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A REPORT

ON

HYPERCRASH AUTOMATION

BY

RAHUL ROCHLANI 2011A4PS289H

AT

Altair Engineering India Pvt. Ltd., Bangalore

A Practice School-II station of

BIRLA INSTITUTE OF TECHNOLOGY AND SCIENCE, PILANI

(May-July, 2013)

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ACKNOWLEDGEMENT

Through this report, I would like to express my heartiest thanks to the all

those who have contributed in the materialization of the project. I would

like to thank our university B.I.T.S, Pilani for giving me the opportunity

to help me carry out our training at Altair Engineering India Pvt. Ltd,

Bangalore. I am grateful to Dr. P B Venkataraman who has constantly

supported and encouraged me to pursue this project work actively,

suggesting areas of improvement.

A special note of thanks to Mr. Ravi Chinthapalli, my team manager,

who has given me an extremely resourceful opportunity of working on

this challenging project. This project is entirely an outcome of his ideas.

I would always be grateful for all that he has taught me in the past three

months. This project work would not have been possible without his

guidance and patience with me.

Finally, my heartiest gratitude to all my friends in the company with

whom I have had many long enlightening discussions.

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Table of Contents:

Acknowledgement………..……….2

Abstract……………………..…..…4

Introduction…………………….....5

Computer Aided Engineering…......6

HyperCrash Introduction……...…..8

HyperCrash Automation..………..11

CONCLUSION..…………………17

BIBLIOGRAPH.…………………18

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ABSTRACT

Altair’s HyperCrash product provides support to various CAE solver

interfaces grouped under different applications. This is mainly to cater to

variety of target customer’s needs. In the Crash simulation category,

Altair currently provides support to RADIOSS and LS-Dyna solvers.

This project majorly deals with automation of HyperCrash through batch

mode, i.e., invoking HyperCrash without the graphical user interface,

creating and modifying HyperCrash entities. The basic purpose of the

training aims at building code to take input in the form of an XML file,

parse the input, perform the tasks specified by running HyperCrash in

batch-mode and generate an output file. Invoking HyperCrash through

batch mode is not common as of now but a few years down the line it is

going to become prominent as it is a more efficient way of invoking

crash models.

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Introduction

Crash simulations are used by all Computer Aided Engineering (CAE)

users during their analysis for crashworthiness in the Computer-aided

design (CAD) process of modelling new components. Most automobile

and aircraft makers utilize different solvers for performing Crash

simulation on their vehicle designs to ensure the safety of its vehicle

passengers during a crash. Commonly used solvers are RADIOSS, LS-

Dyna, Pamcrash etc. RADIOSS and Pamcrash are generally used by

automakers while LS-Dyna is used by many Aircraft makers.

Hyperworks provides an interfacing to all such solvers for pre & post

processing of the CAD models.

HyperCrash is a robust pre-processing environment specifically

designed to automate the creation of high-fidelity models for crash

analysis and safety evaluation. It supports various solvers out of which

most important are LS-Dyna and RADIOSS.

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Computer Aided Engineering

Computer-aided engineering (CAE) is the broad usage of computer

software to aid in engineering analysis tasks. It includes Finite Element

Analysis (FEA), Computational Fluid Dynamics (CFD), Multibody

dynamics (MBD), and optimization.

CAE tools are very widely used in the automotive industry. In fact, their

use has enabled the automakers to reduce product development cost and

time while improving the safety, comfort, and durability of the vehicles

they produce. The predictive capability of CAE tools has progressed to

the point where much of the design verification is now done using

computer simulations rather than physical prototype testing. CAE

dependability is based upon all proper assumptions as inputs and must

identify critical inputs (BJ). Even though there have been many

advances in CAE, and it is widely used in the engineering field, physical

testing is still used as a final confirmation for subsystems due to the fact

that CAE cannot predict all variables in complex assemblies (i.e. metal

stretch, thinning).

CAE Process:

A typical CAE process comprises of pre-processing, solving, and post-

processing steps. In the pre-processing phase, engineers model the

geometry and the physical properties of the design, as well as the

environment in the form of applied loads or constraints. Next, the model

is solved using an appropriate mathematical formulation of the

underlying physics. In the post-processing phase, the results are

presented to the engineer for review.

