整车瞬态响应分析规范

Q/SZJ191001-2017整车瞬态响应分析规范SpecificationofTransientResponseAnalysis20XX20XX-12-31实施20XX-11-27发布XXXX汽车工程技术有限公司发布Q/SZXX-X-2017整车瞬态响应分析规范范围本标准规定了整车瞬态响应分析的方法。本标准适用于CAE部门整车瞬态响应分析。规范性引用文件无。术语和定义无。摘要Abstract整车瞬态响应分析用于计算整车上特定激励输入的短暂响应。典型的激励有一个缓冲块凸起、一个路面凹坑、一段伸缩缝或其它不规则路面，这些将导致对整车的冲击作用。响应点包括方向盘、座椅导轨和车厢内噪声等。瞬态响应分析是指模拟对缓冲块激励的响应来对比试验和分析的结果，特别是悬架左右侧同时过缓冲块对悬架跳跃模态和左右侧不同时过缓冲块对悬架踏步模态两种情况。本规范讨论了使用NASTRAN并使用超单元进行整车瞬态响应分析方法，也可用于不采用超单元的情况。进行瞬态响应分析可以使用直接法和模态法两种。在直接法中，整车响应通过直接数值积分求解一系列耦合方程。直接法支持线性和非线性模型。瞬态响应分析不支持复数系数，因此结构阻尼必须转换成等价的粘性阻尼。这种转换方法局限在于结构阻尼和等效粘性阻尼仅在某一频率下相等，使用者必须提供这些数据。如果小于这个频率时，阻尼减少；如果高于这个频率时，阻尼增大。结构阻尼和单元结构阻尼都会出现这种情况。当进行模态瞬态响应分析时，结构模态振型用来减少计算规模，使数值积分更有效率来求解（当使用模态阻尼时）。这种方法通过汇总单独的模态响应结果来求解总的响应。如果阻尼矩阵存在，则系统矩阵不能对角化。因此如果使用粘性阻尼（包括结构阻尼转换而来的），模态瞬态分析方法求解解耦问题数值积分问题和直接法一样。在模态空间中求解与在物理空间类似，但是求解的模态数目要远远少于物理空间，在模态空间进行直接积分效率更高。但模态求解方法的缺点是由于模态数目的缩减导致误差，但可以通过残余向量来减少。Transientresponseanalysisofvehiclesystemsisusedtoevaluatethevehicle’sresponsefordeterministicinputsinwhichthetemporalresponseofthevehicleisneeded.Atypicalvehicleexcitationcouldbeabump,pothole,expansionjointoranyotherroadirregularitythatwouldjaravehicleresultinginanimpacttypeofloading.Responsepointsofinteresttoimpacttypeloadsincludethesteeringwheelandseattracksaswellasinteriorcabinnoise.Transientanalysisusedtosimulateavehicle’sresponsetoabumpalsoprovidesanexcellentmeansofevaluatingthecorrelationbetweenavehicletestandavehiclesystemmodel,thesuspensionimpactingabumpwiththeleftsideandrightsideofavehicleatthesametimeexcitesthesuspensionhopmodeswhileexcitingtheleftandrightsideofavehicleatdifferenttimesexcitesthesuspensiontrampmodes.ThisprocedurediscussesthemethodsforperformingNASTRANtransientresponseanalysesforvehiclesystemmodelsusingsuper-elementswithCMS.Thesameprocedurescanbeusedforsystemmodelswithoutsuper-elementsbyomittingthoseNASTRANcardsrelatedspecificallytosuper-elementsandCMS.Therearetwomethodsusedtoperformtransientresponseanalysis,thedirectmethodandmodalmethod.Indirecttransientresponse,avehicle’sresponseiscomputedbysolvingasetofcoupledequationsusingdirectnumericalintegration.Thedirectmethodallowsforbothlinearandnon-linearfiniteelementmodels.Transientanalysisdoesnotpermitcomplexcoefficients;therefore,structuraldampingmustbeconvertedtoequivalentviscousdamping.Thelimitationwiththisconversionisthatthestructuraldampingandtheequivalentviscousdampingwillonlybeequalatonefrequency,whichmustbeprovidedbytheuser.Thestructurewillbeunderdampedbelowthisfrequencyandoverdampedabovethisfrequency.Thisistrueforbothoverallstructuraldampingandelementstructuraldamping.Whenperformingamodaltransientanalysis,themodeshapesofthestructureareusedtoreducethesize,makethenumericalintegrationmoreefficient,andifmodaldampingisused,uncoupletheequationsofmotion.Thesolutiontoadeterministicforcingfunctionisobtainedthroughthesummationoftheindividualmoderesponses.Ifadampingmatrixexists,typicallythesystemnormalmodesarenotabletodiagonalizeit.Therefore,ifviscousdamping(includingstructuraldampingconvertedtoviscousdamping)isused,themodaltransientapproachsolvesthecoupledproblemwiththesamedirectnumericalintegrationroutineasadirecttransientsolution.Theequationsofmotioninthemodalspaceareverylikethoseinthephysicalspace,butbecausethenumberofretainedmodesismuchlessthanthenumberofphysicaldegreesoffreedom,directintegrationinthemodalspaceisgenerallymuchmoreefficient.Thedrawbackofthemodalmethodisthemodaltruncationerrorcausebyusingareducednumberofmodes,howeverthiserrorcanbeminimizedusingresidualvectors.