1

PresentationPresentation of PAMof PAM--CRASH v2004 CRASH v2004

Part 1: Part 1: SolverSolver NewsNews..

2

OverviewOverviewNew Options

ElementsMaterialsOthers

QualityNumerical precision and robustness

3

CRASH/SAFE 2G EvolutionCRASH/SAFE 2G Evolution

V2002:Basic reengineeringCommon source SMP/DMP solver

V2003:DMP PerformanceFull DMP (implement missing SAFE-options)

V2004:QualityNumerical robustness

4

CRASH/SAFE 2G EvolutionCRASH/SAFE 2G Evolution

26 31 48 70 90 138175250

320

575

735766

0100200300400500600700800900

V11.0

V11.1

V12.0

V94 V95 V96 V97 V98V20

00V20

02V20

03V20

04Lines (K)

Pam Solid core library Sources:10000 pages 2800 files31.8 Mbyte

5

OverviewOverview

New OptionsElementsMaterialsOthers

QualityNumerical precision and robustness

6

New 4 Node TetraNew 4 Node Tetra

New ‘real’ 4-node tetra element in V2004Implemented for all solid material lawsOne integration point, hourglass freeFaster then degenerated Hexa

Hourglass control is skippedOnly 4 nodes are treated

Degenerated 4-node Hexa not accepted by default

Highly recommended for compressible materials:Foam, Honeycomb

Good for compressible elastic (i.e. MTYPE 1 – elastic)Don’t use for incompressible materials (locking occurs)

Elastic-plasticRubber

7

New 4 Node TetraNew 4 Node Tetra

Foam example:Impactor on foam blockHexa (SOLID / ), 10-node tetra (TETRA / ) and 4-node tetra (TETR4 / ) give slightly the same resultDegenerated Hexa is too soft

8

New 4 Node TetraNew 4 Node Tetra

Elastic-plastic exampleTension testHexa (SOLID / ), 10-node tetra (TETRA / ) and 4-node tetra (TETR4 / ) give slightly the same result for elastic domainDegenerated Hexa is too softFor Plasticity TETR4 is too stiff (locking)

9

OverviewOverview

New OptionsElementsMaterialsOthers

QualityNumerical precision and robustness

10

MaterialsMaterials

New materialsMATER 121 – nonlinear visco-elastic materialMATER 128 – anisotropic elastic-plastic material with failure criteria (MATFEM)

Enhanced materialsStiffness proportional damping for all solid materialsInitial equivalent plastic strain for elastic-plastic shell materialsMATER 105/106 – element elimination controlMATER 107 – optional FLD per integration pointMATER 108 – added orthotropic elastic behaviorMATER 223 – user rupture model

11

Shell: MTYPE 121Shell: MTYPE 121

G’Sell modelInitially meant for plastics forming

Visco-elastic modelFor CRASH/SAFE: Temperature dependency is inactive

Validated by with U. of Valenciennes & Visteon

springspring NLNL--damperdamper

ve ε+ε=ε

ve σ=σ=σ

ee Eε=σ

vv εη=σ

withwith

( ) 1mp2p2p1w hh1e1K p −ε− εε+ε+⎟

⎠⎞⎜

⎝⎛ −=η

ww

KKmm

hh22hh

11

12

Shell: MTYPE 128Shell: MTYPE 128

MATFEM’s CRACH Library (Optional)Model takes into account different rupture mechanismsAccounts process historyValidated for HSS & Aluminum sheet metal (BMW)Parameter identification methodology developed by MATFEM

Availability:As an option in PAM-CRASH 2004 and special versions of PAM-STAMP 2001.PAM-STAMP 2G: planned for version 2005

13

Stiffness Proportional Damping Stiffness Proportional Damping for Solidsfor Solids

Stability improvementsDamp out artificial numerical noiseVery good experiences for shell structuresHighly recommended for solids tooto be use by default

Enhances dynamics behavior of materials

Instability without stiffnessInstability without stiffness--proportional dampingproportional damping

Critical example:very large displacementssingle precisionnot for typical crash cases

14

Initial equivalent plastic strainInitial equivalent plastic strain

Initial equivalent plastic strainImplemented for all elastic-plastic shell Material modelsUser imposed value on PART cardCould be used for:

investigation of pre-straining in an early stage (no stamp results are available)parametric studies of pre-strain influence