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Preprocessing:

This step comprises input of required data in the CAE software.

The required data comprises of the following

Geometry: The computational domain is specified (drawn)

for the software.

Governing Equations: The set of mathematical equations

used to solve the problems are defined.

Boundary conditions: The appropriate boundary conditions

correspond to each governing equation being solved.

Initial conditions: These include velocity, acceleration and

other initial properties.

Properties: The material properties (such as thermal

conductivity, density, etc) needed for the problem are

specified.

Meshing: In this step the model is divided into small simple

shapes called elements.

Time steps: For time dependent problems the time step

increment and time over which problem needs to be solved

are defined for the solver.

Approach for solving algebraic equations: Out of the

available equations which one to choose is defined in this

step.

Tolerances: This is set to control the error in the output.

Analysis: This step is typically automated and performed based

on input provided in preprocessing. The governing equations are

transformed into algebraic equations and solved for unknown

variables.

Postprocessing: This step involves visualization of the results

obtained by analysis.

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HyperCrash Introduction

Preprocessing for RADIOSS Crash Analysis

HyperCrash is a pre-process for RADIOSS which is tailored to meet

the needs of automotive crash users. HyperCrash enables the users to

build the highest quality model, with significant decrease in modeling

time, and with highest level of homogeneity. Also, HyperCrash has

an Automotive Safety module which consists of the following tools:

Dummy Positioner, Seatbelt Generator, Airbag Folder and Seat

Deformer. HyperCrash has various quality checks, including it most

powerful intersection/penetration checking and fixing routine, which

enables the users to setup a model that is perfectly consistent with the

RADIOSS solver. HyperCrash has built-in automated routines that

allow the users to significantly reduce the modeling time. Also, it

allows the users in a specific group to build a homogeneous model by

allowing these users to access the same databases like materials,

properties, spot-weld connections, dummies, barriers, same checks

and etc.

Various Entities supported in Hypercrash

The Hypercrash GUI(Graphical User Interface) is designed to support

all the entities that should be defined for RADIOSS and LS-DYNA

solvers. These include the following:

Node: A node is a coordinate location in space where the

degrees of freedom (DOFs) are defined. The DOFs for this point

represent the possible movement of this point due to the loading

of the structure. The DOFs also represent which forces and

moments are transferred from one element to the next. The

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results of a finite element analysis, (deflections and stresses),

are usually given at the nodes.

Elements: An element is the basic building block of finite

element analysis. There are several basic types of elements.

Which type of element for finite elements analysis that is used

depends on the type of object that is to be modeled for finite

element analysis and the type of analysis that is going to be

performed.

Parts: Many elements combined with nodes form a part.

Assembly: An assembly is a collection of parts which have

some contacts and relative motion.

Contact: A contact is a connection defined between two two

parts one of which is master and other of which is slave.

Materials: A material is the substance of which the part is

made. Materials have different properties.

Initial velocity: This is the initial velocity of the part or

assembly to which it is applied.

Control cards: These are the various cards which control the

outcome of the result.

Time history: This entity contains the behavior of different

entities like nodes and elements at different time steps.

These entities have certain properties which are called attributes. Every

time an entity is created its properties need to be defined. Various

properties have their type defined for example Poisson ratio has a type

float so the block containing Poisson ratio value is set to throw an error

when any other type of value such as string is defined in it.

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Entities are defined in deck

Here entities have various attributes i.e. properties like material

defined in the first deck has MID, RHO, E, PR, VP.

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HyperCrash Automation

Hypercrash automation means calling hypercrash in batch mode by

using a batch file, taking an input using an XML file, performing

tasks specified on a model file and giving an output file.

Automation means coding to run the tasks automatically and reduce

the human effort to repeatedly perform same task on different models.

By hypercrash automation for reading and executing the code, same

XML input file can be used for different model files and the user will

not have to repeat the same tasks in GUI for those models.

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Input XML file

In the xml file above there are various tasks specified. Every task has

a title and an ID which can be used to refer to that task. Apart from

title and id every task has an action. An action is the command i.e.

what has to be done. There are currently four actions defined in the

code:

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1. Create: This action as implied by its name is used to create

entities. While creating entities the user has to give ID, Title and

type as the input. Id can be given as “-1” then the program will

assign the next available Id to the created entity. Type means

fulltype of the entity which has to be created.

