讲义说明讲稿iabu

Lessoncontent:IntroductionTieConstraintsRigidBodiesCouplingConstraintsShell-to-solidCouplingConnectorElementsFasteners Demonstration12:DefiningaRigidBodyWorkshop12:TieConstraints:PumpModelLesson12:ConstraintsandConnections3hoursIntroduction(1/7)Constraintsvs.connectionsConstraintsallowyoutomodelkinematicrelationshipsbetweenpoints.Examplesofconstraintsinclude:TieconstraintsRigidbodyconstraintsCouplingconstraintsShell-to-solidcouplingConnectionsmodelactualconnectionsbetweenparts,suchas:balljoints,springs,dampers,bushings,links,hinges,spotwelds,rivets,adhesives,bonds,etc.Examplesofconnectionsinclude:ConnectorelementsMesh-independentfastenersIntroduction(2/7)TieconstraintsAllowyoutofusetogethertworegionseventhoughthemeshescreatedonthesurfacesoftheregionsmaybedissimilar.Tieconstraintsusedtojoinameshcontaininghexahedralandtetrahedralelements.NotallhexmeshableIntroduction(3/7)RigidbodyconstraintsAllowyoutoconstrainthemotionofregionsoftheassemblytothemotionofasingle(reference)point.Usedtomodelpartswhicharemassiveandstiffcomparedtootherbodiesintheassembly(e.g.,toolsinaforminganalysis).RollingofasymmetricI-sectionRollersaremodeledasrigidIntroduction(4/7)CouplingconstraintsCouplinginteractionsprovideacouplingbetweenareferencenodeandthenodesonasurface(thecouplingnodes).Thecouplingtypecanbeeitherkinematicordistributing.Typicalapplications:ApplyingloadsorboundaryconditionstoamodelModelingendconditionsModelinginteractionswithotherconstraints,suchasconnectorelementsbeamconnectorelementregiononsurfaceofthesolidoverwhichtheconnectortransfersloadingIntroduction(5/7)Shell-to-solidcouplingCouplesthemotionofashelledgetothemotionofanadjacentsolidfaceIntroduction(6/7)ConnectorelementsConnectorelementsmodeldiscrete(point-to-point)physicalconnectionsbetweendeformableorrigidbodiesRigidmulti-bodymechanismwithconnectorelementsIntroduction(7/7)FastenersMesh-independentfastenersallowyoutoconvenientlydefinepoint-to-pointconnectionsbetweensurfaces.Fastenerscanmodelspotwelds,rivets,screws,bolts,orothertypesoffasteningmechanisms.FastenersFastenersTieConstraints(1/4)Thetieconstraintprovidesasimplewaytobondsurfacestogetherpermanently.Easymeshtransitioning.Surface-basedconstraintusingamaster-slaveformulation.Theconstraintpreventsslavenodesfromseparatingorslidingrelativetothemastersurface.tieconstraintsTieConstraints(2/4)Example:TubecrushproblemBotTubeBotPlateThebottomofthetubeisattachedtothebottomplateviatieconstraints.TieConstraints(3/4)Surface-basedconstraint.(Canselecteitherpredefinedsurfacesorregionsdirectlyintheviewport.)Slavenodescanbemovedontothemastersurfaceintheinitialconfigurationwithoutanystrain.Onlyslavenodeswithinthisdistancefromthemastersurfacearetiedtothemastersurface.Bothtranslationalandrotationaldegreesoffreedomcanbeconstrained.Warningswillbeissuedinthedata(.dat)fileforthesenodes.Edit

Constraint

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boxTieConstraints(4/4)Donotapplyboundaryconditions,equations,orMPCstotheslavenodesofatieconstraint.Thiswillcausethenodestobeoverconstrained,resultinginerrorsintheanalysis.Symptoms:ZeropivotwarningsintheJobDiagnostics

dialogboxandthemessage(.msg)fileinAbaqus/Standard.DeformationwavespeederrorsinAbaqus/Explicit.RigidBodies(1/8)Abaqushasageneralrigidbodycapability.Arigidbodyisacollectionofnodesandelementswhosemotionisgovernedbythemotionofasinglenodecalledthe“referencenode.”Anybodyorpartofabodycanbedefinedasarigidbody.Arigidbodycanundergoarbitrarilylargerigidbodymotions.Rigidbodiesarecomputationallyefficient.Theirmotionisdescribedcompletelybynomorethansixdegreesoffreedom.Therearenoelementcalculationsforelementsmakinguparigidbody.Modelabodyasrigidifitismuchstifferthanotherbodieswithwhichitwillcomeincontact;forexample,diesinametalformingsimulation.RigidBodies(2/8)Thegeometryoftherigidbodyisdefinedby:

Meshingthebodywithnodesandelements(discreterigidbody)