流程图收集模型收集模型CollectDetailedFiniteElementModels创建计算卡片SetuptheDataDeckwithFileManagement,ExecutiveControl,CaseControl&BulkDataSections模型检查ChecktheModelwithGroundcheck&WeightCheck求解RunthemodelwithSOL112(ModalTransient)orSOL109(DirectTransient)绘制响应曲线（加速度/时间）PlottheResponse(Accelerationsvs.Time)图1流程图工具描述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后处理(Postprocessors):Hypergraph建模和分析过程Modeling/AnalysisProcedure为了得到更高的精确度，相关频率范围内的整车模态要准确。特别是前后悬架，包括衬套刚度、阻尼和质量等值。默认使用频率相关的衬套属性线性值。衬套和安装点的非线性值在加载发生改变时优先使用。Toachievehigherlevelsofaccuracy,accuraterepresentationofthevehiclemodesisrequiredforthefrequencyregionofinterest.Thefrontchassisandsuspensionareofspecialinterest,inadditiontotheaccuratebushingstiffness,damping,mass,andsuspensionproperties.Linearfrequencydependentcharacteristicsofkeybushingpropertiesarepreferred(e.g.,frontsuspensionlowercontrolarmridebushing).Non-linearcharacteristicsofkeybushingsandmountsarealsopreferredwhentravelduringloadingresultsinratechanges.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无。坐标系CoordinateSystems无。建模技巧ModelingTechniques无。假设和限制Assumptions/Limitations无。载荷和边界条件Loads/BoundaryConditions约束无。载荷两种不同的方法来描述缓冲块的形状。半正弦波形状的缓冲块用TLOAD2卡片描述，AES缓冲块用TLOAD1和TABLED1卡片描述。在NASTRAN中，通过不同时间点缓冲块高度来描述运动，这意味着加载随时间改变。时间段等于缓冲块长度除以整车速度。在测试中，使用1/512=1.953125E-03秒。分析中需要更好的方法，推荐使用2.0E-04秒，总时间为2秒，则总步长为10000。每隔10步输出结果。Twodifferentmethodsfordescribingtheshapeofabumpwillbedescribedintheexamplesthatfollow.AbumpwiththeshapeofahalfsinepulseisdescribedwithananalyticalfunctionusingaTLOAD2cardwhileanAESimpactbumpisdescribedwithdiscreetpointsusingaTLOAD1andTABLED1cards.ToenforcethemotionspecifiedbythebumpinNASTRAN,theshapeofthebumpisdescribedasbumpheightversustime,whichmeanstheloadingconditionsarevelocitydependent.Thetimevaluesforthebumparedeterminedbydividingthebumplengthbythevehiclespeed.Inthetestdata,theresolutionusedis1/512=1.953125E-03seconds.Thefiniteelementanalysisrequiresfinerresolutionthanthetest.Therecommendedtimeincrement(t)is2.0E-4seconds;totaltimeis2seconds;andthetotaltimestepwillbe10,000.Printtheoutputatevery10steps.图2两种不同的方法描述缓冲块形状结果Results无。相关测试CorrelationTests无。性能要求PerformanceRequirements如下设计优化方向可以提高瞬态振动性能：悬架的垂向和纵向阻尼（减振器、液压衬套、副车架安装点）；减少弹簧下质量或增加弹簧上质量；悬置阻尼；高的动力总成垂向表现质量（加速度导纳）。调整液压悬置在车轮跳跃模态时最大表现质量（包括摩擦）；对于非液压动力总成悬置，考虑将动力总成在接地状态下的跳动模态频率高于车轮跳跃模态频率；Designchangedthatcanimprovetransientvibration:Verticalandlongitudinaldampinginsuspension(e.g.,shocks,hydraulicridebushing&sub-framemounts)Reduceunspringmassorincreasesprungmass.Dampinginpowertrainmounts.Highverticalapparentmassofthepowertrain.Tunehydraulicstoachievemaximummassatdynamicwheelhopfrequency(inclusiveoffrictioneffects)Fornon-hydraulicpowertrainmounts,considerplacingpowertrain-to-groundbouncemodeabovedynamicwheelhopfrequency.分析要求ANALYSISREQUIREMENTS无。参考文件DOCUMENTATION无。联系人CONTACTS无。例子EXAMPLES带线性轮胎的整车瞬态响应分析例子：$SOL112CEND$SDAMP=1SPC=1MPC=1$ResidualSUBCASE=99METHOD=990DLOAD=1TSTEP=1$BEGINBULK$Extractsystemnormalmodesupto40HzEIGRL,990,,40.0$Modaldamping,2%ofcriticalforallmodesTABDMP1,1,CRIT,,0.00,0.0,100.0,0.02,ENDT$Convertelementstructuraldamping(tire)toviscousdampingat12.5HzPARAM,W4,78.5$HighestFrequencyofinterest=40HzTSTEP,1,1000,.001$WheelDynamicLoads$RHSFrontWheelSpindle=Grid3135002,LHSFrontWheelSpindle=Grid3130002$RHSRearWheelSpindle=Grid406000,LHSRearWheelSpindle=Grid401000$Note:WheelSpindlesareconnectedtopatchpointswithasimpletiremodel,i.e.,springwithelementstructuraldamping$movebothwheelsoverthebump,notetimeto