefix.asf are created. These two files can then be complemented and modified in order to contain the full Abaqus set-up. The exported mesh file (prefix.inp) has the following format. It can be used directly in the Abaqus set-up.

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The exported mechanical data file (prefx.asf ) has the following format (to be used directly in the Abaqus set-up - see hereafter)

The following figure is a zoom on the above one.

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The Abaqus set-up file (prefix.inp) shown hereafter was "built" direclty from the exported files from PreCAST. One should of course make sure that the material properties and models used in Abaqus are well the same (or consistent) as the ones used in ProCAST.

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Sysweld Import

The PreCAST export is creating the Sysweld format files *.ASC for the mesh and *.SSF for the stress results. These files can be used in the Sysweld set-up with the following procedure : • Prepare your Sysweld case, using the standard preprocessing methodology (use

the same - or consistent - mechanical and thermophysical properties as in ProCAST).

• Run the project to generate one state card in transitory files.

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• Import the thermo-mechanical state using the ad-hoc SIL script (see next figures). This state is automatically stored in card N° 1 of the transitory files.

• Reload the heat treatment project to create a restart project. • Run the restart project.

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PARALLEL SOLVER (DMP) INTRODUCTION

The goal of Parallel processing is to accelerate the computing time of a calculation, by distributing it on several processors. Different techniques are available and are described hereafter. SMP : Symmetric MultiProcessing In the SMP technique (often called Shared Memory Processing), the calculation is split in different CPU's which are sharing the same memory (see figure below). This technology is usually limited to a maximum of 32 CPU's.

DMP : Distributed Memory Processing Distributed Memory Processing is an architecture where each CPU accesses its own memory. Data are shared between processors through message passing. The send and receive operations require actions by the processors on both ends of the communication. The Message-passing Interface, or MPI, is the software standard that has been developed by an industry/government consortium. Such a configuration (see picture below) requires a very fast network between the CPU's.

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SMP/DMP combined architecture When each computer (node) has more than one CPU, sharing the same memory, one can combine the SMP and DMP principles to make a SMP/DMP combined architecture. Such a configuration (see picture below) requires a very fast network between the CPU's.

ProCAST Parallel architecture The Parallel version of ProCAST is based upon the DMP technology, using MPI. Depending upon the machine/cluster which is used, one can use either a DMP or a combined SMP/DMP architecture. One should note that it is also possible to use a single computer with several CPU's sharing the same memory.

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As the MPI technology is based upon the "Message Passing Interface", it means that the CPU's have to communicate between them. This emphasizes the importance of the network linking the different nodes. One can use either a network with a 1 Gigabit/s Ethernet switch to link the nodes. It is possible to have faster communications with for instance a Myrinet network (from Myricom). This latter solution is more expensive, but the gain in performances can be quite significant. As communications are critical for the performances, it is very important to use the appropriate switch as well as the appropriate cables (e.g. for a 1 Gigabit/s Ethernet switch, one should use Category 6 cables - or above).

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HOW DOES PROCAST PARALLEL WORKS ?

In order to distribute the calculation between the N processors, the geometry (model) is split in N sub-domains. This partitioning is done fully automatically by the software. It is done in order to balance the load between the processors as evenly as possible (i.e. almost the same number of nodes in each sub-domain) and in such a way that the amount of communication between the processors is minimized (i.e. the least number of common nodes between the sub-domains). This principle is illustrated in the figure hereafter.

Then, each sub-domain is allocated to one processor, as shown in the figure below (each color represents a sub-domain). The communication between the sub-domains is done automatically, through the fast network.

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The following pictures illustrate the partitioning of different cases. In the lower geometry, the partitioning for 2 and 4 CPU's is shown on the left and right, respectively.

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If such a partitioning is very efficient for thermal, radiation and stress calculations (as well as for flow calculations with an already filled cavity), it is not the case for filling calculations. As illustrated in the figure below (where the filling starts from the biscuit in the bottom of the picture), the first stage of the filling will occur only in the red sub-domain (CPU 1), whereas the final stage of the filling will take place in the purple sub-domain (CPU 2). This means that the CPU 2 will not do anything during a while at the beginning of the calculation, whereas CPU 1 will "sleep" near the end of the calculation. This will lead to a very poor balancing between the processors and thus a very bad performance.

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In order to prevent such detrimental behavior, one should rather have a partitioning like the one on the right (in the figure below), rather than the one on the left.

However, as one does not know how the cavity will be filled (this is why a calculation is performed !), a "dynamic partitioning" algorithm has been developed. At a given step, the flow front is at a given location (in blue in the figure below). The software is creating a layer ahead of the the flow front (the width of this layer corresponds to a number of elements, defined by the Run Parameter NFFWID). Then, both the liquid region and this layer are partitioned in sub-domains. Once the liquid is reaching the end of this layer (i.e. when the distance between the flow front and the end of the layer is less than NFFSAF elements), a new partitioning is performed. Thus, the frequency of the partitioning

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is directly influenced by the value of NFFWID. The smaller the value, the larger the numbers of partitioning. As the partitioning is taking some CPU time, one should specify a not too small value for NFFWID).

One should note that in the case of a filling problem, in the presence of a mold, two distinct partitioning are made. One for the thermal and radiation problem (which is done only once at the beginning of the calculation) and one for the casting domain only, which is dynamically re-partitioned. In order to perform this automatic domain decomposition, to manage the communication between the processors and to solve the linear system in a distributed fashion, several libraries are used : HP-MPI A Portable Implementation of MPI (Message Passing Interface). Depending upon the platforms, MPI can be called with different names. Parmetis A Parallel graphic partitioner PetSc The Portable, Extensible Toolkit for Scientific computation

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USE OF THE PARALLEL SOLVER

The Parallel solver is fully compatible with the Scalar solver. This means that the input and output files are strictly identical (except two additional Run parameters for the Parallel solver called NFFWID and NFFSAF). Thus, the Pre- and Post-Processing should be made in the Scalar version, as usual. The two "Parallel" Run Parameters (NFFWID and NFFSAF) should be added manually in the p.dat file. If they are not specified, the default values of NFFWID = 10 and NFFSAF = 2 are used. Recommended values are NFFWID = 10 to 20 and NFFSAF = 2 to 5 (see the "How does ProCAST Parallel works" section for more details about the meaning of these Run Parameters). Once a case is set-up in PreCAST, the standard "DataCAST" should be called.

Parallel version settings The Manager provides a direct access to the Parallel solver. To do so, the ProCAST Parallel option should be activated in the "Software Manager / Installation Settings / Parallel" window (see the "Software Manager/Software configuration" section for more details).

Additional settings can also be defined: Options (1) and (2): can be used to define additional default options to the mpirun command.

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MPI_ROOT : indicates where MPI run times and libraries are located. The different MPI used are delivered in the ProCAST installation and default locations are provided. Host file The "host file" list allows to select which CPU have to be used for a given calculation. If you have only one machine (with several CPU's), the "host file" list can remain blank. If you have more than one machine, you should fill the "host file" list (use the "Edit" button) with all the available machines followed by the number of CPU's of each one. Then, when you want to launch a DMP calculation on specific machines, you should select them in the list (highlight the desired ones in blue - hostname1 and hostname3 in the above example) and then launch the calculation on 4 CPU's (as hostname1 has 2 CPU's and hostname3 has also 2 CPU's). The hostname selection (as shown above) is valid for all the subsequent calculations which will be launched (even in the Manager is closed in the mean time) until the host file list is modified. If a DMP calculation is launched with less CPU's than the number of CPU's selected in the "host file" list, then only the first CPU's in the list will be used (i.e. it is not necessary to deselect the unused CPU's).

Parallel version execution Once the Manager is configured as described above, the "ProCAST" button will open the following window :

One can see in the above execution windows that a "Parallel" section is appearing. Please note that the format of the window may vary from one platform to an other.

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For the ProCAST solver, one still have in both cases the possibility to "Execute DataCAST first". On Linux, the execution in batch mode can also be used (in this case, the Batch log file can be defined - if nothing is specified, a file named DMP_runlog.txt will automatically be created

Then, for the Parallel solver, some parameters and options should be defined, before the Run can be launched.

First, the number of processors should be defined. If the radio button "Number of Processors" is selected. With the current version, the "Options(1)" and "Options(2)" fields may remain blank (no specific options are necessary by default). The Parallel solver can also be launched from the "Run List" of the Manager (see the "Software Manager/Run list" section for more details).

Parallel version execution with commands It is also possible to launch the Parallel solver "manually", from a Command Window. Depending upon the platform, the following syntax should be used : Linux (HP-MPI) : cd .../working_directory/ $ProCAST20091/bin/procastDMP_run prefix CPU selection -mpiroot $ProCAST20091/hpmpi prefix : case name CPU selection : selection of processors and hosts See HOSTFILE and HOSTLIST definition for HP-MPI at the end of this section for more details -np N selection of N processors -hostfile hostfilename which contains list of hosts - See remark at the end of this section

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or -np N selection of N processors -hostlist "hostname list" - See remark at the end of this section Example : cd .../working_directory/ $ProCAST20091/bin/procastDMP_run Test -np 4 -hostfi le hostfile.dat -mpiroot $ProCAST20091/hpmpi For Windows (HP-MPI) : cd .../working_directory/ %ProCAST20091%\HPMPI\bin\mpirun CPU_selection %ProCAST20091%\bin\procastDMP.exe prefix prefix : case name CPU_selection : selection of processors See HOSTFILE and HOSTLIST definition for HP-MPI at the end of this section for more details -np N selection of N processors -hostfile hostfilename which contains list of hosts - See remark at the end of this section

or -np N selection of N processors -hostlist "hostname list" - See remark at the end of this section Remark 1 : If DMP calculations have to be launched on CPU's which are physically on different machines, it is highly recommended to use Linux, rather than Windows. As the communications between the machines are managed by the Operating System, it has been observed that in some cases, the communication between Windows machines was not optimum, thus slowing down the overall calculation, leading to a poor scalability. This was not observed on Linux, where good scalability on multi-machines was always obtained. Remark 2 : Depending upon the machine configuration, it may be necessary to add the following option (after the CPU_selection) : -e LD_LIBRARY_PATH="%MPI_ROOT%\bin" Example : cd .../working_directory/ %ProCAST20091%\HPMPI\bin\mpirun -np 4 %ProCAST20091%\bin\procastDMP.exe Test

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HOSTFILE and HOSTLIST definition for HP-MPI (for both Linux and Windows) On HP-MPI, there is two ways to specify which CPU's have to be used for a given calculation : the "hostfile" and the "hostlist". In both cases, the hostfile or the hostlist should be specified in the launch command (or in a script which will launch the calculation). In order to explain how it is working, let's assume that the cluster has 4 machines with 2 dual cores each (for a total of 16 CPU's). The machines are named machine1, machine2, machine3 and machine 4. Hostfile : A hostfile (named "hostfile.dat") should be created (for instance in the local working directory), with the list of machines on which the calculation has to be run. The synthax of the the hostfile.dat is the following (ASCII file) :

machine_name_1 Number_of_CPU machine_name_2 Number_of_CPU

For instance, if a calculation with 8 CPU's has to be run on the machine3 and machine4, the hostfile.dat should be the following (located in the local working directory or in any directory which will be specified in the command line) :

machine3 4 machine4 4

and the calculation should be launched in the following way (let's assume that the calculation is located in the /Data/Test working directory) : cd .../working_directory/ $ProCAST20091/bin/procastDMP_run prefix -np 8 -hos tfile .../working_directory/hostfile.dat -mpiroot $ProCAST20091/hpmpi Hostlist : It possible to launch the same calculation as above (8 CPU's on machine3 and machine4) with a hostlist instead of a host file. In this case, the synthax of the command to launch the calculation is the following : cd .../working_directory/ $ProCAST20091/bin/procastDMP_run prefix -np 8 -hos tlist machine3,machine4 .../working_directory/hostfile.da t -mpiroot $ProCAST20091/hpmpi

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If we want to launch a job on 4 CPU's, distributed on machines 3 and 4 (which have 4 CPU's each), thus using 2 CPU's of each machine, one can specify "machine3:2,machine4:2" in the hostlist : cd .../working_directory/ $ProCAST20091/bin/procastDMP_run prefix -np 4 -hos tlist machine3:2,machine4:2 .../working_directory/hostfil e.dat -mpiroot $ProCAST20091/hpmpi

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REPEATABILITY

The goal of a parallel solver is to obtain the same results as the scalar version and regardless of the number of processors. This is called "Repeatability". One should note that Parallel processing (using an implicit solver like in ProCAST), involves the resolution at once of a linear system on distributed processors, with the appropriate communications between the processors. As a first consequence, the algorithms which are used in the parallel version (especially for the pre-conditioner) can not be exactly the same as the ones used in the scalar version. This may lead to small differences in convergence (and thus in timesteps) and in round-off. Moreover, as iterative solvers are used, the solution is never exact and it may slightly depend upon the way it is solved (which can be slightly different on 1, 2, 4 or 8 processors). Thus, one should expect to have very similar results between the scalar and the parallel version and between runs made with different numbers of processors, however, most of the time, one will not have exactly the same result. This is especially true in filling calculations where very small differences may have an effect on the filling pattern (as different meshes or different COURANT values may have too).

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L IMITATIONS

In ProCAST 2009.1, not all the modules and features of ProCAST have been parallelized yet. This section is describing the limitations of the current version, as well as the precautions in the use of the parallel solver. As the use of a non-parallelized feature may degrade completely the performances of the solver, these features are made non accessible and the solver will stop in such case. The tests are mainly done through the values of the corresponding Run Parameters. However please note that when a Parallel calculation is terminated, many MPI print-out may appear. This means that the ProCAST error message may be "embedded" into MPI messages. In ProCAST 2009.1, only the THERMAL, RADIATION, FLOW (including thixo, foam and centrifugal [without periodic BC]), MICRO and STRESS modules are parallelized. The parallelization of the other modules is not planned at this stage. The following features are not parallelized (the list may not be exhaustive) and thus should not be used with the parallel solver : THERMAL module : • POROS = 4 and 8 (only POROS = 1 is available) • Periodic boundary conditions • MiLE algorithm (for non-steady continuous casting) • Solid Transport (for steady state continuous casting) FLOW module : • RESERVOIR option STRESS module : • User functions for the stress properties as a function of microstructure Remark: Please note that the path of the working directory should not contain any blank space (or special characters).

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MACHINE CONFIGURATION

In order to have an efficient parallel processing, it is important to set-up the machines in the right way. This section explains the basics principles of the machines installation and configuration in order to run the ProCAST Parallel solver. Please note that the following is not necessary for the Windows DMP version. Cluster of processors When a cluster of processors is used (e.g. Linux cluster of 4 machines, having each 2 CPU's), they should be connected through a dedicated fast network, such as a 1 Gigabit/s Ethernet or a Myrinet switch. Please note that the ProCAST Parallel installation (with the libraries) may be different if a 1 Gigabit/s Ethernet or a Myrinet switch is used. A special care should be taken upon the type of cables which are used. The cable should be designed for fast communication (for 1 Gigabit/s Ethernet, Category 6 cables - or above - should be used). Concerning the operating system, it is important to make such that the installation of each node is the same in order to optimize the performances. SSH During the Parallel calculation, the software is communicating with the different nodes (computers of the cluster) through "Secured shells" (ssh). Thus, the machines should be configured in order to allow "ssh" communication between the nodes. If a "paraphrase" (password) is set to activate the ssh, one should perform the two following commands when a new Command Window is used :

ssh-agent $SHELL ssh-add

then, the "paraphrase" should be given. If this operation is not done, the paraphrase will be asked for each node when the ProCAST Parallel solver will be launched. If ssh is configured without paraphrase, then, this is not necessary. If the Parallel solver is launched from the Manager, it is necessary to perform the above operation in the Command window before the Manager is launched (in this same command window). Disk mounting procedure The disk on which the software and libraries are installed, as well as the disk(s) on which the data will be located (it can be different disks) should be mounted in such a way that they can be accessed in the same way (i.e. with the same path) from any machine (node).

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HARDWARE AND OS

The pre-requisites and requirements for the hardware and for the operating systems (OS) are the following (at this stage only Linux and Windows are available) :

Windows - HP-MPI Windows XP and Windows CCS (Compute Cluster Server) only. The following versions of libraries and compilers were used:

HP-MPI 1.1 Petsc-2.3.2 Parametis-3.1 icc 9.1 compiler

Linux (32 bits) - LAM-MPI The requirement for Linux is the level of the Linux kernel and of the glibc. One should have levels higher or equal to :

• kernel : >= 2.4.20 • glibc : >= 2.3.2

In order to get the level of the kernel or of glibc, the following commands should be run on the machine :

• rpm -q kernel • rpm -q glibc

With these requirements, the ProCAST parallel version is technically compatible with any Linux operating system (e.g. RedHat, Suse, Mandrake, ...). However, the version is guaranteed (i.e. tested) only on Redhat EL3 (RedHat Entreprise Linux 3). The following versions of libraries and compilers were used :

LAM-7.1.1 Petsc-2.3 Parametis-3.1 gcc-3.1 compiler(for LAM, Petsc and Parametis) icc 8.1.026 compiler (for ProCAST)

Linux (64 bits) - HP-MPI The requirement for Linux is the level of the Linux kernel and of the glibc. One should have levels higher or equal to :

• kernel : >= 2.4.21

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• glibc : >= 2.3.2 In order to get the level of the kernel or of glibc, the following commands should be run on the machine :

• rpm -q kernel • rpm -q glibc

With these requirements, the ProCAST parallel version is technically compatible with any Linux operating system (e.g. RedHat, Suse, Mandrake, ...). The following versions of libraries and compilers were used :

HP-MPI 2.2.5 Petsc-2.3.2 Parametis-3.1 gcc-3.2.3 compiler(for Petsc and Parametis) icc 8.1.026 compiler (for ProCAST)

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ADVANCED POROSITY MODULE

The Advanced Porosity Module (also called APM) is using the multi-gas approach in order to model gas and shrinkage microporosity, as well as macroporosity and pipe shrinkage.

Porosity calculations are performed as a "post-processing" of the thermal results. Thus, one should first configure and run a thermal calculation as usual and then to configure and run the porosity model.

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INTRODUCTION

The porosity module of ProCAST is based upon the model developed by Pequet, Gremaud and Rappaz. For further details, please refer to :

• Ch. Pequet, M. Gremaud, M. Rappaz (2002), "Modeling of Microporosity, Macroporosity and Pipe Shrinkage Formation during the Solidification of Alloys using a Mushy-Zone Refinement Method", Met. Mater. Trans. 33A, 2095-2106.

It is developed jointly by Calcom ESI (ESI Group) and the Swiss Federal Institure of Technology, Lausanne, Switzerland. The model can be summarized as follows (abstract of the above mentioned paper) : A microporosity model, based on the solution of Darcy's equation and microsegregation of gas, has been developed for arbitrary three-dimensional (3D) geometry and coupled with macroporosity and pipe shrinkage predictions. In order to accurately calculate the pressure drop within the mushy zone, a dynamic refinement technique has been implemented: a fine and regular Finite Volume (FV) grid is superimposed onto the Finite Element (FE) mesh used for the heat flow computations. For each time step, the cells, which fall in the mushy zone, are activated and the governing equations of microporosity formation are solved only within this domain, with appropriate boundary conditions. For that purpose, it is necessary to identify automatically the various liquid regions that may appear during solidification: open regions of liquid are connected to a free surface where a pressure is imposed; partially-closed liquid regions are connected to an open region via the mushy zone and closed regions are totally surrounded by the solid and/or the mold. For partially-closed liquid pockets, it is shown that an integral boundary condition applies before macroporosity appears. Finally, pipe shrinkage (i.e., shrinkage appearing at a free surface) is obtained by integration of the calculated interdendritic fluid flow over the open region boundaries, thus ensuring that the total shrinkage (microporosity plus macroporosity and pipe shrinkage) respects the overall mass balance. The principle of the porosity calculation is the following : a) A thermal calculation is performed first in ProCAST (please note that it is mandatory to use PIPEFS = 0 and it may be advised to use POROS = 0 if macroshrinkage are observed). b) The temperature and fraction of solid results are then processed in the Advanced Porosity Module in order to calculate the macro- and micro-porosity, as well as the pipe shrinkage.

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c) To do so, a finer grid is automatically superimposed to calculate the liquid pressure drop in the mushy zone (solution of the Darcy's equation) and the nucleation and growth of pores are computed. d) The calculation of the nucleation and growth of the pores is made according to the gas model. The APM that was initially designed only for binary Al-based alloys in which a single gas – hydrogen - was responsible for porosity (see paper above), has been extended to multi-gas systems. In this module the effect of several alloying elements on gas solubilities, and of course on final porosity fraction, is now taken into account. For details on the modeling of porosity formation in a multi-gas and multi-component configuration, see the following papers (can be found in the software installation, under "dat/manuals/Pdf/APM_papers.pdf") and also in the "APM Examples" section (see in the "Alloying elements effects" and "Several gases" paragraphs) :

• Couturier G., Rappaz M. (2006). "Modeling of porosity formation in multicomponent alloys in the presence of several dissolved gases and volatile solute elements", TMS, Symposium on Simulation of Aluminium Shape Casting Processing.

• Couturier G., Desbiolles J-L., Rappaz M. (2006). "A porosity model for multi-gas systems in multicomponent alloys", TMS, Modeling of Casting Welding and Advanced Solidification Processes, pp. 619-626.

• Couturier G., Rappaz M. (2006). "Effect of volatile elements on porosity formation in solidifying alloys", Modelling and Simulation in Materials Science and Engineering, 14, pp. 253-271.

The flowchart of this porosity module is described in the following figure (for a more detailed description, please refer to the "APM Appendix/APM Flow Chart" section) :

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In order to achieve a porosity calculation, the appropriate settings should be defined for the thermal calculation and then the porosity input file (named "prefix_poro.d") should be configured. These settings are described in the "Advanced Porosity Pre-Processing" section.

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ADVANCED POROSITY PRE-PROCESSING

Configuration of the thermal calculation

The configuration of the thermal model in ProCAST should be made in the standard way. The only precaution is to set the case in order to prevent piping (i.e. PIPEFS = 0). If macroshrinkage are observed (creating "holes" inside the casting), it is advised to use POROS = 0 (this is because in the piping or in macroshrinkage, the temperature are not anymore calculated when the volume becomes empty and thus the temperature are remaining constant since that time. As the temperature are used in the APM calculation, these constant temperatures may affect the quality of the APM results). Please note that there are no restriction to activate other models during the thermal calculation, such as fluid flow or stress. However, it is important to remember that the Advanced Porosity model does not handle remelting. If this occurs, it is not guaranteed that the solution will converge. As the APM calculation is using the temperature results of a thermal calculation done before, it is necessary that the whole temperature history of interest for the APM calculation is present in the result files. This means in particular that if a thermal calculation is "splitted" is two or more calculations, using the "Extract" capability to chain the different calculations, it will not be possible to run an APM calculation on more than one of these thermal "sub-calculations". As a consequence, the APM will be possible only on single thermal calculations, without any Extract in the middle. It is however possible to run an APM calculation on a thermal calculation which has been started as an Extract at the end of the filling, as the whole casting is still fully liquid at the beginning of the thermal calculation (although the thermal field is inhomogeneous). Restarts are however possible as the results are append to the existing result files. Configuration of the porosity model The calculation condition file (prefix_poro.d (ASCII format)) contains all the necessary information to perform a calculation. It is divided in blocks of data containing different type of information : Material properties alloy.param: specific.mass.param: viscosity.param: coarsening.param: Gas and bubble properties nucleation.growth.param: gas.param:

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Process information pressure.param: feeding.param: gravity.param: Calculation settings grid.param: calculation.param: Each block starts by the "block.name" and ends by "end". Inside a block, parameters are inserted. Each parameter is always followed by one argument (always one argument). The order of the blocks or of the parameters within a block is free. In the description hereafter, each block is presented according to the following format.

Please note that only SI units must be used for the porosity calculation definition (however the thermal calculation can be set-up as usual with any units). The frames shown hereafter in light blue correspond to examples of settings. The following sections are describing these different inputs. Many of the following parameters are optional: for them a default value is defined in the APM source code. The user has the possibility to change this hard-coded value: he can define it in the "prefix_poro.d" file, but if he wants to customize the APM he can also define it in a "default_poro.d" file located at "dat/pref/default_poro.d". The definition of a parameter in the "prefix_poro.d" file takes over the definition in the "default_poro.d" file. The definition of a parameter in the "default_poro.d" file takes over the hard-coded value. Below, for each block description, a table mentions if each parameter is needed, optional or not required (i.e. can not be defined at this location) in the "prefix_poro.d" and the "default_poro.d" files. The hard-coded value is also mentioned.

Material Properties

When the "Advanced Porosity Model" is used in conjunction with a ProCAST calculation, all the necessary thermo-physical properties (alloy composition, fraction of solid, density and viscosity curves) are automatically extracted from the ProCAST input data file ("prefixg.unf") if they have been defined in PreCAST and stored in "prefixg.unf" by DataCAST. Thus, nothing has to be specified and

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no special care has to be taken. But such parameters can be defined also in "prefix_poro.d" file as described below. The definition in "prefixg.unf" takes over the definition in "prefix_poro.d" file. alloy.param: (optional) The effects of several solute elements on gas solubility products can be taken into account by the APM. This is valid if the gas.db database contains the "interaction coefficients". See the Appendix 3 for the description of Gas Thermodynamic Database. For this, the APM reaches the concentration of each solute element in the liquid phase: the solidification path is previously calculated by PreCAST. Three segregation models can be used in PreCAST: lever rule, Scheil or back diffusion. The resulting file, "prefix.phs", contains the concentration of each solute element in the liquid phase as a function of solidification. The APM extracts directly these concentrations in "prefix.phs". If this file does not exist, the solute element concentrations are assumed constant: they are read in "prefixg.unf" file or in "prefix_poro.d" if not found in "prefixg.unf":

The figure above shows, at which stage in PreCAST, in the material database, the "prefix.phs" file is created. By selecting and applying the Scheil, Lever or Back diffusion model this file is written out. The alloying elements which appears in the list above are also used by the APM module: the APM detects the alloying elements, and then reaches their respective concentration evolution in "prefix.phs" file. If the "prefix.phs" file does not exit, the solute element concentrations are assumed constant by the APM (values entered by the user in PreCAST: see figure above). Please note that the APM module reads the "prefixg.unf" file and not the "prefixd.dat" file. Therefore datacast has first to be used to generate the

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"prefixg.unf" out of the "prefixd.dat" file to make this information available for the APM module. Important remark : Please note that the file "prefix.phs" must be present in the working directory of all APM calculations (whereas this file is created only during the material properties calculation in PreCAST). This means that if the same alloy is used for several calculations, one should not forget to copy this file in the local working directory.

Example for an Al-2.5wt%Si3.6wt%Cu:

specific.mass.param: (optional) Of course, in order to allow porosity calculations, one has to have an alloy density which is defined as a function of temperature. This density curve is defined in PreCAST. If this density curve has not been defined in PreCAST, the user can define it in "prefix_poro.d" with the following parameters:

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Note that this version of the "Advanced Porosity Model" does not allow to have "expanding" materials (i.e. volume increasing for decreasing temperature). viscosity.param: (optional) In addition to the ProCAST thermo-physical data mentioned above, the viscosity defined in PreCAST is an important quantity to access to the liquid pressure drop calculated in the mushy zone from the alloy mass conservation equation coupled to the Darcy's equation (i.e. flow through the mushy zone). The viscosity can be taken either as a constant, or as a function of temperature. If not defined in PreCAST, the user can also define it as a constant value in the "prefix_poro.d" file:

coarsening.param: (optional)

Another important parameter for the calculation of the liquid pressure drop is the permeability (K) of the mushy zone, which is described by the Kozeny-Carman relationship:

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Beside the fraction of solid (gs), the permeability is a function of the secondary

dendrite arm spacing (λ2), which can be calculated according to the following coarsening law :

where tL is the time at which the liquidus temperature was reached and M is the coarsening constant. The coarsening constant can be calculated as follow, for a binary alloy :

with :

σsl : solid liquid interface energy

Dl : Liquid solute diffusion coefficient

TM : Melting point of the pure base metal L : Latent heat k : partition coefficient m : liquidus slope

cl(t) : current concentration of solute in the liquid

cl,o : initial solute concentration The following frames are showing both possibilities available for the user: a) The coarsening constant (M) is specified

b) A constant secondary dendrite arm spacing value is specified

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Gas and Bubble Properties

nucleation.growth.param:

The nucleation and growth parameters of pores (i.e. bubbles) are defined in this above block. All these parameters are optional. In the APM an optional parameter - the "cavitation.pressure" - can be used to define the macropore formation critical pressure: if the liquid pressure in a closed or semi-closed liquid pocket becomes lower than this value, a macropore is formed at the top of this pocket. As the APM user might not know this critical value, this parameter is optional: If this critical value is not defined in the "prefix_poro.d" file, it is set automatically to the sum of the nominal gas partial pressures. It means that Laplace's overpressure is neglected for the macropores formation: it is quite relevant as some bubbles entrapped in the liquid pocket will go up, stop at the top of the liquid pocket and coalesce; the macropores will form from theses quite big bubbles. When a pore will nucleate, it will appear with the radius defined under "nucleation.radius" (optional). Please note that this initial pore radius value should not be defined with smaller values than 5 microns. Otherwise, the pressure inside the bubble will be so high that it will never nucleate and the calculation will not run well. The nucleation of the pores is defined by a "pore.density" (optional). The "gas.metal.surface.tension" will determine the Laplace's overpressure due to the pore curvature.

