Strengths and Weaknesses of the different contact formulations available in explicit software
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Strengths and Weaknesses of the different contact formulations available in explicit software

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Strengths and Weaknesses of the different contact formulations available in explicit software Strengths and Weaknesses of the different contact formulations available in explicit software Presentation Transcript

  • Innovation Intelligence®Gérard WINKELMULLER, Chief Scientist Finite Element Analysis, Altair dev. FranceRégis LATRILLE-SEIGNEUR, Support Technical Specialist, Altair dev. FranceAltair Technical ConferenceTorino April 2013Strengths and Weaknessesof the different contact formulationsavailable in explicit software
  • Copyright © 2012 Altair Engineering, Inc. Proprietary and Confidential. All rights reserved.Summary• New contact formulation• Numerical Robustness• Numerical Sensitivity• Contact and Advanced Mass Scaling• ConclusionPGap maîtreSVt1Vt2Vt3VSt         TextTooTToTooToTextoLFFMLMbHbLbLLMHbLbLLMLLMbLMLMbMLLMFFMbdtvLbLdtvvbvLint112112111111int10,110/
  • Copyright © 2012 Altair Engineering, Inc. Proprietary and Confidential. All rights reserved.Mains contact formulation• Kinematic contact treatment• Perfect contact treatment• Lagrange multiplier• Lagrange multiplier matrix has to beinverted at each cycle• Not well adapted for explicit code• expensive• Penalty contact treatment• Linear penalty (type 24)• Approximate contact treatment• Large penetration can be observed locally• Limited time step effect• Non linear penalty (type 7)• contact treatment with smallapproximation• penetration bounded by the gap• Large time step decrease in some cases• or large mass increase with mass scalingshellshellshellsolidsolidsolid
  • Copyright © 2012 Altair Engineering, Inc. Proprietary and Confidential. All rights reserved.New contact formulation type 24• Why a new contact formulation• Interface type 7 is well adapted for shell to shell orshell to solid• Interface type 7 can only work with non zero gapvalue giving some limitations for solid to solid contact• Electronic component drop test• A mobile phone is very complex, involving many partsand often with initial penetrations• Zero gap treatment become critical here• New interface type 24 was develop to answer tothese requests and will also provide a contactformulation similar to competitor approachFront coverWindow andTouch sensorGasketButtonsLCD moduleCarrierPCBBatteryFrameScrewsBack coverSpecial thanks toFredrik NordgrenAltair Sweden
  • Copyright © 2012 Altair Engineering, Inc. Proprietary and Confidential. All rights reserved.Numerical Robustness Analysis• Robustness analysis is done on a simple CrashBox collapsed between 2 rigid walls• Medium mesh quality is used to increase potentialrobustness issues• Simulation is pushed as far as possible• Up to complete box flattening t= 15.4ms (an still more)• 3 contact formulations are compared• Kinematic with Lagrange multiplier• Type 7 non linear penalty• Type 24 linear penalty• 3 time step control are compared• Free time step (no time step control)• /DT/SHELL/CST• Small strain after 15% time step decrease (about15% strain)• /DT/NODA/CST• Mass scaling
  • Copyright © 2012 Altair Engineering, Inc. Proprietary and Confidential. All rights reserved.Numerical Robustness AnalysisT=6ms T=11.4ms T=14.6ms T=15.1ms T=16msLagrange multipliersInt7 non linear penaltyInt24 linear penaltyImpossible to invertLagrange Multiplier MatrixAfter 14.6 msTime stepdecline to zeroafter 15.2 ms
  • Copyright © 2012 Altair Engineering, Inc. Proprietary and Confidential. All rights reserved.Numerical Robustness AnalysisT=6ms T=11.4ms T=14.6ms T=15.1ms T=16msInt7 non linear penaltyInt24 linear penalty
