LS-DYNA

Introduction to LS-DYNA

Nishant Jain

February 2006 2CROWN Technology Confidential ©

Outline1. LS-DYNA Architecture

1. Nodes and Elements,

2. Section Properties,

3. Material Model

2. Rigid Parts

3. Boundary Conditions

4. Loading

5. Contact Definition

6. Resources

7. Example

Detail Information

*CONTROL …………………………..20

*DATABASE …………………………35

ADAPTIVITY………………………….40

MATERIAL MODELS ……………….45

*CONTACT …………………………..53


Resources

Web Siteswww.dynasupport.comwww.feainformation.comwww.metalformingsimulation.comwww.dynaexamples.com

Tutorials1. Introduction to DYNA : IntroDyna.pdf2. User’s Guide: Users_Guide.pdf3. Keywords Manual : ls-dyna_971_manual-k.pdf4. Example Manual : examples.pdf

Input Decks : ....\examples5. Sample Problems :Sample Problems.pdf

Input Decks : ....\Sample Problems6. Theory Manual :theory.pdf

Metal Forming Tutorials1. Forming Parameters : forming_parameters2.pdf2. Spring-back : springback_parameters.pdf

http://www.dynasupport.com/support/howto

http://www.dynasupport.com/support/tutorial


Description of Keyword Input

Data Block(Space Delimited)

Keyword

LS-DYNA, unlike ABAQUS, does not follow any hierarchy. So, in an input deck, boundary conditions can be defined before defining the nodes.


Keyword - Example


Nodes and ElementsNode Definition

ABAQUS*NODE** NID X Y Z 400, 2, 3, 4,

DYNA*NODE$ NID X Y Z 400 2 3 4$0123456789012345678901234567890123456789

Element Definition

ABAQUS*ELEMENT,TYPE=S4R,ELSET=Blank** EID N1 N2 N3 N4 1, 1, 2, 3, 4,*ELEMENT,TYPE=C3D8,ELSET=Blank** EID N1 N2 N3 N4 N5 N6 N7 N8 1, 1, 2, 3, 4, 5, 6, 7, 8

DYNA*ELEMENT_SHELL$ EID PID N1 N2 N3 N4 1 1 1 2 3 4*ELEMENT_SOLID$ EID PID 1 1$ N1 N2 N3 N4 N5 N6 N7 N8 1 2 3 4 5 6 7 8

ABAQUS• Type of element (shell or solid) is identified in the data line

by parameter “Type”• Element is associated to a part by its “Name”• The type of particular element within a shell or solid

element is defined in type of element.

DYNA

• Type of element (shell or solid) is identified in the keyword • Element is associated to a part by its “ID”• The type of particular element within a shell or solid

element is defined in section properties.


SectionSection Properties ABAQUS

*SHELL SECTION, ELSET=Blank, MATERIAL=CreaSteel, SECTION INTEGRATION = GAUSS** T NIP 0.17 , 7

DYNA*PART$ PID SID MID ADPOPT 1 2 1 1 *SECTION_SHELL$ SID ELFORM NIP QR 2 16 0.8333 7 0$ T1 T2 T3 T4 0.17 0.17 0.17 0.17

This specifies type of element formulation within shell or solid element (eg axisymmetric) . ABAQUS does this in element definition (S4R, S3R, SAX)

Flag to Indicate Adaptive meshing is used

ABAQUS• *SHELL SECTION defines the element set name for which the section properties are defined. • It also specifies the name of the material identifying the material properties that will be used.

DYNA• A part (collection of elements) is given a unique id using a *PART card.

This part is associated to particular section properties defined by unique idThis part is associated to particular material properties defined by unique id.