The "available.half.spacing" is a table function of the solid fraction of the available half spacing (normalized by λ2) for a pore constrained to grow inbetween dendrite arms. See the details of this model in the Appendix 2 (Growth model of a pore). Finally "transition.solid.fraction" is the critical solid fraction below which the pore is spherical, and upper which the pore is constrained by the dendrite network.

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gas.param: The gases responsible for porosity in the considered alloy are detected by the porosity module. The thermodynamic data of the gases responsible for porosity in the alloy are read in the gas database "dat/db/gas.db" by the porosity solver. See the Appendix 3 for the description of Gas Thermodynamic Database. The user can change the location of the gas database with an environment variable: with $ProCAST20091_DB the path becomes "$ProCAST20091_DB/db/gas.db". It is first recalled that the gases responsible for porosity in the considered alloy are now detected by the porosity module. The alloy is found in ProCAST run-files ("prefixg.unf" file). If not found, the alloy category has to be defined in "prefix_poro.d" file (see alloy.param: section).

The user has to define in atomic fraction the nominal concentration of each gaseous element in solution in the liquid phase. Let's assume a copper base alloy.

The gases responsible for porosity in this alloy are: H2, SO2 and H2O. The user has to define the nominal concentration of H, S and O in solution in the liquid alloy in the "prefix_poro.d" file:

If the user does not remember the gaseous elements responsible for porosity, he can run the APM module in order to read these gaseous elements in the console.

For H2 in Al-base alloys, the APM also specifies the typical concentration levels:

- low: 2.3e-6 at, this value corresponds to 0.1 ccSTP/100g Al.

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- medium: 4.6e-6 at, this value corresponds to 0.2 ccSTP /100g Al.

- high: 6.9e-6 at, this value corresponds to 0.3 ccSTP/100g Al.

The "dat/db/gas.db" ASCII file contains thermodynamic properties of gases responsible for porosity in Al- , Cu- and Fe-base alloys. If the user wants to run an APM calculation with a different alloy category and if he does not know the thermodynamic properties of gases responsible for porosity in this alloy, he has to follow the procedure described below. This procedure will lead to a porosity formation behaviour similar to the one of Al-base alloys in which dihydrogen is the single gas responsible for porosity: 1/ in PreCAST, the user mentions the alloy base (ex: Ni) in the composition panel of the casting material:

2/ then he runs DataCAST and ProCAST, or DataCAST –u if the thermal calculation has been already done, 3/ then he opens the database "dat/db/gas.db", and replaces the keyword "YourAlloy" by the chemical symbol of the alloy base (ex: Ni), 4/ in the YourAlloy gas database he specifies a "gas.formation.coefficient:", (where YA means YourAlloy), which has to be equal to:

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with

is the solubility product of dihydrogen in pure Aluminium at the melting temperature ( )

is the molar mass of Al (26.9 g/mol),

is the density of Al at the melting point (2390 kg/m3),

is the melting temperature of Al (933 K), is the molar mass of the base of YourAlloy (ex: =58.7 g/mol),

is the density of the base of YourAlloy at the melting point (ex: =7780 kg/m3),

is the melting temperature of the base of YourAlloy (ex: =1728 K), For example, for Ni base alloys, B = 2.762, and so gas.formation.coefficient = 2.24e+10 This is the actual default value specified in YourAlloy gas database.

Concerning the typical Hydrogen nominal concentrations in YourAlloy, , they have to be equal to:

- as low in Al means 2.3e-6 at, low in Ni will mean 2.3e-6/2.762=8.3e-7 - as medium in Al means 4.6e-6 at, medium in Ni will mean 4.6e-6/2.762=1.66e-6 - as high in Al means 6.9e-6 at, high in Ni will mean 6.9e-6/2.762=2.49e-6 These are the actual default values specified in YourAlloy gas database. 5/ finally run the APM. The above procedure has already been applied to Ni, Ti, Mg base alloys in "dat/db/gas.db" ASCII file. With this procedure in term of porosity, the alloy will have a behaviour similar to Al-base alloys in which dihydrogen is the single gas responsible for porosity. Of course, if the user has a way to obtain thermodynamic properties of gases responsible for porosity in his alloy, he can create his own database in "dat/db/gas.db" See the Appendix 3 for the description of Gas Thermodynamic Database.

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One should be careful that the initial gas element concentrations do not induce formation of bubbles in the liquid metal before the pouring of the metal. In order to prevent such case, a warning will be printed at the beginning of the calculation (see figure below) if the following situation arises. Then it is advised to reduce the initial gas element concentrations.

With APM, it is also possible to run a porosity calculation with no gas element (concentrations equal to zero). In this case the uncoupled resolution algorithm will be forced and microporosity will form as soon as the liquid pressure will reach minus Laplace's overpressure (see "coupled.solving" parameter description).

Process Information

pressure.param

The type of process, as well as the pressure definition are specified in this block (casting.type). Firstly, one should specify the process ("casting.type") which is modelled, among three choices : gravity, injection or continuous. gravity : For all types of gravity casting (sand, permanent mould, investment, ...), the "gravity" type should be used. In this case, the software is automatically setting the pressure to the highest surface of the casting. This means that the user does not

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need to specify anything, except the value of the pressure ("p.imposed"). The highest surface is determined with the help of the gravity vector. With this mode, the metal at the top of the casting will be free to pipe, according to the value of "mobility.limit" (see "feeding.param" block). injection : The type "injection" has to be used for hpdc, lpdc and squeeze casting, as well as all processes where the liquid metal is injected. In this case, the injection point has to be specified with the "x,y,z.pressure.coordinate" (see below) - it is advised to select the last point to solidify as the feeding will be stopped when this point will solidify. As the metal is injected, no piping will occur, as there will be a continuous feeding of metal (however, depending upon the geometry and the thermal conditions, macroshrinkage may occur). In this case, the "mobility.limit" does not need to be specified and it will be automatically set to 1. continuous : For all continuous casting processes, the "continuous" type should be used. As for "injection", one will have a continuous feeding of metal and thus, the "mobility.limit" does not need to be defined. In this case, it will automatically be set to 1. Moreover, the feeding point (usually the last point to solidify) should be specified with the "x,y,z.pressure.coordinate" (see below - please note that the coordinates have to be set in [m]). In addition, in the case of a vertical continuous casting, one should specify the liquid level (with "p.level"). In this case, the value of the applied pressure will be automatically adapted to take into account the appropriate metallostatic pressure. In the case of "injection" or "continuous", the location where the pressure is applied should be defined (whereas it is automatically set to the highest surface in the case of "gravity"). This is done with the keywords "x.pressure.coordinate", "y.pressure.coordinate" and "z.pressure.coordinate". It is strongly advised to specify a point at the injection location which will solidify last as the feeding will be stopped when the fraction of solid at this location will reach a value of 1. The applied pressure is specified with "p.imposed". This pressure is either applied on the highest surface (in the case of "gravity"), or at the "x,y,z.pressure.coordinate" location in the case of "injection" or "continuous". The value of p.imposed can be defined either by a constant or by a function of time (with a value block F(TIME)). In order to define the pressure as a time table, one should replace the pressure value by a pointer (i.e. a name starting by a "*" - see below).

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Then, an additional value block should be specified with the time function. The name of the value block should be the same as the one of the pointer (without the "*"). Then, the following syntax should be used :

If the level of the liquid is not corresponding to the level of the coordinate where the pressure is applied, this can be accounted for with the keyword "p.level". This has to be used in continuous casting (as the "effective" level of the liquid is changing during the process) or if a part of the casting is not modeled. When both "p.level" and "x,y,z.pressure.coordinate" are defined, the pressure applied at the p.level altitude (in absolute axis coordinated. in the direction of the gravity) corresponding to the applied pressure (defined by "p.imposed"). Below p.level, the metallostatic contribution is added to p.imposed. This can be described with the following piece of code (considering that the gravity is in the -Z direction) :

if (z > p.level) then pcell = p.imposed else pcell = p.imposed + rho * g * (p.level - z) endif where z is the current altitude of the cell for whi ch the pressure (pcell) is calculated.

The value of "p.level" can be defined either by a constant or by a function of time (with a value block F(TIME)). Multiple pressure definition In the case of injection, it is possible to define more than one pressure point. This is especially useful when one does not want to model the gating system but still apply the pressure at the biscuit to the different gates.

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As the "injection points" can now be also defined "inside" a volume (and not only on the surface), this allows to mimic the effect of a third phase to still apply the pressure in front of a gate while it is totally frozen. To do so, addition injection points can be defined with the keyword "injection.points", and then a point to a list should be set (like "*pts". Then, the list should be defined with the value block, using "data PARAMETERS" as shown below.

The point defined by "x.pressure.coordinate, y.pressure.coordinate and z.pressure.coordinate" will correspond to the "master" pressure point. This means that the pressure defined by "p.imposed", will be set at this point and that the pressure of the other injections points will be calculated from this point (to take into account the corresponding metallostatic pressure). If the "x.pressure.coordinate, y.pressure.coordinate and z.pressure.coordinate" point is not defined (but there are only points in the "injection.points" list, the first one in the list will be considered as the "master". The two above examples (in the blue tables) are totally equivalent.

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The following example is showing how these multiple injection points can be used. In case A, the full gating system is modeled and one injection point at the biscuit is used. In example B, the gates are not modeled and an injection point in front of each gate is defined (please note that the injection point is inside the gate and not inside the casting). In case C, the gating system is modeled (like in A), but the injection points are set as in B (in front of each gate). One can see in the following graphs that the results are identical in the three cases. The green arrows are showing the injection points.

The main advantage of using the middle approach (case B) is that the CPU time of the APM calculation is significantly reduced, as the volume of the gating system and the biscuit (which can be sometimes rather large) is not taken into account in the APM calculation. In the above example, the CPU time of case B was reduced

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by a factor 8 with respect to case A (or case C) - the number of APM cell was reduced in this case by a factor 7. In the next example, the left injection point was removed in the right figure. One can see directly the effect on the porosity results.

feeding.param

The "mobility.limit" corresponds to the critical solid fraction from which the liquid at the top free surface can not move anymore locally (for piping). If the "mobility.limit" is very low (0.01), it means that as soon as the solid fraction is equal to 1%, the liquid can not move down anymore to feed the liquid pockets below. Thus one will have almost no piping, but macroshrinkage in the center of the casting. On the other hand, if a larger value of "mobility.limit" is used (0.9), the liquid can move down up to a fraction of solid of 90%. This will induce a significant piping and thus reduce the amount of macroshrinkage which may

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occur in the center of the casting. The value of "mobility.limit" is dependent upon the type of microstructure. In the case of columnar structure, the dendrites are linked to the solid shell and thus can not move too much, leading to a small value of the "mobility.limit". On the other hand, in the case of equiaxed grains, they can move down more freely and thus, the "mobility.limit" is higher. If one would like to prevent piping (such as in high pressure die casting, squeeze casting or continuous casting), the "mobility.limit" has to be set to 1.0. In this case, the liquid will continuously feed the casting. The value of "mobility.limit" can be defined either by a constant or by a function of time (with a value block F(TIME)). This can be used in order to model the end stage of a DC casting process. In this case, the mobility limit will be changed from 1.0 to a smaller value, when no more liquid metal will be poured in the ingot. The "permeability.solid.fraction.cutoff" is used to cut-off the permeability at high solid fractions. As it can be seen in the following Kozeny-Carman relationship:

when the solid fraction (gs) is becoming one, K is equal to zero. As in the Darcy's equation 1/K is used, it is going to infinity. In order to prevent that, the permeability is taken as a constant for fractions of solid above the value of "permeability.solid.fraction.cutoff". Values around 0.95 to 0.98 are recommended. If values higher than 0.98 are used, a value of 0.98 is automatically set. If nothing is specified, a value of 0.98 is used. In the presence of eutectic, the permeability drop at the dendrite root is limited because the dendrite network does not coarse anymore as soon as gs>1-ge (ge is the final eutectic fraction). The "permeability.solid.fraction.cutoff" parameter can be used to model this effect.

At very high solid fractions, the interdendritic flow becomes very small and the pressure drop calculation becomes very difficult (on a mathematical point of view). In order to improve the convergence of the model, the feeding calculation is stopped at a fraction of solid above "feeding.solid.fraction.cutoff". Values around 0.95 to 0.98 are recommended. If values higher than 0.99 are used, automatically a value of 0.99 is set. If nothing is specified, a value of 0.98 is used. This value has to be decreased in the case of bad convergence of the model. In order to reduce the number of activated cells, the "activation.fraction" parameter can be used to truncate artificially fs(T) curve:

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Cells with fs < "activation.fraction" minus 5% are seen as liquid by the APM solver. The consequences are: - calculation time drastically reduced (even for low values of "activation.fraction"), - microporosity more and more concentrated for increasing value of "activation.fraction", - microporosity replaced by macroporosity for increasing values of "activation.fraction", - for intermediate values of "activation.fraction" (~30%), APM macroporosity looks like what is obtained by ProCAST standard porosity module (when POROS=1 and PIPEFS=30%). It is recommended to set a value lower than 30%, otherwise macroporosity is overestimated. For consistency reasons, and for the conservation of the global volume of porosity (micro-macro), viscosity and density curves are also truncated in APM solver.

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gravity.param In principle, the gravity vector is already defined in PreCAST as it is required for the thermal-flow calculation. This vector, also required for a porosity calculation, is automatically read out the ProCAST run-files ("prefixg.unf" file) by the APM. One should note that the gravity should be parallel to one reference axis (i.e. parallel to x, y or z). In addition, it is not possible to have a rotating gravity. Thus, some drastic simplifications have to be done to use this module for tilt or centrifugal cases: - for tilt: use the APM calculation on an already filled part in its final orientation (making sure that in the final position, the gravity is well parallel to one reference axis), - for centrifugal: orient the model in order to have one component of the cluster parallel to one axis. Create one domain for this component. Run the thermal-flow calculation. Then, redefine in PreCAST a gravity vector normal to the rotation axis and parallel to the axis of the component. The length of this vector has to close to an estimated centrifugal acceleration. After having changed the gravity vector, run DataCAST –u, and then run the APM. The user has to define the gravity vector in the "prefix_poro.d" file if not defined in PreCAST (The three components of the gravity must be defined):

Calculation Settings

grid.param

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The "grid.spacing" corresponds to the cell size of the FVM mesh. One should select a size which is in relationship with the size of the mushy zone (in order to have several cells through the mushy zone thickness). The "grid.calculation.tolerance" is used in order to remove duplicate cells which would lie at the limit in between two elements. If a regular orthogonal FEM mesh is used and if the cell size (or grid spacing) is exactly matching the FEM mesh (i.e. FEM elements have a size of 1 cm and FVM cells have a size of 1 mm.), it happens that many cells are lying exactly on the element borders. The algorithm which is used involves long loops to guarantee no double cells. The grid.calculation.tolerance is used to check whether a cell is aligned with element borders. If this tolerance is too large, doublon checks will be made many times and the CPU time can rise very strongly. If this tolerance is too small, it is possible to create "holes" in the FVM mesh. Thus, a value of 1.e-8 is recommended. If the cellular meshing becomes very long, it is advisable to change slightly the cell size from 1.00 to 1.00001 in order to remove these alignments. If unstructured FEM meshes are used, this problem never happens. In cases, such as hpdc, sometimes, the gates between the casting and the overflows are very thin. This may lead to a lack of cells at the gate and thus, the overflow may become "isolated" form the casting (i.e. no cells in between the casting and the overflow). In such case, the porosity calculation will not be possible, as there is no way to "transmit" the pressure from the casting to the overflow. This could also happen if very thin sections, such as flashes are modelled. In this case, these "orphan" cells should be removed in order to allow the calculation to run. As this procedure of "orphan search" is CPU intensive, it can be disabled in cases where it is clear that this will not occur (for bulky parts). Otherwise, it is highly recommended to set the "grid.search.orphan" value to ON.

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calculation.param:

Finally, a few calculation parameters should be defined. The "region.number" (or domain number) in which the porosity calculation should be done must be specified at this time. Please note that it is possible to run a porosity calculation in more than one domain. In this case, the domain list should be specified in a value block (see below). One should however make sure that all the domains are connected. The "convergence.tolerance" is the value of the tolerance which is used in the pressure iterative solver. The "maximum.iterations" corresponds to the number of iterations that are run before the iterative solver stops (if the "convergence.tolerance" is not reached before). "LU.preconditioner" allows to make a LU (LU.preconditioner=1) or a diagonal (LU.preconditioner=0) preconditioning of the linear system. By default the diagonal preconditioning is done: this accelerates the SMP parallel version of the APM solver. If the iterative solver did not converged, it is advised first: - to refine the FE and FV meshes, - to decrease the thermal time step, - to store all thermal steps. If it is still not converging, it is advised then to force the LU preconditioning: LU.preconditioner = 1. Concerning the porosity results storage, two formats are available: a) "Advanced Porosity Post-processor" format b) "ProCAST" format In the "Advanced Porosity Post-processor" format, the porosity and the liquid pressure are stored at each FVM cell. This allows a very fine resolution of the results that can be displayed with the "Advanced Porosity Post-processor" (see the "Advanced Porosity Post-processing" section for more details).

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In the "ProCAST" format, the porosity results, calculated at the FVM cells are "interpolated" to the FEM nodes. This allows to view the "Advanced Porosity" results in ViewCAST. Nevertheless, it is recommended to visualize the results with the "Advanced Porosity Post-Processor" because a loss of small macroporosities and small microporosity regions is induced by this "interpolation". The "store.type" allows to select which result files format should be stored. 0 : "Advanced Porosity Post-processor" format only, 1 : "ProCAST" format only, 2 : both formats. "restriction.type" is a parameter used for the definition of the "interpolation" at the FEM nodes. restriction.type = 1: restriction using average value of cells located in the neighborhood (see below) of the node. Each term in the sum is weighted by the value at cell of the shape function associated to the node. restriction.type = 0: restriction using maximum value of cells located in the neighborhood (see below) of the node. 0 <restriction.type < 1: The cells for which the value of the shape function associated to the node is higher than (1-"restriction.radius") are taken into account in the restriction calculation. The "store.frequency" parameter defines the frequency of storage of the porosity results. It is possible to store the pore fraction only (and not the liquid pressure) with "store.pore.fraction", however, if the pressure-only storage is defined (with "store.pressure"), the pore fraction will also be stored. These parameters will be valid only for the "Advanced Porosity Post-processor" format results. The ProCAST format results will be stored at the same frequency as the ProCAST temperatures, whatever values are specified for these parameters.

In order to define a list of regions (to perform the porosity calculation in more than one region), the region.number should be specified by a pointer (i.e. a name starting by a "*" - see below).

Then, an additional value block should be specified with the list of regions. The name of the value block should be the same as the one of the pointer (without the "*"). Then, the following syntax should be used :

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coupled.solving In copper- and iron-base alloys, as soon as the nucleation criterion is reached, the pore growth rate is larger than the solidification shrinkage rate, whereas this is never the case in aluminium-based alloys. As a consequence, whatever the initial gas concentration is, liquid will always be rejected from the mushy zone in copper- and iron-base alloys. This will induce a fast liquid pressure increase in the mushy zone. A very small time step is thus required to capture this increase. For cases with a great number of active cells, the calculation time will be too long. Two solving modes are thus possible: calculation.param: coupled.solving 1 end -> as soon as nucleation criterion is reached, alloy mass conservation equation is coupled to gas conservation equations and pore growth is deduced from gas conservation equations. calculation.param: coupled.solving 0 end -> the alloy mass conservation equation is not coupled to the gas conservation equations, and solidification shrinkage is assumed to be entirely compensated by pore growth (no liquid flux) as soon as nucleation criterion is reached (when liquid pressure will reach minus Laplace's overpressure). coupled.solving parameter is optional. Its default value is equal to 1 for all alloys, excepted for Fe and Cu-base alloys for which it is equal to 0. crit.pore.fraction The "crit.pore.fraction" parameter allows to analyse the results of a calculation. For example, it allows to "measure" the volume in which the porosity fraction exceeds a specified value (e.g. higher than "crit.pore.fraction"). This volume is calculated in the casting, as well as in each domain where the APM is computed. The results are stored in the "prefix_res.log" file (see the end of the section "Advanced Porosity Solver" for more details) .

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Macroporosity predicted by the APM in a complex HPDC part.

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Example of the type of porosity calculation that can be carried out for a complex shape

A383 casting. The geometry is shown in figure (a), while the calculated porosity fraction is displayed on selected cuts when the applied pressure is 100 bars (b) and 1

bar (c) and (d). The effect of solute elements on hydrogen solubility has not been taken

into account in (b) and (c) and has been taken into account in (d). cH =

0.2ccSTP/100g, λλλλ2 = 50µµµµm. Here the cellular mesh was composed of 400'000 cells. Warnings

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• The APM allows to predict porosity in complex geometries (see figures

above). The number of FVM cells is no longer limited to 2 millions as a 64 bits executable is now available for 64 bits machines. But a number of cells lower than 2 millions is recommended to obtain a first result in 24 hours.

• One should note that the "Advanced Porosity" module is based upon very

complex physical algorithms and thus its mathematical handling may be quite delicate in some cases. It is thus possible that the solution is not converging (or is giving error with the pre-conditioner). In such case, it is advised to either : store more thermal timesteps, reduce the cell size and the finite element size.

• One should also take a special care to make sure that there is no remelting. • Finally, when the mushy zone is quite small (in case of large castings with low

conductivity materials), the finite element size and the cell size should be adapted (i.e. they should be much smaller than the mushy zone thickness).

Examples of prefix_poro.d input file

A lot of parameters in the "prefix_poro.d" file are optional. Each optional parameter has a default value coded in the APM. The user has still the possibility to change this value: he can define it in the "prefix_poro.d" file, but if he wants to customize the APM, he can also define it in the "default_poro.d" file located in the software installation: "dat/pref/default_poro.d". The definition of a parameter in the "prefix_poro.d" file takes over the definition in the "default_poro.d" file. The definition of a parameter in the "default_poro.d" file takes over the hard-coded value. Let's look now at the strictly needed parameters in "prefix_poro.d" for gravity casting, injection and continuous casting.

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Gravity

Example of the simulated final porosity fraction in a "simplified" window shape

gravity casting, without (left) and with (right) solid fins, "cooling channel", "copper chill" and "riser".

For gravity casting, in the "prefix_poro.d" file, the list of strictly needed parameters is (the $$$ are indicating where a value should be specified by the user) : #--------- Gas Information ----------

gas.param: H $$$ # typical value for Al: 2.3e-6 to 6.9e-6 [molar fraction] end

#------------ Process Information --------------

pressure.param: casting.type gravity # Gravity se tting p.imposed $$$ # [Pa.s] 101 325.0 [Pa.s] = 1 bar end

#------------ Calculation settings -------------

grid.param: grid.spacing $$$ # [m] end

calculation.param: region.number *regions store.frequency $$$ end

value regions data PARAMETERS $$$ # Porosity D omain 1 $$$ # ... $$$ # Porosity d omain N end value

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Injection

Simulated final porosity fraction (slices) in a complex shape High Pressure Die Casting

(100 bar). For injection, in the "prefix_poro.d" file, the list of strictly needed parameters is : #--------- Gas Information ----------


#------------ Process Information -------------- pressure.param: casting.type injection # Injection setting p.imposed $$$ # [Pa.s]. 1 01325.0 [Pa.s] = 1 bar x.pressure.coordinate $$$ # [m] y.pressure.coordinate $$$ # [m] z.pressure.coordinate $$$ # [m]

end


grid.param:

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grid.spacing $$$ # [m] end


value regions data PARAMETERS $$$ # Porosity Domain 1 $$$ # ... $$$ # Porosity domain N end value

Continuous casting

Simulated final porosity fraction in a continuous casting case.

For continuous casting, in the "prefix_poro.d" file, the list of strictly needed parameters is : #--------- Gas Information ----------


#------------ Process Information --------------

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pressure.param: casting.type continuous # Continuou s setting p.imposed $$$ # [Pa.s]. 1 01325.0 [Pa.s] = 1 bar x.pressure.coordinate $$$ # [m] y.pressure.coordinate $$$ # [m] z.pressure.coordinate $$$ # [m] p.level *plevel end

value plevel data F(TIME) $$$ $$$ # Time [s] level [m] $$$ $$$ # Time [s] level [m] $$$ $$$ # Time [s] level [m] end value


grid.param: grid.spacing $$$ # [m] end


value regions data PARAMETERS $$$ # Porosity Domain 1 $$$ # ... $$$ # Porosity domain N end value

APM Examples

This section of the manual is illustrating the effect of different parameters (gas concentration, secondary dendrite arm spacing, viscosity, pressure) on the porosity results. An Al-7wt%Si-0.3wt%Mg alloy containing hydrogen is used to test the APM under several conditions. The solidification path was calculated by PreCAST with the Scheil assumption.

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Casting geometry, and cooling conditions. Here the solid fraction is represented at the same time for "good cooling" conditions (a) and for"bad cooling" conditions (b).

The geometry used in the examples below is given in the figure above. Two kinds of cooling conditions are used: in the first case an adiabatic condition is applied at the top of the casting and on the vertical walls connected to the top (a), while in the second case the adiabatic condition (dashed line) is only applied on the top side (b). Elsewhere the cooling is governed by a convective heat transfer coefficient. Cooling conditions of figure (a) will be called "good cooling conditions", and those of figure (b) will be called "bad cooling conditions". Such a simple geometry could be employed by a user to calibrate the APM for his alloy (see paragraph "Configuration of the porosity model" concerning the generic "default_poro.d" file).

Gas concentration The effect of the nominal gas concentration is illustrated in the figure below in the case of good cooling conditions: as expected, the final porosity amount increases with the nominal gas concentration.

Final porosity fraction for a nominal hydrogen concentration equal to (a) 0

ccSTP/100g, (b) 0.1 ccSTP/100g, (c) 0.2 ccSTP/100g, (d) 0.3 ccSTP/100g. Good

cooling conditions, λλλλ2 = 20µµµµm, µµµµ = 1e-3 Pa.s, imposed pressure = 1 bar. As shown in the figure below, this effect is still observed in the case of bad cooling conditions. One has to pay attention to the fact that this effect can be

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totally hidden if the cooling conditions are so bad that the pure shrinkage porosity fraction becomes predominant over the gas-shrinkage porosity fraction.

Final porosity fraction for a nominal hydrogen concentration equal to (a) 0

ccSTP/100g, (b) 0.1 ccSTP/100g, (c) 0.2 ccSTP/100g, (d) 0.3 ccSTP/100g. Bad

cooling conditions, λλλλ2 = 20µµµµm, µµµµ = 1e-3Pa.s, imposed pressure = 1 bar.

Secondary dendrite arm spacing

To study the effect of λ2, it is assumed here that the value of this parameter is not linked to the cooling rate (wrong in reality). As the liquid pressure drop in the

mushy zone is very high for very low λ2 (see Kozeny-Carman relation) the

porosity amount is expected to be higher for very low λ2 values. This effect is slightly compensated by the curvature contribution since the maximum pore

radius varies also with λ2 (see appendix 2 in the "APM Appendix" section). The

effect of the secondary dendrite arm spacing (λ2) is illustrated in both following figures in the case of good and bad cooling conditions. As observed, the expected trend is found by the APM.

