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ID:38567572
大小:1.56 MB
页数:28页
时间:2019-06-15
《ls-dyna预应力加载简绍相当详细》由会员上传分享,免费在线阅读,更多相关内容在教育资源-天天文库。
1、PreloadsinLS-DYNAIntroductionAnalysisTechniques(General)DynamicRelaxationExplicitImplicitTransientExplicitwithMassDampingImplicitAnalysisBoltPreloadTechniquesThermalInterferenceContactStressinSolidCross-sectionForceinBeamsPreload-IntroductionSometimesitisimportanttoinduceasteadystatepreload
2、beforeperformingatransientdynamicanalysis.Rotatingfanorturbineblades,rotatingflywheelsGravityPressurevesselsortiresShrink-fitpartsStressesinducedbyatorquedboltExplicitDynamicRelaxation(DR)ExplicitDRisanoptionaltransientanalysisthattakesplacein‘pseudo-time’(precedesregulartransientanalysis).
3、DRistypicallyusedtopreloadamodelbeforeonsetoftransientloading.Preloadstressesaretypicallyelasticanddisplacementsaresmall.InexplicitDR,thecomputednodalvelocitiesarereducedeachtimestepbythedynamicrelaxationfactor(default=.995).ThusthesolutionundergoesaformofdampingduringDR.Thedistortionalkine
4、ticenergyismonitored.WhenthisKEhasbeensufficientlyreduced,i.e.,the“convergencefactor”hasbecomesufficientlysmall,theDRphaseterminatesandthesolutionautomaticallyproceedstothetransientanalysisphase.Alternately,DRcanbeterminatedatapresetterminationtime.ExplicitDynamicRelaxationDRistypicallyinvo
5、kedbysettingparameterSIDRinaloadcurve(*DEFINE_CURVE)to1or2.RamptheloadduringDRphaseandthenholdloadconstantuntilsolutionconvergesMakesureconvergenceoccursafter100%ofpreloadisappliedMaintainthepreloadinsubsequenttransientanalysisphase(useseparateloadcurvewithouttheramp)DRconvergesSIDR=1(DRpha
6、se)SIDR=0(transientphase)*CONTROL_DYNAMIC_RELAXATION*CONTROL_DYNAMIC_RELAXATIONparametersIterationsbetweenconvergencecheck(default=250)Alsoaffectsoutputintervalfor“d3drlf”Convergencetolerance(default0.001)RatioofdistorsionalKEatconvergencetopeakdistorsionalKESmallervalueresultsinconvergedso
7、lutionnearertosteadystatebutrunwilltakelongertogetthereDynamicrelaxationfactor(default=0.995)ReductionfactorfornodalvelocitieseachtimestepIfvalueistoosmall,modelneverreachsteadystateduetooverdampingOptionalterminationtimeforDR(default=infinity)DRwillstop
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