Explicit-Dynamics-Chapter-8-Analysis-Settings

1-1ANSYS,Inc.Proprietary©2009ANSYS,Inc.Allrightsreserved.February27,2009Inventory#002665Chapter8ExplicitDynamics:AnalysisSettingsANSYSExplicitDynamicsExplicitDynamics:AnalysisSettings1-2ANSYS,Inc.Proprietary©2009ANSYS,Inc.Allrightsreserved.February27,2009Inventory#002665TrainingManualAnalysisSettings•AnalysisSettingsaregroupedinsixcategories–StepControls–SolverControls–DampingControls–ErosionControls–OutputControls–AnalysisDataManagement•Specifiesdirectorywhereprojectdatawillbestored•EndTimeistheonlyrequiredinput–AllotheroptionshavedefaultsExplicitDynamics:AnalysisSettings1-3ANSYS,Inc.Proprietary©2009ANSYS,Inc.Allrightsreserved.February27,2009Inventory#002665TrainingManualStepControls•SolveInitiation–ResumeFromCycle•Specifiesthecycle(timestep)fromwhichtostarttheSolve.–Default(cycle0)istostartatthebeginning(timezero).•Whenresumingasimulation,changestoanalysissettingswillberespectedwherepossible.–e.g.youoftenwishtoresumeasimulationwithanextendedEndTime.•Changestoanyotherfeaturesinthemodel(geometrysuppression,connections,loads,etc….)willnotberespected.•Listofcyclesfromwhichtoresumewillonlybepopulatedifaprevioussolvehasbeenexecutedandrestartfilesgenerated.•SolveTermination–MaximumNumberofCycles•Specifiesthemaximumnumberofcycles(timeincrements)allowedforthesimulation.–Thesimulationwillstoponcethespecifiedvalueisreached.–Enteralargenumber(default)toensuresimulationrunstotheEndTime.–EndTime(nodefault)•Definesthetimescalethatyouwantthesimulationtorun.•Enterareasonableestimateforthisparametersinceitcontrolsthelengthoftimethesimulationwilltaketorun.•Usedinotherpre-processingobjects(suchastabularloads)andalsotodefinethescaleforChartoutputofresultsobjects.ExplicitDynamics:AnalysisSettings1-4ANSYS,Inc.Proprietary©2009ANSYS,Inc.Allrightsreserved.February27,2009Inventory#002665TrainingManualStepControls•MaximumEnergyError–SolutionstopsiftheenergyerrorexceedstheMaximumEnergyError(expressedasafraction)ReferenceEnergy=InternalEnergy+KineticEnergy+HourglassEnergyCurrentEnergy=InternalEnergy+KineticEnergy+HourglassEnergyWorkDone=Workdonebyconstraints+Workdonebyloads+Workdonebybodyforces+Energyremovedfromsystembyelementerosion+Workdonebycontactpenaltyforces•ReferenceEnergyCycle–Definesthecycleatwhichthesolvercalculatesthereferenceenergy•Usuallythestartcycle(default)ExplicitDynamics:AnalysisSettings1-5ANSYS,Inc.Proprietary©2009ANSYS,Inc.Allrightsreserved.February27,2009Inventory#002665TrainingManualStepControls•ExampleenergyconservationgraphformodelwithsymmetryplaneanderosionExplicitDynamics:AnalysisSettings1-6ANSYS,Inc.Proprietary©2009ANSYS,Inc.Allrightsreserved.February27,2009Inventory#002665TrainingManualStepControls•TimeStepControls–InitialTimeStep•IfleftonProgramControlled(recommended),theinitialtimestepwillbeautomaticallysetto½thesmallestinitialelementstabilitytimestep–MinimumTimeStep•Ifthetimedropsbelowthisvaluethesimulationwillstop•IfleftonProgramControlled(recommended),thevaluewillbesetto1/10ththeInitialTimeStep–MaximumTimeStep•Solverwillusetheminimumofthisvalueorthecomputedstabilitytimestep•ProgramControlledisrecommended–TimeStepSafetyFactor•Safetyfactorisappliedtothecomputedstabilitytimestep–Default(0.9)shouldworkformostsimulationsExplicitDynamics:AnalysisSettings1-7ANSYS,Inc.Proprietary©2009ANSYS,Inc.Allrightsreserved.February27,2009Inventory#002665TrainingManualStepControls•AutomaticMassScaling–Massesinsmallerelementsarescaleduptoincreasethetimestepusedinthesimulation–Additionalinputisrequiredforthisoption•MinimumCFLTimeStep–MinimumCFLtimesteptobeobtainwithmassscaling•ShouldbelargerthattheobservedCFLtimestep•MaximumElementScaling.–Limitstheratioofscaledmass/physicalmassthatcanbeappliedtoeachelementinthemodel.•Ifthisratioisexceeded,thesimulationwillstopwithanerrormessage.•MaximumPartScaling–Limitstheratioofscaledmass/physicalmassthatcanbeappliedtoanindividualbody.•Ifthisratioisexceeded,thesimulationwillstopwithanerrormessage.•UpdateFrequency–Thefrequency(incycles)thatmassscalingisperformed.•Avalueofzero(default)meansmassscalingisonlydoneonce,atthestartofthesimulation•Caution!MassscalingintroducesadditionalmassintothesystemtoincreasetheCFLtimestep.Introducingtoomuchmasscanleadtounphysicalresult.ExplicitDynamics:AnalysisSettings1-8ANSYS,Inc.Proprietary©2009ANSYS,Inc.Allrightsreserved.February27,2009Inventory#002665TrainingManualSolverControls•SolveUnits–Theunitsthesolverwilluseforthesimulation•Foraccuracy,only(mm,mg,ms)areallowed•Differentunitscanbeusedtosetupproblemsandviewresults.•BeamSolutionType–Bending(default,mostaccurate)–Truss•BeamTimeStepSafetyFactor•HexIntegrationType–Exact(default,mostaccurate)–1ptGauss(faster)•ShellSublayers–UsedtocomputeStressResultantsandBendingMoments–Default(3)usuallyprovidessufficientaccuracyExplicitDynamics:AnalysisSettings1-9ANSYS,Inc.Proprietary©2009ANSYS,Inc.Allrightsreserved.February27,2009Inventory#002665TrainingManualSolverControls•ShellShearCorrectionFactor•ShellBWCWarpCorrection•ShellThicknessUpdate–Nodal–Elemental•TetPressureIntegration–AverageNodal–Constant•ShellInertiaUpdat