ls-dyna预应力加载介绍相当详细

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1、PreloadsinLS-DYNAIntroductionAnalysisTechniques(General)DynamicRelaxationExplicitImplicitTransientExplicitwithMassDampingImplicitAnalysisBoltPreloadTechniquesThermalInterferenceContactStressinSolidCross-sectionForceinBeamsPreload-IntroductionSometimesitisimport

2、anttoinduceasteadystatepreloadbeforeperformingatransientdynamicanalysis.Rotatingfanorturbineblades,rotatingflywheelsGravityPressurevesselsortiresShrink-fitpartsStressesinducedbyatorquedboltExplicitDynamicRelaxation(DR)ExplicitDRisanoptionaltransientanalysisthat

3、takesplacein‘pseudo-time’(precedesregulartransientanalysis).DRistypicallyusedtopreloadamodelbeforeonsetoftransientloading.Preloadstressesaretypicallyelasticanddisplacementsaresmall.InexplicitDR,thecomputednodalvelocitiesarereducedeachtimestepbythedynamicrelaxat

4、ionfactor(default=.995).ThusthesolutionundergoesaformofdampingduringDR.Thedistortionalkineticenergyismonitored.WhenthisKEhasbeensufficientlyreduced,i.e.,the“convergencefactor”hasbecomesufficientlysmall,theDRphaseterminatesandthesolutionautomaticallyproceedstoth

5、etransientanalysisphase.Alternately,DRcanbeterminatedatapresetterminationtime.ExplicitDynamicRelaxationDRistypicallyinvokedbysettingparameterSIDRinaloadcurve(*DEFINE_CURVE)to1or2.RamptheloadduringDRphaseandthenholdloadconstantuntilsolutionconvergesMakesureconve

6、rgenceoccursafter100%ofpreloadisappliedMaintainthepreloadinsubsequenttransientanalysisphase(useseparateloadcurvewithouttheramp)DRconvergesSIDR=1(DRphase)SIDR=0(transientphase)*CONTROL_DYNAMIC_RELAXATION*CONTROL_DYNAMIC_RELAXATIONparametersIterationsbetweenconve

7、rgencecheck(default=250)Alsoaffectsoutputintervalfor“d3drlf”Convergencetolerance(default0.001)RatioofdistorsionalKEatconvergencetopeakdistorsionalKESmallervalueresultsinconvergedsolutionnearertosteadystatebutrunwilltakelongertogetthereDynamicrelaxationfactor(de

8、fault=0.995)ReductionfactorfornodalvelocitieseachtimestepIfvalueistoosmall,modelneverreachsteadystateduetooverdampingOptionalterminationtimeforDR(default=infinity)DRwillstop