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Final porosity fraction for a secondary dendrite arm spacing equal to ((a) λλλλ2 = 10µµµµm,

(b) λλλλ2 = 20µµµµm, (c) λλλλ2 = 30µµµµm, (d) λλλλ2 = 100µµµµm. Good cooling conditions, cH =

0.1ccSTP/100g, µµµµ = 1e-3Pa.s, imposed pressure = 1 bar.

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Final porosity fraction for a secondary dendrite arm spacing equal to (a) λλλλ2 = 10µµµµm,

(b) λλλλ2 = 20µµµµm, (c) λλλλ2 = 30µµµµm, (d) λλλλ2 = 100µµµµm. Bad cooling conditions, cH =

0.1ccSTP/100g, µµµµ = 1e-3Pa.s, imposed pressure = 1 bar. It is observed in the figure below that the liquid pressure drop is negligible for a

high λ2 value ((d) 100µm). But as the available spacing is high, the porosity growth is facilitated. That is the reason why the porosity fraction is globally higher in case (d) than in case (c) (see figures above).

Ultimate liquid pressure for a secondary dendrite arm spacing equal to (a) λλλλ2 = 10µµµµm,

(b) λλλλ2 = 20µµµµm, (c) λλλλ2 = 30µµµµm, (d) λλλλ2 = 100µµµµm. Good cooling conditions, cH =

0.1ccSTP/100g, µµµµ = 1e-3Pa.s, imposed pressure = 1 bar.

Liquid viscosity The effect of the liquid viscosity is illustrated in both figures below. As expected the APM shows that the final porosity fraction increases with the liquid viscosity (see Darcy's law). This effect is accentuated when the cooling conditions are bad.

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Final porosity fraction for a liquid viscosity equal to (a) µµµµ = 1e-4Pa.s, (b) µµµµ = 1e-3Pa.s,

(c) µµµµ = 5e-3Pa.s, (d) µµµµ = 1e-2Pa.s. Good cooling conditions, cH = 0.1ccSTP/100g,

λλλλ2 = 20µµµµm, imposed pressure = 1 bar.

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Final porosity fraction for a liquid viscosity equal to (a) µµµµ = 1e-4Pa.s, (b) µµµµ = 1e-3Pa.s,

(c) µµµµ = 5e-3Pa.s, (d) µµµµ = 1e-2Pa.s. Bad cooling conditions, cH = 0.1ccSTP/100g,

λλλλ2 = 20µµµµm, imposed pressure = 1 bar.

Imposed pressure The effect of the imposed pressure is illustrated in both figures below. As expected the APM shows that the final gas-shrinkage porosity fraction can be significantly reduced if the imposed pressure is increased. Nevertheless the APM will never predict the reduction or pure shrinkage porosity for an increasing imposed pressure because actually not mechanical effect is taken into account in the porosity model.

Final porosity fraction for an imposed pressure equal to (a) 0.1bar, (b) 1bar, (c) 5bars,

(d) 10bars. Good cooling conditions, cH = 0.1ccSTP/100g, λλλλ2 = 20µµµµm, µµµµ = 1e-3Pa.s.

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Final porosity fraction for an imposed pressure equal to (a) 0.1bar, (b) 1bar, (c) 5bars,

(d) 10bars. Bad cooling conditions, cH = 0.1ccSTP/100g, λλλλ2 = 20µµµµm, µµµµ = 1e-3Pa.s.

Alloying elements effect Alloying elements can modify the gas solubilities. For example, it is known that hydrogen solubility in aluminum is decreased in the presence of Si, and increased in the presence of Mg. As a consequence, for a given gas nominal concentration and a given solidification path, it is expected that the final porosity fraction is increased in the presence of Si, and decreased in the presence of Mg. This effect is reproduced by the APM (see figure below) with an Al-7wt%Si-2wt%Mg alloy. As shown in the figure, the final porosity fraction is increased (compare (a) and (b)) when the effect of Si on hydrogen solubility is taken into account. When the effect of Mg on hydrogen solubility is taken into account, the final porosity fraction is decreased (compare (a) and (c)). Of course, as illustrated in figure (d), the combined effect of several alloying elements can be studied.

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Final porosity fraction in an Al-7wt%Si-2wt%Mg part when (a) the effect of Si and Mg

on H solubility are not taken into account, (b) only the effect of Si is taken into account, (c) only the effect of Mg is taken into account, (d) the effects of Si and Mg on

H solubility are both taken into account. Good cooling conditions, cH =

0.2ccSTP/100g, λλλλ2 = 20µµµµm, µµµµ = 1e-3Pa.s, imposed pressure = 1 bar.

Several gases In brasses, the formation of several gases and a volatile solute element are

responsible for porosity: H2O, H2, SO2 and Zn. Zinc is a volatile element in melted copper base alloys, and thus can contribute to the formation of microporosity. This Zn contribution is explained in the following reference (can be consulted in "dat/manuals/Pdf/APM_papers.pdf"): Couturier G., Rappaz M. (2006). "Effect of volatile elements on porosity formation in solidifying alloys", Modelling and Simulation in Materials Science and Engineering, 14, pp. 253-271. The porosity module is applied here to a brass alloy: Cu-10wt%Zn alloy. In the results presented in the figure below, the alloy was assumed free of sulfur: only the combined effect of hydrogen, oxygen and zinc in solution was taken into account in the porosity calculation. The "gas.param:" block in the "prefix_poro.d" file looks like: gas.param:

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H 0.000020 # [molar frac tion] S 0. # [molar frac tion] O 0.000020 # [molar frac tion] end

Nominal Zn concentration is not mentionned in the "gas.param:" block because Zn is a solute element of the alloy: its concentration evolution in the liquid phase is directly loaded by the APM from the solidification path file: "prefix.phs" file. As observed in the figure below, the final gas-shrinkage porosity fraction strongly depends on the nominal concentrations of H and O in solution in the liquid alloy.

Final porosity fraction in an Cu-10wt%Zn alloy part when (a) cH=20e-6[at]

cO=20e-6[at], (b) cH=10e-6[at] cO=20e-6[at], (c) cH=20e-6[at] cO=10e-6[at], (d)

cH=10e-6[at] cO=10e-6[at]. Good cooling conditions, λλλλ2 = 20µµµµm, µµµµ = 1e-3Pa.s, imposed pressure = 1 bar.

In iron base alloys, H2, N2, CO gases are responsible for porosity. The porosity module is applied here to a Fe-1wt%C alloy. The evolution of the carbon concentration in the liquid phase is stored in the file containing the solidification path: "prefix.phs" ASCII file. As a consequence the concentration of carbon, which is one element of a gas responsible for porosity (CO), has not to be defined in the "gas.param:" block of "prefix_poro.d" file: its concentration will be directly read by the APM in the "prefix.phs" file. Only the concentration of N, H and O has to be defined: gas.param:

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N 0.00020 #[mo lar fraction] H 0.00010 #[mo lar fraction] O 0.00002 #[mo lar fraction] end

As observed in the figure below, the final gas-shrinkage porosity fraction strongly depends on the nominal concentrations of N, H and O in solution in the liquid alloy.

Final porosity fraction in an Fe-1wt%C alloy part when (a) cN=200e-6[at]

cH=100e-6[at] cO=20e-6[at], (b) cN=0[at] cH=100e-6[at] cO=20e-6[at], (c)

cN=200e-6[at] cH=0[at] cO=20e-6[at], (d) cN=200e-6[at] cH=100e-6[at] cO=0[at].

Good cooling conditions, λλλλ2 = 100µµµµm, µµµµ = 1e-3Pa.s, imposed pressure = 1 bar.

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ADVANCED POROSITY SOLVER

Once the "Advanced Porosity" case is set-up (i.e. when the ProCAST Thermal calculation is run and when the prefix_poro.d input file is ready), one can launch the "Advanced Porosity" solver. To do so, the "ProCAST" solver button of the Manager should be used. This opening the following window :

The "Run" button should be hit (in the "Advanced Porosity Solver" section) to start the calculation. If the ProCAST Thermal calculation is not yet run, it is possible to click on the "Execute DataCAST/ProCAST first" check box before the "Run" button. It is also possible to automatically launch a serie of calculation using the "Run list" of the Manager. If the above window does not show the "Advanced Porosity Solver" section, one can activate it in the "Installation settings" window (by clicking in the "Advanced Porosity module" check box, under "Modules display") :

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APM Global results At the end of an APM calculation, a file named "prefix_res.log" is created. This file contains different information about the amount or micro and macroporosity and volume of "porous" metal in the different domains. This file has the following stucture : general: number.of.domains 3 casting.process.time.sec 3.408665e+002 CPU.time.sec 9.200000e+001 end

casting: volume.m3 all.domains 5.204001e-006 domain 1 2.601000e-006 domain 2 2.000000e-009 domain 3 2.601000e-006 end

modeling: cell.size.m cells.number all.domains 1.000000e-003 5204 domains 1 1.000000e-003 2601 domains 2 1.000000e-003 2 domains 3 1.000000e-003 2601 end

microporosity: affected.volume.m3 porosity .fraction.in.affected.volume

xxx yyy all.domains 4.831001e-006 3.686847 e-002

4.719001e-006 3.770333e-002 domains 1 2.439000e-006 3.408665 e-002

2.343000e-006 3.541561e-002 domains 2 0.000000e+000 0.000000 e+000

0.000000e+000 0.000000e+000 domains 3 2.392000e-006 3.970494 e-002

2.376000e-006 3.995928e-002 end

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macroporosity.pipe: affected.volume.m3 all.domains 3.710001e-007 domains 1 1.620000e-007 domains 2 0.000000e+000 domains 3 2.090000e-007 end

The first block (general:) contains the number of domains in which the APM calculation is run (number.of.domains), the time (in seconds) for which the solidification has been calculated in the Thermal ProCAST calculation (casting.process.time.sec) and the CPU time for the APM calculation in seconds (CPU.time.sec). The second block (casting:) contains the total volume (all.domains), as well as the

volumes of each APM domain (in m3).

In the third block (modeling:), the cell size (which is the same for each domain), as well as the number of cells in all the domains and in each domain are indicated. The microporosity in all the domains and in each domain are given in the fourth block (microporosity:). The "affected.volume.m3" column corresponds to the

volume in which the porosity is larger then zero (in m3). The

"porosity.fraction.in.affected.volume" corresponds to the average microporosity in the "affected.volume.m3" (the value is in fraction). The next column (labeled by the "xxx" above due to the very long keyword) corresponds to the "volume.upper.crit.fraction.m3". This is the volume in which the microporosity is above the value defined in the "prefix_poro.d" by the keyword "crit.pore.fraction"

(in m3). Finally, the last column (labeled by the "yyy" above due to the very long

keyword) corresponds to "porosity.fraction.in.volume.upper.crit.fraction". This is the average of the microporosity in the "volume.upper.crit.fraction.m3" (the value is in fraction). Finally, the last block (macroporosity.pipe) is giving the volumes where there is

pipe shrinkage and macroporosity (in m3).

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ADVANCED POROSITY POST-PROCESSING

Two different formats are available for the storage of the porosity results : a) "Advanced Porosity Post-processor" format b) "ProCAST" format In the "Advanced Porosity Post-processor" format, the porosity is stored at each FVM cell. This allows a very fine resolution of the results that can be displayed with the "Advanced Porosity Post-processor". In the "2009.1" format, the porosity results, calculated at the FVM cells are “interpolated“ to the FEM nodes. This allows to view the "Advanced Porosity" results in ViewCAST. Nevertheless, it is recommended to visualize the results with the “Advanced Porosity Post-Processor” because a loss of small macroporosities and small microporosity regions is induced by this “interpolation“. The "store.type" allows to select which result files format should be stored (see the "Calculation Settings" section for more details). The "2009.1" format results can be visualized in VisualCAST or ViewCAST with the Contour "Thermal/Advanced Porosity". As for the "Shrinkage Porosity" contour, automatically the last timestep is shown in cut-off mode (above 1%) (see picture below).

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It is also possible to view the "Porosity Pressure" which corresponds to the Pressure drop calculated in the mushy zone in the Advanced Porosity model.

To access the "Advanced Porosity Post-processor", one has to make a right mouse click on the "VisualCAST" button of the manager. This will open a sub-menu and one should select "Advanced Porosity results" (see below) :

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This is automatically opening the "Advanced Porosity Post-processor" and the porosity field is shown. One should use the tape player to visualize the last timestep.

When a cut-off value of 1% is used, the following result is obtained (which is very similar to the ViewCAST result above) :

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One should note that the "Advanced Porosity Post-processor" results are more precise than the "ProCAST" format results. This is due to the fact that the Advanced porosity calculation is performed at cells (which are all shown in the "Advanced Porosity Post-processor" format, whereas these cells results are "interpolated" to the FEM nodes for the "ProCAST" format results. If there is only a few cells which are empty (i.e. a small macroshrinkage), this may be "diluted" in the surrounding microporosity during the extrapolation to the FEM nodes. Thus, this small macroshrinkage may not be visible in the ViewCAST. Concerning the "Advanced Porosity Post-processor" format, the microporosity is shown using the yellow-green scale, whereas the macroshrinkage is shown in orange and red. In practice the macroshrinkage are negative values (from 0 to -100), whereas microporosity are positive values (from 0 to 100). The macroporosity between 0 and 50% is shown in orange, whereas the one between 50 and 100% is shown in red. In "ProCAST" format, this distinction can not be made and both the microporosity and the macroporosity is shown (as positive values). In the "Advanced Porosity Post-processor" to see macroporosities present in the core of the casting, proceed as highlighted in the figure below.

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APM APPENDIX

The flowchart followed by the Thermal and APM calculations is summed-up in Appendix 1. In Appendix 2, a growth law of a pore constrained by the dendrite network is proposed. The gas thermodynamic database structure (“dat/db/gas.db”) is described in Appendix 3. Finally, Appendix 4 is the table giving the full list of the APM parameters.

APM Flow Chart

The complex porosity model implemented in the APM is not detailed here (for a complete description of this model, see Ref [1-4] in the "APM References" section). But the flowchart followed by the APM is described below to understand how and where all the necessary information for a porosity calculation are found by the APM.

Flowchart followed by the APM

The Finite Volume porosity solver is a "post treatment" of the thermal results obtained with the Finite Element ProCAST solver:

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• The temperatures at nodes (“prefixt.unf” file) are read by the APM and interpolated at the center of cells (1),

• The solid fraction at cells (2) is deduced from these temperatures and from the gs(T) curve defined in the pre-processor of ProCAST (PreCAST) (read in “prefixg.unf” file).

• The physical properties (ex: density curve and viscosity of the alloy) and some casting process parameters (ex: gravity) are directly defined in PreCAST (3) and read in the “prefixg.unf” file by the APM because these properties are also required for the thermal-flow calculation.

• APM is a complete approach that takes into account the effect of solute elements segregation on gas solubility if the solidification path has been calculated by PreCAST (“prefix.phs” file). The alloy characteristics (alloy base and composition) defined in PreCAST and the solidification path, are directly read by the APM (4) in the “prefixg.unf” file and the “prefix.phs” file respectively. That information allows the porosity solver to detect automatically the gases responsible for porosity in the considered alloy and to load the corresponding gas thermodynamic properties and solute elements interaction coefficients (5). This data is loaded from the gas thermodynamic database (“dat/db/gas.db” file).

The list of the strictly needed parameters in the “prefix_poro.d” file is limited (6). A warning message is written by the APM each time a badly spelled keyword was defined in the “prefix_poro.d” file. Other parameters are optional: for them a value is defined in the APM source code. The user has the possibility to change this hard-coded value: he can define it in the “prefix_poro.d” file, but if he wants to customize the APM he can also define it in a “default_poro.d” file located at “dat/pref/default_poro.d” (7). The definition of a parameter in the “prefix_poro.d” file takes over the definition in the “default_poro.d” file. The definition of a parameter in the “default_poro.d” file takes over the hard-coded value. The porosity results can be post-processed (8): • with the Finite Volume "Advanced Porosity Post-processor", • or with the standard Finite Element post-processor, ViewCAST (not

recommended because a loss of small macroporosities and small microporosity regions is induced by the interpolation of porosity at Finite Element nodes).

Growth model of a pore

The growth law has changed since the original Pequet et al. model [1] (for more

details see references [2-3]). As the interface energy, γgl, is on the order of 1 Jm-2 and the pore curvature radius, r, is equal to a few tens of micrometers, the curvature contribution (Laplace's overpressure) cannot be neglected and strongly

influences the pore fraction, gp. While the relationship between gp and r is

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straightforward for spherical pores, a simple model for the curvature of a pore constrained to grow in a well developed dendritic network (i.e, gas-shrinkage porosity) is derived in this section.

Regular stacking of dendrite arms showing the space available for pores (rmax): hexagonal arms without impingement (left), and cylindrical arms with impingement

(right). The left scheme of the above figure is an illustration of a too simple geometrical solution that does not take into account secondary dendrite arms impingement. The present model considers a simplified 3-dimensional network of cylindrical secondary dendrite arms and takes into account their impingement (right scheme in the above figure). Assuming that pores can grow in between the cylindrical arms, assumed to be infinite in length, the maximum radius of the pore is simply given by:

As the liquid phase is assumed to completely wet the solid, the contact angle at the triple point (pore-solid-liquid) is zero. Equations above are shown in the

following figure, together with another relation, rmax = 0.5 λ2(1 - gs0.5

), that corresponds to the solution of the left geometry in the above figure. It appears that the new relations above seem more adapted to the modelling of gas-shrinkage

porosity. Indeed, with rmax = 0.5 λ2(1 - gs0.5

), rmax/λ2 does not exceed 0.025

for gs >0.9 . Taking λ2 = 40 µm, rmax will be smaller than 1 µm, and ∆pr will

be greater than 1.8 MPa (for γgl = 0.9Jm-2

). Therefore, pores will have almost no

chance to grow if they do not nucleate before gs = 0.9. Doing the same

calculation with the above equation (rmax/λ2 < 0.15 for gs > 0.9), the curvature

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contribution is on the order of 300 kPa during the last stage solidification, thus allowing gas-shrinkage porosity formation.

Representation of the maximum radius of a pore (normalized by the secondary dendrite arm spacing) growing in a mushy zone for both geometrical models shown in the above

figure (the solid curve ("relations (2.1)") refer to the equations above.

The above equations, i.e. (rmax/λ2)(gs), have been hardcoded in the APM. The

user will also have the possibility to define his own (rmax/λ2)(gs) relationship in the "prefix_poro.d" file or in the "default_poro.d" file. As the reading function of

"prefix_poro.d" can not read any table function of gs, (rmax/λ2)(gs) table is assumed to be a function of the temperature (although the values of the abcissa are indeed solid fractions) : nucleation.growth.param: available.half.spacing *r(gs) end

value r(gs) data f(temp) 0 0.7 0.2 0.6 0.8 0.5 1. 0 end value

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Gas Thermodynamic Database

APM communicates with a structured database that contains properties of the gases responsible of porosity for different alloy categories: "dat/db/gas.db" ASCII file. The simplicity of this database structure will allow the user to modify and complement the database. Its structure is explained hereafter. First, the equations governing the formation of gases are given (for details see ref [2]). The involved reactions are : • formation of gas α,

• formation of gas λ,

The solubility product of gas α, composed of two chemical elements, A and B, is governed by the following equation:

with

A gas conservation equation is written for each element, A, contained in at least one gas:

Second, the gas database structure is given in the following table. It is organized in three levels represented by three colours. The first level (red) specifies the alloy category. In each category, this database has to distinguish properties of gases and properties of chemical elements that compose these gases because an element can be contained in several gases and a gas can be composed of several elements. As a consequence the second level (blue) contains some separate blocks of information

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that concern each gas and each element. For example in the category Cu, "gas:" blocks called water, dihydrogen, sulphur dioxide are defined. The existence of these gases implies the definition of a "gas.element:" block for each of the following chemical elements that appear at least one time in these gases: H, O and S. In each "gas:" (or "gas.element:") block, characteristics and thermodynamic properties of the gas (or element) are specified (third level in green). The reading functions of gas.db file allow the definition of these properties in any order.

Representation of the structure of the gas database stored in file dat/db/gas.db (dummy

values are shown in this table) Below is the correspondence between the gas parameters of the above equations and parameters represented in green in the above table. For a given gas, α:

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• The composition of the gas ("composition:") and the gas formation coefficient ("gas.formation.coefficient:") are needed parameters. The last parameter

corresponds to Aα in the following equation :

• The standard enthalpy ("standard.enthalpy:") of a formation reaction is an

optional parameter. If this parameter is not given, it is assumed equal to zero.

This parameter corresponds to ∆Hαo in the above equation.

For a given gas element, A: • The partition coefficient of A ("partition.coefficient:") between the solid and

the liquid phase (kA in the following equation) is also a needed parameter, as well as the activity coefficient of A ("activity.coefficient:") in the liquid phase

in absence of solute element ('flA in the above equation).

• The optional interaction coefficients ("interaction.coefficients:") are

parameters "eAs" and "rA

s" of the following equation :

• The parameter "concentration.level:" is an optional parameter that will make

the APM display the typical nominal concentrations of the gas element A.

List of the APM Parameters

The following table is the list of all the APM parameters. For each parameter it is mentioned if it is needed, optional or not required (i.e. can not be defined at this location) in the "prefix_poro.d" and the "default_poro.d" files. The hard-coded value is also mentioned.

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The definition of a parameter in the "prefix_poro.d" file takes over the definition in the "default_poro.d" file. The definition of a parameter in the "default_poro.d" file takes over the hard-coded value.

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APM References

The following references can be found in the software installation (dat/manuals/Pdf/APM_papers.pdf) [1] Péquet Ch., Gremaud M., and Rappaz M. (2002), “Modeling of Microporosity,

Macroporosity and Pipe Shrinkage Formation during the Solidification of Alloys using a Mushy-Zone Refinement Method”, Met. Mater. Trans., 33A, 2095.

[2] Couturier G., Desbiolles J-L., Rappaz M. (2006). "A porosity model for

multi-gas systems in multicomponent alloys", TMS, Modeling of Casting Welding and Advanced Solidification Processes, pp. 619-626.

[3] Couturier G., Rappaz M. (2006). "Modeling of porosity formation in

multicomponent alloys in the presence of several dissolved gases and volatile solute elements", TMS, Symposium on Simulation of Aluminium Shape Casting Processing.

[4] Couturier G., Rappaz M. (2006). "Effect of volatile elements on porosity

formation in solidifying alloys", Modelling and Simulation in Materials Science and Engineering, 14, pp. 253-271.

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MICROSTRUCTURES

The Microstructure models were improved in version 2006.0. In particular, the treatment of the thermal algorithm was significantly improved. This allows to have much larger timesteps than before. Please note that due to this change the maximum timestep should be kept to reasonable values (i.e. one should make sure that the solidification range is crossed in several timesteps). Concerning the prediction of the Casting strength, previously it was only a function of the grain size. It has been improved in order to be also a function of the ferrite-perlite fractions. As a consequence, the Casting strength will not be only dependent upon the thermal history near the solidification, but also upon the further cooling (i.e. it will depend upon the cooling rates between 700 and 900°C).

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INTRODUCTION

The microstructure module of ProCAST is now able to calculate automatically the microstructures, based upon the composition of the alloy. This can be achieved with the link of the module with thermodynamic databases. Depending upon the chemical composition, the microstructure module automatically detects the phases which will appear and the type of microstructure which should be computed (dendritic, eutectic, nodular, ...). For instance, if an Al-7%Si-0.3%Mg alloy is specified (A356), automatically, the software will detect that primary dendrites will form, followed by an interdendritic eutectic. On the other hands, if the composition of a Nodular Cast Iron (SGI) is defined, the nodule counts, the austenite radius, the pearlite and ferrite fractions will be computed, together with the corresponding mechanical properties (such as hardness, yield and tensile strength). The software will also automatically detect that if there is no Magnesium in the cast iron, the structure will be lamellar rather than spheroidal. In the same way, if the composition is hypo-eutectic, primary dendrites of austenite will form first before the eutectic precipitation. The only parameters that the user may need to specify are the nucleation parameters (see below). This is due to the fact that this is not an intrinsic property and that it may depend upon the metal treatment. Moreover, it may be necessary to define the growth kinetics of the eutectic phase (see below) As the microstructure module is linked with the thermodynamic databases, it is necessary to have the corresponding database license, for the desired base material.

Nucleation of the primary dendritic grains The primary dendritic phase (if any) will nucleate and grow as equiaxed grains. The nucleation of these grains strongly depends upon the alloy treatment and thus the nucleation parameters should be defined. The model which is used is based upon the "Gaussian distribution" model proposed in 1987 by Rappaz et al.(Acta Metall., 35, (1987), 1487 and 2929). This model defines the relationship between the number of nuclei and the undercooling. The distribution of the nuclei with undercooling has the form of a Gaussian distribution and thus, the integral of this curve is an "S-shape" function (see graphs below).

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The mathematical description of this "S-shape" curve is as follows :

with the following definitions :

Thus, the nucleation behavior of the primary dendritic phase is fully defined by the three above parameters.

Nucleation of the eutectic grains The nucleation of the eutectic grains is based upon the model proposed in 1966 by Oldfield (ASM Transaction, 598, (1966), 945). The number of nuclei is a powerlaw (Oldfield proposed a quadratic law) of the undercooling. The model is described by the following equations :

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Thus, the nucleation behavior of the eutectic phase is fully defined by the two above parameters.

Growth kinetics of the eutectic grains The eutectic is growing with a quadratic power of the undercooling :

Thus, the above constant fully defines the growth characteristics of the eutectic growth.

Default values The following table is showing the default values which are used in the microstructure module for the models described above and for the different alloys. Of course, the nucleation data may change from one alloy to the other, due to different metal treatment. These default values corresponds to values proposed in the literature.

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CASE SET-UP AND RESULTS

Set-up The set-up of a microstructure calculation is very simple as the model is based upon the chemical composition. Firstly, the problem should be defined as a usual thermal case. Then, the chemical composition of the alloy should be specified in the corresponding material properties tab (see below).

For the thermal properties, only the thermal conductivity and the density should be defined in addition to the chemical composition. Then, the enthalpy needs to be calculated in PreCAST, with the Thermodynamic database (based upon the specified chemical composition), using the Lever model for Fe alloys and the Scheil model for the other systems. Thus, at the end, the thermal conductivity, the

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density, the enthalpy, the fraction of solid, the liquidus and solidus temperatures are defined. Finally, the Run Parameter MICRO should be set to 1 (for the users of previous versions, one should not anymore use values different from 1, as the selection of the micro model is now automatic). A value of 0 will disable the microstructure calculation. If the nucleation or growth parameters have to be changed from the default values (see Table below), the corresponding Run parameters can be modified (see the Microstructure Run Parameters section for more details).

Coupled/Uncoupled algorithm Since version 2006.1, the micro module can be used in a "coupled" or "uncoupled" mode (see the Microstructure Run Parameters section for more details about how to activate these modes). The difference between the two modes can be described by the following flow chart.

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In the "coupled" mode, the microstructure calculation is fully coupled with the thermal calculation. The solid fraction is calculated inside the thermal calculation loop by the micro solver. The source term (i.e. the latent heat release) for the energy conservation calculation is given by the micro calculation. The micro calculation is called at every iteration until convergence is obtained. This mode will lead to very accurate results, but at the expense of rather small timesteps and larger CPU time (2-5 times larger than with the "uncoupled" mode). In the "uncoupled" mode, the microstructure calculation is not coupled with the thermal calculation inside the thermal calculation loop. The micro calculation is called only after the convergence of the thermal calculation and thus it is called only once per timestep. The source term (i.e. the latent heat release) for the energy conservation calculation is based upon the solid fraction change between the last timestep (t-dt) and the step before the last one (t-2dt). As a consequence, the contribution of the latent heat is "delayed" for one timestep. For this reason, the timestep should not be too large in order to have relatively accurate results. This algorithm is fast, however, the results are less accurate and the timestep should be controlled. The default mode is "uncoupled" (before version 2006.1, all the micro calculations were performed in "uncoupled" mode).

