控制臂疲劳疲劳分析规范

Q/SZJ191001-2017控制臂疲劳疲劳分析规范Specificationofanalysisforcontrolarmfatigue20XX20XX-XX-XX实施20XX-XX-XX发布XXXX汽车工程技术有限公司发布Q/SZXX-X-2017控制臂疲劳分析规范范围本标准规定了术语和定义、控制臂疲劳分析方法及结果处理方法。本标准适用于CAE部门控制臂疲劳分析。规范性引用文件无。术语和定义本规范涉及到的术语及其定义如下：控制臂（ControlArm）连接副车架和转向节的底盘零部件。摘要Abstract本流程根据应变-寿命理论描述了控制臂裂纹萌生疲劳分析方法。Thisproceduredescribescrackinitiationfatigueanalysisaccordingtothestrain-lifeconceptforcontrolarm.疲劳分析的目的是识别因重复或变化的载荷而导致的危险区域，而这些载荷远未达到一次就可导致结构发生破坏的程度。Thepurposeofanyfatigueanalysisistoidentifycriticalareasduetorepeatedorotherwisevaryingloading,whichneverreachesalevelhighenoughtocausefailureinasingleoccurance.对于控制臂疲劳分析而言，是由线弹性应力分析，循环材料，交变载荷以及损伤模型等组成。Forcontrolarmsfatigueanalysisiscomposedofalinearelasticstressanalysis,cyclicmaterialconsideration,varyingloadingapplicationandthedamage-modellingpart.在有限元分析中，在载荷作用点施加单位载荷。随后将每个单位载荷下的应力分布与对应的载荷历程相组合。这种组合的结果就是交变载荷作用在部件上的应力历程。最后通过线性叠加得到每个单元的载荷历程。Inthefiniteelementanalysisunitloadsareappliedtoloadapplicationpoints.Subsequently,thestressdistributionforeverysingleunitloadinputiscombinedwiththecorrespondingtimehistoryofloading.Theresultsofthisfactorizationareasmanystresshistoriesasvaryingloadsactingonthecomponent.Finally,alinearsuperpositionisperformedfromwhichoneloadinghistoryperfiniteelementisobtained.应力历程和循环载荷作用下的材料响应描述输入到实际的疲劳分析当中。Togetherwithadescriptionofthematerialresponsetocyclicloading,thesecombinedstresshistoriesareinputtotheactualfatigueanalysis.疲劳分析软件会进行弹塑性转换。载荷历程最终会被提取成等效的常幅循环载荷。使用Palmgren-Miner累积损伤假设，开展疲劳寿命预测分析并给出施加载荷的重复循环次数信息。Thefatigueanalyzercodecarriesoutelastic-plastictransformations.Thesequencesoftheloadinghistoriesareextractedassetsofequivalentconstantamplitudecycles.UsingthePalmgren-Minersummationdamagehypothesis,fatiguelifepredictioniscarriedoutwhichgivesinformationabouttherepeatabilityoftheappliedhistories.流程图ProcessFlowDiagram准备准备强度分析输入Gatherinputforstrengthanalysis目标达成？TargetReached?准备模型Preparatoryworkonmodel准备材料Preparatoryworkonmaterial准备载荷PreparatoryworkonloadingDocumentandreport运行疲劳分析RunfatigueanalysisObtainfiniteelementinputfile.Inquireaboutmaterialandloadinghistories.获取有限元输入文件，查询材料和载荷历程曲线。

Editinputfileforfatigueanalysis.Ifnecessary,refinemesh.Carryoutalinearelasticstressfiniteelementanalysis.编辑疲劳分析输入文件，如有必要优化网格。开展线弹性有限元静力学分析。Lookforappropriatecyclicmaterialinformationandentermaterialpropertiesintomaterialdatabase.查找恰当的循环材料信息并将材料属性输入到材料数据库中。

Checktheloadinghistoriesintermsofsamplingrate,noise,spikesetc.Importhistoriesintoloadingdatabase.检查载荷历程的采样频率，噪声，尖峰值。将载荷历程导入到载荷数据库中。Importmodelwithfiniteelementresultsofunitloadcasescalculation.Associatethefiniteelementloadswiththeirtimevariations.导入单位载荷有限元结果模型。将载荷历程与有限元计算结果相关联。Selectstrain-lifefatigueanalysis.UseSmith-Watson-Toppermeanstresscorrection.SelectNeuberplasticitycorrection.Activateabiaxialitycheck.Performfatigueanalysisonelementsusingaveragingformaximumabsoluteprincipals。选择应变-寿命疲劳分析，使用Smith-Watson-Topper平均应力修正。选择Neuber塑性修正，激活二轴率检查。使用单元平均绝对值最大主应力开展疲劳分析。

Checkdamagemodelatthecriticalareas.Modifymodel,ifnecessary.检查模型危险区域的损伤值。如有必要，修改模型。