  • Copyright © 2012 Altair Engineering, Inc. Proprietary and Confidential. All rights reserved.Numerical Robustness Analysis & time step controlInterface type 7 Interface type 24Free time step •Final time 15.2 (dt too small)•Dt: 4.6e-4 (t=0) -> 0 (t=15.2)•338000 cycles•105000 cycles at t= 14.9•Final time >16•Dt: 4.6e-4(t=0) -> 2.9e-5 (t=16)•232000 cycles•179400 cycles at t= 14.9/DT/SHELL/CSTDt = 4.e-4Small strain after about 15%deformation•Final time 15.3 (dt too small)•Dt: 4.6e-4 (t=0) -> 0 (t=15.3)•143400 cycles•43100 cycles at t= 14.9•Final time >16•Dt: 4.6e-4(t=0) -> 2.6e-4 (t=16)•45100 cycles•40900 cycles at t= 14.9/DT/NODA/CSTDT = 4. e-4Mass scaling•Final time 15. (energy error)•Dt: 4. e-4(t=0) -> 3.8e-4 (t=15)•37700 cycles•37300 cycles at t= 14.9•Final time 14.9 (mass error)•Dt: 4. e-4(t=0) -> 3.9e-4 (t=14.9)•37300 cycles•37300 cycles at t= 14.9
  • Copyright © 2012 Altair Engineering, Inc. Proprietary and Confidential. All rights reserved.CRASH_BOX Numerical Sensitivity Analysis8912 shellsInitial velocity : 5 mm/ms onRBody with free rotationaround YUsed a free time stepInterface:1 TYPE7 or TYPE24RADIOSS_DP SMP SPMD CPU time Nb_Cycles Time/CyclesTYPE7 8 1 925 226762 0.004TYPE24 8 1 771 187663 0.004• Sensitivity analysis is done on a Crash Boxconnected to an articulated rigid body and fixedat the other end• 10 runs with random noise on nodalcoordinates• maximum noise 10-6 mm• Variable seed
  • Copyright © 2012 Altair Engineering, Inc. Proprietary and Confidential. All rights reserved.CRASH_BOX Numerical Sensitivity AnalysisTYPE7
  • Copyright © 2012 Altair Engineering, Inc. Proprietary and Confidential. All rights reserved.CRASH_BOX Numerical Sensitivity AnalysisTYPE24
  • Copyright © 2012 Altair Engineering, Inc. Proprietary and Confidential. All rights reserved.CRASH_BOX Numerical Sensitivity AnalysisTYPE24TYPE7• Interface type 24 is much more sensitive than Interface type 7
  • Copyright © 2012 Altair Engineering, Inc. Proprietary and Confidential. All rights reserved.Numerical Robustness Analysis & time step controlLagrange multiplier Interface type 7Non linear penaltyInterface 24Linear penaltyContactQuality ***** **** ***NumericalRobustness * *** *****Numericalsensitivity?**** ***
  • Copyright © 2012 Altair Engineering, Inc. Proprietary and Confidential. All rights reserved.Contact formulation and Advance Mass Scaling• NEON1M14 (80ms)• 1M elements• Rigid Wall• Interface formulation• interface TYPE7 with variable gap• Interface TYPE24 (use variable gap by default)• Time step control• /DTNODA/CST dt=0.5µs (mass scaling)• AMS DT=10µs• AMS DT=20µs
  • Copyright © 2012 Altair Engineering, Inc. Proprietary and Confidential. All rights reserved.Constant nodal time step dt=0,5 µsNEON1M14 (80ms)1M elementsRigid Wall19 numbers of interfaceTYPE24RADIOSS Objective (µs) Mean time step (µs) Nb of cyclesTYPE7_Igap1 0.5 0.495 161802TYPE24 0.5 0.496 161230
  • Copyright © 2012 Altair Engineering, Inc. Proprietary and Confidential. All rights reserved.Advanced Mass Scaling dt=10 µsNEON1M14 (80ms)1M elementsRigid Wall19 numbers of interface TYPE24RADIOSS Objective (µs) Mean time step (µs) Nb of cyclesTYPE7_Igap1_AMS 10 5.43 14707TYPE24_AMS 10 9.99 8001
  • Copyright © 2012 Altair Engineering, Inc. Proprietary and Confidential. All rights reserved.Advanced Mass Scaling dt=20 µsNEON1M14 (80ms)1M elementsRigid Wall19 numbers of interface TYPE24RADIOSS Objective (µs) Mean time step (µs) Nb of cyclesTYPE7_Igap1_AMS 20 8.88 9002TYPE24_AMS 20 19.99 4001
  • Copyright © 2012 Altair Engineering, Inc. Proprietary and Confidential. All rights reserved.ConclusionLagrange multiplier Interface type 7Non linear penaltyInterface 24Linear penaltyPROS •Contact quality•Perfect kinematiccontinuity•Contact quality•Limited contact penetration•Low numerical sensitivity•Allow zero gap•Allow small initialpenetration•Robust formulation•Efficient with element timestep controlCONS •Too expensive•Not robust for crash (shellto shell contact)•Smaller time step•Not efficient with elementtime step control•Not adapted for solid tosolid contact•Possible large penetration•Possible topology contacterrors for complex meshfolding and large penetration•More numerical sensitivityOVERALL •Not recommended forexplicit•Recommended for highquality car crash simulation•Recommended forsensitivity analysis•Recommended forelectronic components droptest•Can be used for car crashsimulation (especially if AMSis used)
  • Copyright © 2012 Altair Engineering, Inc. Proprietary and Confidential. All rights reserved.Thanks You