Results Depending upon the alloy composition, the type of microstructure will be different. As a consequence, the type of results which are computed will also be different. All the microstructure results can be visualized in the post-processing, in the "Contour/Micro" menu.

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a) Dendritic primary phase and eutectic secondary phase Most alloys are solidifying with a primary phase of dendrites, followed by inter-dendritic eutectic. In this case, the following quantities are calculated :

The "Primary Dendrite Radius" corresponds to the primary grain size. The "Secondary Dendrite Arm Spacing" (also called SDAS) is the distance between the secondary dendrite arms of the primary phase. The "Primary Solid Fraction" corresponds to the fraction of primary phase, whereas the rest corresponds to the "Fraction of Eutectic". The "Eutectic Grain Radius" corresponds to the radius of equiaxed eutectic grains which are nucleating in between the dendrites of the primary phase. Finally, the "Eutectic Inter-lamellar Spacing" is the characteristic distance of the eutectic structure. b) Special case of Fe-C alloys - grey iron (lamellar eutectic) In the case of grey iron (lamellar eutectic), in addition to the quantities described above, other quantities can be calculated :

Metastable phases ("Fraction of Metastable Eutectic" and "Metastable Eutectic Grain Radius"), may appear depending upon the chemical composition and the local cooling conditions.

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The solid state transformations of austenite decomposition into Ferrite and Pearlite is calculated ("Fraction of Ferrite" and "Fraction of Pearlite", "Pearlite Spacing"), as well as the corresponding final mechanical properties ("Tensile Strength", "Yield Strength" and "Brinell Hardness"). If Mg is present in the chemical composition of the base alloy, please note that if the amount is larger than 0.004%, the software will consider that it is corresponding to a Nodular cast iron (SGI). If it is well a grey iron, please decrease the amount of Mg in the chemical composition to less than 0.004%. c) Special case of Fe-C alloys - nodular cast iron (eutectic composition) In the case of Nodular cast iron, nodules of graphite, surrounded by austenite are formed, instead of eutectic grains. Thus, the "Nodule count" (which corresponds to the density of graphite nodules), as well as the "Austenite Radius" and "Graphite Radius" are calculated. The solid state transformations, as well as the mechanical properties are calculated, as described above. In addition, the "Elongation" is calculated from the microstructure results.

The Nodular cast iron (SGI) model is activated as soon as there is an amount of Mg in the chemical composition larger than 0.004%. d) Special case of Fe-C alloys - nodular cast iron (hypo-eutectic composition) In the case of a hypo-eutectic nodular cast-iron, the same properties as described above are obtained, in addition to the primary phase calculation of the austenite dendrites.

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The Nodular cast iron (SGI) model is activated as soon as there is an amount of Mg in the chemical composition larger than 0.004%. e) Special case of Fe-C alloys - steel In the case of a steel with the composition of carbon equivalent less than 0.53 , the following properties are obtained.

The fraction of peritectic is the solid fraction formed from the reaction of liquid and the existing primary solid phase. The fraction of proeutectoid refers to the fraction of proeutectoid ferrite or cementite formed from the austenite phase as a function of time during the solid phase transformation. The carbon equivalent value controls which type of the proeutectoid phase will form (the "carbon equivalent" corresponds to %C + (%Si + %P)/3 ). References For cast iron, the mechanical properties calculations are based upon the microstructure, according to two following papers : Stefanescu et al, Proceedings of the 4th Decennial International Conference on Solidification Processing, Sheffield, (July 1997), 609. Goettsch et al, Metallurgical and Materials Transactions, 25A:5, (1994), 1063

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EXAMPLES

In order to illustrate the application of the microstructure module on the solidification of nodular cast iron, two calculations were performed with two different chemical compositions. To do so, a very simple geometry was used, as shown below. The casting is cooled from the right with a chill, whereas the rest is in a sand mold.

This set-up produces a full range of cooling rates, as shown in the cooling curves hereafter.

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The following figure is showing the two alloys which were used, with the corresponding chemical compositions. The only difference between the two calculations is the amount of Carbon (from 3.2% to 3.5%).

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The above figure is showing the different kind of results which are automatically computed for the two alloys. One can see that for the Alloy B, there is no "Primary phase", as the alloy is lying on the eutectic composition. The following figures are showing the comparison of the different results. On the left, the Alloy 1 is shown (3.2% C - Hypo-eutectic) and the Alloy 2 is shown on the right (3.5% C - Eutectic). Eutectic phase fraction

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Nodule counts

Austenite Radius

Ferrite fraction

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Pearlite fraction

Brinell Hardness

Elongation

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Tensile strength

Yield strength

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Secondary Dendrite Arm Spacing (SDAS)

One can see that the SDAS is only available for Alloy 1, as there is no dendrites (i.e. no primary phase) in Alloy 2.

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IRON AND STEEL

In order to run iron micro modeling, the following set-ups are needed in PreCAST : a. Run Parameters/Micro:

i. MICRO=1 ii. Select Default Values (Gray Iron or Ductile Iron) iii. Based on the inoculation level change the values accordingly

1. EUNUCL (For ductile iron, default value is 2000 ) 2. EUPOWER (For ductile iron, default value is 2.5 )

b. Run Parameters/Thermal

i. MACROFS ii. PIPEFS iii. FEEDLEN iv. MOLDRIG (0~1, change it according to the hardness of mold)

c. Run Parameters/Micro i. GRAPHITE (0~1, default=1.0) ii. FADING (0~1, default=1.0) (0 for large castings, 1 for small ones) iii. MGTREAT (time between the Mg treatment and the beginning of the calculation)

Introduction to Iron and Steel

The study of the micro structure of steels and irons must start with the iron-carbon equilibrium diagram. Many of the basic features of this system (Fig. 1) influence the behavior of even the most complex iron alloys. For example, the phases found in the simple binary Fe-C system persist in complex steels. The iron-carbon diagram provides a valuable foundation on which to build knowledge of both plain carbon and alloy steels in their immense variety.

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Figure 1. The iron-carbon diagram.

It should first be pointed out that the normal equilibrium diagram really represents the metastable equilibrium between iron and iron carbide (cementite). Cementite is metastable, and the true equilibrium should be between iron and graphite. Graphite occurs extensively in cast irons (2-4 wt % C), but it is usually difficult to obtain this equilibrium phase in steels (0.03-1.5 wt %C). Therefore, the metastable equilibrium between iron and iron carbide should be considered for steel, because it is relevant to the behavior of most steels in practice. It is convenient to combine the effect of the silicon with that of the carbon into a single factor which is called the carbon equivalent (CE):

CE=%C+%Si/3 It is called iron if CE is greater than 2, otherwise it is called steel.

Steel When the weight percent sum of all elements other than Fe is more than 5% (such as some alloy steel or stainless steel), only equiaxed dendrite model will be activated.

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1) Carbon content less than 0.53% (such as Alloy A in Fig. 1) When the melt alloy cools from an initial temperature higher than the liquidus temperature down to a temperature slightly below it, the primary delta dendrite phase begins to nucleate in the liquid until a recalescence occurs due to the heat released from the growing nuclei. During the recalescence, the nucleation ceases and the nuclei grow rapidly into dendritic grains and soon impinge on each other at the end of recalescence. Then the growth of delta dendritic grains is replaced by the coarsening of delta dendritic arms. When the temperature reaches to the peritectic temperature, the peritectic transformation starts if there is still liquid available. Otherwise, the austenite phase precipitates from the delta phase until all of the delta phase is transformed into the austenite phase. Lastly, when the temperature of the casting is cooled down to the alpha phase transformation temperature, the alpha phase precipitates from the austenite phase to the eutectoid

temperature. Below the eutectoid temperature, the graphite of Fe3C phase nucleates initially on the boundary of the austenite grains and then the coupled

growth of alpha and Fe3C phases leads to the formation of pearlite phase. 2) Carbon content is greater than 0.53% (such as Alloy B in Fig. 1) When the melt alloy cools from an initial temperature higher than the liquidus temperature down to a temperature slightly below it, the primary austenite dendrite phase begins to nucleate in the liquid. The austenite phase will grow until the end of solidification. There is no peritectic reaction here. When the temperature of the casting is cooled down to the alpha phase(C<0.8%) or cementite phase(C>0.8%) transformation temperature, the alpha phase or cementite phase precipitates from the austenite phase to the eutectoid temperature.

Below the eutectoid temperature, the coupled growth of alpha and Fe3C phases leads to the formation of pearlite phase. The eutectoid temperature is around 723°C while the eutectoid composition is 0.80% C. Slowly cooling alloys containing less than 0.80% C, hypo-eutectoid ferrite is formed from austenite in the range 910-723°C with enrichment of the residual austenite in carbon, until at 723°C the remaining austenite, now containing 0.8% carbon transforms to pearlite, a lamellar mixture of ferrite and iron carbide (cementite). In austenite with 0.80 to 2.06% carbon, cooling in the temperature interval 1147°C to 723°C, cementite first forms progressively depleting the austenite in carbon, until at 723°C, the austenite contains 0.8% carbon and transforms to pearlite. Steels with less than about 0.8% carbon are thus hypo-eutectoid alloys with ferrite and pearlite as the prime constituents, the relative volume fractions being determined by the lever rule which states that as the carbon content is increased, the volume percentage of pearlite increases, until it is 100% at the eutectoid composition. Above 0.8% C, cementite becomes the hyper-eutectoid phase, and a

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similar variation in volume fraction of cementite and pearlite occurs on this side of the eutectoid composition.

Cast Iron The term cast iron, like the term steel, identifies a large family of ferrous alloys. Cast irons are multicomponent ferrous alloys. They contain major (iron, carbon, silicon), minor (<0.01%), and often alloying (>0.01%) elements. Cast iron has higher carbon and silicon contents than steel. Because of the higher carbon content, the structure of cast iron, as opposed to that of steel, exhibits a rich carbon phase. Depending primarily on composition, cooling rate and melt treatment, cast iron can solidify according to the thermodynamically metastable

Fe-Fe3C system or the stable Fe-graphite system. When the metastable path is followed, the rich carbon phase in the eutectic is the iron carbide; when the stable solidification path is followed, the rich carbon phase

is graphite. Referring only to the binary Fe-Fe3C or Fe-C system, cast iron can be defined as an iron-carbon alloy with more than 2% C. Important notice is that silicon and other alloying elements may considerably change the maximum solubility of carbon in austenite. The formation of stable or metastable eutectic is a function of many factors including the nucleation potential of the liquid, chemical composition, and cooling rate. The first two factors determine the graphitization potential of the iron. A high graphitization potential will result in irons with graphite as the rich carbon phase, while a low graphitization potential will result in irons with iron carbide. The metastable phase amount has both direct and indirect effects on the properties of ductile iron castings. Increasing the volume percent of hard, brittle carbide increases the yield strength, but reduces the tensile strength and elongation, of ductile iron castings. Because there is no graphite expansion for the metastable phase, the formation of carbide increases the likelihood of internal casting porosity. The two basic types of eutectics - the stable austenite-graphite or the metastable

austenite-iron carbide (Fe3C) - have wide differences in their mechanical properties, such as strength, hardness, toughness, and ductility. Therefore, the basic scope of the metallurgical processing of cast iron is to manipulate the type, amount, and morphology of the eutectic in order to achieve the desired mechanical properties. The structure of the matrix is essentially determined by the cooling rate through the eutectoid temperature range. Slow cooling rates prevalent in heavy sections promote the transformation of ferrite.

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Classification Historically, the first classification of cast iron was based on its fracture. Two types of iron were initially recognized: • White iron: Exhibits a white, crystalline fracture surface because fracture

occurs along the iron carbide plates; it is the result of metastable solidification

(Fe3C eutectic)

• Gray iron: Exhibits a gray fracture surface because fracture occurs along the graphite plates (flakes); it is the result of stable solidification (Graphite eutectic).

With the advent of metallography, and as the body of knowledge pertinent to cast iron increased, other classifications based on microstructural features became possible: • Graphite shape: Lamellar (flake) graphite (FG) as shown in Fig. 4.1 and 4.2,

spheroidal (nodular) graphite (SG) as shown in Fig. 5.1 and 5.2, compacted (vermicular) graphite (CG), and temper graphite (TG); temper graphite results from a solid-state reaction (malleabilization.)

• Matrix : Ferritic, pearlitic, austenitic, martensitic, bainitic (austempered). The correspondence between commercial and microstructural classification, as well as the final processing stage in obtaining common cast irons, is given in Fig. 2.

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Fig.2. Basic microstructures and processing for obtaining common commercial

cast irons Graphite is a hexagonal-close pack form of carbon that can grow in both the liquid and solid forms of iron. In theory, in irons above the eutectic composition of carbon, the graphite first nucleates in the liquid, and then continues to grow in the solid. In irons below the eutectic composition, the carbon does not start to grow until the iron reaches eutectic temperature. As seen in a micro, the larger nodules are from growth initiated in the liquid, and the smaller nodules are from growth that does not start until solidification temperatures are reached. The graphite nodules continue to grow as the iron cools, so the amount of growth that occurs in the liquid is smaller than what would be assumed by the micro. The expansion from the graphite that grows in the liquid pushes liquid back into the riser, and does not offset shrinkage. So in order to minimize shrinkage, it is necessary to maximize the late formation of graphite without having to reduce the actual amount of graphite. Understanding what happens in a non-steady state solidification of Ductile Iron suggests a way that this can be done. In a hypoeutectic mode of solidification, austenite forms as a solid with a lower than average carbon content. This increases the carbon content of the remaining liquid until it reaches the eutectic composition. Likewise, in a hypereutectic mode of solidification, graphite nodules form in the liquid, removing carbon from the liquid until it is reduced to the eutectic composition

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Fig. 3 Phase diagram showing movement of carbon concentration in liquid metal

as iron solidifies. It can be seen from the diagram on the previous page, which the maximum amount of carbon that can be formed in late graphite is determined by the eutectic composition, and as long as the iron is at eutectic or above, the amount of late graphite will be the same.

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Iron and Steel models

The following micro models are available in ProCAST:

Equiaxed Dendrite Model The model is based upon the model proposed in 1987 by Rappaz et al. This model defines the relationship between the number of nuclei and the undercooling. The distribution of the nuclei with undercooling has the form of a Gaussian distribution and thus, the integral of this curve is an "S-shape" function. Following nucleation, the dendrite tip growth is controlled by the supersaturation at the dendrite tip. This means that the tip growth is based on the total undercooling at the tip. As the tip grows, the solid fraction in each grain is not known from the tip position. In fact, the fraction solid is less than the fraction of the grain obtained from the tip position. At each time, the new tip concentration and fraction solid are known from a thermal and solute balance at the scale of the grain. The tip growth velocity is obtained from the Lipton-Glicksman-Kurz model, which simulates the growth of an isolated dendrite tip. The tip continues to grow until it reaches the end of the grain. At this point, solid fraction is still less than unity. However, mixing of the solute is complete at this stage. Therefore, a back diffusion type equation can be used to calculate solid fraction. If the phase diagram has a terminal reaction, e.g., eutectic, the remaining liquid gets rapidly transformed into a solid structure. It is assumed that the temperature of the grain is uniform and curvature undercooling is neglected. Also it is considered that the thermal undercooling is negligible. The growth of the dendrite tip is controlled mainly by solute diffusion. Therefore, only solutal undercooling is considered.

Eutectic Model This model can be applicable to both regular and irregular eutectics. In the case of regular eutectics, growth of both phases of the eutectic structure is non-faceted in nature. For irregular eutectic, the growth process of one of the phases is faceted. Growth of the faceting phase requires considerably higher entropy of fusion. Examples of faceted growth are graphite growth in stable austenite/graphite eutectic and Silicon in Al-Si eutectic. The metastable austenite/cementite eutectic is an example of non-faceted/non-faceted type eutectic growth. Growth of both the stable and metastable eutectic are addressed here. Growth of the stable eutectic usually proceeds at a higher temperature. A higher cooling rate results in the formation of a metastable eutectic. This model assumes bulk heterogeneous nucleation at foreign sites which are already present within melt or intentionally added to the melt by inoculation. The nucleation of the eutectic grains is based upon the model proposed in 1966 by Oldfield (ASM Transaction, 598, (1966), 945). The number of nuclei is a power law (Oldfield proposed a quadratic law) of the undercooling. The growth of the grains is controlled by thermal undercooling at the solid/liquid interface. Solutal undercooling is neglected here since solute diffusion during eutectic solidification

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is negligible. The thermal undercooling is given by the difference between the eutectic temperature and the actual solid/liquid interface temperature.

Ductile Iron Eutectic Model The eutectic growth process in ductile iron is a divorced growth of austenite and graphite, which do not grow concomitantly. At the beginning of the liquid/solid transformation, graphite nodules nucleate in the liquid and grow in the liquid to a small extent. The formation of graphite nodules and their limited growth in liquid depletes the melt locally of carbon in the vicinity of the nodules. This facilitates the nucleation of austenite around the nodules, forming a shell. Further growth of these nodules is possible by diffusion of carbon from the melt through the austenite shell. Once the austenite shell is formed around each nodule, the diffusion equation for carbon through the austenitic shell is solved in 1-D spherical coordinates. The boundary conditions are known from the phase diagram because thermodynamic equilibrium is maintained locally. Conservation of mass and solute is maintained in each grain. Because of the density variation resulting from the growth of austenite and graphite, the expansion/contraction of the grain is taken into account by allowing the final grain size to vary. Toward the end of solidification, the grains impinge on each other. This is taken into consideration by using the Johnson-Mehl approximation.

Gray/White Iron Eutectic Model This model is a special case of eutectic growth model and is applicable to cast gray/white iron only. In cast iron, one may obtain both gray and white iron depending on the melt composition and cooling conditions. Given a controlled melt composition, the most important factor that will determine whether a given region will solidify as white or gray is the cooling rate. It has been observed that for a specific melt composition and solidification condition, there exists a parameter called a critical cooling rate. If a region of a casting solidifies with a cooling rate higher than the critical cooling rate, then it will be white. The reverse is the case for gray iron.

Ductile Iron Eutectoid Model This model can be used during the eutectoid transformation while describing the phase transformation of ductile iron to room temperature after solidification. The eutectoid reaction leads to the decomposition of austenite into ferrite and graphite for the case of the stable eutectoid and to pearlite for the metastable eutectoid transformation. Usually, the metastable eutectoid temperature is lower than the stable eutectoid temperature. Slower cooling rates result in more stable eutectoid structure. If the complete transformation of austenite is not achieved when the metastable temperature is reached, pearlite forms and grows in competition with ferrite.

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Growth of Ferrite: Even though ferrite can form either from the breakdown of pearlite or from the direct decomposition of austenite, it is assumed here that ferrite results only from the latter source. The following assumptions are made for modeling the growth of ferrite: 1) The austenite to ferrite transformation occurs at steady state and is controlled by carbon diffusion. 2) The ferrite grains grow as spherical shells within austenite grains and the number of ferrite grains is equal to the number of graphite nodules. 3) Thermodynamic equilibrium exists at graphite/ferrite and ferrite/austenite interfaces. These are defined by equilibrium solvus lines extended below the equilibrium eutectoid temperatures. 4) Diffusion from the ferrite/austenite interface towards austenite is neglected as diffusion coefficients and concentration gradients in austenite are small compared to those in ferrite. Nucleation and Growth of Pearlite: The nucleation of pearlite usually occurs at austenite grain boundaries. It has been demonstrated that pearlite colonies grow either as spheres or hemispheres following nucleation. By the movement of high mobility (i.e., low interface energy) incoherent interfaces, these colonies can grow edgewise or sidewise into the austenite. This means that pearlite grows in competition with ferrite until austenite is completely transformed. Transformation of austenite into pearlite is usually modeled with an Avrami equation because the study of nucleation of pearlite is difficult, especially under continuous cooling conditions. Also, pearlite grains impinge on each other at an early stage, especially at a relatively high cooling rate.

Gray Iron Eutectoid Model The gray iron eutectoid transformation model is based on the approach used for gray iron eutectic. Nucleation and growth of ferrite takes place once the temperature drops below the stable eutectoid temperature. If the transformation of austenite is not complete when the metastable eutectoid temperature is reached, then nucleation and growth of pearlite takes place. The nucleation and growth rate expressions for pearlite are the same as those for the ductile iron eutectoid model.

Peritectic Transformation Model In a peritectic transformation, liquid reacts with an existing solid phase to form a new solid phase. In conventional models, the new solid is assumed to form at the interface between the parent liquid and solid phases. Once the new solid phase is formed, further reaction between the parent phases is limited by the layer of solid formed. Hence the rate of reaction is controlled by the diffusion of solute through the shell of the transformed product. It has been suggested by some researchers

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that the peritectic transformation may be achieved through a liquid layer in between the parent and the product solid phases. This mechanism has been adopted in the present model. For example, in the case of steel, the austenite phase forms initially at the root of the dendrite arms of the delta phase and grows along the delta/liquid interface. The speed of this growth is the same as that with which liquid moves toward the delta phase. The diffusion problem can be simplified as the liquid layer is very thin and the diffusion of carbon in the liquid is very rapid so that the carbon concentration gradient in the liquid is negligible.

Solid Transformation Models This model is only applicable to the Fe-C system and is used for tracking the fraction transformed for the cases of gamma to ferrite and gamma to cementite. Prior to reaching the eutectoid temperature, some of the austenite phase may transform into alpha phase as part of a pro-eutectoid transformation. If you started with a hypereutectoid composition, the pro-eutectoid transformation will be from austenite (gamma) to cementite. Both of these pro-eutectoid transformations are addressed by the current model. The wt% carbon equivalent determines whether the gamma to ferrite or gamma to cementite transformation will be used. Both of these models require that the equiaxed dendrite model be chosen for the initial liquid/solid phase transformation.

Density calculation during iron alloys solidification During gray or ductile solidification, the densities of the different phases are computed according to the composition of the phase at that particular temperature. In the calculation, the graphite expansion is included. The densities are updated at each time based on the temperature. The porosity calculation is based upon the calculated density (see the "Cast Iron Porosity model" section for more details). The input density curve in PreCAST will not affect the calculated porosity formation if micro model is activated.

Iron micro model inoculation setup In ProCAST, you can modify the phase nucleation depending on the inoculation practice in the foundry for iron alloys solidification simulation. The inoculation will be good if it is in-mold or in-stream with additional melt pretreatment. It is not as good if the inoculation is only in-ladle. You can change the run parameters to represent the practice of different inoculation. The higher value of EUNUCL (a micro run parameter) represents better inoculation. The default value is set to 2000 which should represent pretty good inoculation. Metastable phase can form in the faster cooling area if the inoculation is not good enough. The following figure is showing the effect of the inocculation parameter EUNUCL on the microstructure and thus on the densities and porosity values.

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Graphite precipitation One more micro run parameter for iron alloys solidification simulation is added called graphite precipitation (GRAPHITE Run Parameter -see the "Micro Run Parameters" section for more details) which tells the degree of graphite precipitation during solidification. It varies from 0 to 1. 1 means that the graphite expansion potential is completely considered in the simulation so the casting will have a relatively low tendency of shrinkage. 0 means that the graphite expansion does not occur hence there is no compensation for the shrinkage of the liquid during solidification by graphite expansion. During the micro calculation, the computed expansion part of the density (as a function of the phases present) is multiplied by GRAPHITE. If GRAPHITE = 0, there will be no expansion, whereas with a value of 1, the full expansion contribution will be taken into account in the density. This density is only used if a porosity calculation (POROS = 1) is made during the microstructure calculation (see the "Cast Iron Porosity model" section for more details). The value of GRAPHITE will not affect at all the computed microstructure. The default value is set to 1.0. This parameter is used to adjust the porosity formation to the real foundry condition. The following figure is showing the effect of GRAPHITE.

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Magnesium Treatment (Fading effect) FADING : Nodular cast iron (SGI) is obtained by a Magnesium treatment of the melt. The graphite formation tends to diminish as the time interval between the treatment and the solidification increases (fading effect). As a consequence, the expansion effect will be reduced as graphite formation is decreasing. This will of course have an effect on the amount of porosity. Fading occurs as a result of a general coarsening of the inclusion population with time. The mean inclusion diameter d is given by the Wagner equation :

Where do is the inclusion diameter at the time of addition of the inoculation, k is a kinetic constant. The effects of some treatment material fade more slowly than others depending on their composition and condition to use, such as in some heavy section ductile iron castings. The run parameter FADING will allow to adjust the inoculants coarsening speed as :

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Where k1 is the Wagner constant. Normally the value of FADING can be any number between 0 and 1. The default value is 1. Small FADING value corresponds to slow coarsening, which is the case for heavy section ductile iron castings. Thus, for large castings, it is advised to set FADING to 0. The value of FADING will affect microstructure results, thus the densities and thus the porosity results as illustrated in the following figure.

MGTREAT : As the calculation is starting usually at the beginning of the filling or when the casting is full, one should take into account the time between the Mg treatment and the beginning of the calculation. To do so, one can define the Run parameter MGTREAT (see the "Micro Run Parameters" section for more details).

Case studies

A simple geometry casting is used to illustrate the application of the microstructure module on the solidification of different alloys. The casting is cooled from the right with a chill (higher heat transfer coefficient). The two bigger surfaces (back and front) are symmetry. All the other faces are adiabatic.

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1. Al 4.9wt%Si For this alloy, as the temperature cools down, the primary phase forms first. The possibility to have and the amount of eutectic phase depends on the cooling rate. With faster cooling rate, there is less amount of primary phase but more eutectic phase. Fig. 6 shows the comparison of current calculation with some experiment and other modeling results for the solidification of this alloy.

Fig. 6 Fraction of Eutectic

1) Primary dendrite radius The PRIMARY DENDRITE RADIUS provides the current position of the dendrite tip and volume fraction of the dendritic grain as it varies with time. At the end of the primary solidification, this parameter will equal the final grain radius.

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Primary dendrite radius

2) Primary solid fraction This reflects the volume fraction of the primary phase formed during solidification. As stated above, there is more primary phase for lower cooling.

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3) Eutectic grain radius (grain radius of the eutectic phase)

4) Fraction of eutectic

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5) Eutectic interlamellar spacing The INTER-LAMELLAR SPACING parameter determines the fineness of the eutectic. Smaller values of this parameter provide better mechanical properties.

2. Ductile Iron (GGG 60) This is a eutectic ductile iron. There is no primary austenite phase but only eutectic phase during solidification. If the Carbon Equivalent is less then the eutectic composition, the first phase comes out would be primary austenite phase then eutectic. The AUSTENITE RADIUS and GRAPHITE RADIUS provide the instantaneous values of the solidified grain size and nodule size respectively. At the end of solidification, they provide a correct description of the final grain size and nodule size. AUSTENITE RADIUS AND GRAPHITE RADIUS can be related to the mechanical properties of castings. Density is calculated from the local fraction of graphite, austenite, and liquid, thus capturing the contraction and expansion behavior of ductile iron. As explained earlier, the stable eutectoid growth refers to the decomposition of austenite into ferrite and graphite and the metastable eutectoid growth refers to the decomposition of austenite into pearlite, which is a coupled growth of ferrite and cementite. The properties of the iron depend strongly on the relative amounts of ferrite and pearlite in the matrix. As the pearlite content increases, tensile and yield strengths also increase, but at the cost of ductility. Ferrite content controls fracture toughness and dynamic properties of iron. The FRACTION OF FERRITE and FRACTION OF PEARLITE give the relative amount of stable and metastable eutectoid structures. The pearlite/ferrite ratio can be related to tensile strength through its effect on matrix microhardness. Usually, a finer pearlite grain size is associated with a finer interlamellar spacing with better mechanical properties.

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The following run parameters are used. EUNUCL=1000 EUPOWER=2.5 1) Nodule counts

2) Austenite radius

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3) Graphite radius

4) Pearlite Spacing

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5) Fraction of Ferrite

6) Fraction of Pearlite

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7) Fraction of Eutectic

8) Fraction of Metastable Phase

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9) Tensile Strength

10) Yield Strength

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11) Elongation

12) Hardness

We can see that it is not 100% stable phase (Eutectic) every where for this casting after solidification. On the higher cooling area (right side), the metastable phase (ledeburite) formed. The fraction of stable phase plus the fraction of metastable phase is 1. The hard brittle metastable phase can form at higher cooling area when the inoculation is not good enough. The metastable phase can increase the yield strength but reduce the tensile strength of the ductile iron castings.