Reportonanalysis.Documentwithdamagecontourplot.编写报告，记录损伤云图。

NOYES图1流程图Fig1ProcessFlowDiagram工具描述ToolDescription仿真分析过程中需要用到的如下软件:Thefollowingsoftwarefacilitatestheanalyticalsimulationprocess:前处理(Preprocessors):Hypermesh求解器(AnalysisCode):Nastran,nCode后处理(Postprocessors):Hyperview建模和分析过程Modeling/AnalysisProcedure单位Units分析中所用单位制如下所示:Theunitsusedintheanalysisareasfollows:力(Force) 牛顿(N)质量(Mass) 吨(Ton)长度(Length) 毫米(mm)时间(Time) 秒(Second)内容Contents疲劳分析模型与结构静力学分析并无差异。Thefatiguemodeldoesnotdifferfromthestructureanalysismodel.坐标系CoordinateSystems除特殊说明，本规范一般使用整车坐标系。（X轴向后，Y轴向右，Z轴向上）Generally,theglobalvehiclesystemisused.Mathdataforthebody-in-whiteisdesignedinthevehiclecoordinatesystem(ie.X-axisrearward,Y-axisrightandZ-axisupward)建模技巧ModelingTechniques根据材料的循环应力-应变曲线和寿命-应变寿命曲线，建立应变-寿命理论开展裂纹萌生疲劳分析。Crackinitiationfatigueanalysisaccordingtothestrain-lifeconceptbuildsuponthecyclicstress-straincurveandthestrain-lifecurve.另外需要考虑的材料信息是抗拉强度（UTS）和屈服强度（Ys）。Additionalmaterialinformationtakenintoaccountistheultimatetensilestrength(UTS)andtheyieldstress(Ys).值得注意的是材料循环属性高度依赖于表面加工质量和后处理。Beawarethatcyclicmaterialpropertiesarehighlydependentonfactorssuchassurfacetreatmentandfinish.假设和限制Assumptions/Limitations假设Assumptions就应力计算而言：Asfarasstresscalculationsareconcerned:习惯性使用线弹性理论（NASTRANSOL101求解器）；Customaryassumptionsofthelineartheoryofelasticityareused(NASTRANSol101);材料的性能是在室温下测定的。Materialperformanceistestedatroomtemperature限制Limitations疲劳天生就是随机的：载荷历程受驾驶员、路面和天气条件影响，材料属性受制造工艺的影响，仿真分析受模型的影响等。Bynature,fatigueisstochastic:loadinghistoriesareinfluencedbydriver,roadandweatherconditions,materialpropertiesareinfluencedbythemanufacturingprocess,simulationisinfluencedbythemodellingetc.载荷和边界条件Loads/BoundaryConditions边界条件BoundaryConditions对于试验场载荷仿真，使用惯性释放方法。对于台架测试试验仿真，边界条件和测试规范相同。Forprovinggroundsimulationinertiareliefisperformed.Fortestrigsimulationtheboundaryconditionsareaccordingthetestspecification.载荷Loads试验场仿真分析，控制臂上需加载9个作用力。Whenperformingaprovinggroundsimulation9singleforcesactonthecontrolarm.图2控制臂载荷示意图Figure2Loadsatcontrolarm力Fx，Fy，Fz作用在ForcesFx,Fy,andFzapplyat•球铰theballjoint(Fbjt)•副车架前安装点thefrontsubframemount(Fsmf)•副车架后安装点therearsubframemount(Fsmr)性能要求PerformanceRequirements控制臂扭转疲劳的寿命应不小于1200次循环。Thelifeofcontrolarmfatigueshouldnotlessthan12,00repeats.在疲劳分析的后处理中确定结构的寿命。对于0.1%失效概率的估算寿命为：N=Ncal*DM*Tm(-1/2)其中：Ncal：50%存活率下的计算寿命DM：Miner常量Tm：制造分散性Youmightascertaintheservicelifewithinthepost-processingofthefatigueanalysis.Theestimatedservicelifefor0.1%probabilityoffailureis:N=Ncal*DM*Tm(-1/2)with:Ncal:calculatedservicelifefor50%probabilityofsurvivalPSDM:Miner’sconstant.Tm:manufacturingscatter使用Miner常量DM考虑分析方法的系统误差。DM的典型值为0.4。考虑制造分散性Tm，典型值为3~5。UsetheMiner’sconstantDMtotakeintoaccountsystematicerrorsofthemethod.AtypicalvalueforDMis0.4forcasts.TakeintoconsiderationthescatterofmanufacturingTm.TypicalvaluesofTmarebetween3and5.分析要求ANALYSISREQUIREMENTS对于控制臂的疲劳分析，推荐使用壳单元绝对值最大主应力。Themaximumabsoluteprincipalelementstressesarerecommendedforfatigueanalysisonthesolidcontrolarmswithshellskins.选择最保守的Smith-Watson-Topper平均应力修正方法。使用Neuber塑性修正将局部弹性应变转换成局部弹塑性应变。SelectSmith-Watson-Toppermeanstresscorrectionmethodwhichisgenerallythemostconservativemethod.Inordertotranslatefromthelocalelasticstraintothelocalelastic-plasticstrain,useNeuber’splasticitycorrection.激活二轴比检查评估使用方法的正确性。Activateabiaxialitychecktoassessthevalidityoftheusedapproach.检查是否为单轴加载，其为疲劳分析的隐含假设。Checkifuniaxialityisgiven,asthisassumptionisimplicitforthedescribedfatigueanalysis.单轴加载是指在交变载荷作用下，只有结构响应的应力幅发生，而应力的方向不变。这种情况