ansys中阻尼的设置

ANSYS/LS-DYNA中阻尼的设置ANSYS/LS-DYNA中阻尼的设置总结如下：EDDAMP,PART,LCID,VALDMP(用此命令流来定义阻尼)Definesmassweighted(Alpha)orstiffnessweighted(Beta)dampingforanexplicitdynamicsmodel.（默认有质量阻尼与刚度阻尼两种）图1LS-DYNA中的阻尼选项PARTPARTnumber[EDPART]identifyingthegroupofelementstowhichdampingshouldbeapplied.IfPART=ALL(default),dampingisappliedtotheentiremodel.（定义施加阻尼的Part号，如果Part=ALL(orblank)，整体质量阻尼将被应用于整个模型。）LCIDLoadcurveID(previouslydefinedwiththeEDCURVEcommand)identifyingthedampingcoefficientversustimecurve.Iftime-dependentdampingisdefined,anLCIDisrequired.（用来指定相对于时间的质量阻尼）VALDMPConstantsystemdampingcoefficientorascalefactorappliedtothecurvedefiningdampingcoefficientversustime.（可以用来代替对时间的质量阻尼曲线，或者使用LCID命令中的比例系数）注意：Mass-weighted(Alpha)orstiffness-weighted(Beta)dampingcanbedefinedwiththeEDDAMPcommand.Generally,stiffnessproportionalorbetadampingiseffectiveforoscillatorymotionathighfrequencies.Thistypeofdampingisorthogonaltorigidbodymotionandsowillnotdampoutrigidbodymotion.Ontheotherhand,massproportionaloralphadampingismoreeffectiveforlowfrequenciesandwilldampoutrigidbodymotion.Thedifferentpossibilitiesaredescribedbelow:1.GlobalDampingMass-weightedorAlphadamping（质量阻尼）WhenPART=(blank)orALL(default),mass-weightedglobaldampingcanbedefinedinthefollowing2ways.Inthiscase,thesamedampingisappliedfortheentirestructure.1.Whenthedampingcoefficientversustimecurve(LCID)isspecifiedusingtheEDCURVEcommand,VALDMPisignoredbyLS-DYNA(althoughitiswrittenintheLS-DYNAinputfileJobname.K).Thedampingforceappliedtoeachnodeinthemodelisgivenbyfd=d(t)mv,whered(t)isthedampingcoefficientasafunctionoftimedefinedbytheEDCURVEcommand,misthemass,andvisthevelocity.2.WhentheLCIDis0orblank(default),aconstantmass-weightedsystemdampingcoefficientcanbespecifiedusingVALDMP.Theconstantandtime-dependentdamping,describedabove,cannotbedefinedsimultaneously.Thelastdefinedglobaldampingwilloverwriteanypreviouslydefinedglobaldamping.2.DampingdefinedforaPART（1）Mass-weightedorAlphadamping（质量阻尼）WhenbothavalidPARTnumberisspecifiedandthedampingcoefficientversustimecurve(LCID)isspecifiedusingtheEDCURVEcommand,mass-weightedtime-dependentdampingwillbedefinedfortheparticularPART.Inthiscase,VALDMPwillactasascalingfactorforthedampingversustimecurve(ifVALDMPisnotspecified,itwilldefaultto1).AvalidPARTnumbermustbespecifiedtodefinethistypeofdamping.Forexample,usePART=1(andnotblank)whentheentiremodelconsistsofonlyonePART.IssuethecommandrepeatedlywithdifferentPARTnumbersinordertospecifyalphadampingfordifferentPARTS.（2）Stiffness-weightedorBetadamping（刚度阻尼）WhenavalidPARTnumberisspecifiedwithLCID=0or(blank)(default),astiffness-weighted(Beta)constantdampingcoefficientforthisparticularPARTcanbedefinedbyVALDMP.Thestiffness-weightedvaluecorrespondstothepercentageofdampinginthehighfrequencydomain.Forexample,0.1roughlycorrespondsto10%dampinginthehighfrequencydomain.Recommendedvaluesrangefrom0.01to0.25.Valueslowerthan0.01mayhavelittleeffect.Ifavaluelargerthan0.25isused,itmaybenecessarytolowerthetimestepsizesignificantly.IssuethecommandrepeatedlywithdifferentPARTnumbersinordertospecifybetadampingfordifferentPARTS.Time-dependentstiffness-weighteddampingisnotavailableinANSYSLS-DYNA.Themass-weightedandstiffness-weighteddamping,describedabove,cannotbedefinedsimultaneouslyforaparticularPARTnumber.ThelastdefineddampingfortheparticularPARTnumberwilloverwriteanypreviouslydefinedmass-weightedorstiffness-weighteddampingforthisPART.Inordertodefinethemass-weightedandstiffness-weighteddampingsimultaneously,youcanusetheMP,DAMPcommandtodefinestiffness-weighted(Beta)constantdampingcoefficient.However,donotusebothofthesecommandstogethertodefinestiffness-weighted(Beta)constantdampingcoefficientforaparticularPART.Ifyoudo,duplicatestiffness-weighted(Beta)constantdampingcoefficientsforthisPARTwillbewrittentotheLS-DYNAinputfileJobname.K.ThelastdefinedvaluewillbeusedbyLS-DYNA.Also,notethattheMP,DAMPcommandisappliedontheMATnumber,andnotonthePARTnumber.SinceagroupofelementshavingthesameMATIDmaybelongtomorethanonePART(theoppositeisnottrue),youneedtoissuetheMP,DAMPcommandonlyonceforthisMATIDandthestiffness-weighted(Beta)dampingcoefficientswillbeautomaticallydefinedforallthePARTswiththatMATID.Mass-weightedandstiffness-weighteddampingcanbedefinedsimultaneouslyusingtheEDDAMPcommandonlywhenmass-weighteddamping(constantortime-dependent)isdefinedasglobaldamping(EDDAMP,ALL,LCID,VALDMP)andstiffness-weighteddampingisdefinedforallnecessaryPARTs(EDDAMP,PART,,VALDMP).Toremovedefinedglobaldamping,reissuetheEDDAMP,ALLcommandwithLCIDandVALDMPsetto0.ToremovedampingdefinedforaparticularPART,reissueEDDAMP,PART,wherePARTisthePARTnumber,withLCIDandVALDMPsetto0.ThereisnodefaultfortheEDDAMPcommand,i.e.,issuingtheEDDAMPcommandwithPART=LCID=VALDMP=0willresultinanerror.Stiffness-weighteddampingdefinedbytheMP,DAMPcommandcanbedeletedusingMPDELE,DAMP,MAT.Inanexplicitdynamicsmallrestart(EDSTART,2)orfullrestartanalysis(EDSTART,3),youcanonlyspecifyglobalalphadamping.Thisdampingwilloverwriteanyalphadampinginputintheoriginalanalysis.Ifyoudonotinputglobalalphadampingintherestart,t