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3. Gray Iron (GG 20) Mechanical properties of the cast grey iron part are a function of the stable and metastable eutectic volume fractions and grain sizes. FRACTION OF EUTECTIC gives the amount of the gray eutectic, whereas FRACTION OF METASTABLE EUTECTIC gives the amount of the white eutectic. In most cases, the gray structure is more desirable as it gives improved tensile strength and ductility. The EUTECTIC GRAIN RADIUS parameter gives the gray eutectic grain radius. The INTER LAMELLAR SPACING parameter calculates the spacing of the gray eutectic. 1) Fraction of Primary phase

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2) Fraction of Eutectic

3) Fraction of Metastable Eutectic

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4) Eutectic grain Radius

5) Eutectic Interlamelar Spacing

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6) Fraction of Ferrite

7) Fraction of Pearlite

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8) Pearlite Spacing

9) Tensile Strength

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10) Yield Strength

11) Brinell Hardness

Metastable phase can form if the cooling is high enough.

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4) Carbon Steel (Plain Carbon AISI 1008 steel) From the phase diagram, we know that the first phase formed during solidification is primary austenite. The peritectic reaction happens when the temperature drops to the peritectic temperature. Usually, peritectic growth is limited by the formation of the solid transformed product at the reacting liquid/solid phase boundary. The PERITECTIC FR. OF SOLID parameter gives the volume fraction of solid resulting from this reaction. It is important to know the amount of the phase formed through this reaction, as it usually forms as a surface layer on the primary dendritic solid phase. As temperature cools down, pro-eutectoid ferrite or cementite will form depends on the composition until when the temperature reaches to the eutectoid temperature. Below the eutectoid temperature, the pearlite forms. FRACTION OF PROEUTECTOID PHASE refers to the fraction of proeutectoid ferrite or cementite formed from the austenite phase as a function of time. The carbon equivalent value controls which type of the proeutectoid phase (ferrite or cementite) will form. If the carbon content is less than the eutectoid composition 0.8%, the proeutectoid phase would be ferrite phase, otherwise would be cementite phase. 1) Primary dendrite arms

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2) Primary solid fraction

3) Secondary dendrite arm spacing

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4) Fraction of peritectic

5) Fraction of eutectoid

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6) Fraction of proeutectoid

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TTT/CCT MODELS

Introduction The formation of microstructures associated with solid state phase transformations during cooling or during heat treatment can now be simulated with ProCAST using models based upon time-temperature-transformation (TTT) or Continuous Cooling-transformation (CCT) diagrams. TTT/CCT diagrams can be found in handbooks or scientific publications for a variety of alloys. They provide information about the starting and ending times of a phase transformation for isothermal (see illustration hereafter) or continuous cooling conditions.

The TTT/CCT module of ProCAST is based on the Kolmogorov-Johnson-Mehl-Avrami (KJMA) expression for the overall kinetics of a phase transformation governed by a nucleation and growth process. The volume fraction of the transformed phase (e.g. volume fraction of ferrite) is obtained with:

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where fmax is a maximum for the fraction transformed (e.g. equilibrium amount

of ferrite), n is an exponent and τ is a characteristic transformation time. These parameters are determined from the information contained in the TTT/CCT diagram. They depend on the local temperature and cooling rate. A differential form of this expression is integrated over the cooling path in order to account for the local thermal conditions. It permits to calculate microstructure maps based on the thermal history at every node of the finite element mesh.

Pre-processing Coded TTT/CCT diagrams are grouped in a database which contains an entry for each of them. In short, the operations required to activate the TTT/CCT module simply consist of assigning in PreCAST an entry of the TTT/CCT database to the casting domains and setting to 1 the TTTMIC Run Parameter. In more details the operations are as follows: 1/ A TTT/CCT diagram should be assigned to all casting domains. This is achieved in the Material/Assign/TTT mic menu.

On the right of the window, two frames are shown. The top one shows the list of the casting materials. Mold materials are not visible in this list as the TTT/CCT microstructure module is not applicable to these materials. The lower frame contains the list of all available TTT/CCT diagrams in the database.

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To assign a TTT/CCT diagram, one should select the desired TTT/CCT diagram in the database list and click on the Assign button. The selected diagram will be assigned to all the casting materials as the model is currently limited to one diagram only. After assignment, the corresponding entry number in the TTT/CCT database is displayed in the right column of the upper frame. 2) The TTT/CCT module should then be activated by setting to 1 the TTTMIC parameter in the Micro tab of the Run parameters panel.

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Database Currently the TTT/CCT database contains 8 steels which are coming from the Sysweld database.

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A description of the chemical compositions, phases and CCT diagrams of these alloys can be found in the document "Sysweld-CCT-description.pdf" located in the software installation (dat/manuals/Pdf/ directory). Each alloy is described :

These alloys can also be found in the standard database (for the thermophysical properties).

Post-processing The results of TTT/CCT microstructure calculations can be visualized in the VisualCAST post-processor.

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The list of available constituents is automatically displayed in the menu.

Results As an illustration the TTT/CCT microstructure module has been applied to the heat treatment of a carbon steel gear component. The figure hereafter illustrates the proportion of microstructure constituents (pearlite, bainite and martensite) obtained after heat treatment for two types of cooling conditions: water quenching and air cooling.

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MICROSTRUCTURES - STRESS COUPLING

Two different type of coupling between Microstructures and Stress are available in ProCAST : • Stress properties depending upon the microstructure, during a calculation (see

the "Stress properties depending upon microstructure" section) • Final stress properties, at room temperature, as a function of the final

microstructure (see the "Final stress properties as function of microstructure" section)

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STRESS PROPERTIES DEPENDING UPON MICROSTRUCTURE

In some cases, the mechanical properties during the process can depend upon the microstructure. This is especially true during heat treatments. Moreover, mechanical properties can also be affected locally by defects, such a porosity. For a stress calculation, ProCAST allows to define mechanical properties which are not only temperature dependant, but also microstructure and/or defects dependant. At this stage only the microstructures calculated by the TTT/CCT models are available (in future versions all the microstructure models calculated by the Micro module will be available). As such dependencies may be very different from one alloy to an other one, the definition of these mechanical properties are done with the help of User Functions. When these User Functions are activated, at each timestep and each node (or Gauss point), the mechanical properties are evaluated in the corresponding User Function. This allows to well see the effect of the microstructure on the mechanical behavior of the part, during the process. The mechanical properties which can be defined in this way are the following : Elasticity

• Youngs modulus • Poisson ratio • Thermal expansion Plasticity

• Yield stress • Hardening parameters

• Plastic modulus • Ultimate stress • Hardening exponent • Kinematic hardening 1 • Kinematic hardening 2

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Viscoplasticity

• Viscoplastic parameters • Viscous param • Power • Strain power

The corresponding User Functions (C functions) have the following names :

• func_youngsmodulus() • func_poissonratio() • func_thermalexpansion() • func_yieldstress() • func_hardeningplasticmodulus() • func_hardeningultimatestress() • func_hardeningexponent() • func_hardeningkinematic1() • func_hardeningkinematic2() • func_viscoplasticviscousparam() • func_viscoplasticstresspower() • func_viscoplasticstrainpower()

In order to activate the corresponding User Function, the "Table" radio button should be selected. Then, the "User Function" check box should be selected. Even the "Table" radio button is selected, it is possible to leave the table empty (if everything is defined in the User function). It is however possible to fill the table and the corresponding values can be retrieved in the User function itself.

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The unit of the Stress property, used in the User Function, is the one specified in the Table window (MPa in the exemple below) :

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Please note however, that the Temperature unit used in the User Function is the one specified in the default unit file, "UserFunctions_units.dat", located in the "dat/pref" directory, or the one given in "prefix_units.dat" file, located in the execution directory (see the "User Functions" section for more details). Once the "User Function" is selected in the Stress properties definition, the user should copy the corresponding User Functions from the Template files (using the "Copy" function of the Manager - the templates are in the ...\templates\MechanicalProperties\ directory of the software installation).

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In the example shown previously, it should correspond to the func_youngsmodulus.c template which should be copied in the local directory as prefix_youngsmodulus.c. The figure hereafter is showing an example of this C function. The yield stress is assumed to be the average value of the yield stresses of pearlite, bainite and martensite weighted by the local fractions of these phases.

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In the User Function, the user has access to the following entities : • Phase fractions : getFraction( Phase_fractions_quantities ) • Defects quantities : getDefect( Defect_quantities ) • Mechanical properties defined in the Table : getFuncTemp()

The Phase fractions and Microstructural parameters are calculated by TTT/CCT module (in future versions it will also be calculated by the Micro module). For the different alloy families, the available quantities (which should be specified as argument of the above functions) are described in the following tables :

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Phase_fraction_quantities [ getFraction() ]

Defect_quantities [ getDefect() ] (at this stage only one quantity is available) Defect.porosity_POROS1 (porosity amount calculated by the POROS = 1 model) Mechanical properties defined in the Table [ getFuncTemp() ] getFuncTemp() is the function which will return the value of the mechanical property define (if any) in the Table, at the temperature of the location where the function is evaluated. No argument should be specified (just "()"). Warning When Phase fractions are used, one should of course make sure that the corresponding quantities are well calculated by the Microstructure module for this particular alloy system. If one of the variables is not activated, the calculation is stopped with an explicit error message. In order to know which variable are available, one could run a calculation with constant stress properties and see in the post-processor which microstructure fields are displayed. In the argument of each function, there is the Material ID (or Domain ID). This means that if such function should be used in different materials, it is possible to set different properties for each domain (respectively material). The variable is "matID ". The other available variable is the temperature ("temp ").

real func_yieldstress(int matID , real temp )

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FINAL STRESS PROPERTIES AS FUNCTION OF MICROSTRUCTURE

ProCAST has the possibility to compute the final stress properties as a function of the final microstructure. To do that, five User Functions are provided to the user in order to define up to five mechanical properties. The templates of these functions are in the directory ...\templates\MechanicalProperties\ of the software installation. They are called : func_mechprop1.c, ...., func_mechprop5.c

In order to activate such a function(s), the corresponding file(s), named "prefix_mechpropi.c" (where "i" is equal to 1, 2, 3, 4 or 5) should be present in the local directory and they will be compiled upon the launch of the solver. The structure of these User Functions is identical as the ones described in the "Stress Properties depending upon the Microstructure" section. The Phase fractions, Microstructure parameters and Defects quantities that can be used in the Function are the same. The only difference is that as we are calculating the final mechanical properties at room temperature, the temperature is not available as an argument of the function. However, the Material ID (matID) is available to the user. The following figure is showing an example of the final Yield Stress at room temperature as a function of the phase fractions. Please note that the name of the

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property, as well as the units are defined in the function, and will be displayed in the post-processing.

Notes • If a flow-thermal-micro calculation has already been done with no mechanical

property user function, it is not necessary to redo the complete ProCAST calculation. As the mechanical property is only calculated at the ultimate step of a ProCAST calculation, it is just necessary to do a restart with a INILEV close to the ultimate step.

• It is worth to note that it is possible in VisualCAST post-processing to

compute the same type of material properties, using the mathematical functions of VisualCAST. However, the usage of these User Functions allows

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to prepare these properties automatically during (i.e. at the end) of the calculation in order to be readily available at the launch of the post-processing.

The following figure is showing the final Yield stress property in a simple part, after two different heat treatments (quenching and air cooling). As the microstructure is different in both cases, the final properties are thus also different.

Final Yield stress properties in the part, as function of the microstructure

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"2-D"

Since version 2008.0, two possibilities are available for 2D modelling : a) real 2D solver (available since version 2008.0) b) pseudo 2D modelling, using the 3D solver In order to use the real 2D version, nothing special has to be done, except to load in PreCAST a 2D mesh instead of a 3D one (if a "planar" surface mesh *.sm is to be used, just rename it as *.mesh before loading it into PreCAST). At this stage, no specific documentation is available (besides the standard ProCAST documentation) for the real 2D solver. The documentation for the pseudo-2D modelling is described in the following sections.

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INTRODUCTION

Pseudo 2D modelling The principle is that 2-D calculations are replaced by 3-D calculations on one layer of elements. To do so, the 2-D mesh generator was modified in order to automatically create this layer of element, in order to reproduce either a 2-D cartesian situation or a 2-D axi-symmetric case. On the left (see figure below), the original 2-D mesh is transformed in a "one layer" 3-D mesh (right) for cartesian calculation (only a small thickness is modeled).

On the left (see figure below), the original 2-D mesh is transformed in a "one layer" 3-D mesh (right) for axisymmetric calculation (only a small sector is modeled).

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MESHING

To call the 2-D mesh generator, one should do a RIGHT mouse click on the "MeshCAST" menu in the manager and the following sub-menu will appear

One can then select between 2-D or 3-D meshing. If MeshCAST-2D is selected, a new windows opens with the 2-D meshing interface. This interface was adapted from the 2-D mesh generator of CALCOSOFT. It allows to mix triangles and quadrangles in the same mesh and to control quite well the size and the shape of the mesh. A brief description of the 2D mesh generator is made hereafter. Firstly, the MeshCAST-2D window opens and the user can select between a new project (i.e. a new mesh) or to load a previous project.

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When a 2D mesh is generated, a file named "prefix.restart" is created. This allows to restore either the Geometry, the Domains, or everything up to the mesh itself. It is also possible to retrieve ProCAST 2-D meshes generated in the previous versions of ProCAST.

Then, the drawing area should be defined. The units should be selected (1), and the size of the drawing area must be defined (2). A grid is superimposed to the drawing area (to help for the drawing). Its characteristics can be defined (3). Finally, the type of problem (cartesian or axisymmetric) has to be selected (4). The "Continue" button should be used to go to the next window (5).

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The drawing can start at this stage. The type of entity to draw should be selected with the corresponding icon (1). Then, this entity can be drawn in the graphics area (2). One can change between the select and deselect mode with the corresponding button (3). The check box in-between is to activate the select or deselect all mode. One should notice that the intersections should be defined by the user, with the left icon in (4). One should select the two lines which are intersecting and then press this icon. Once the drawing is finished, the domains definition can be done in the next window, after pressing the "Continue" button (5).

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Before meshing, the different domains should be defined. One should first "Add" a new domain (1) - the corresponding domain number will appear in the list (2). Then, the contour of the domain should be selected in the graphics area (3). This operation should be repeated for each domain. Then, one can go in the "Meshing" window with the "Continue" button (4).

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The different domains are listed in (1). This mesh generator allows to define both structured meshes (quadrangles) or free triangular meshes (2). Firstly, one should select the domain to be meshed (1). Please note that structured meshes should be meshed first. Then the type of mesh should be selected (2). If a structured mesh is selected, one should define the four faces defining this domain (3). Then, the number of elements along each of the four faces should be defined (3). Please note that it is possible to have more than one line to define a face. Finally, the mesh button can be pressed (4) to generate the mesh.

In the case of "unstructured" mesh (i.e. triangles), the operation is more simple as one should just select the domain to be meshed (1), select the "triangle" mode (2), define the average mesh size (3) and mesh (4). Once all the meshes are generated, one can "Continue" to the next window.

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The last operation which can be done is the grouping of different domains ("combine"). This operation is optional. One should highlight all the domains which should be grouped into one (1) and then the "Combine" button should be pressed (2). Once this is done, it is possible to save the mesh (3). At this stage, automatically, the 2D mesh is extruded into a 3D one.

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In the case of axisymmetric cases, it is important to make sure that the axis of symmetry is well at y = 0. Due to round-off errors, one may have slightly negative coordinated of the nodes which are on the axis. In this case, the "Tools/Check Axisymmetric" menu should be activated.

The software than is asking for a confirmation for this operation.

We are now ready to set-up the case in PreCAST.

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CASE SETTING

After meshing, the "2-D" extruded mesh can be loaded in PreCAST. If the "cartesian" option was selected, the mesh will look like that :

If the "axisymmetric" option was selected, the mesh will look like that :

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Such cases should be set-up exactly in the same way as 3-D cases. One should just take care of the following points : A symmetry boundary condition should be set on the two large faces of the model, as shown hereafter.

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The boundary conditions should be defined on the small faces :

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CAFE-3D

Pre-processing The set-up and the use of the CAFE-3D module is fully described in the CALCOSOFT-3D manual (this manual is available in PDF format in the ProCAST installation, in the dat/manuals/pdf directory). This section is summarizing the specific aspects of the CAFE model related with ProCAST. The CAFE model can be used in 3 different modes :

• "post-processing" mode • weak coupling mode • full coupling mode

In all cases, the ProCAST thermal case should be set as usual in PreCAST. In addition to the standard set-up, one should specify in PreCAST the "nucleation" boundary conditions. To do so, in the "Boundary Conditions/Assign surface" menu, one should "Add" nucleation BC's in the list (one entry per type of nucleation BC).

Then, the different surfaces of the casting should be selected and stored in the corresponding nucleation entry (as for any other BC). Please note that no data

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should be allocated to these nucleation entries, as this will be done in the separate CAFE pre-processor.

If the "full" or "weak" coupling mode is used (for the CAFE calculation), the two following run parameters should be set as :

THERMAL = 2 MICRO = 1024

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Before starting the CAFE set-up (in the CALCOSOFT-3D CAFE pre-processor), one should run first DataCAST. This will create the unformatted mesh file (prefixg.unf), which is necessary for the loading into the CAFE pre-processor. Then, the CAFE-3D pre-processor can be started. To launch it, one should make a right click in the Manager and select the "CAFE pre-processor".

Please refer to the CAFE-3D manual for details about the CAFE-3D set-up.

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The CAFE-3D pre-processor will create all the necessary inputs for the microstructure calculation. All these inputs are stored in an ASCII file called "prefix_mica.d". This file can also be edited by hand.

Solver To run the CAFE calculation, one should press the "ProCAST" button of the Manager which will open the following window :

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Run in "Post-processing mode" To run a "Post-processing" CAFE calculation, click on the Run button under "CAFE Solver (Post-processing mode)". You have the choice to run DataCAST and ProCAST first or not. In all cases, the ProCAST result files should be converted in the CAFE format (i.e. epf format of CALCOSOFT) before starting the CAFE calculation. Run in "Full and weak coupling modes" To use the Full or weak coupling mode, the standard ProCAST executable must be launched (one can in this case either use the Standard Run button or the one under "CAFE Solver (full-weak coupling mode)". The CAFE will be activated as the Run parameter MICRO=1024 is defined. The distinction between weak and full coupling is defined by the parameter "nheat" (card 70) in the prefix_mica.d input file (weak coupling : nheat = 0 / full coupling : nheat = 1).

Post-processing To view the CAFE results, the CALCOSOFT-3D post-processor must be used. It can be accessed directly from the ProCAST Manager with a right click on the "ViewCAST" button.

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The use of the CALCOSOFT-3D post-processor is explained in details in the CALCOSOFT-3D manual (which is available in the software installation in the dat/manuals directory).

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INVERSE MODELING INTRODUCTION

The Inverse Modeling module of Procast allows to determine, from simple and well controlled temperature measurements, thermophysical data or boundary conditions. The principle of direct and inverse modeling is presented in the figure hereafter.

Direct calculation In a standard Procast calculation (i.e. a "direct" calculation), one has the following inputs and outputs : Inputs : • geometry • thermophysical properties • initial conditions • boundary conditions Outputs : • thermal history

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Inverse calculation The principle of inverse modeling is to provide the thermal history as an input (i.e. measured cooling curves at several locations) and to have one of the four inputs described above as an output (i.e. unknown). Thus, two possibilities are proposed in the Procast inverse module : a) Thermophysical calculation The "thermophysical calculation" consists in the determination of unknown thermophysical data of a material, such as volumic specific heat, thermal conductivity and/or latent heat. Thus, the inputs and outputs are : Inputs : • geometry • initial conditions • boundary conditions • thermal history Outputs : • thermophysical properties b) Boundary conditions calculation The "boundary conditions" calculation consist in the determination of unknown boundary conditions, such as interface heat transfer coefficient, film coefficient, heat flux and/or emissivity. Thus, the inputs and outputs are : Inputs : • geometry • thermophysical properties • initial conditions • thermal history Outputs : • boundary conditions A thermophysical calculation and a boundary conditions calculation cannot be mixed in the same analysis (i.e. it is not possible to determine a specific heat and a heat transfer coefficient within the same calculation). In this manual, the unknowns will be called by the generic name of "properties" or "beta value". A "property" (or a "beta value") can thus be a specific heat, a thermal conductivity, a latent heat, an interface heat transfer coefficient, a film coefficient, a heat flux or an emissivity.

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MODEL SET-UP

Before running any inverse calculation, first, the "direct" problem has to be set-up. For the setting of a direct ProCAST calculation, please refer to the Pre-processing chapter. Once the direct problem is set-up, the file prefixd.dat contains all the information about : • geometry (mesh) • thermophysical properties of materials • interface heat transfers • boundary conditions • initial conditions • run parameters The inverse modeling set-up intend to specify on which data the inverse calculation will be done and to configure the run parameters for the calculation. PreCAST allows to set-up the inverse problem in an interactive manner (with the "inverse" menu), in order to create the prefixid.dat file.

One have first the choice to select among a "Material Properties" problem or a "Boundary Conditions" problem.

Material Properties If one wants to run a "Material Properties" inverse calculation, the following panel should be activated (with the "Activate" check box) and configured. For each material present in the model, the user has to decide whether he would like to run an inverse calculation on the Specific heat (Cp), the thermal conductivity (K) and/or the latent heat (L).

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By default, all the properties are deactivated ("N" stands for No). By clicking on the "green N", it will toggle to "Y" (for Yes). In the example below, it is intended to run an inverse calculation on the Aluminium alloy specific heat and latent heat (no inverse calculation on the thermal conductivity).

Please note that one should run an inverse calculation on one material domain only. If the property (like the specific heat) is defined in the material property file as a constant, the inverse calculation will be done on this constant value. If the value is defined as a temperature function, the inverse calculation will be performed for each temperature of this function. Important For an inverse calculation involving "Specific heat" determination, the RUN PARAMETER "THERMAL" should be set to 2 ( THERMAL 2 ). This is mandatory, otherwise, the solution will not converge. In any other configuration not involving specific heat, any thermal model can be used (THERMAL = 1 or 2).

Boundary conditions

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If one wants to run a "Boundary Conditions" inverse calculation, the following panel should be activated (with the "Activate" check box) and configured. On the left, all the available interfaces are listed, whereas on the right, all the "Heat" boundary conditions are present. For interfaces, one should decide on which interface(s) it is planed to perform an inverse calculation (by toggling between N and Y). In the example hereafter, the inverse calculation is run on the interface 3. For Boundary conditions, one has the choice to perform an inverse calculation on either the heat transfer coefficient (H), the heat flux (Q) and/or the emissivity (E).

If the property (like the interface heat transfer coefficient) is defined in the database as a constant, the inverse calculation will be done on this constant value. If the value is defined as a temperature (or time) function, the inverse calculation will be performed for each temperature (time) of this function.

Inverse settings Finally, some setting should be defined. The node numbers, corresponding to the measurement points must be specified. It is important to note that the node numbers should be determined in ViewCAST, on results (as the creation of interfaces in PreCAST, after MeshCAST is adding new nodes and the optimization of PreCAST is renumbering the nodes). Moreover, the order with which the nodes are entered into the list should be the same as the order of storage of the nodes in the prefixim.dat file.

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If the measurements are in different units than °C, one should specify it with the "Measurement Units" setting.

Then, the Inverse "Run Parameters" should be specified at this stage. tau : Time constant for the filtering of the measurements In order to remove small perturbations which might occur during the measurements, the curves are filtered using the time constant, tau . The units of TAU are [s]. Default value : 1 sigma : Weighting coefficient for temperature The weighting coefficient for temperature should be kept small in order to have a good convergence. A value of O.1° C has always given good results. Default value : 0.1 conv : Convergence tolerance The convergence will be reached when the relative variation, between two iterations, of each property will be smaller than the value, conv. Default value : 0.05 varb : Variation of each beta value during an iteration During an iteration, the beta values will be perturbed one after the others in order to determine the sensitivity coefficients of each property. To do so, each beta value will be changed by a given amount corresponding to the value of varb

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multiplied by the beta value. Values of varb between 0.05 - 0.2 are convenient and correspond to a variation of 5 to 20% of the beta values Default value : 0.1 itermax : maximum number of iterations before the stop of the calculation It is useful to define the maximum number of iteration at which the calculation is stopped. In some cases, if the tolerance is too small, the variation of the beta values will not be within the tolerance, although the calculation would have converged. A value between 15 and 30 iterations is reasonable. Default value : 15

Beta values settings The structure of the prefixid.dat file is described in the File formats section. For each beta value (i.e. for each unknown property), the following parameters are defined (default values are automatically proposed by precast, see below): ibindex : material number, interface number, boundary number (this corresponds to the number which appears before the material, interface or boundary condition item in the corresponding window) itunit : unit code for the temperature or time "tbeta" used for temperature-dependant or time-dependant properties ibunit : unit code for the beta value tbeta : temperature or time corresponding to the beta value (zero when a CONSTANT value is used) beta : beta value (unknown property), initial guess the initial guess corresponds to the value initially defined in the HEAT boundary condition of the direct calculation. ibeta : flag to indicate what is the type of the beta value (constant, time- or temperature-dependant) : 0 : The corresponding beta value is not used in the Inverse calculation (i.e. a constant value equal to "beta" will be used in the calculation and nothing will be done at the level of the inverse calculation). This is very convenient to "freeze" a given beta value which does not need anymore to be calculated. 1 : The type of the beta value is CONSTANT 2 : The type of the beta value is TEMPERATURE dependant 3 : The type of the beta value is TIME dependant weight : weighting coefficient for the beta value betamin : minimum accepted value for beta betamax :

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maximum accepted value for beta relax : maximum variation of the beta value between two iterations (i.e. if relax=3, the beta value can increase at maximum by 3 times the previous value or can be no smaller than 1/3 of its previous value within the same iteration). PreCAST proposes default values that may be changed by the user in the prefixid.dat file (by editing the prefixid.dat file). The default values are : ibeta : This value is automatically set to 1, 2 or 3. This value should not be changed by the user. tbeta : This value prompts the time or temperature value of the corresponding beta value. This value can not be changed by the user. If ibeta = 1 (CONSTANT type). a zero value is written. beta : This value corresponds to the initial guess. By default, it is the value which was in the corresponding dataset. weight : By default this value is set equal to initial guess of the beta value. This value should be of the same order of magnitude than the final beta value or larger (for a good convergence). betamin : This value is the minimum allowed value for beta. It should be set to the physical minimum that can be expected. By default, betamin is set to 1/100 of beta betamax : This value is the maximum allowed value for beta. It should be set to the physical maximum that can be expected. By default, betamax is set to 100 times beta relax : By default relax is set to 3. If a property is defined as both temperature and time dependant, it is strongly advised not to perform an inverse calculation in the same time on both the temperature-dependant beta values and the time-dependant beta values.

Additional information concerning the Inverse Settings : weight : weighting coefficient for the beta value. This weighting coefficient determines the importance of the allowed variation of the beta value during an iteration. If the value is large, the beta value could vary in a large extent. If this value is small, the beta value could not vary much. In fact, for practical use, this value should be in the order of magnitude of the beta value in order to give satisfactory results. betamin : minimum accepted value for beta

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For physical reasons, the beta values should not be smaller than a specified value, betamin (i.e. a heat transfer coefficient should not be negative !). This limit is set in order to speed up the convergence. betamax : maximum accepted value for beta For physical reasons, the beta values should not be larger than a specified value, betamax (i.e.. a thermal conductivity of steel can not exceed a value of pure copper or pure silver !). This limit is set in order to speed up the convergence. relax : maximum variation of the beta value between two iterations In order to reduce divergence problems of the inverse calculation, it is possible to limit the variation of the beta values from one iteration to the next one. A value of relax=3 would mean that the new beta value will be limited to 3 times the previous one or 1/3 of the previous one. The value of relax should be strictly larger than 1. If the relax value is rather small, the convergence will be obtained in more iterations, however, the convergence should be obtained more smoothly.

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INVERSE RUN

In order to run an inverse calculation, the following files should be present : • prefixd.dat (ProCAST input file) • prefixp.dat (ProCAST Run parameters • prefixid.dat (Inverse input file) • prefixim.dat (Inverse measurements) Then, the calculation can be started. To do so, a right click on the "ProCAST" button on the manager is opening a sub-menu, which allows to start the inverse solver.