For instance for a LS-DYNA material 24 the fulltype will be :

/MAT/MAT_024.

<TASK Title=”TASK1” ID=”-1” Action=”Create”>

<Entity Title=”Automation_Entity” ID=”-1”

Type=”/MAT/MAT_024”>

<\TASK>

2. Edit: This action is used to modify the entities which were

already there or even the entity which is created in the same

XML. While editing an entity, user has to give entitybytype or

entitybytitle which decides the search method for the

entity,setattrib, and skeyword. If there is entitybyid and id is

given as current then the modification will be done in the entity

created in current XML.

<SetAttrib Value=”2.32” Skeyword=”AREA”/>

<SetTabAttrib Value=”2.32” Skeyword=”AREA”/>

<SetTabAttribValue Value=”2.32” Skeyword=”AREA”/>

SetAttrib is used for single values of properties. SetTabAttrib is

used for dynamic arrays of attributes which take input in terms

of values. And finally SetTabAttribIndex is used for static

arrays which have fixed index numbers.

Static arrays have a fix number of members and their size

cannot be modified, while dynamic arrays are the ones which

are flexible and have a variable size.

Skeyword is the variable name for the property to which the

modification has to be applied.

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Value is the value of the property to which the modification has

to be applied.

The SetTabAttrib instruction will allow to fill fully an array

attribute : so the values will given as an enumeration in CDATA

block : 0.,1.,2.,…,5. The dots … mean that the value will

increase by one given up to last value. For instance in the

enumeration 0.,1.,2.,….,5. used for filling an array of 10

elements : 0. 1. 2. 3. 4. 5. 0. 0.

SetTabAttribIndex instruction will enable to fill value at

selected index(es) array. Index={indexes} will give the indices

to fill :

it may be an enumeration,

a rangenumeration of ranges.

Enumeration : 0,1,5, 9

Range : 0-3,4,5-6,7-9

The values will be filled accordingly to the specification of the

indexes.

3. Delete: These instructions will allow deleting entities, including

Parts, elements, node and groups. When HC will execute them,

it will call Remove_MCDS functions.

<TASK Title=”TASK1” ID=”-1” Action=”Delete”>

<EntitybyTitle>< Title=”Automation_Entity” ID=”-1”

Type=”/MAT/MAT_024”> <\EntitybyTitle>

<\TASK>

For deletion user has to give task action as delete, entitybyid or

entitybytitle same as in edit and title and type. The type that has to be

input here needs to be just the basic type and not the full type.

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Batch file used

The figure shows the batch file for LS Dyna solver. The last line of the batch

file is the command line arguments where nowindow means without opening

the HC window after -file is the path of the model on which the checks are to

be performed and after exec-file is the path of the XML file and after odyn is

the path of the exported file.

Now, we can compare the new exported model to the previous ones so as to

check whether the new entities are created or not. Fig 15 in the next page

clearly shows the difference between the models. A few new entities have

been created like data base history nodes , materials etc. .The values for

different attributes have also been assigned.

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Comparing model files

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Conclusion

Crash simulations have been an important part of CAE analysis,

performed by most of the CAE users to ensure crashworthiness of its

vehicles. Almost all automakers and aircraft manufacturers perform a

destructive crash test using different CAE solvers like RADIOSS, LS-

dyna, Pamcrash etc. in order to examine the level of safety of their

vehicles and its occupants during a crash.

Automation is a growing area and more and more companies are

adopting automation to do their work faster and more efficiently. In this

project software automation is used but there can be automation of

various other physical processes. The basic advantage of automation is

that it can increase the efficiency by reducing the time and effort

required for the task and also by reducing the possibility of error.

Automated tasks can be performed by less skilled workers also as just

pressing the button is much easier than doing the whole process.

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Bibliography

Wikipedia- “Altair Engineering”,

http://en.wikipedia.org/wiki/Altair_Engineeing

Wikipedia- “Computer Aided Engineering”

LS-DYNA manual

Hypercrash-Introduction manual