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1、MPC184Page1of19ElementReference
2、PartI.ElementLibrary
3、MPC184MultipointConstraintElements:RigidLink,RigidBeam,Slider,Spherical,Revolute,Universal,SlotMPMEST<><>PR<><><>PPEDMPC184ElementDescriptionMPC184comprisesageneralclassofmultipointconstraintelementsthatimplementkinemat
4、icconstraints.Theelementsarelooselyclassifiedhereas“constraintelements”and“jointelements.”Youcanusetheseelementsinsituationsthatrequiresometypeofkinematicconstrainttobeimposed.Theconstraintmaybeassimpleasthatofidenticaldisplacementsatajoint.Constraintscanalsobemorecomplic
5、ated,suchasthoseinvolvingmodelingofrigidparts,orkinematicconstraintsthattransmitmotionbetweenflexiblebodiesinaparticularway.Thetypeofconstraintuseddependsonthedesiredapplication.Forexample,astructuremayconsistofsomerigidpartsandsomemovingpartsconnectedtogetherbysomerotati
6、onalorslidingconnections.TherigidpartofthestructuremaybemodeledusingtheMPC184Link/Beamelements,whilethemovingpartsmaybeconnectedwiththeMPC184slider,spherical,revolute,slot,oruniversaljointelement.Thekinematicconstraintsareimposedusingoneofthefollowingtwomethods:òThedirect
7、eliminationmethod,whereinthekinematicconstraintsareimposedbyinternallygeneratedMPC(multipointconstraint)equations.ThedegreesoffreedomofadependentnodeintheMPCequationsareeliminatedinfavorofanindependentnode.ôThedirecteliminationmethodshouldbeusedwheneveritisavailablesincet
8、hedegreesoffreedomatthedependentnodesareeliminated,therebyreducingtheproblemsizeandsolutiontime.ôSincethedependentdegreesoffreedomareeliminated,theconstraintforcesandmomentsarenotavailablefromtheelementoutputtable(ETABLE)foroutputpurposes.However,theglobalconstraintreacti
9、onforcesareavailableatindependentnodesintheresultsfile,Jobname.rst(PRRSOLcommand,etc.).òTheLagrangemultipliermethod,whereinthekinematicconstraintsareimposedusingLagrangemultipliers.Inthiscase,alltheparticipatingdegreesoffreedomareretained.ôTheLagrangemultipliermethodshoul
10、dbeusedwhenthedirecteliminationmethodisnotavailableornotsuitablefortheanalysispurposes.ôInthisme