It could also be launched manually from a Command Window as : inverse prefix Automatically, DataCAST is launched and the inverse calculation is starting. The status of the inverse calculation can be viewed with the "invstat prefix" command (from a second Command Window). Output Files : During the execution of the calculation, several files are created, beside the usual ProCAST files : prefixir.dat This file contains the evolutions of the beta values along the iterations, as well as the evolution of the residual. prefix.stat This file contains information of the status of the calculation (see below)prefixic.dat

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This file contains the calculated temperature evolutions (of the last calculated iteration) corresponding to the locations of the measured curves. prefix.tmp This file is a temporary file created during the calculation. This file is needed only during the calculation and is useless for the user. This file is automatically deleted at the end of the calculation However, if the calculation is interrupted by the user before completion, it should be deleted manually by the user. prefix.list When the calculation is run in the background mode, the printout which appears normally on the screen is listed in this file. This file is not written in a continuous mode, but only when the buffer of the machine is unloaded (thus, this may take a few minutes after the beginning of the calculation before having something in this file). Monitoring the calculation : As inverse calculation could be quite long and are often run in "background mode", there are three ways to monitor the status of the calculation. The monitoring of the calculation is a good way to check whether the calculation is stable and whether it is converging in good conditions. The three monitoring options are the following : a) Status of the calculation : the following command : invstat prefix prints the status of the calculation (it is equivalent to "prostat" in Procast). The number of iterations already calculated is printed as well as the beta values of the last iteration. This can also be accessed from the manager with a right click on the "Status" button.

The residual of the current iteration is also printed. The residual is the average temperature difference between the measured and the calculated curves (average

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on all the steps and all the curves, at the given iteration). The residual will decrease towards zero along the iterations. The monitoring of the residual is a good way to see how the convergence is reached. In addition, it is mentioned if the calculation is still under progress or if it is completed (if the calculation was interrupted by the user, it will still display that the calculation is under progress). This command should be called in the current directory where the prefix* files are present (this is not like "prostat" which can be called from any directory). b) Evolution of the beta values The beta values obtained at each iteration are stored in the file prefixir.dat Thus, during the calculation, it is possible to visualize the evolution of each beta value (from the first to the current iteration) and see whether the calculation is converging or not. The format of the file prefixir.dat is the same than the one of

the measurement. Curve "i" of the file prefixir.dat correspond the ith

beta value. In addition, the residual is stored as the last curve of this file. Thus, it is possible to graph the evolution of the residual as function of the iterations. c) Comparison between the measurements and the calculated curves The goal of inverse modeling is to find the best set of beta values with which the calculated temperature curves will match the measured ones. At the end of each iteration, the calculated curves corresponding to the location of the measurement points are stored in a file labeled prefixic.dat This file is updated at each iteration. Thus, it is possible to visualize during the calculation (with ViewCAST) the superimposition of the measured curves and the calculated ones. Of course, during the first iteration, the match will be bad, however, at the end of the calculation, the match should be quite good. Final result At the end of the calculation, the final beta values correspond to the values of the last iteration in the file prefixir.dat. At the end of the calculation, it is advisable to check the quality of the convergence. To do so, the file prefixir.dat can be graphed (see section "Monitoring the calculation" above). The convergence is good if the beta values are not changing much during the last iterations and if the residual is small (the residual has the unit of degrees and a residual of "1" means that the average difference between the measured and calculated curves is 1 degree). Depending on the convergence tolerance which is chosen, it is possible that the beta values stay almost constant (but oscillate around an average value), however, the calculation is continued until the maximum number of iterations which was specified is reached. In such case, it is possible to reduce the maximum number of

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iterations (for a further run) in order to reduce the computing time, without changing the quality of the result. In order to check the quality of the determined beta values, one can superimpose the measured and the calculated curves (see section "Monitoring the calculation" above). The quality of the match will be an indication of the quality of the final beta values, as given by the residual. Remarks Inverse modeling involves many direct ProCAST calculations. At each direct ProCAST calculation, the results are written in the result file at each time-step. This is resulting in many disk access. If the calculation in performed in a network, it is advisable to run the calculation in a directory which is on the closest disk from the CPU, otherwise, these disk access through a network may slow down significantly the calculation. It is always possible to run the calculation in the directory /tmp and then move the final results to the home directory of the user. Limits The following limits have been set in the inverse solver : Maximum number of beta values : 10 0 Maximum number time-steps for the measurements : 50 0 Maximum number of thermocouples : 20 Maximum number of iterations : 10 0

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FILE FORMATS

Inverse settings file All the inverse settings are stored in the file prefixid.dat. Like the file prefixp.dat the user may change this file "by hand" with an editor and then run again inverse. The format of this inverse settings file is described hereafter. Definitions : ntcunit : unit code for the temperature measurements ntccode : code which specifies how the thermocouple locations are defined : ntccode = 0 : coordinates of the thermocouple ("0" is not implemented in the current version, use only ntcode=1) ntccode = 1 : node number corresponding to the thermocouple location node : node number in the mesh used for the calculation corresponding to the measurement points (ntccode=1) (the order of the node numbers should correspond to the order of the cooling curves in the file prefixim.dat) imat : material number where the thermocouple is located (ntccode=0) ixyzunit : unit code for the coordinates when ntccode=0 x,y,z : x, y and z coordinates of the thermocouple tau : time constant for the filtering of the measurements [s] sigma : weighting coefficient for temperature [K] conv : convergence tolerance [-] varb : variation of each beta value during an iteration [-] itermax : maximum number of iterations before the stop of the calculation ibindex(i) : material number, interface number, boundary number itunit(i) : unit code for the temperature tbeta(i) ibunit(i) :unit code for the beta value, beta(i) tbeta(i) : temperature corresponding to the beta value, beta(i) beta(i) : beta value (unknown property), initial guess ibeta(i) :

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flag to indicate if the beta value will be taken into account in the inverse calculation 1: the beta value is an unknown of the problem and will be taken into account in the calculation (it is a constant value) 2: the beta value is an unknown of the problem and will be taken into account in the calculation (it is a temperature-dependant value) 3: the beta value is an unknown of the problem and will be taken into account in the calculation (it is a time-dependant value) weight(i) : weighting coefficient for the beta value betamin(i) : minimum accepted value for beta betamax(i) : maximum accepted value for beta relax(i) : maximum variation of the beta value between two iterations All the parameters and variables defined above are defined in groups (or families), which are labeled by keywords. The keywords are : MEASUREMENTS PARAMETERS THERMAL_CONDUCTIVITY SPECIFIC_HEAT LATENT_HEAT INTERFACE_HEAT_TRANSFER EXTERNAL_FILM_COEFFICIENT EXTERNAL_HEAT_FLUX EXTERNAL_EMISSIVITY Format : MEASUREMENTS ntcunit [integer] Loop on the thermocouples (i) ntccode(i) [integer] if ntccode(i)=0 imat(i) [integer] ixyzunit(i) [integer] x(i) [real] y(i) [real] z(i) [real] else if ntccode(i)=1 node [integer] endif End Loop on the thermocouples PARAMETERS tau [real] sigma [real] conv [real]

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varb [real] itermax [integer] For all the following keywords, the structure of data is the same. Only the necessary keywords should be specified, which correspond to the desired beta values. THERMAL_CONDUCTIVITY SPECIFIC_HEAT LATENT_HEAT INTERFACE_HEAT_TRANSFER EXTERNAL_FILM_COEFFICIENT EXTERNAL_HEAT_FLUX EXTERNAL_EMISSIVITY Loop on the beta values (i) ibindex(i) [integer] itunit(i) [integer] ibunit(i) [integer] tbeta(i) [real] beta(i) [real] ibeta(i) [integer] weight(i) [real] betamin(i) [real] betamax(i) [real] relax(i) [real] End Loop on the beta values As the data are read by a "Free Format Reader", data can be placed in any fashion (lines, columns,...), as long as the sequence of the data corresponds to the specified one. However, each line should not exceed 256 characters. Moreover, comments can be included in the data file after a "#" sign (all the characters between the "#" sign and the end of the line will be ignored and can be used as comments).

Inverse measurement files : X-Y format The format of the measurement file (prefixim.dat), as well as the files prefixir.dat and prefixic.dat is the following (it corresponds to the prefix.tt file format of ViewCAST) : Sequential formatted file (ASCII) nx, ny, node#1,node#2,node#3, .... , node#ny x(1),y(1,1),y(2,1),...,(ny-1,1),y(ny,1) x(2),y(1,2),y(2,2),...,(ny-1,2),y(ny,2) x(1),y(1,3),y(2,3),...,(ny-1,3),y(ny,3) ... ... x(1),y(1,nx),y(2,nx),...,(ny-1,nx),y(ny,nx)

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Description : nx : number of values on the X-axis (this corresponds to the number of time-steps if the X-axis is time) ny : number of curves node#i : node number corresponding to the curves. These number can be any integer numbers (as they are not used by the inverse calculation). The only requirement is that ny integer values are present. The reason of these values is that it corresponds to the format which is compatible with PostCAST. x(j) : value "j" on the X-axis y(i,j) : value "j" on the Y-axis for curve "i"

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INVERSE APPENDIX

Inverse model

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Inverse calculation involves a large number of direct calculations Inverse modeling involves many direct calculation. For each iteration, it is necessary to perform one direct calculation for each unknown of the problem, plus the "original" calculation. Thus, if the problem to solve has N unknowns and M iterations are needed to reach convergence, it will involve (N+1) x M calculations. For instance if one has

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10 unknowns and it is necessary to calculate 15 iterations, it make a total of (10+1) x 15 = 165 direct calculations ! This shows that in order to keep reasonable computing times, it is necessary that each direct calculation is small and quick. Indeed, if one direct calculation is lasting 1 minute, the inverse problem example shown above will take 165 minutes to solve (about 3 hours). If instead, one direct calculation is lasting 2 days of CPU time, the inverse calculation will take 1 year !!!

"Pseudo 2D modeling" - simple calculations Considering the above conclusion about short CPU times for the direct calculation, it shows that it is necessary to run the inverse calculation on simple geometries. Thus, the use of 2D geometries is strongly recommended (or is even in most cases "mandatory"). One should realize that it is impossible to consider to perform an inverse calculation on a real casting geometry, as the CPU time for one direct calculation will be just too large. Thus, inverse modeling involves the design of specific experiments, which are used for this purpose only. Thus requirement is reasonable as the unknowns (i.e. the boundary conditions or the material properties) are usually not depending upon the small geometrical details or of the complex shapes. One should however be careful to design an experiment which is representative of the behavior of the real part.

How to design the appropriate experiment As mentioned above, the experimental set-up should be designed so as to be as representative as possible from the real process where the result of the inverse calculation are to be used. There are no generic rules about the design of inverse experiments as it depends upon the goals that are set. The main and most important rule is "Make it simple". This means that one should stick to 2D models and that if possible only one type of unknown should be determine at a time. In principle, there are no limitation in the inverse modeling towards the maximum number of unknowns. However, it is strongly advised to determine one thing at a time. For instance, design one experiment for the determination of the heat transfer coefficient between the water and the mould in the case of a cooling channel and design an other experiment for the determination of the casting-mould interface heat transfer coefficient. Although it is possible in the principle to determine both together, it is advisable to simplify the problem by decomposing it. The quality of the result of an inverse calculation is proportional to the quality of the inputs of the inverse model. As a reminder, the 4 inputs which are necessary for the inverse modeling are :

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a) geometry b) initial conditions c) temperature measurements d1) material properties (in case of boundary condition determination) d2) boundary conditions (in case of material properties determination) It is thus of primary importance to make sure that the quality of these 4 inputs are as good as possible. a) geometry The best way to have an accurate geometry description in 2D is to consider 2D axi-symmetric problems. Thus, the modeling of cylinders or tubes is recommended. One should be careful that the running system and the feeding system must also be axi-symmetrical. In some cases, the use of 2D cartesian can also be applied with success for the modeling of plates or the determination of boundary conditions on flat surfaces. b) initial conditions Usually, within the direct solver, it is only possible to set easily constant initial temperatures. Thus, it is important to perform an experiment where the initial temperatures of the different domains are as constant and well known as possible. If the filling stage is very important (as one can loose a significant amount of superheat during the filling), one should consider whether the design is appropriate or if a lower average constant initial temperature can be considered. c) temperature measurements The quality of the temperature measurements are of primary importance in order to have a good result. Thus, one should be careful to use appropriate thermocouples (not too thin or not too big). The time response of the thermocouples is also important if one wants to capture fast transient phenomena. When measuring in a solid material, one should ensure that there is an intimate contact between the tip of the thermocouple and the material. Concerning the placement (location) of the thermocouples, please refer to the next section. d1) material properties (in case of boundary condition determination) As it is not always easy to know well the material properties of the materials which are used in the real process, it may be advisable to use different materials for the inverse experiments. For instance if one wants to determine the heat transfer coefficient at the casting-mould interface in a high pressure die casting mould (with an aluminium alloy casting and a steel mould), it is possible to cast a well known Al-Si7%-Mg0.3% in a block made out of a well known steel alloy. The idea is to use similar materials where the materials properties are better known, as the heat transfer coefficient will not depend upon slight differences in material properties. For instance, in the example shown above, it is not important to take a steel which is resistant at high temperatures (like it is needed for an hpdc

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die), as the inverse experiments will be run only a few times (unlike the hpdc die which will undergo many cycles, under high loads). d2) boundary conditions (in case of material properties determination) This point is probably the most critical in inverse modeling when one wants to determine the thermophysical properties of a material. Unlike case (d1) above where it is possible to use well known materials, in this case, one has to find a method to determine the boundary conditions in the experimental set-up. Usually, one have to run a first inverse model to determine the boundary conditions and then to run a second inverse calculation for the material properties determination. An other solution is to use some of the measured temperatures as boundary conditions (fixed temperature boundary conditions). However, in such a case, one can only determine the diffusivity of the material (the diffusivity is the ratio of the thermal conductivity over the volumic specific heat). It is thus impossible to separate the thermal conductivity from the specific heat (without knowing the flux).

Model first your experiment As it was mentioned in the previous section, it is not possible to give generic rules about design of inverse experiments. However, the user is able to check the quality of its design by himself. It is strongly recommended to model first the experimental set-up before even building it. Of course, as the properties or boundary conditions, such a modeling has to be done with guessed values (one should notice that it is important to have at least an idea about the order of magnitude of the unknown value before starting to explore inverse modeling techniques). Based upon this first modeling, it is possible to run a few additional calculations by modifying the guessed values. This corresponds to some kind of "sensitivity analysis". Based upon the results of these calculations, it will be possible to see whether the calculated temperature curves at different locations are sensitive or not to the variation of the unknown (or guessed) values. This provides a useful mean of determining where are the best locations to place the thermocouple. Indeed, one would like to have the largest temperature variations when the unknown values are changing slightly (for instance, it is useless to place a thermocouple at the first floor of a building to measure the influence of the opening of a window at the 15th floor !). Of course, it is advised to place thermocouples as close as possible from the location where the property has to be determine. For instance, if one wants to determine an interface heat transfer coefficient, it is advisable to place thermocouples quite close from that interface, on either sides. However, one should be careful not to place thermocouples too close from the surface as it is very difficult to measure accurately very close from surfaces. Thus, it is better to have a better quality measurement, a little bit further away from the surface, than a low quality measurement, very close from the surface.

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Concerning the number of thermocouples, one shall first say that the computing time does not depend at all upon the number of thermocouples (it only depends upon the number of unknowns). However, experience shows that it is advisable to use a small number of thermocouples (less then 10) to obtain good results. Thus, the user has to concentrate its attention about where are the optimum locations of the thermocouples rather than "flooding" the experiments with many thermocouples. Moreover, the inverse solver is based upon a "least square fit" on all the thermocouples, in a global fashion. Thus, if some thermocouples are "useless" and provide not very accurate measurements, they may degrade the final answer. Finally, the advantage of modeling first the experiments, before running them, is also to show how much CPU time will be needed to run one direct calculation. Thus, it will show whether the set-up is appropriate or not for fast inverse calculations.

Run a direct calculation with your initial guesses and compare it with the measurements At this stage, the experimental set-up is built and measurements were performed. Before running the inverse analysis, it is advisable to re-run once the direct calculation with the initial guesses of the unknown. Then, the calculated temperature curves corresponding to the location of the thermocouples can be compared to the measured curves in the experimental set-up. If the calculated curves are quite close from the measured ones, one can run the inverse calculation. If on the opposite, the calculated curves are very far away from the measured ones, it is good to re-run once more the direct calculation with new guesses which seems more appropriate. This "manual" inverse modeling may speed-up considerably the inverse calculation as convergence will be reached much faster.

Start by simple calculations and then increase the complexity (i.e. the number of unknowns) Inverse modeling can be used for the determination of quite complex boundary conditions (e.g. time- or temperature-dependent heat transfer coefficients, temperature-dependant equivalent specific heat,…) which may involve a rather large number of unknowns. In order to reach a good and quick convergence of the inverse calculation, it is advisable to decompose the problem in several simpler stages. In order to illustrate this, let's consider the example of the determination of specific heat, the thermal conductivity and the latent heat (all in the same time) of an Al-alloy.

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One expects that the thermal conductivity and the specific heat will be both function of the temperature. However, in a first stage, it is good to run an inverse calculation with constant properties. This means that the inverse modeling is looking for one value of specific heat, one value of thermal conductivity and one value of latent heat. Figure A1.1 shows the result of such a calculation with the superimposition of the measured and calculated curves. The corresponding constant material properties are also shown. One can see that the correspondence between the measurements and the calculation is only fair, which is not a surprise as constant properties were considered. This first calculation provides a way to "calibrate" the unknowns. Then, it is possible to refine those unknowns in a second inverse calculation. Figure A1.2 shows the superimposition of the calculated and measured curves, when thermal conductivity is described by a temperature function using 3 unknowns and the specific heat by a temperature function using 4 unknowns (the latent heat is still described by one value). The initial guesses used in this second inverse calculation corresponded to the result of the first inverse calculation. One can see on figure A1.2 that the correspondence between the calculation and the measurements are much better in this second case. Then a third inverse calculation was performed, using a 6 points specific heat curve and a 5 points thermal conductivity curve (an one latent heat). Again the initial guesses used in this latter calculation were taken as interpolation of the results of the previous calculation. Figure A1.3 shows a very good correlation between measurements and calculation. One shall notice that in the above example, it would certainly been possible to find directly the final result (of Figure A1.3). However, in complex problems, it is not always possible to start with a reasonable initial guess and thus, convergence can be hard to find (or even impossible in some cases).

Figure A1.1 Comparison of the measured and calculated curves obtained with 1 values of thermal conductivity, 1 specific heat values and 1 latent heat.

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Temperature- or Time-dependant boundary conditions or properties Usually, the thermophysical properties are temperature-dependent and the boundary conditions may be time- or temperature-dependent too.

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In such a case, the user has to decide the type of dependency that should be used in the inverse calculation. To illustrate that, one can use the example of the determination of the equivalent specific heat of an alloy (as shown in Figure A1.4). One can see that the curve is almost constant above and below liquidus, whereas it exhibits very strong variations between the liquidus and solidus In such a case, the user has to define himself the temperature points at which the unknowns will be calculated. As in the above mentioned example, these points should be selected in between the solidus and liquidus temperatures (with a reasonable number of points in order to describe the curve). Above the liquidus or below the solidus, one can consider constant values or variable values as desired. Concerning the number of points to be selected, one should select enough points, but not too many. Indeed, if too many points are selected, one can obtain oscillations of the final beta values.

Figure A1.4 Equivalent specific heat obtained by inverse modeling, showing the tabulation points (tabulated temperatures) that were chosen.

What to do if it does not converge ? In some cases, it is possible that the solution does not converge. This can be seen if the residual is not decreasing or is even increasing, if the correspondence between the measured and calculated curves is completely wrong or if the beta values are oscillating. Usually, convergence should be obtained within 15-20 iterations. If more iterations are needed, it means that something goes wrong. In such case, one should check the following points :

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• Are the thermocouples well defined ? Is the order of the list of the thermocouple corresponding to the order of the measured curves in the measurement file ?

• In case of time- or temperature-dependent beta values, are the tabulation points appropriate (for instance, if one is looking for a variation between 500 and 700 and the tabulation points are chosen between 600 and 800, it might not work).

• Are they any (or enough) measurements in the range of the tabulation points? (for instance if one looks for a temperature dependant heat transfer coefficient between 100 and 800°C and that the measurements are only between 400 and 700°C, the values below 400 and above 700°C will never converge).

• Are the initial temperatures of the model corresponding to the ones of the measurements (or are the initial measured temperatures constant ?).

• Is the geometry of the model and the known boundary conditions well defined ?

• Are the material properties of the different materials used in the measurements well known ?

Remarks and Tips • In a thermophysical calculation, it is possible to determine in the same time

specific heat, thermal conductivity and latent heat properties However, one has to be careful that these properties are not totally independent as the diffusivity is the ratio of the thermal conductivity over the specific heat and that the specific heat and the latent heat are both contained in the enthalpy.

• The calculation will converge much faster if the initial beta values (i.e. initial guess) are the closest for the final values. It is thus advised to run first a direct calculation with the initial guess in order to check that the calculated curves are not too far from the measured ones.

• The time-steps of the measurements can be completely free and is totally independent from the one used in the calculation.

• For time- or temperature dependant properties, one has to perform the inverse calculation on all the values of the table.

• For specific heat determination, the RUN PARAMETER "THERMAL" has to be set to 2 ( THERMAL 2 ). In all other cases, not involving the specific heat determination, any thermal model can be used (THERMAL = 1 or 2).

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CONTINUOUS CASTING

This chapter presents the methodology to model continuous casting with ProCAST.

Two different approaches, steady state and non steady state, will be presented.

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PRINCIPLES

The modeling of Continuous casting can be addressed in two different ways :

• steady state calculations • non-steady calculations (also called transient calculations)

Note : "DC casting" can be addressed as well and it should be understood that it is included in the generic name of "continuous casting". ProCAST can address both cases. For steady state computations, a fixed domain is modeled and the solid is transported at the casting speed through this domain. For non-steady calculations, the domain is extending with time, as the continuous casting process proceeds. A new algorithm has been developed and implemented in order to allow this evolving domain. This algorithm is called MiLE (for Mixed Lagrangian-Eulerian).

Steady state continuous casting modeling Steady state calculations allow the modelling of both straight and curved continuous casting processes (including strip casting). It is possible to perform either thermal only calculations, or thermal + flow calculations. In both cases a transport term of the solid is used (equal to the casting speed). In the case of a thermal only calculation, both the solid and the liquid are transported at the velocity corresponding to the casting speed.

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In order to reach steady state, a pseudo non-steady calculation is performed (from an initial user defined thermal field) until steady state is reached (i.e. the temperature are not anymore changing with time). The temperature history before the steady state is reached have no special meaning. As a consequence, it is not possible to perform a coupled thermal - stress calculation of continuous casting using the steady state method. In order to do that, the MiLE algorithm has to be used. In the same line, it is not possible to model the start-up phase of continuous casting with the steady state method (again the MiLE algorithm allows to do that).

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Non-steady modelling of continuous casting (MiLE algorithm) In order to allow the possibility to have a domain which is enlarging with time, as the continuous casting process goes on, a MiLE algorithm was developed. The principle of the MiLE algorithm is the following :

At the beginning, the casting is divided into two domains (1 and 2 above). Then, as the continuous casting process starts, the bottom domain (2) is moving down (while the domain 1 is staying at the same position). In order to have a continuity between domains 1 and 2, new elements have to be introduced between domains 1 and 2 (creating the domain 3 above). During the process, layers of new elements are introduced in domain 3 at the interface between domains 1 and 3. The following figure is showing the principle of the MiLE algorithm (Mixed Lagrangian-Eulerian), with the region where the calculation is Eulerian and the ones where it is Lagrangian.

In practice, in order to introduce the new layers of elements, at the beginning of the calculation (in DataCAST), a given number of layers of elements of zero

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thickness are created in between domains 1 and 2. Then, during the casting process, these layers are "unfolded" as an accordion.

The number of pre-defined layers as well as the thickness of the layers are specified in the pre-processor (see the pre-processing section for more details). During the calculation process, the domain 2 is translated at the casting speed and the accordion will unfold itself in between domains 1 and 2.

The following figure is showing how the accordion is unfolding during the continuous casting process.

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The MiLE algorithm is designed such as to have the continuity of temperature, fraction of solid, velocity and pressure across the accordion as shown in the figures hereafter.

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As the mesh in the accordion and in the domain below the accordion (labeled domains 2 and 3 in previous figures) are moving, a transport term of the mesh in accounting for this motion. The MiLE algorithm allows only to model "straight" continuous casting processes. It is not possible to use this algorithm to model curved continuous casting (e.g. steel curved continuous casting) or strip casting (in this case the steady state method should be used). However, the MiLE allows to couple stress calculations with the heat and fluid computations. The only restriction is that the solid should not cross the "accordion interface" (i.e. the interface between domains 1 and 3). Thus, the accordion interface should be located in the appropriate position in order to avoid such situation (it is possible to have a non-planar accordion interface to resolve this question - see the pre-processing section for more details).

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PRE-PROCESSING

Steady State cases

In order to model continuous casting at steady state, a long enough casting domain (in blue in the figure hereafter) should be modeled.

To handle the fact that we have a continuous process, a transport term of the solid is added to the equations. As soon as the metal is solid (dark red in the figure above), it should be transported at the casting speed (i.e. the continuous casting velocity - see the blue arrow in the figure above). If fluid flow is activated, the flow will automatically account for the transport of the heat in the liquid zone (light yellow in the figure above). In the mushy zone, the model accounts for a "mix" of the transport term of the solid and the transport of fluid of the liquid.

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If the fluid flow model is not activated, the transport term is not only applied to the solid, but also to the liquid and to the mushy zone.

Thermal only setup The setup of a thermal only continuous casting case is performed in the following way (the setup in the mold(s) is made as usual) : 1. At the inlet, a fixed Temperature BC should be applied. 2. At the outlet (or exit), an adiabatic BC (zero flux) should be applied. 3. At the interface between the mold and the casting, an interface heat transfer coefficient is set as usual. 4. On the outside faces of the casting, a Heat BC is set as usual.

5. In the Casting domain, a "Solid transport" velocity should be defined in the "Process/Assign" Volume menu.

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To define the "Solid transport" velocity, the following panel should be filled :

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The initial temperature of each domain is defined, however these initial temperature do not affect the final steady state solution. For the casting, the inlet temperature is usually selected and for the mold, the temperature of the cooling media is selected. The calculation is then performed, starting from a "dummy" state corresponding to the specified initial temperature until the steady state is reached. The figure hereafter shows the evolution of temperature in the casting and in the mold during the calculation. After about 150 seconds, the steady state is reached (i.e. the temperatures are not changing anymore).

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One can see in the figure below how the temperature are changing in the casting during the calculation. Only the last result corresponding to the steady state is of interest. All the other intermediary results should be discarded.

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Thermal + Flow setup

When the fluid flow model is activated, the following setup should be made, in addition to the thermal setup described above. An inlet and an outlet velocity should be specified. If there is no nozzle (or no inlet section smaller than the casting section), the same inlet and outlet velocity should be set, corresponding to the casting speed (and to the solid transport velocity).

A Wall BC (zero velocity) should be applied on the external faces of the casting domain and on the interfaces between the casting and the mold if a non-coincident interface is used (please note that in the present example, the large faces are set as symmetry planes).

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A Pressure BC should be applied (with a 1 bar pressure) on one node of the inlet (on top of an inlet velocity BC).

Finally, the FLOW = 1 Run Parameter should be set. In addition, the value of LVSURF should be set to a higher value than 1 (e.g. 1.10). As mentioned above, the value of PREF should be set to the same value as the one used in the Pressure BC (1 bar in this example). It is also very important to set FREESF = 0.

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Thermal + Flow setup (with nozzle) In the case a Nozzle is present or if there is a small inlet surface (i.e. the inlet flow is not applied on the whole top surface of the ingot), the following precautions should be taken. The mesh should contain a small extra volume which has the same area than the real inlet (see the picture below).

This allows to specify exactly the inlet velocity corresponding to the casting speed (by making the ratio of the surfaces).

