adams接触参数.ppt

ContactModelinginADAMSToddMcDevitt,Ph.D.,P.E.,July25,2000,ProblemDescription,EOM,RigidBody2,RigidBody1,Plusunilateralcontactconditions,ContactKinematics,Gapfunction,RigidBody2,RigidBody1,R3,O,Contactbasis,UnilateralNormalContactConstraints,Kuhn-Tuckercomplimentaryconditions,nopenetration,compressivenormalcontactforce,nopenetration,noforce,persistencycondition,UnilateralNormalContactConstraints,IDEA:variationalinequalityvariationalequalityCHOICES:LagrangeMultipliersenforcesthecontactconstraintsexactlydifficulttoimplementPenaltyRegularizationintroduceserrorsintocontactconstraintseasytoimplementhasphysicalinterpretation,PenaltyRegularization,Introducethescalarquantitykn.As,theconstrainterror.,constrainterror,IMPACTFunction,IMPACT=,viscousdampingcontribution,RigidBody2,RigidBody1,IMPACTFunction,IMPACT=,workingrange,unfriendlyderivative,n1,NormalContactParameters,Fortruerigidbodycontactk=aslargeaspossiblewithoutintroducingill-conditioningn=1cmax=0,NormalContactParameters,TheIMPACTfunctionallowstheanalysttointroducealocal,1Ddeformablecontinuummodelatthecontactinterface.ConsidertheHertziansolutionfortwocontactingspheres:,RigidBody2,RigidBody1,NormalContactParameters,Acontactforcemodelwithhysteresisdampingcanalsobeconsidered.,RigidBody2,RigidBody1,Reference:H.M.LankaraniandP.E.Nikravesh,“ContinuousContactForceModelsforImpactAnalysisinMultibodySystems”,NonlinearDynamics,5:193-207,1994.,Outline,IntroductionthenclickOK.FromtheFileImportdialogbox,enterppm.cmdintheFiletoReadfieldchecktheUpdateScreenboxunchecktheDisplayModelUponCompletionbox,Workshop:PawltoGearToothContact,Youareviewingthegeartooth-parkingpawlinterfaceThemodeliscompleteexceptforacurve-to-curveunilateralcontactconstraintbetweentheREDgeartoothandtheparkingpawl.YOURTASK:createthismissingcontactconstraint.,3StepstoAutomaticContactConstraints,Definegeometry.points,curves,circles,planes,spheresDefinecontactforceelement.Selecttypeofcontactmanifold,i.e,plane,curve,etc.Identifycontactmanifolds.Verifyoutwardnormals.Definecontactforceparameters.Definenormalandfrictionalforceparameters.,Workshop:PawltoGearToothContact,CreatesurrogatesplineAccessGeometricModelingpanel.Build-Bodies/GeometriesSelecttheSplinetool.Addaclosedsplinetoanexistingpart.Pickthebody:gear.Pick8arbitrarypointswiththeleftmousebutton.Create(end)withrightmousebutton.,Workshop:PawltoGearToothContact,EditsplineAccessModifyGeometricSplinepanel.Rightclickonsurrogatespline.SelectBspline:GCURVE_27471-Modifyfromthecascadingmenus.,Workshop:PawltoGearToothContact,EditsplinecontrolpointsClickontoaccesspointLocationTable.Clickonandselectfilebspline_t8.dat.ClickonOKintheLocationTablepanel.,Before,After,Remark:Curvedatamustbeinx-yplanerelativetoreferencemarker.,Workshop:PawltoGearToothContact,EditsplineClickontorecalculatesegments.Changereferencemarkerto.park.gear.MAR4197223.ClickonOKintheModifyGeometricSplinepanel.,Workshop:PawltoGearToothContact,ModifysplinetensionBuild-DataElements-Curve-Modify.SelectCURVE_3fromtheDatabaseNavigator.ChangetheTensionfieldfrom0.05to7.ClickonOK.,3StepstoAutomaticContactConstraints,Definegeometry.points,curves,circles,planes,spheresDefinecontactforceelement.Selecttypeofcontactmanifold,i.e,plane,curve,etc.Identifycontactmanifolds.Verifyoutwardnormals.Definecontactforceparameters.Definenormalandfrictionalforceparameters.,Workshop:PawltoGearToothContact,Accessthe“CreateContactForce”panelZoomin/outuntilredtoothandpawlarevisible.FromtheMainToolbox,fromtheCreateForcestoolstack,selecttheContactforcetool.,Workshop:PawltoGearToothContact,CreateContactForcepanelSelecttypeCurvetoCurve.RightclickintheFirstCurvefield,selectBspline-Guesses-GCURVE_27471fromthecascadingmenus.RightclickintheSecondCurvefield,selectBspline-Pick.ThenrightclicknearthePawl.Fromthepop-upSelectpanel,choosePawl.GCU14496.,Workshop:PawltoGearToothContact,ExamineoutwardnormalsonBsplinesZoominontooth.Notethatthewhiteoutwardnormalonpark.gear.GCURVE_27471isinoppositedirection.NegateitwiththeoutwardnormaldirectionswitchtoolZoominonpawl.Notethatoutwardnormaliscorrect.,3StepstoAutomaticContactConstraints,Definegeometry.points,curves,circles,planes,spheresDefinecontactforceelement.Selecttypeofcontactmanifold,i.e,plane,curve,etc.Identifycontactmanifolds.Verifyoutwardnormals.Definecontactforceparameters.Definenormalandfrictionalforceparameters.,Workshop:PawltoGearToothContact,CreateContactArrayRightmouseclicktheContactArrayfield;selectcontact_array-Create.FillouttheCreateContactArraypanelasshown.ClickOKonCreateContactArraypanel.ClickOKonCreateContactForcepanel.,Workshop:PawltoGearToothContact,SimulatemodelFromthemainmenu;selectSimulate-ScriptedControls.VerifythattheSimulationScriptNamefieldreadspark.SIM_SCRIPT_1.ClickontheStartsimulationbutton.Whentheanalysisiscomplete,reviewtheanimation.Clickontheanimationtool.Clickonthe“animation:forward”button.,Outline,Introductionincreaseuntilinsignificantdeviationinresultsorspecificstiffnessvaluesaremet.,NumericalIssues&Debugging,TimeintegrationUsesmalltimesteps,decreaseHMAX.improvescontactdetectionalgorithmsimprovespredictorandconvergencebehaviorUseSI2.SI2employsvelocityerrorcheckingSI2isgenerallymoreexpensive,Outline,Introduction&MotivationTheoreticalBackgroundContactModelinginADAMS/VIEWWorkshop:PawltoGearToothContactFrictionNumericalIssues&DebuggingContactModelsConcludingRemarks,ADAMSContactElementsAchievements/Shortcomings,Achievementsrobust2Dcontactcapabilityimprovedcontactsearchanddetectionalgorithmspointtocurveplanetocurvecircletocurvecurvetocurvemulti-pointcontact,boundariesnolongerneedtobeconvexintegrationwithADAMS/Viewforeasytousepre-andpost-processing,Shortcomingssimplisticfrictionmodel,nostictionlimited3Dcontactfeatures(addressedinADAMS11.0