• The section properties are defined separately using *SECTION card


Material

DYNA

*MAT_3-PARAMETER_BARLAT$ MID Density E PR 1 8.0E-09 200000.0 0.3 $ R0 R45 R90 LCID 1.65 2.27 2.31 3 *DEFINE_CURVE$ LCID 3 0 1.0 1.0 0.0 0.0 0$ Strain Stress 0.00000 200.0 0.00995 227.2 0.02960 257.5

ABAQUS

*MATERIAL, NAME=CreaSteel*DENSITY8.0E-09*ELASTIC, TYPE = ISOTROPIC** E PR200000.0 ,0.3 *PLASTIC** Stress Strain 200.00 ,0.00000 227.25 ,0.00995 257.50 ,0.02960*POTENTIAL1 ,1.0587 ,1.2433 ,0.9149 ,1.0 ,1.0

ABAQUS

•Different cards are used to define different properties

DensityElasticPlasticAnisotropy

•Depending on what is required, either a card is included or excluded.

DYNA

•There are different material models which require certain parameters.•Depending on the properties to be included, different material models are used. For Example,

Only Elastic:*MAT_ELASTICPlasticity without anisotropy:*MAT_PIECEWISE_LINEAR_PLASTIC


LS-DYNA Architecture


Rigid Parts

DYNA *PART$ PID SID MID 2 1 3 *MAT_RIGID$ MID RO E PR 3 8.0E-09 200000.0 0.3 $ CMO CON1 CON2 1.0 6 7

$$Rigid body constraints in DYNA are applied through material definition using $$parameters CMO, CON1 and CON2$$CMO: Center of mass constraint$$ 1: in global direction$$ 0: no constraints$$ CON 1 $$ 0: no constraints$$ 1: constraint x displacement$$ 2: constraint y displacement$$ 3: constraint z displacement$$ 4: constraint x and y displacements$$ 5: constraint y and z displacements$$ 6: constraint z and x displacements$$ 7: constraint x, y and z displacements$$CON2: is for Rotations and follow similar pattern to CON1

ABAQUS*ELEMENT,TYPE=R3D3,ELSET=Punch 60090, 60442, 60415, 60441*NSET, NSET=Ref_Punch 30027,*BOUNDARY Ref_Punch,1, ,0.0 Ref_Punch,3,6,0.0

ABAQUS

1. The rigid properties are defined using rigid elements (R3D3, RAX...)

2. A node from the rigid element is constrained (using *BOUNDARY), to constrain the rigid part.

LS-DYNA

1. The rigid properties are defined using rigid material card (*MAT_RIGID)

2. The constraints for the rigid part are defined in the *MAT_RIGID card


Boundary ConditionsABAQUS*NSET, NSET=Ref_Punch 30027,*AMPLITUDE, NAME =Punch-Displacement, DEFINITION = TABULAR, SMOOTH = 0.50.0 ,0.0 ,0.025 ,20.0 *BOUNDARY, TYPE = DISPLACEMENT, AMPLITUDE = Punch-Displacement Ref_Punch,1, , 0.0 Ref_Punch,2, ,1.0 Ref_Punch,3,6,0.0

DYNA – Rigid Part*BOUNDARY_PRESCRIBED_MOTION_RIGID ID DOF VAD LCID SF 2 2 2 1 1.0 0 $$DOF: applicable DOF$$ 1 - x translation, 2 - y translation, 3 - z translation$$VAD: type of boundary condition$$ 0 – Velocity, 1 – Acceleration, 2 – Displacement*DEFINE_CURVE LCID SFA SFO 1 0 1.0 1.0 0.0 0.0 0 Time Multiplier 0.0 0.0 0.025 20.0

ABAQUS

1. The boundary conditions to the rigid part is given to the reference node of the rigid part.

2. Type of boundary condition (Displacement, Velocity, Acceleration) is specified using TYPE parameter.

3. The curve is defined using *AMPLITUDE card.

LS-DYNA

1. The boundary condition to the rigid part is given to the part id.

2. Type of boundary condition (Displacement, Velocity, Acceleration) depends on the value of VAD

3. The curve is defined using *DEFINE_CURVE card.DYNA – Deformable Part*BOUNDARY_SPC_NODE$ NID XT YT ZT XR YR ZR 1 0 1 1 1