Then, a Wall BC should be applied to the rest of the top surface (see below).

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Finally, the Pressure BC should be applied on one node of the inlet surface.

Curved continuous casting setup ProCAST allows to model curved continuous casting (as well as strip casting). In such case, the solid is moving along a curved trajectory (corresponding to the curved casting shape). To account for that, the solid transport term should be set to the vector corresponding to the local position (i.e. with a turning direction). Such non constant solid transport velocity should be defined in the ad-hoc User functions. Firstly, the velocities at the inlet, outlet and along the faces of the casting should be assigned to a given Velocity BC (please note that in the example of the following figure, the large faces are defined as symmetry planes).

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The corresponding velocity BC should be defined as follows (the symmetry planes are perpendicular to the Z axis) with Functions for both the X and Y velocity components :

The corresponding functions "prefix_vximposed.c" and "prefix_vyimposed.c" should be copied in the local directory and programmed in the following way :

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Example of the "prefix_vximposed.c" function

Example of the "prefix_vyimposed.c" function (end of the function only)

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In the same way, the solid transport term should be set with User functions. Firstly the Solid transport entry should be defined as follows (with Function for the X and Y components) :

The corresponding functions "prefix_vxsolidtransport.c" and "prefix_vysolidtransport.c" should be copied in the local directory and programmed in the following way :

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Example of the "prefix_vxsolidtransport.c" function

Example of the "prefix_vysolidtransport.c" function (end of the function only)

This will allow to have the velocities defined as shown in the following picture (only the imposed velocities are shown in this case) :

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When the calculation is run, the following temperature and velocities are obtained, showing well that the velocities in the solid and in the mushy zone are transported at the casting speed (which is turning with the casting).

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Finally, as for any flow calculation, a Pressure BC should be set on the top of the casting inlet.

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Thermal + Flow setup (initial thermal only calculation) As mentioned above (in the Thermal only section), a non-steady calculation is made until the steady state is reached. Depending upon the size of the ingot, the time needed to reach steady state can be quite long. When a coupled thermal + flow calculation is performed, the timesteps are usually rather small and thus it can lead to long CPU times. In order to speed-up the calculations, the following procedure can be used. Firstly a thermal only calculation can be run until the steady state is reached. Then a new calculation is set where both the thermal and the flow solvers will be activated. However, the initial temperatures of this new calculation will be the one of the first thermal only calculation. As the steady state was already reached in the first thermal only calculation, the steady state of the second (thermal+flow) calculation will be reached much quicker (as the influence of the flow on the thermal solution will reach steady state very quickly). For instance, in the previous example of curved continuous casting, the steady state with the thermal+flow calculation was reached after about 50 seconds (of physical time), corresponding to 170 steps, whereas the steady state of the thermal only calculation was reached already after 60 steps - corresponding also to 50 seconds. (in addition, please note that the CPU time for a thermal only calculation is much shorter as a calculation for a thermal-flow calculation). When applying this method, one has to be careful when a nozzle is present (or when the inlet of metal is not applied on the whole top surface). In this case, it is necessary, in the thermal only calculation, to set an "imposed temperature" on the whole inlet surface (and to remove it afterwards for the thermal+flow calculation). Remark Please note that the POROS 1 model is not suitable for continuous casting (both steady state or MiLE) and thus POROS should be set to 0.

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Non Steady State cases (MiLE)

This section describes the settings in PreCAST of a non-steady continuous casting problem using the MiLE algorithm. For the sake of simplicity, a "pseudo-2D" model is used for the description, but of course, this algorithm is applicable to full 3D cases. The following set-up corresponds to a THERMAL ONLY case. For the activation of the fluid flow or of the stress, please check the MiLE Examples.

Meshing The first requirement is at the level of the mesh. The initial casting domain should be meshed in two distinct domains, as shown in the figure hereafter (the molds and bottom blocks should be defined as usual).

This will allow to define the "Accordion" location, which will be at the interface between these two domains. The Accordion should be located high enough in

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order to make sure that there will be no solid which will "cross" the accordion (i.e. the Accordion interface should remain fully liquid). In this chapter, the domain "above" the accordion (shown in green in the previous figure) will be called the "upstream domain" (considering that we are casting in the vertical downwards direction). The domain "below" the accordion (shown in red) will be called the "downstream domain". Moreover, if a Nozzle is used, it should be fully located in the upstream domain (shown in green in the figure hereafter)

If the nozzle is deep and the solidification along the mold wall is expected to reach a higher level than the bottom of the nozzle, it is allowed to have a non-planar accordion interface (see below).

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In the case of a non-planar Accordion interface, some precautions should be taken in order to allow for a smooth unfolding of the Accordion (see figure below). It is not allowed to have an Accordion interface which is parallel to the casting direction (vertical in the example hereafter) or a re-entrant corner. In mathematical terms, the interface should correspond to a function (i.e. one single value of Y for each value of X). It is also advised to have inclined interfaces which are not to "steep" in order to avoid very deformed elements in the unfolded accordion.

Geometry menu The definition of the parameters in the "Geometry menu" should be done as usual. The MiLE algorithm allows to use symmetries, however, as it is not possible to activate the radiation with View Factors (ON) with the MiLE algorithm, it is not necessary to define symmetries in this menu (but only in the Boundary Conditions menu). One should note that it is not possible to use a Virtual mold with the MiLE algorithm. The Volumes which are indicated in this menu correspond to the initial volume of the mesh (and not the volume when the Accordion is unfolded).

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Materials definition The materials should be defined as usual. Useless to say that the material properties on both side of the accordion should be identical and it should be labeled as "Casting". The Stress properties can also be defined in the usual way.

Interfaces All the interfaces between mold domains should be defined as usual. The "Accordion interface" should be defined as coincident (COINC), but no interface heat transfer coefficient value should be assigned (a * should remain). The interface(s) between the upstream domain and the mold(s) can be set as coincident (COINC). The interface(s) between the downstream domain (including the bottom block if any) and the mold(s) should be set as non-coincident (NCOINC). This is because the downstream domain (including the accordion which will belong to this domain) and the bottom block will move with respect to the mold during the casting process. Thus, a non-coincident interface will handle the heat transfer between the moving casting and the stationary mold.

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Boundary conditions In order to set the Accordion link, two steps should be done in the set-up. a) A Periodic boundary condition should be applied in order to link both sides of the Accordion. To do so, a "Periodic" Boundary condition should be added (1), the first "Periodic entry" should be assigned to the Accordion nodes (at the Accordion interface) which are on the "upstream domain" and the second "Periodic entry" should be assigned to the nodes of the Accordion interface on the "downstream domain" (2-3). Once these nodes are selected, both sides should be linked with the "Link" button (4).

The "Link" button will open the following panel. The "Apply" button should be pressed without any change in the content of the default panel (i.e. zero translation vector and it is important to have one non-zero value in the Rotational Axis definition).

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b) The characteristics of the Accordion should be specified in the "Accordion BC". This BC should be assigned to the surface of the "downstream domain" which is at the Accordion interface.

The Accordion definition panel is the following :

The number of layers of the Accordion, as well as the element thickness (once the element is unfolded) should be defined. As all the layers are created at the beginning of the calculation (in DataCAST), it is advised to define a number of layers which is not too large, corresponding to the final desired length of the casting (in order to keep a reasonable size of the model). Once the Accordion is set, it is necessary to define the cooling conditions on the side of the continuous casting slab, once it is going out of the mold (if there is a mold). As shown in the figure hereafter, the lateral cooling of the casting (below the accordion interface) is rather complex. One has first an interface heat transfer

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between the casting (and bottom block if any) and the mold. Then, as the casting is going out of the mold, there is a convective cooling (i.e. a Heat BC). As the domain is moving, one should be able to handle the transition between an interface heat transfer and a Heat BC transfer.

The interface heat transfer coefficient is defined in the previous section. Concerning the Heat BC, it should be applied on the lateral faces of the downstream domain (and possibly on the lateral faces of the bottom block if any), as shown in the following figure.

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In order to achieve that, the Heat BC must be defined by a User function (see the "User Functions" section of the manual for all the details). To do so, firstly, the Heat BC entry should be defined as follows :

The Film coefficient should be defined by a "Function". This user function will allow to define a film coefficient as function of the position of the surface element, so that it applies only when the corresponding surface of the casting is outside the mold. If we suppose that we have a vertical continuous casting (downwards), the heat transfer coefficient will be set to zero if the position of the surface is higher than the exit altitude of the mold (e.g. 0.02 m in the Y-direction) and it will be set to a given value (e.g. 3000 W/m2K) if the position is lower than the exit altitude of the mold.

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Such a User function (which can be of course much more sophisticated) will allow that there is no convective heat transfer inside the mold and that the right convective cooling will be applied for any surface going out of the mold. The other boundary conditions should be set as a usual ProCAST calculation.

Process conditions A Translation velocity (corresponding to the casting speed) should be applied to the "downstream domain", as well as to the bottom block (if any).

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To do so, the standard "Translation" conditions (in the "Process/Assign Volume" menu) should be applied to the corresponding domains. The "Translation" panel allows to define the translation as x(t), v(t) or v(x) - see below.

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Initial conditions The initial conditions will be defined as usual.

Run Parameters In addition to the usual Run parameters, one Run parameter should be added manually in the p.dat file. This Run parameter is :

ACCORDION 1 This will allow to activate the MiLE algorithm. Remark Please note that the POROS 1 model is not suitable for continuous casting (both steady state or MiLE) and thus POROS should be set to 0.

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M ILE EXAMPLES

Thermal + Flow

In addition to the Thermal set-up (see the "Non Steady State cases (MiLE) section"), the following definitions should be done to activate the flow.

Boundary conditions An inlet velocity BC should be set on the top surface. In the following example, the inlet velocity is applied on the whole top surface (which is equal to the exit section of the ingot). In such case, the inlet velocity should be equal to the translation velocity, applied to the downstream domain and the bottom block.

In addition to the inlet velocity BC, it is necessary to apply a Pressure BC on one node of the inlet surface. The applied pressure should be set to 1 bar (and the value of the Run parameter PREF should be set to the same value).

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As non-coincident interfaces are set between the "downstream domain" of the casting and the mold, it is necessary to set a Wall BC (zero velocity) on the casting side of those interfaces, in order to prevent "leaks" of liquid (please remember that in this example the large faces are set with Symmetries).

Run Parameters Finally, the FLOW = 1 Run Parameter should be set. In addition, the value of LVSURF should be set to a higher value than 1 (e.g. 1.10). As mentioned above, the value of PREF should be set to the same value as the one used in the Pressure BC. Finally, one should set FREESF = 0.

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Inlet with a Nozzle (or small inlet surface) In the case a Nozzle is present or if there is a small inlet surface (i.e. the inlet flow is not applied on the whole top surface of the ingot), the following precautions should be taken. The mesh should contain a small extra volume which has the same area as the real inlet (see the picture below).

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This allows to specify exactly the inlet velocity corresponding to the casting speed (by making the ratio of the surfaces).

Then, a Wall BC should be applied to the rest of the top surface (see below).

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Finally, the Pressure BC should be applied on one node of the inlet surface.

Thermal + Stress

This section describes the setup of a Thermal-Stress case. For the setup of the Thermal part, please refer to the "Non Steady State cases (MiLE) section").

Stress properties The stress properties should be specified as usual in the Materials/Stress menu.

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One should remind that it is mandatory that the solidification front does not "cross" the Accordion interface (i.e. the "upstream domain" should remain fully liquid). Please note that at this stage, it is not possible to perform a stress calculation in the bottom block. However, the mold(s) can be considered as Rigid, Vacant or a stress calculation can be performed.

Boundary conditions No Displacement BC should be set on the Casting domain. This is due to the fact that the liquid nodes are automatically set with a zero displacement. Thus, the model will be enough constraint for the stress calculation. If stresses are also calculated in the mold, it is necessary to set the usual Displacement BC on the mold.

Run Parameters Beside the STRESS = 1 Run parameter, a special care has to be taken with the SCALC value. Due to the MiLE algorithm, the number of elements in which the stress calculation will be done will increase with time. It was observed that the

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maximum timestep (dtmax), the casting velocity (V), the thickness of the accordion elements (E) and the SCALC values should be defined in order to satisfy the following relationship (in order to have a good accuracy of the results) :

( V * dtmax * SCALC ) / E should be smaller than 0.1 to 0.2. As a consequence, it is advised to use a SCALC value equal to 1. In order to limit the size of the result files, the value of SFREQ (storage frequency of the stress results) can be set to a higher value (e.g. SFREQ = 20 or higher).

Finally, for a better accuracy, it may be advised to "strengthen" the stress convergence tolerance from 1e-2 to 1e-3.

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CORE BLOWING

ProCAST allows to model the core blowing process.

Introduction When modeling the sand injection process, the air and sand are modeled as a homogeneous fluid in which the air-sand mixture is treated as a single phase. Thus, the process is considered as a filling with ad-hoc material properties and boundary conditions. In order to model core blowing, a non-Newtonian model is used. The viscosity is described by the following relationship :

where,

Model set-up Material properties The viscosity model should be defined using the Carreau-Yasuda input panel with the following correspondence table:

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Please note that the "Yasuda" parameter is not used in the Core blowing viscosity model. Thus, this value (which is recommended to be set to 0) will be ignored. Remark : It is important to notice that when a core blowing calculation is performed (NNEWTON = 7), the equation behind the Carreau-Yasuda model (shown above) is not the same as the one used for non-newtonian fluid.

In all cases, the viscosity is never allowed to decrease below the µ0 value. The last term of the viscosity relation measures the amount of contraction of the velocity field. Only positive contractions are used to increase the effective viscosity. This contraction term is modeling the increased resistance to flow that occurs when intra-particle spacing decreases as the velocity field contracts. Typical recommended values are :

zero viscosity : 1 Pa.s infinite viscosity : 0.2 Pa.s Phase shift : 3e-5 s Power : 100 Yasuda : 0 (not used)

Beside the viscosity, it is necessary to define the density, the specific heat and the thermal conductivity. Please note that as no thermal model is performed, the specific heat and the thermal conductivity are not explicitly used in the calculation. However these two values should be defined (dummy values can be used).

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Geometry-mesh / Boundary conditions In order to have a successful calculation, it is necessary to model the "upper sand container" as shown in the following figure.

The boundary conditions to be applied should be : Pressure, Vent and zero velocities (Wall).

A pressure condition should be applied to the sand in the upper container to force the sand down through the nozzle assembly and into the core box. Usually, this pressure is around 4 bars.

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Vents should be specified in order to allow the air to escape. The two following figures are showing different vent selections.

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Typical vent boundary conditions are the following :

Run parameters The Standard Flow Run parameters should be set as usual. One should not forget to set GAS = 1 to activate the gas model (mandatory) :

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In addition, the core blowing model is activated by setting the following flow run parameters: HIVISC = 2 and NNEWTON=7 (in the Flow/Advanced 1 Run Parameter tab).

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Experimental comparison The following figure is showing the comparison between experimental measurements (left) and the ProCAST calculation (right) at 3 different times.

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HOT CRACKING (FOR CONTINUOUS CASTING)

This chapter describes the Hot Cracking module of ProCAST.

Remarks Please note that this Hot Cracking model (HCS) can be used only in steady-state conditions, as encountered in continuous (or DC) casting. Thus, this model can not be used for shape casting (as it is non-steady by essence). Moreover, the HCS model can be used only for straight continuous casting.

INTRODUCTION

In many continuous casting processes, the appearance of hot tears has a detrimental effect on the productivity, especially for some very sensitive alloys. The new hot tearing criterion, recently derived by Rappaz, Drezet and Gremaud [1] has been implemented in calcosoft for 3D geometries and steady state situations in order to model the run conditions of a continuous casting process. The strategy adopted here is very similar to the Stationary Inverse module of calcosoft : once the temperature field reaches steady state, a set of profiles are drawn parallel to the casting speed in order to determine the position of the Tcg (temperature at coalescence of grains) isotherm and the value of the components of the thermal gradient at that position. Then the hot tearing sensitivity (HCS) is calculated using the so-called RDG criterion for each profile. Hence in 3D situations, HCS is represented in a section perpendicular to the casting speed.

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THE RDG HOT TEARING CRITERION

The present section gives an overview of the hot tearing criterion recently derived by Rappaz, Drezet and Gremaud. A detailed description of the model can be found in [1,2,3]. The following figure is a schematic diagram of the equiaxed dendritic growth as observed in inoculated aluminum alloys. In this case, the dendrites are assumed to

grow in a given thermal gradient, G, and with a velocity given by vT. Above a certain volume fraction of grains, mass feeding can no longer compensate for shrinkage, the specific mass of the solid being larger than that of the liquid for most metallic alloys. Therefore, the liquid has to flow from right to left in a packed bed of solid grains. If the dendritic network is submitted to a tensile deformation perpendicular to the thermal gradient, the flow should also compensate for that deformation if no hot tears form. The pressure in the interdendritic liquid is schematically represented at

the bottom of Figure 1: it decreases from the metallostatic pressure, pm, near the end of mass feeding.

Above the mass feeding temperature, Tmf, the grains have not yet coalesced and are free to move within the liquid. On the other hand, below the temperature at

which coalescence of the grains takes place, Tcg, all the grains form a coherent solid network which can transmit the thermal stresses induced by cooling. Note that the temperature at which coalescence between two grains occurs depends on

their misorientation. Between Tmf and Tcg, the film of liquid can only resist up to a cavitation pressure at which a void is nucleated and can develop into a hot tear. Any opening of the continuous interdendritic liquid film present in the packed bed of grains can hardly be compensated for by feeding from the upper region of the mush because of the high volume fraction of solid (i.e., low permeability).

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Schematic of the formation of a hot tear between equiaxed grains as a result of a localized strain transmitted by the coalesced dendrites below. The pressure drop in the

interdendritic liquid is also indicated. The RDG criterion is therefore based on the derivation of the two pressure drop contributions associated with deformation and shrinkage respectively. To do so, a mass balance is performed at the scale of a small volume element of the mushy zone in a reference frame attached to the isotherms [1].

Assuming no porosity formation, the volume fraction of liquid, fl, is equal to (1-

fs) and the specific masses of the two phases, rs and rl, are assumed to be constant, but not equal (solidification shrinkage factor b). The velocity of the liquid is related to the pressure gradient in the liquid via the Darcy equation and the permeability of the mushy zone is given by the Carman-Kozeny approximation [1]. Considering that the fluid moves along the thermal gradient only, whereas the solid deforms in the transverse direction, one can calculate the pressure within the mush (eq. 1):

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where pa is the atmospheric pressure, ρgh the metallostatic contribution. ∆psh and

∆pmec are the pressure drop contributions in the mush associated with the solidification shrinkage and the deformation induced fluid flow, respectively. In steady state conditions and assuming an uniform mechanical deformation rate

throughout the mush, , these two contributions are given by (eqs. 2):

Tcg is the temperature at which coalescence (solid bridging) of the dendrite arms

between grains occurs and m the viscosity of the liquid. λ is the mean grain size

for equiaxed structures or the secondary dendrite arm spacing, λ2, for columnar structures. The two parameters A and B depend only on the nature of the alloy and

on its solidification path, i.e. on the relationship between fs and T. Equation 2 reveals that the shrinkage contribution is proportional to the speed of the isotherms whereas the mechanical contribution is proportional to the strain rate. Both contributions are inversely proportional to the square of the grain size. Eventually, if the pressure, P, given by equations (1) and (2), falls below the

cavitation pressure, Pc, a hot tear forms. This condition can be rewritten in terms of depressions (eq. 3) :

where the cavitation depression is defined as Dpc = pa - pc. This condition allows

the calculation of the maximum strain rate sustainable by the mushy zone, ,

and a hot cracking susceptibility, HCS, can be defined as . The higher HCS, the more susceptible the alloy. Two alloy dependent integrals, A and B, have to be computed first [1,2,3]. To do so, the solid fraction versus temperature curve is needed, as well as the solid

fraction, Fcg, at which coalescence of grains occurs. Note that the integration:

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• can be performed between Tcg and Tliq instead of Tmf (mass feeding temperature) without modifying much their values

• is performed for each solid phase if needed (e.g. eutectic as well as peritectic reactions can be treated)

To compute the maximum strain rate the mush can sustain, the following data are required: • the alloy cavitation depression, ∆Pc [Pa]; • the thermal gradient (3 components) at Tcg [°C/m]; • the total liquid height relative to the iso-Tcg line [m];

• the gravity vector [m/s2

];

• the density for the liquid and for each solid phase [kg/m3

];

• the viscosity of the liquid [Pa.s]; • the mean grain size (for equiaxed microstuctures) or secondary dendrite arm

spacing (for columnar microstructures) [m]

The hot cracking susceptibility, HCS, can be defined as 1/ [s], is then

computed. In case [1/s] is negative, the mush cannot sustain any tensile deformation, thus a crack is to be formed and HCS is set to a high value, 1.e6.

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STRUCTURE OF THE INPUT FILES

The steady state hot tearing modelling is carried out after a transient direct calculation has run and converged to a steady state regime. At least two steps must be saved in the computation of the thermal field. The steady state regime is considered to be reached when the maximum variation between the two last saved steps, of the temperature at all nodes is smaller than the value, stationary.t.tol. The HCS value is calculated on the last step which is supposed to correspond to steady state conditions. If the maximum temperature difference computed between the last two saved steps is larger than the given tolerance (stationary.t.tol) beyond which steady state is assumed, the tolerance and/or the number of computation steps to get the steady state temperature field should be increased. To decrease the computation time, it can be useful to restart a calculation from a first approximation of the steady state temperature field by using the restart option. The steady state hot tearing module needs the following input files : prefixg.unf (geometry file) prefixt.unf (results file - temperature) prefixfs.unf (results file - fraction of solid) Two additional files are required : prefix_hcsinput.d (data file) prefix_hcsfst_plot.d (fs-T file)

Structure of the input file prefix_hcsfst_plot.d The file prefix.hcsfst_plot.d has the following structure (plot.d file structure): n, Nphase

where n is the number of lines and Nphase the number of solid phases (a, b, g, ...) (which may be present together with the liquid phase) that are considered (1 for

eutectic reactions, 2 for peritectic reactions). are the solid fractions (varying between 0.0 and 1.0) at temperature Ti for solid phases a, b, g , … (only the solid phases which appear together with the liquid should be considered, i.e. no solid phase transformations are considered). Note that the total solid fraction is

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the sum of these quantities. These data are required to compute the parameters A and B. IMPORTANT • the temperatures Ti are stored in the order of increasing values, thus the solid

fraction are decreasing and Tn is the liquidus temperature of the

alloy at which (or the mass feeding temperature at which

). • the number of values, n, should be large enough in order to precisely compute

the two integrals A and B, notably at high solid fractions. • the integration of A and B are performed from Tcg to Tn (liquidus or mass

feeding temperature). • the solid fractions have no unit and should not be expressed in %

• T1 is the solidus temperature at which

Structure of the input file prefix_hcsinput.d The benefit of symmetry planes is taken into account and only one fourth of the slab is modeled. Moreover, the casting speed and the gravity vector must be parallel to one axis of coordinate given by Naxis (this means that only vertical casting can be treated at this time - downwards or upwards). The input file named prefix_hcsinput.d has the following structure: 12 8 # nx ny 1 # Domain number ( casting domain) 1. # liquid height ( liquid surface level) 0.15 # stationary t.to l 3 # Naxis : casting and gravity direction # 1 : X directio n # 2 : Y directio n # 3 : Z directio n 1.e-3 # casting velocit y (positive or negative) 9.81 # gravity (positi ve or negative) 2600. 2 # liquid density & number of solid phases 2782. 2365. # solid density o f each solid phase (phase1, phase2, ...) 1.e-3 # viscosity 200.E-6 # Average microst ructure size [m]

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7000. # Cavitation depr ession [Pa] 0.972 # Fraction of solid a t grain coalescence nx [-] : number of profiles in the X-direction ny [-] : number of profiles in the Y-direction Domain number [-] : Domain in which the HCS calculation is performed (it should be in one and one domain only) liquid height [m] : coordinate of the height of the top of the liquid pool (it can be outside the domain). This height will be taken parallel to the gravity vector. stationary t.tol [°C] : If t.tol is positive, it represents the maximum acceptable temperature difference between the last two saved steps to insure that stationary conditions are reached. If it is equal to 0.0, only the last saved step is considered (without checking of the stationary condition). If it is negative, then the RDG is computed and stored at all saved steps (the .csv file contains the last step). Naxis : Direction of the casting velocity and of gravity (1: X-direction, 2: Y-direction, 3: Z-direction). This number should always be positive velocity [m/s] : casting velocity (velocity can be positive or negative). If velocity is negative, it will go along the negative direction of the axis of coordinate (defined by Naxis above) gravity [m/s2] : gravity value (gravity can be positive or negative). If gravity is negative, it will go along the negative direction of the axis of coordinate (defined by Naxis above). For vertical casting downwards, both gravity and velocity have the same sign. For upwards vertical casting, the gravity and the velocity have opposite signs. liquid density [kg/m3] : density of the liquid (at liquidus) number of solid phases [-] : the number of solid phases should be defined (e.g. : 2 for a peritectic reaction) solid densities [kg/m3] : density of each solid phase (at solidus) viscosity [Pa.s] : viscosity of the liquid (at liquidus) average microstructure size [m] : usually, the SDAS is considered cavitation depression [Pa] : cavitation depression coalescence fraction [-] : fraction of solid at which coalescence of grains occurs. This fraction will determine Tcg (coalescence temperature).

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Notes Stationary.t.tol: Maximum acceptable variation in temperatures (°C) The steady state regime is considered to be reached when the maximum variation, between the two last saved steps, of the temperature at all nodes is smaller than the value, stationary.t.tol. The HCS value will be calculated on the last step which is supposed to correspond to steady state condition. A reasonable value of stationary.t.tol. is 0.1-1.0 °C. Cavitation depression: The cavitation depression depends on the alloy composition and on gas and impurities content. Typical values for metallic alloys vary between 10 to 100 kPa. Mesh refinement near the Tcg isotherm: The mesh should be fine enough (or refined) near the iso-Tcg isotherm in order to precisely compute not only the position of this isotherm but also the values of the thermal gradient, which is the derivative of the temperature and which requires even more mesh points.

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RUNNING A CASE

The HCS calculation can be launched from the Manager. The "ProCAST" button gives access to the following panel (if activated in the Installation Settings) :

The results file prefix_resuhcs.epf will be automatically created and the following print-out will appear together with the values of the two parameters A and B :

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Please note that the HCS module is coming from Calcosoft-3D. The computed values of the hot tearing sensitivity are stored in the file prefixhcscrit.usf. In addition, using the Excel csv (comma separated values) format, these values are also stored in the two files prefix_hcs-column.csv and prefix_hcs-array.csv, in column and array formats, respectively. If there are more than one domain (e.g. casting and mould), the values of HCS in the mould are set to -1.

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If the hot cracking sensitivity is very high, it is limited to a maximum value of 1e6. In this case, one can say that there is cracking in any case.

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VIEWING OF THE RESULTS

The results saved in the file prefixhcscrit.usf can be viewed with the help of the post-processor. After loading the case, one has to select Field/Additional/HCS_criterion to represent the selected field. A typical result is shown in the following Figure.

Viewing the results in the post-processor.

One can also represent the results with the help of Excel by drawing some surfaces. The two files prefix_hcs-column.csv and prefix_hcs-array.csv, can be opened in Excel which automatically recognizes the csv (comma separated value) format. The file prefix_hcs-column.csv contains the following data, stored in columns as indicated in the following figure : x (x coordinate), y (y coordinate), z (z coordinate of the iso-Tcg surface), rdg (hcs value obtained with the rdg model), Gx, Gy, Gz (components of the thermal gradient at the location (x,y,z)). Note that the coordinate system is the system defined in the mesh (see the Figure after the next).

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Viewing the file prefix_hcs-column.csv with the help of Excel.

The file prefix_hcs-array.csv contains the same data, but this time stored in arrays as indicated in the next Figure. The five quantities, z-tcg, rdg, Gx, Gy and Gz are given as a function of x and y. This allows the user to get 3D graphics of each array following the procedure described in the following Figures.

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Viewing the arrays in the file prefix_hcs-array.csv with the help of Excel.

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Clear the number nx*ny (60 here) before getting a 3D graphs of the array.

