電子器件 技術(shù)文件COMSOL-Fatigue-v44

FatigueModuleinCOMSOLMultiphysics?2013COMSOL.Allrightsreserved.ProductSuite–Version4.4“Fatigueaccountsforatleast90%ofallservicefailuresduetomechanicalcauses.”COMSOLProductsforFatigueAnalysisRequiredmodulesCOMSOLMultiphysicsTheCOMSOLMultiphysicsbaseproductisrequiredforalladd-onsStructuralMechanicsModuleFatigueModuleAdd-ontotheStructuralMechanicsModulePossibleextensionsNonlinearStructuralMaterialsModuleAvailableasadd-ontotheStructuralMechanicsModuleMultibodyDynamicsModuleAvailableasadd-ontotheStructuralMechanicsModulePurposeofFatigueModuleTosimulatetheinfluenceofrepeatedloadingandunloadingontheintegrityofstructuralcomponentsToestimatethefatiguedamagebasedondifferentfatiguemodelsToevaluatetheinfluenceofgeometricaldimensionsandmaterialselectiononfatigueWheelrim:Surfaceinitiatedfatiguecausedbyarotatingload.FatigueAnalysisFatigueanalysisrequirestwosteps:loadcyclesimulationandfatiguemodelevaluation.Intheloadcycle,theloadhistoryofrepeatableornonrepeatableloadeventsissimulatedTheentirehistoryoftheloadcycleisprocessedinthefatiguestepLoadcycleFatigueLoadCycleSimulationLoadcycleSolidMechanicsShellPlateThermalStressJouleHeatingandThermalExpansionPiezoelectricDevicesMultibodyDynamicsViscoplasticsolderjoints:Thermo-mechanicalfatiguesimulatedwiththethermalstressinterface.FatigueModelsStress-basedFindleyMatakeNormalStressStrain-basedSmith-Watson-Topper(SWT)Wang-BrownFatemi-SocieCoffin-MansonEnergy-basedMorrowDarveauxCumulativedamageRainflowCountingPalmgren-MinerFatigueModuleKeyFeaturesCriticalPlaneModelsStress-basedfatiguemodelsFindleyMatakeNormalStressStrain-basedfatiguemodelsSmith-Watson-Topper(SWT)Wang-BrownFatemi-SocieCylindricaltestspecimen:Fatigueevaluatedusingthreedifferentcriteria.ConstantLoadCycleStrainbasedfatigueElastoplasticanalysisNotchassumptionusingNeuber’srulewithHoffmannSeegerapproximationShearrangeevaluationatnon-proportionalloadingMaximumdistanceCircumscribingcirclePipewithahole:SWTfatiguemodelbasedonelastoplasticresponse.Calculationtime11min.Pipewithahole:SWTfatiguemodelbasedonnotchassumptionresponse.Calculationtime4sec.HighCycleFatigueandLowCycleFatigueHighcyclefatigue(HCF)Stress-basedLowcyclefatigue(LCF)Strain-basedEnergy-basedThermalFatigueinNonlinearMaterialsFatiguebasedoninelasticstrainsCoffin-MansonUserdefinedstrainsFatiguebasedondissipatedenergyMorrowDarveauxUserdefinedenergySurfacemountresistor:Thermalfatiguebasedonenergydissipation.VariableLoadCycleLoadcycledefinitionLoadcasesParametricsweepTransientanalysisGeneralizedloadsRainflowcountingstressPrincipalstressSignedvonMises(largestprincipalstress)SignedvonMises(hydrostaticstress)Palmgren-MinerdamageruleS-NcurveR-valuedependenceRandomloadexperiencedbyawindturbine.ConceptofGeneralizedLoadBasedontheprincipleofsuperpositionStructuralresponseisdefinedusingafewgeneralizedloadsTheexternalloadisappliedthroughamultiplicationofthegeneralizedloadsbythecorrespondingtimehistoriesSignificantcalculationtimegainssincethesimulationoftheloadhistoryisdoneinthefatiguestepusingadedicatedalgorithmSuitableforsimulationoflong,usuallyrandom,loadhistoriesOnlyforlinearproblemsFramewithcutout:ExternalloadsimulatedusingthreegeneralizedloadcasesMatrixHistogramDedicatedplotforfatiguedistributionparametersResultsprovidedforthemostcriticalpoint3DgraphwiththeheightoptionFatigueModuleModelLibraryModelsHighCycleFatigueEvaluationExample:Fatigueevaluationofanon-proportionallyloadedcirculartestspecimeninnormalandtwistingload.Multiplestress-basedfatiguecriteria(Findley,Matake,normalstress),oftenusedforhighcyclefatigue,areevaluatedinthesamestudystep.Multithreadingisusedtofindthecriticalplaneandtoevaluatethefatiguecriteria.Inmostcasesfatigueissurfaceinitiated.Itisthenmoreefficienttoevaluateitasasurfacefeature.LowCycleFatigueEvaluationExample:Anelastoplasticcylinderisloadedwithparameterizedsinusoidalforce.Alowcyclefatiguemodel,Smith-Watson-Topper,isevaluated.Theupperlifelimit,whichcanbeseenasinfinitelife,iscontrolledwithacut-offparameterinthefatiguemodelinterface.Duetoplasticitytwoloadcyclesarenecessarytoobtainasteadystatestresscycle.Thenon-linearmaterialresponseisdefinedusingtheNonlinearStructuralMaterialsModule.TheNotchEffectUsingElasticMaterialExample:Acylinderwithaholeisloadedwithasinusoidalload.ThenonlinearbehavioraroundtheholeiscomputedusingNeuber’srulewiththeHoffmannSeegerapproximation.Usingalinearelasticmaterialonlythreeloadstepsarenecessarytocovertheinfluenceofthewholeloadcycle.Whentheloadcycleunloadsthestructure,itisnecessarytoincludethezerosolutionsincetheapproximationisbasedontheeffectivestress.Thetotalcomputationaltimeforallstepsinthisanalysisis4sec.Usinganelastoplasticmaterialmodeltheanalysisrequires11min.CumulativeDamageEvaluationExample:Athinwalledframewithacutoutissubjectedtoarandomloadhistory.Thestructureismodeledwithshellelements.TheRainflowcyclecountingalgorithmreducestherandomstressdataintoadiscretestressdistribution.TheaccumulateddamageisbasedonthePalmgren-Minerlineardamagerule.Theloadcycleisdefinedusingthreegeneralizedloadcasesinsteadof1000loadevents.Thelongloadhistoryisprocessedusingtheconceptofsuperposition.Thealgorithmprocessesthestresscycledatainthefatiguestepwhichresultsinsignificantperformancegains.ThermalFatigueinNonlinearMaterialsExample:Amicroelectroniccomponentissubjectedtoacyclicthermalload.Ther