Loading

DYNA*LOAD_RIGID_BODY PID DOF LCID SF 4 2 2 1.0 *DEFINE_CURVE LCID SFA SFO 2 0 1.0 1.0 0.0 0.0 0 Time Multiplier 0.0 0.0 0.005 7357.5 0.025 7357.5

ABAQUS*NSET, NSET=Ref_Clamp 60027,*AMPLITUDE, NAME =Load, DEFINITION = TABULAR0.0 ,7357.5 ,0.025 ,7357.5 *CLOAD, AMPLITUDE = Load Ref_Clamp,2,1.0

ABAQUS1. The loading condition to the rigid part is given to the reference node of the rigid part.2. Different cards used to change type of loading conditions (Concentrated force - *CLOAD; Distributed force *DLOAD)3. The curve is defined using *AMPLITUDE card.LS-DYNA1. The boundary condition to the rigid part is given to the part id.2. Different cards used to change type of loading conditions (Concentrated force - *LOAD_RIGID_BODY (For Rigid

Body) / *LOAD_NODE ; Distributed force - *LOAD_SHELL / *LOAD_SEGMENT (For Solid Element))3. The curve is defined using *DEFINE_CURVE card.


Contact

DYNA*CONTACT_FORMING_ONE_WAY_SURFACE_TO_SURFACE $ SSID MSID SSTYP MSTYP 1 2 3 3 FS FD 0.1 0.01 20.0

$ SOFT 0.0/4.0$$SSID: Slave Id (can be node set, element set, part id depends on SSTYPl)$$MSID: Master Id (can be node set, element set, part id depends on SSTYPl)$$SSTYP: For Slave, 0 - Segment Set Id$$ 1 - Shell element set Id$$ 2 - Part set Id$$ 3 - Part Id$$ .....$$MSTYP: Same as Slave $$FS: Static Coefficient of friction$$FD: Dynamic coefficient of friction

Detail Information: http://www.dynasupport.com/Support/tutorial/contact.modeling

Other Contact Definitions

*CONTACT_FORMING_SURFACE_TO_SURFACE

*CONTACT_AUTOMATIC_SINGLE_SURFACE

*CONTACT_AUTOMATIC_GENERAL


Resources









Example

Problem: Measure the deflection of the block, under given pressure loading


Example

*CONTROL_


Resources









*CONTROL_TERMINATION

Only this parameter will be required in most cases.


*CONTROL_TIMESTEP

Used for Mass Scaling : Specify the time step

Use (-)time step to specify variable mass scaling

It is a new development in LS-DYNA where in by using this parameter the springback results are not affected by mass scaling. In my knowledge, it does not apply mass scaling to rigid elements and that somehow takes away the negative effects of mass scaling

*CONTROL_TIMESTEP

$$ DTINIT TSSFAC ISDO TSLIMT DT2MS LCTM ERODE MSIST

-8.0e-8

$$ IMSCL

-1 Here 1 refers to the part set id of deformable parts


*CONTROL_SHELL

For Thermal Analysis


*CONTROL_HOURGLASS

IHQ = 4 for Reduced Integration Shell Element (Section type “2”)

IHQ = 8 for Fully Integrated Shell Element (Section type “16”)


*CONTROL_CONTACT

There are 4 more cards which are optional and are rarely used


*CONTROL_IMPLICIT_GENERAL


*CONTROL_IMPLICIT_SOLVER

Use default values


*CONTROL_IMPLICIT_SOLUTION

There are 3 more cards which are optional

Use Default for ALL

If there is a convergence issue, use

ILIMIT = 1; MAXREF = 200 (recommended for springback)

DO NOT CHANGE DCTOL and ECTOL


*CONTROL_IMPLICIT_AUTO

Use Default for ITEOPT and ITEWIN

If there is a convergence issue, use

ITEOPT = 150; ITEWIN = 0 coupled with changes in *CONTROL_IMPLICIT_SOLUTION (recommended for springback)