Select the data of the array.

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Select the type of 3D graph you want.

3D graph of the HCS values.

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REFERENCES

[1] M. Rappaz, J.-M. Drezet and M. Gremaud : "A new hot tearing criterion", Met. Trans. Vol. 30A, pp-449-455, Feb. 1999. [2] J.-M. Drezet and M. Rappaz: "A New Hot Tearing Criterium for Aluminium Alloys", proceedings of the First EsaForm Conference on Material Forming, Ecole des Mines de Paris, CEMEF, Sophia Antipolis, France, March 1998, pp. 49-52. [3] J.-M. Drezet, M. Gremaud, R. Graf and M. Gaümann, A new hot tearing criterion for steel, proceedings of the 4th European Continuous Casting Conference, IOM communications, Birmingham, UK, October 2002, pp. 755-763.

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INPUT-OUTPUT FILES

This section is listing the different files which are created and used by the different modules of ProCAST.

MeshCAST files PREFIX.gmrst IO Binary Restart file for mes hing PREFIX.sm IO ASCII Surface mesh PREFIX.stlsm O ASCII Surface mesh from ST L file PREFIX.igs I ASCII IGES file PREFIX.iges I ASCII IGES file PREFIX.stp I ASCII STEP file PREFIX.step I ASCII STEP file PREFIX.xmt_txt I ASCII Parasolid file PREFIX.x_t I ASCII Parasolid file PREFIXd.dat I ASCII ProCAST restart file PREFIX_pre_sh.sm I ASCII Shell meshing recove ry file PREFIX.patran I ASCII Patran file (volume mesh) PREFIX.out IO ASCII Patran file (surface mesh) PREFIX.ideas I ASCII I-DEAS file (volume mesh) PREFIX.unv I ASCII I-DEAS file (surface mesh) PREFIX.nastran I ASCII Nastran file (volume mesh) PREFIX.ansys I ASCII ANSYS file (volume m esh) PREFIX.stl I ASCII STL ASCII file PREFIX.bstl I ASCII STL Binary file PREFIX.mesh IO ASCII Volume mesh PREFIX_sub.sm O ASCII Surface mesh extract ed from volume mesh PREFIX_sub_act.sm O ASCII An active subset of original surface mesh PREFIX.elem O ASCII Ansys element file PREFIX.node O ASCII Ansys nodal file PREFIX.wrk O ASCII Temporary working fi le for surface mesh merge PREFIX.ceg O ASCII Temporary working fi le for surface mesh merge usr_cmnds IO ASCII User defined icons *.gif GIF capture mesh.print PREFIX.psm

PreCAST files PREFIXd.dat IO ASCII General model setup ( including the geometry), also used for Restarts PREFIXp.dat IO ASCII Run Paramerters file, also used for Restarts PREFIX.ini IO Binary Extracted initial con ditions PREFIX.enc IO Binary Element number corres pondance file in case of Add/Delete Material PREFIX.nnc IO Binary Node number correspon dance file in case of Add/Delete Material PREFIXg0.dat IO ASCII Cut-off values per do main for Thixo casting bc.db I ASCII Boundary conditions d atabase matl.db I ASCII Material properties d atabase stress.db I ASCII Stress properties dat abase intf.db I ASCII Interface heat transf er database proc.db I ASCII Process database

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CT_Al.db I ASCII Al Thermodynamic data base CT_Fe.db I ASCII Fe Thermodynamic data base CT_Ni.db I ASCII Ni Thermodynamic data base CT_Mg.db I ASCII Mg Thermodynamic data base CT_Ti.db I ASCII Ti Thermodynamic data base PREFIXt.unf I Binary Temperature results f or extracting initial condition PREFIX.rnm I Binary Node renumbering PREFIXd.unf I Binary Time step information , used for IC extraction PREFIXid.dat IO ASCII Inverse data PREFIX.out I ASCII PATRAN mesh neutral f ile PREFIX.unv I ASCII IDEAS mesh universal file PREFIX.mesh I ASCII Meshcast file predefined_%d_p.dat ASCII Pre-defined p.dat fil es default_p.dat ASCII Default values of the p.dat file

INPUT files (for the ProCAST solver - generated by DataCAST) These files are also Output files for ViewCAST PREFIXd.dat IO ASCII General model set-up (including the geometry), also used for Restarts PREFIXg.unf O Binary Model description (Me sh, Material Settings , BC settings) PREFIXt.unf O Binary Temperature results f ile, storing initial values PREFIXs.unf O Binary Solid node coordinate s for moving elements PREFIXo.unf O Binary Enclosure node coordi nates PREFIX.rnm O Binary Node renumbering info rmation, used by PreCAST for temperature extraction PREFIXff.unf O Binary Free faces informatio n (for faster post-processing) PREFIXd.out O ASCII DataCAST synopsis inf ormation file

OUTPUT files (for ViewCAST) PREFIXa.unf O Binary Start and end time of solidification PREFIXb.unf O Binary Gas porosity PREFIXc.unf O Binary Shrinkage porosity fi le PREFIXci.unf O Binary Cracking indicator PREFIXcv.unf O Binary Pore volume PREFIXcpv.unf O Binary Contact pressure PREFIXd.unf O Binary Time step - step PREFIXe.unf O Binary Turbulent dissipation rate PREFIXemg.unf O Binary Electric field PREFIXes.unf O Binary VON MISES stresses PREFIXf.unf O Binary Fluid fraction (FVOL) PREFIXfl.unf O Binary Fatigue life PREFIXfr.unf O Binary Freckle indicator PREFIXfs.unf O Binary Solid fraction PREFIXft.unf O Binary Filling (wetting) tim e PREFIXgn.unf O Binary Strain values at the gauss points PREFIXgs.unf O Binary Stress values at the gauss points PREFIXht.unf O Binary Hot tearing indicator PREFIXk.unf O Binary Turbulent kinetic ene rgic file PREFIXmg.unf O Binary Magnetic field PREFIXn.unf O Binary Non newtonian shear r ate and viscosity PREFIXo.unf O Binary Nodal coordinates off set for enclosure PREFIXp.unf O Binary Pressure PREFIXpa.unf O Binary Peak acceleration for core blowing PREFIXpp.unf O Binary Peak pressure for cor e blowing PREFIXpv.unf O Binary Peak velocity for cor e blowing

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PREFIXprt.unf O Binary Particle traces PREFIXq.unf O Binary Heat flux PREFIXr.unf O Binary Compressible density PREFIXs.unf O Binary Solid node coordinate s for moving elements PREFIXtv.unf O Binary Turbulent viscosity PREFIXx.unf O Binary X displacements PREFIXy.unf O Binary Y displacements PREFIXz.unf O Binary Z displacements PREFIXu.unf O Binary X velocity PREFIXv.unf O Binary Y velocity PREFIXw.unf O Binary Z Velocity PREFIX.vf O ASCII View factors after sy mmetrization PREFIX.view O ASCII View factor groups PREFIX.serr O ASCII View factor row sum e rrors PREFIXp.out O ASCII ProCAST run informati on file

Files necessary for a RESTART (some of these files are needed for ViewCAST) PREFIXAmtx.unf O Binary Magnetic potential us ed with boundary integral method PREFIXbs0.unf O Binary Back stress 0, used i n kinematic hardening PREFIXbs1.unf O Binary Back stress 1, used i n kinematic hardening PREFIXcr.unf O Binary Curing reaction for R TM PREFIXcp.unf O Binary Contact force PREFIX.ctoc O Binary Radiation view factor information PREFIX.fic O Binary Virtual mold informat ion PREFIX.fom O Binary Lost foam information PREFIXfv.unf O Binary Fraction of void, use d in cracking indicator PREFIX.glue O Binary Status of glue nodes in lost foam PREFIXgp.unf O Binary Contact gap PREFIXmdc.unf O Binary Stored mass and diffu sion matrices PREFIX.mcf O Binary Stored coefficients f or momentum equation PREFIX.mrv O Binary Lost foam information PREFIXm1.unf O Binary Micromodel, Ductile I ron Eutectic PREFIXm2.unf O Binary Micromodel, Primary D endrite PREFIXm4.unf O Binary Micromodel, Coupled S table/Metastable Eutectic Growth PREFIXm16.unf O Binary Micromodel, Gray/Whit e Iron Eutectic PREFIXm32.unf O Binary Micromodel, Ductile I ron Eutectoid PREFIXm64.unf O Binary Micromodel, Gray Iron Eutectoid PREFIXm128.unf O Binary Micromodel, Peritecti c Transformation PREFIXm256.unf O Binary Micromodel, Delta/Gam ma, Gamma/Alpha, Gamma/Cementite PREFIXm512.unf O Binary Micromodel PREFIXpn.unf O Binary Average penetration, penalty number PREFIX.pr O Binary Pressure relaxation i nfo PREFIX.rmp O Binary Radiation face remapp ing PREFIX.sel O Binary Highest filled elemen t (FREESURF=2) PREFIX.shk O Binary Shrinkage data, obsol ete PREFIXsm.unf O Binary Slave-master data PREFIXsr.unf O Binary Load residual PREFIXst.unf O Binary Thermal load PREFIXsth.unf O Binary Last thermal load PREFIX.t2q O Binary Tri-to-quad (Radiatio n) PREFIXtb.unf O Binary Turbulence data, obso lete PREFIXthx.unf O Binary Thixocasting viscosit y PREFIXl.prf O Binary Temperature gradient at the solidus PREFIXlp.unf O Binary Filling BC shut-off t imes

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Files generated by ViewCAST PREFIXes.unf O Binary Effective stress resu lts PREFIXs1.unf O Binary Principal stress 1 re sults PREFIXs2.unf O Binary Principal stress 2 re sults PREFIXs3.unf O Binary Principal stress 3 re sults PREFIXss.unf O Binary Maximum shear stress PREFIXsp.unf O Binary Average normal stress PREFIXsx.unf O Binary Normal stress in X di rection PREFIXsy.unf O Binary Normal stress in Y di rection PREFIXsz.unf O Binary Normal stress in Z di rection PREFIXsxy.unf O Binary Shear stress on X-Y p lane PREFIXsyz.unf O Binary Shear stress on Y-Z p lane PREFIXszx.unf O Binary Shear stress on Z-X p lane PREFIXepn.unf O Binary Effective plastic str ain PREFIXac.unf O Binary Alpha case PREFIXac.ntl O Binary Alpha case neutral fi le PREFIXdas.unf O Binary Secondary dendrite ar m spacing PREFIXdas.log O ASCII SDAS log PREFIXdas.ntl O ASCII SDAS neutral file PREFIXm.unf O Binary Mapping factor (RGL) PREFIXm.log O ASCII Mapping factor log PREFIXm.ntl O ASCII Mapping factor neutra l file PREFIXi.unf O Binary Isochrons PREFIXi.log O ASCII Isochrons log PREFIXi.ntl O ASCII Isochrons neutral fil e PREFIXl.unf O Binary Feeding length PREFIXl.log O ASCII Feeding length log PREFIXl.ntl O ASCII Feeding length neutra l file PREFIXr.ntl O ASCII Radiation face geomet ry PREFIXg.ntl O ASCII Mesh neutral file PREFIXf.ntl O ASCII Radiation face to gro up neutral file PREFIXe.ntl O ASCII Radiation row sum err or neutral file PREFIXs.ntl O ASCII Stress results neutra l file PREFIXt.ntl O ASCII Temperature neutral f ile PREFIXt.log O ASCII Temperature log file PREFIXq.ntl O ASCII Heat flux neutral fil e PREFIXq.log O ASCII Heat flux log file PREFIXp.ntl O ASCII Pressure neutral file PREFIXp.log O ASCII Pressure log file PREFIXv.ntl O ASCII Velocity neutral file PREFIXv.log O ASCII Velocity log file PREFIXd.ntl O ASCII Displacement neutral file PREFIXd.log O ASCII Displacement log file PREFIX.tt O ASCII Temperature-time PREFIX.lv O ASCII Last view PREFIX.clip O ASCII Slice data *.gif O ASCII GIF file

Miscellaneous (Some files are created for internal purposes) PREFIX.cm PREFIX.mtx bem.out PREFIXc.out debug.out dbg.out mem_usage poros.out PREFIX.rhs PREFIX.lhs

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PREFIX.sol PREFIXrf.out PREFIX.rhs_v sconv PREFIXf.out PREFIX.phs PREFIX_rho.dat PREFIX_k.dat PREFIX_mu.dat PREFIX_tdd.dat PREFIX.err PREFIXt.out

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TIPS & TRAPS INLET VELOCITY

When a velocity Boundary condition is set in order to define an inlet of liquid metal, the question of the value of the velocity and the value of the inlet diameter of the liquid jet is important. The following graph is showing the free fall velocity after a given distance of free fall (a value of gravity of 10 m/s2 was used for this calculation).

One can see on the above graph that after 0.5 mm, the falling velocity is already 10 cm/s. After 1.25 cm, it is 0.5 m/s and after a falling height of 10 cm, the falling velocity is 1.4 m/s. After 20 cm, the falling velocity is 2 m/s. In usual casting conditions, the ladle (or crucible) is very often at a minimum of 10 or 20 cm above the top of the pouring cup. Thus, physically, it is advised to set an inlet velocity (at the limit of the model) between 1 and 2 m/s and not smaller. As a consequence, the inlet diameter should be set accordingly in order to have the right inflow of metal.

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If a too small inlet velocity is defined (e.g. 10 cm/s), the inlet diameter should be too large and due to the strong acceleration on the first centimeters, the diameter of the accelerating liquid jet will decrease very much. This situation is quite difficult to be modeled and should be avoided. Finally, one should always be careful that the mesh size below a falling liquid stream should be fine enough in order to have 2-3 elements through the thickness of the liquid jet. When an "inlet BC" is defined, one should always be careful to set the right inlet surface so that the corresponding inlet velocity is not too small (i.e. not smaller than 1 m/s). To do so, the resulting inlet velocity should be checked at step 0 of the simulation. If this velocity is too small, one should reduce the inlet surface.

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LPDC RECOMMENDATIONS

The design of the ingate in LPDC is especially important in order to have good filling results. Although the real final casting has not anymore an ingate cylinder (see 1 hereafter), it is necessary to model an ingate cylinder which is long enough (see 2 hereafter). If this is not done, the pressure solution is not stable and the results will not be good. There is not an absolute rule about the length of this ingate cylinder, but it is advised to add between 6 to 10 cm.

Concerning the inlet boundary conditions, a pressure curve should be set at the bottom of the ingate cylinder (see figure below).

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Then, the pressure curve which should be applied must be a pressure ramp, starting with a zero pressure (it is supposed that PREF is set to 0 bar) and going up to the metallostatic pressure corresponding to the height h (see the figure above). Thus, the maximum pressure (see 1 in the figure below) should be equal to the metallostatic pressure of the height h (Pressure = density * g * h), at the time (see 2 in the figure below) corresponding to the filling time. The shape of the curve does not need to be a straight line as shown in the graph below.

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Please note that if the bottom of the ingate cylinder does not correspond to the liquid surface in the furnace, the pressure ramp which is measured in the real process should be shifted to correspond to the one sketched above.

The figure above is illustrating the pressure BC used in LPDC. In LPDC, when the solidification is mostly completed, the pressure is released in order to drain the liquid metal which is in the inlet tube. This can be taken into account with the Run parameters DRAINFS and DRAINTIME (see the "Thermal/Run Parameters" section for more details). All the remaining liquid (up to the fraction of solid defined by DRAINFS) which is connected to the inlet pressure boundary condition location will be removed at the time specified by the value of DRAINTIME. The following figure is showing the results of two different calculations with different values of DRAINTIME. As you can see the temperature in the casting and in the mold (taken at the same time) are different, as the "heating effect "of the liquid in the inlet tube is different in both cases.

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The following figures are showing two examples with different values of DRAINTIME. One can well see the effect of the DRAINTIME value on the final shape of the wheel near the inlet tube. In the 20 s. example, it is obvious that the draining was performed too early.

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In the draining algorithm, all the liquid which is between the injection point (where the inlet pressure BC is applied) and the DRAINFS isoline will be removed at the time of DRAINTIME, regardless of the geometry of the casting. In the following example, the draining being applied very early in the solidification process, almost all the cavity is drained (see next figure).

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However, in a normal situation, the volume below the dashed line (see next figure) should remain in the mold and should not be drained. This situation is not taken into account in the algorithm as it is normally not intended in the reality to have such situation.

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The draining algorithm is also applicable in the case of cycling calculations. In the following simple example, one can see very well that due to the heating up of the die during the first cycles, the shape of the casting at the drained location is changing.

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RESTART

What should we do when we would like to restart a calculation after some data modifications ?

• If the content of the d.dat file was not modified, one should not run DataCAST and it is possible to run directly ProCAST. Typically, this happens if the content of the p.dat file only was modified. If PreCAST is loaded, the d.dat file is not modified only if the Run Parameters are changed. If anything else is changed in PreCAST, it is necessary to run first DataCAST and then ProCAST.

• When the d.dat file is modified, DataCAST has first to be run and

then ProCAST should be launched. • When one would like to CONTINUE a calculation from a given

timestep, DataCAST with the -u option should be used. This is mandatory in order not to erase the existing result files (for more details please refer to the "Solver" section of the "Run of the calculation" chapter.

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CONVERGENCE PROBLEMS

If a calculation does not converge or has problem to converge (this can be seen in the p.out file - please refer to the Troubleshooting section for more details), the following operations can be tried : The Thermal model does not converge

• check the thermal material properties (in particular if an enthalpy curve is defined, check that the curve is strictly in an ascending order)

• modify the solver parameters from TDMA to CGSQ (with the CGSQ Run parameter)

• Increase the convergence thermal Run parameter CONVT from 1 to 2 (maximum 5)

• Modify the mesh in order to have a better quality The fluid flow model does not converge (velocities of pressures)

• modify the solver parameters from TDMA to CGSQ (with the CGSQ Run parameter)

• Increase the convergence flow Run parameter CONVV from 0.05 to 0.1 (maximum 0.5)

• Modify the mesh in order to have a better quality

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STRESS CALCULATIONS

• Stress calculations might be rather long (in terms of CPU time), as the six

components of the stress tensor have to be computed, in addition to Temperature, Pressure and the three components of the velocity.

• In order to reduce CPU time, it is recommended to use as much as possible the

"Vacant" and "Rigid" options, as well as the symmetries. • The contact algorithm does not take into account friction. • Stress calculations are starting as soon as the fraction of solid is larger than a

critical fraction defined by the Run Parameter CRITFS. By default, CRITFS = 0.5.

• It is strongly advised to run separately filling calculations and stress

calculations in order to save CPU time and memory.

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GAPS IN STRESS MODELS

During a thermo-mechanical calculation, gaps may form between the different domains (e.g. between the casting and the mold). ProCAST automatically accounts for the modification of the interface heat transfer coefficient when gaps are forming. The model which is used assumes that radiation and heat conduction through an air gap is progressively replacing the transfer due to the contact (see the model in the figure below). If VACUUM is set to 1, the heat conduction part is deactivated. When there is a contact, the heat transfer coefficient is increased as a function of the pressure.

The figure below illustrates the change of the resulting interface heat transfer coefficient, as a function of the air gap width. Please note that the air thermal conductivity corresponds to a temperature of about 800°C.

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User definition of the gap properties By default, the gap is filled with air (with the above properties) or with Vacuum. However, in special cases, the user has the possibility to define other properties for the gap (e.g. flux continuous casting of steel, or water in a bottom block of DC casting of Al). To do so, the "interhtransfer.c" user function should be used. When there is a gap (and the interhtransfer.c function is activated), the value returned by the function

does correspond to h0 in the above equation (thus, if there is no gap, h = h0). Moreover, the values of k (the "gap conductivity") and of the Stefan-Bolzmann constant (which is used to calculate the equivalent radiative heat transfer

coefficient hrad) can be changed within the interhtransfer.c user function. To modify k, one should assign the desired value to the "gap_cond" variable and for the Stefan-Bolzmann constant, one should assign the "stefan" variable (see function hereafter). By this means, it is possible to specify in the user function a gap equivalent heat transfer coefficient as a function of the location for instance. For instance, above a given height, there is some flux, thus, the value of k can be set to a "high" value corresponding to the flux and the Stefan-Bolzmann constant can be set to zero to cancel the radiation. Below a given height, we can model the effect of the water by setting a very large value of h0 (the values of the conductivity and Stefan-Bolzmann will be negligible with respect to water cooling heat transfer

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coefficient). In between, air and radiation can be considered. The following interhtransfer.c routine is illustrating this example.

#include <stdio.h> #include <stdlib.h> #include "common_dll.h" /* please note that this line was added in

2009.0 */ /* version to handle these gap definitions */

#define real double

#ifdef WIN #define EXPORT _declspec(dllexport) EXPORT real func_interhtransfer(char*, int, real, r eal, real, real,

real, real, int); #else real func_interhtransfer(char*, int, real, real, re al, real, real, real,

int); #endif



real func_interhtransfer( char prefix[], /* case name */ int dimension, /* 2 = 2D ; 3 = 3D */ real temp, /* current temperature */ real fs, /* current fraction of solid */ real time, /* current time */ real x_coor, /* local coordinates: x */ real y_coor, /* local coordinates: y */ real z_coor, /* local coordinates: z */ int numBC) /* number of boundary condit ion */ { /* ------------- Do not change anything above this line -------------

* * ------------- Program your function below this l ine -------------

*/

real h0; real hmax; real hmin;

if (z_coor > hmax) /* liquid flux above hmax */ { h0 = 2000. ; gap_cond = 20. ; /* conductivity of the flux in the gap */ stefan = 0. ; /* zero value of Stefan-Bolzmann to cancel the

radiation */ }

else if (z_coor < hmin) /* water cooling in the bottom block */ { h0 = 50000. ;

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gap_cond = 1.e9; /* to have h = h0, Rgap should be very close to zero and */

/* this can be achieved with a very high value of k (gap_cond) */

stefan = 0. ; /* zero value of Stefan-Bolzmann to cancel the radiation */

}

else { h0 = 500. ; /* default value for h0 */ /* default values for air gap , nothing has to be specified */ /* default value : stefan = 1.3541845E-12 (this value should be

always specified in these CGS units) */ /* default value (air) : gap_cond = 0.079 W/m2K (the units should

correspond to the "units.dat" ones) */ }

return h0; /* only h0 is returned, however, the values of gap_cond and stefan

defined above are also returned */ /* and will be used for this location upon exit of the function and

for the next location, it will be */ /* changed at the next call of the function. */ }

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STRESS VISUALIZATION

Stresses are rather complex to view, as it corresponds to a tensor (with 6 components). ProCAST offers different possibilities to visualize these results, in addition to each of the components of the stress tensor.

Effective Stress There are several ways to evaluate the local stress state with a single value. The formula below shows how the Effective Stress in ViewCAST is calculated (e.g. in one dimension, the effective stress corresponds to the stress itself). To simplify, one could consider that it corresponds to some kind of "average" value of the stress. As shown in the equation below, the Effective Stress is always positive and thus, it does not allow to determine whether the state of stress is in compression or in tension. To determine that, the other viewing possibilities should be used.

The stress components which are in the square root correspond to the principal stresses.

Average Normal Stress The following figure is showing the stress state (or the stress tensor) of a unit volume oriented according to the X-, Y- and Z-coordinates. The Average Normal Stress corresponds to the average of the three normal components. This value can be either negative (mainly compressive state) of positive (mainly tensile state).

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Maximum Shear Stress

The shear stresses components are highlighted in red in the figure above. The "maximum shear stress" is defined by the equation below (where the stress components corresponds to the maximum and the minimum normal stresses).

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Principal Stresses Considering the stress state of a given unit volume, it is possible to find a unit cube with a different orientation, where all the shear stresses are zero. Thus, only the normal stresses are remaining and they are called principal stresses. The principal stress 1 is the larger value and the principal stress 3 is the smaller value. Positive values show a tensile state, whereas negative values show a compressive state.

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RESULTS COMPARISONS BETWEEN VERSIONS

The goal of this section is to present results of a set of examples which have been calculated with the current version, with comparisons with the previous one. Comparisons between scalar and parallel (DMP) calculations are also presented. One should note that in some cases (especially in filling), the physical solution can be somehow "unstable". As a consequence, the results of the calculations made with slightly different conditions can exhibit some noticeable differences. For instance, as the solvers are different between the scalar and the DMP versions, the convergences are different and thus the timesteps may be different. This can affect for instance the free surface calculation and thus the results may differ. However, when such behavior will happen in the calculations, it will also happen in reality and vice-versa.

RESULTS COMPARISONS (2009.0)

This section presents comparisons of results which have been calculated as follows : • version 2008.0 (scalar) • version 2009.0 (scalar) • version 2009.0 (DMP 2 CPU on Windows) • version 2009.0 (DMP 8 CPU on Linux) Please note that these cases were calculated with the Default Pre-defined Run parameters. The following examples are a first set of comparisons.

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Gravity-1

Comparisons of the filling sequences at different times of a gravity test casting. Temperature and flow front are displayed.

Temperature

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Temperature

Temperature

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Gravity-2


Temperature

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Temperature

Temperature

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Gravity-3

Comparisons of the filling sequences at different times of a gravity test casting, including a filter. Temperature and flow front are displayed.

Temperature

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Temperature

Temperature

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Filling time

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HPDC-1

Comparisons of the filling sequences at different times of a HPDC test casting. Fluid velocity magnitude and flow front are displayed.

Fluid flow magnitude

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LPDC-1

Comparisons of the filling sequences at different times of a LPDC test casting. Temperature and flow front, filling time and shrinkage porosity are displayed.

Temperature

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Temperature

Temperature

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Filling time

Shrinkage Porosity

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Investment-1

Comparisons of the cooling and solidification sequences at different times of an investment test casting. Temperature are displayed.

Temperature

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Temperature

Temperature

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Stress-1

Comparisons of the thermal, porosity and stresses of an LPDC test casting. Temperature, shrinkage porosity, Effective stress, Average Normal Stress and Principal stress 1 are displayed.

Temperature

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Temperature

Shrinkage Porosity

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Effective stress

Average Normal stress

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Principal stress 1

Principal stress 1 (evolution)

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Microstructure-1

Comparisons of the cooling, solidification, microstructure, porosity and density of a cast iron test casting. Temperature, nodule count, shrinkage porosity and densities (as a function of temperature at different locations) are displayed.

Please note that in this case, as the algorithm for Fading in the presence of graphite expansion was significantly improved in version 2007.0, the comparison with 2006.1 is not relevant.

Temperature

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Nodule count

Shrinkage porosity

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Density curve (as a function of temperature) at different locations of the casting

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Thixo-1

Comparisons of the filling sequences at different times of a thixo test casting. Temperature and flow front are displayed.

Temperature

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Temperature

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Centrifugal-1

Comparisons of the filling sequences at different times of a centrifugal test casting. Temperature and flow front are displayed.

Temperature

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Temperature

Temperature

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Temperature

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Gravity-1


Temperature

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Temperature

Temperature

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Gravity-2


Temperature

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Temperature

Temperature

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Gravity-3


Temperature

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Temperature

Filling time

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HPDC-1



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LPDC-1


Temperature

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Temperature

Temperature

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Filling time

Shrinkage Porosity

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Investment-1


Temperature

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Temperature

Temperature

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Stress-1


Temperature

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Temperature

Shrinkage Porosity

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Effective stress


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Principal stress 1


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Microstructure-1



Temperature

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Nodule count

Shrinkage porosity

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Thixo-1


Temperature

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Temperature

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Centrifugal-1


Temperature

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Temperature

Temperature

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Temperature

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Gravity-1


Temperature

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Temperature

Temperature

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Gravity-2


Temperature

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Temperature

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Gravity-3


Temperature

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Temperature

Temperature

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HPDC-1



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LPDC-1


Temperature

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Temperature

Filling time

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Shrinkage Porosity

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Investment-1


Temperature

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Temperature

Temperature

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Stress-1


Temperature

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Temperature

Shrinkage Porosity

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Effective stress


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Principal stress 1


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Microstructure-1



Temperature

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Nodule count

Shrinkage porosity

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Thixo-1


Temperature

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Temperature

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Centrifugal-1


Temperature

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Temperature

Temperature

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TUTORIALS

The Tutorials are in a separate document.

Pro Cast 20091

Documents

Transcript of Pro Cast 20091