Eitherdeformableorrigidelementtypescanbeused or

Revolvingorextrudingatwo-dimensionalgeometricprofile(analyticalsurface)RigidBodies(3/8)Example:TennisracketframeTheframeismodeledwithS4Relements.EditConstraint

dialogboxAbaquswillusethemassdistributionfromtheelementsmakinguptherigidbodytodeterminethecenterofmass.RigidBodies(4/8)Arigidbodydefinitionconsistsof1referencepoint

andatmost:1regionofelements1regionoftienodes1regionofpinnodes1analyticalsurfaceEachrigidbodydefinitionmustbeunique.Rigidbodydefinitionsmaynotsharenodes,elements,orreferencenodes.RigidBodies(5/8)Pinvs.TienodesdeformablerigidFinalconfigurationaftercounterclockwiserotationthrough45ºtienodepinnodeInitialconfigurationPinnodeshaveonlytheirtranslationaldegreesoffreedomassociatedwiththerigidbody.Connectionstransmitonlydisplacementandforce.Tienodeshaveboththeirtranslationalandrotationaldegreesoffreedomassociatedwiththerigidbody.Connectionstransmitrotationandmomentinadditiontodisplacementandforce.RigidBodies(6/8)InertialpropertiesofrigidbodiesThemassandrotaryinertiaofameshedrigidbodycanbecalculatedbasedon:thecontributionsfromitselements ortheycanbeassignedbyspecifyingmassandrotaryinertiapropertiesattheslavenodesofarigidbodyortherigidbodyreferencenode.Themass,centerofmass,andmomentsofinertiaaboutthecenterofmassofeachrigidbodyareprintedinthedata(.dat)file.RigidBodies(7/8)UsingrigidbodiesformodelverificationItmaybeusefultospecifypartsofamodelasrigidformodelverificationpurposes.Forexample,incomplexmodelswhereallpotentialcontactconditionscannotbeanticipated,elementsfarawayfromtheregionofinterestcouldbeincludedaspartofarigidbody,resultinginfasterruntimeswhiledevelopingamodel.Whensatisfiedwiththemodelandcontactpairdefinitions,rigidbodydefinitionscanberemovedandanaccuratedeformablefiniteelementrepresentationcanbeincorporatedthroughout.RigidBodies(8/8)Example:TennisracketframeTennisracketstrikingatennisballTheinteractionsbetweentheballandthestringsareofprimaryinterest.Sincetheframeisverystiff,itisinitiallymodeledasarigidbodyforcomputationalefficiency.Oncethisanalysishasbeenverified,therigidbodydefinitioncanberemovedtomaketheracketdeformable.CouplingConstraints(1/3)KinematiccouplingRigidconstraintsbetweenthemasternodesandthecouplingnodesProvidesasolutionforlackofrotationalstiffnessatnodesconnectedtosolidelementsDistributingcouplingTheconstraintisenforcedinanaveragesenseCouplingnodeweightfactorsprovidecontroloftheloadtransmission.KinematiccouplingDistributingcouplingCouplingConstraints(2/3)KinematiccouplingdefinitionsurfacereferencepointSpecifywhichdegreesoffreedomonthesurfacearerigidlyconstrainedtothereferencenodeCouplingConstraints(3/3)DistributingcouplingdefinitionsurfacereferencepointUniformlydistributesloadoverthesurfaceOtherweightingmethodsmonotonicallydecreaseloadingwithradialdistancefromthereferencenode.Shell-to-solidCoupling(1/2)AllowsforatransitionfromshellelementmodelingtosolidelementmodelingUsefulwhenlocalmodelingrequires3DsolidelementsbutotherpartsofthestructurecanbemodeledasshellsCouplesthemotionofa“line”ofnodesalongtheedgeofashellmodeltothemotionofasetofnodesonasolidsurfaceUsesasetofinternallydefineddistributingcouplingconstraintsShell-to-solidCoupling(2/2)Definingshell-to-solidcouplingshell_surface

(edge)solid_surface

(face)Theshellsurfacemustbeanedge-basedsurface!ConnectorElements(1/3)Connectorsmodelconnectionssuchas:hingesconstantvelocityjointspin-in-slotconstraintsTheConnectorBuilderinAbaqus/CAEstreamlinestheprocessofdefiningaconnectorelementDetailsonusingconnectorelementsmaybefoundintheFlexibleMultibodySystemswithAbaquscourseConnectorElements(2/3)Asimpleexample:hingeconnectionXLocalx-axisalonghingedirectionTwopartinstances;connectionbetweencoincidentpointsXConnectorElements(3/3)Example(cont’d)DeformedconfigurationsofhingemodelFasteners(1/3)Mesh-independentfastenerscanbelocatedanywherebetweensurfaces.Theyneednotbedefinedatnodallocations.Theycanconnectmultiplelayers;i.e.,thenumberofconnectedsurfacesisnotrestricted.Thefastene