*CONTROL_IMPLICIT_STABLIZATION

*CONTROL_IMPLICIT_STABILIZATION

$$ IAS SCALE TSTART TEND

1 0.01 0.0 1.0

Used for Springback Analysis


*CONTROL_IMPLICIT_DYNAMICSUsed for Dynamic Analysis like

Gravity Analysis

1 0.60 0.38


*CONTROL_IMPLICIT_EIGENVALUEUsed for extracting Eigen Values

Specify number of Eigen values desired


Implicit Simulation

Appendix P of the LS-DYNA 971 Manual provides useful information

R:\OnlineHelp\Tutorials-DYNA\Springback_Manual

*DATABASE_


ASCII Files


Binary Files*DATABASE_BINARY_D3DUMP

$$ DT/CYCL LCDT BEAM NPLTC

7407

With D3DUMP, cycle is specified, I.e.

If the time step is 6.75e-8 and we need to write the dump file every (0.5 ms), the value of

CYCL = time at which restart files are required X time step = 0.0005X6.75e-8 = 7407

Every 7407 cycles the restart file is written

Use option –dpf d3dump on command line while submitting the job

*DATABASE_BINARY_D3PLOT

$$ DT/CYCL LCDT BEAM NPLTC

5.0000E-04

With D3PLOT, specify the time at which state file is required

*DATABASE_BINARY_INTFOR

$$ DT/CYCL LCID

5.0000E-04

With INTFOR, specify the time at which state file is required


*DATABASE_BINARY_INTFOR


Use of INTFOR Binary Database

This database can only be opened using LS PREPOST

Output : Contact Pressure/Force/Shear Stress

Can be used to identify wrinkling (Contact Gap)

Wrinkles\Methodology_evaluate_wrinkling_gap.ppt

Wrinkles\LS_PREPOST_Wrinkles.ppt

Adaptivity


LS-DYNA: Adaptive Meshing

Elements are sub-divided into smaller elements according to the set indicators.

Most widely used indicators for metal forming process are:

Adaptive tolerance angle (ADPTOL)

Maximum level of refinement (MAXLVL)

MAXLVL :- 1 MAXLVL :- 2 MAXLVL :- 3

Change in angle :- 0

Change in angle :- ADPTOL

Change in angle :- 2 * ADPTOL


*CONTROL_ADAPTIVE

*CONTROL_ADAPTIVE$$ ADPFREQ ADPTOL ADPOPT MAXLVL TBIRTH TDEATH LCADP IOFLAG 5.000E-04 1.0 1 2$$ ADPSIZE ADPASS IREFLG ADPENE ADPTH ORIENT MAXEL 1 0.23

Please read forming_parameters2.pdf located at R:\OnlineHelp\Tutorials-DYNA\Forming_ManualFor more information on Adaptivity

Equal to blank thicknessEVERY 1 OR 2 MM OF TOOL TRAVEL


*CONTROL_ADAPTIVE_CURVE

New option in LS 971 – I have not tried this


Added Control on Adaptivity

Material Models


Material Models - Summary

Available on LS-DYNA 971 Manual pg 1401 - 1409


Material Models


*MAT_PIECEWISE_PLASTICITY (MAT_24)

Most frequently used material model to define plasticity

Specify the Failure parameter – effective plastic strain at fialure – FAIL

LCSS – defines the stress-strain curve

LCSR – can be used to incorporate strain rate effect

There are 2 more cards, which are not optional, but should be left blank if LCSS is defined


*MAT_3-PARAMETER_BARLAT (MAT_36)

Gives maximum flexibility in modelling plasticity

Define the plasticity (combination of HR, P1 and P2)

•Using stress-strain curve

•Holloman's law

•Hocket Sherby

•Stress-Strain in 3 directions

Define Anisotropy (R00, R45. R90)


*MAT_3-PARAMETER_BARLAT (MAT_36)These 3 cards are used to define rolling direction