15

Initial equivalent plastic strainInitial equivalent plastic strain

Example:

16

Elimination MTYPE 105/106Elimination MTYPE 105/106

New optional element elimination control for material type 105 and 106:

Default: element eliminated if ALL integration points over thickness reached the strain criterion

Problem: no elimination in pure bendingV2004 new and optional:

element eliminated if ONE integration point is beyond the criterion.The default remains as in previous versionsNew elimination criteria activated by a flag on the material card

17

Elimination MTYPE 107Elimination MTYPE 107

New optional element elimination control for material type 107:

Default:FLD criterion is evaluated on the middle integration point

Problem: FLD don’t see bendingV2004 new and optional:

Criterion is evaluated at each thickness integration pointFails when the FLD curve is reached in one integration pointThe default remains as in previous versionsNew elimination criteria activated by a flag on the material card

18

Orthotropic Elastic Orthotropic Elastic MTYPE 108MTYPE 108

Optional orthotropic elastic behavior is available for Shell element Material type 108

Orthotropic elasticity input by:Either, given orthotropic elastic moduliOr, by extrapolating the coefficients of the orthotropic plasticity law (Hill).

Applications:short fibers sheet molding compounds (SMC)orthotropic elasticity represents:

Proper elastic loadingProper unloading

19

Other Material enhancementsOther Material enhancements

User rupture for 223 Dynamic shared object (as user mat)For modeling spot welds or other 1-D entities which needs high customized failure lawAccess to all 6 DOF’s

DeformationVelocity

MAT 301 for ELINKUser defined sharp angleTo be imposed on PART cardDefault 60° (was fixed in previous versions)

20

OverviewOverview

New OptionsElementsMaterialsOthers

QualityNumerical precision and robustness

21

LINCOLINCO

Linear constraint optionLinear imposed relation for two nodesCan couple different DOFs

Translation X with translation XRotation Y with rotation ZATTENTION translational and rotational DOFs could not be coupled!

Could be used to do simple mechanism:Steering columnThrottle

ATTENTION not compatible with other constraint options

22

Contact PressureContact Pressure

Crash Contacts are focused on:Maximum contact stiffness to avoid penetrationMaximum numerical robustness

Drawback:Contact pressure computation is not exact!!!Why?

Contact stiffnessNodal area

V2004: flag to get precise contact pressure (IPCP flag)Implemented for contact type 33, 34, 36, 44, 54Useful for applications:

Pressure depended frictionPrecise contact pressure output

Don’t use it for std. CRASH/SAFE applications

23

Contact PressureContact Pressure

Example IPCP:Solid cube loaded to get constant pressure

For solid elementsFor contact

Without IPCP

With IPCP

24

Job InteractionJob Interaction

New signal file actionsManage computer resources with running jobs SLEEP

echo SLEEP > signal puts computation into sleep mode

RESUMEecho RESUME > signalreactivates computation

Compatible with SMP and DMP

25

Input/Output EnhancementsInput/Output Enhancements

Default FILE name changed: no FILE keyword:Name of input deck without path and extension is used for all output files

DSY,THP, Plot dumpRestart*.msg, *.LIS, …

Advantage: copied and modified input will not overwrite old resultsUse optional keyword: FILE to keep backward compatibility

26

Input/Output EnhancementsInput/Output Enhancements

Initial mass scaling contourAttention!

Static variable (constant over time)Increase DSY file without delivering additional information

Use for data check to check mass increaseDeactivate for final run

Output listing clean-upName reprint for all optionsNumbers and IDs are printed I8Format improvements…

27

OverviewOverview

New OptionsElementsMaterialsOthers

QualityNumerical precision and robustness

28

Plink RobustnessPlink Robustness

PLINK precision enhancementsSignificant improvement for single precision

Very stiff plinksMany cycles

Less numerical noiseMore stable

2003 2004

Bumper Test

29

Contact Energy ComputationContact Energy Computation

Total energy may not constant for Airbag casesContact identified as problemTwo contributions missing in previous versions

Contact damping workEnergy absorption for kinematic iterations

Improved for V2004

30

Other Numerical ImprovementsOther Numerical Improvements

Rigid body algorithmRigid body with initial velocity may generate high acceleration peak in cycle 1Problem happens in single precision onlyRound off and numerical precision problemCompletely solved in V2004 with internal reorganization of the equations to be less round off sensitive