For other AOPT options see pg 1427 of LS-DYNA 971 Manual

For Rolling direction as X-Axis, specify

A1 = 1, A2 = 0, A3 = 0


Plasticity with Damage

Failure Based on Damage Modelling

Failure Based on FLD


Other Material Models

Lot of Material Models available for

Rubber

Foam

Spring

Concrete

Tissue

*CONTACT

http://www.dynasupport.com/support/tutorial/contact.modeling


ContactSURFACE_TO_SURFACE AUTOMATIC_SURFACE_T

O_SURFACE

FORMING_SURFACE_TO_SURFACE

MasterSlave

1. Normal should point to each other 1. It checks for penetration on

both sides of the shell element so direction of normal does not matter

1. It checks for penetration on both sides of the shell element so direction of normal does not matter

2. ALWAYS takes into account thickness offset.

2. Thickness offset is considered only for SLAVE side (used in metal forming applications).

2. Thickness offset depends on parameters THKOPT Optional Card B of *CONTACT_SURFACE_

Also Parameter SHLTHK comes into picture if THKOPT = 1

THKOPT = 2

THKOPT = 1, SHLTHK = 0

THKOPT = 1, SHLTHK = 1If one of them is rigid

If both of them are rigid

If none of them are rigid


Contact

Thickness offsets are always considered for a single surface contact and constraint method type contact

ONE_WAY_SURFACE_TO_SURFACE SURFACE_TO_SURFACE

It is a one way treatment, slave surface is checked for penetration against the master surface and not the other way round

It is a two way treatment, slave surface is checked for penetration against the master surface and vice versa.

http://www.dynasupport.com/support/tutorial/contact.modeling/contact.types


Contact Card 1 (Required)

Card 1 is used primarily to define the contact surfaces/parts/nodes


Contact Card 1

SSTYP 2: I use it rarely, prefer using Segment

SSTYP 3: Parts with shell elements

SSTYP 0: It is similar to defining Surfaces in ABAQUS. I prefer to use this option while modelling contact where solid elements are involved.

Segments in Contact

SSTYP 0: Also, with shell elements if you want to distinguish between upper and lower surface.


Contact Card 2 (Required)20.0 Card 2 is used primarily to define the

friction, birth and death time of contact


Contact Card 2 (FS = -2)

Define Friction properties between these part ids


Contact Card 3 (Required)Card 3 is used,

If we need to change the penalty stiffness if there is penetration (SFS, SFM)

If we need to specify a different thickness to shell elements (SST, MST)


Contact Card 4

For some Contact types, 4th Required card is there and is different for different option,

_TIEBREAK

_CONSTRAINT

_DRAWBEAD

_ERODING

_INTERFERENCE

And few more


Contact Card A (Optional)

SOFT =1, if the contacting surfaces have wide variation in the elastic bulk moduli for eg. Metal and Foam

SOFT =2, with SBOPT 3 and DEPTH = 5 : This is used if the contacting surfaces have sharp features eg. Contact with shell edges

http://www.dynasupport.com/support/tutorial/contact.modeling/Contact.Parameters

SOFT =4, it is applicable only with _FORMING. It is similar to ABAQUS’s kinematics formulation. If adaptivity is there this contact is not robust. Also it should not be used on both sides of shell. I will not recommend this option


Contact Card B (Optional)


See Slide 54


Contact Card C (Optional)


Treatment of initial penetration in *CONTACT_AUTOMATIC


Other Contact Options

http://www.dynasupport.com/support/tutorial/contact.modeling/contact.types

_SMOOTH option is available in release 971: It converts the meshed rigid surface into smooth geometric surface (internally) I.e. no facets

_TIED is use to tie surfaces. It is recommended to use segment to define the two surfaces (SSTYP = 0)

_TIEBREAK: It can be used to model surfaces which are tied but fails when tensile stress and/or shear stress exceeds the defined values


Other Contact TYPES

*CONTACT_INTERIOR

These contact types doesn’t follow the same format (I.e. 3 required card) as explained earlier. They have different cards associated with them.

*CONTACT_2D

LS-DYNA

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