车身与车架接附点刚度分析规范

Q/SZJ191001-2017车身与车架接附点刚度分析规范SpecificationofBodyandFrameAttachmentPointStiffnessAnalysis20XX20XX-06-30实施20XX-05-29发布XXXX汽车工程技术有限公司发布Q/SZXX-X-2017车身与车架接附点刚度分析规范范围本标准规定了术语和定义、车身与车架接附点刚度分析方法及结果处理方法。本标准适用于CAE部门车身传感器频响分析规范。规范性引用文件无。术语和定义无。摘要Abstract本文介绍车身和车架的接附点刚度分析规范。车辆的行驶和操作、异响、振动和声学性能都取决于车身和底盘系统的刚度性能。本文所列出的过程文件将提供一种简单的、普遍的和实际的方法，用以评价结构关键点的刚度。此处得到的静刚度，考虑了局部、全局和质量的影响，与测试和衬套刚度相当，是不受边界条件影响的。将本文所述的流程与接附点刚度计算方法结合，能够提供一种前端的设计工具，用于设置目标值，提供刚度测量，提供诊断方法。在优化设计重量和成本的同时,提供一种建立有意义的刚度目标以满足噪声和车辆动力学目标的过程。传统的动刚度确定方法是将以mm/N为单位的位移频率响应函数取倒数，得到频率相关的刚度N/mm。对比由位移动刚度得到的结构刚度与动力学衬套刚度，两者的比值需要先设置好。例如，结构刚度与衬套刚度的比为5:1。取位移频响函数在0.0Hz处的数值计算接附点的刚度。对于自由体的分析，位移动刚度在0.0Hz处渐进递增。为了获得一个有限值，需要去除刚体运动。下面的图表（图1）表明有无刚体运动对节点响应的影响。在CAE分析中，0.0Hz处的截距的数值不稳定，所以通常会选用2.0Hz处的截距。（注：早前的有些流程会选用0.5Hz处的截距。我们认为这不能有效避免0.0Hz附近的数值奇异性。）Thisdocumentationoutlinesthespecificationsofbodyandframeattachmentpointsstiffnessanalysis.Avehicle'srideandhandling,squeakandrattle,vibration,andacousticperformancearealldependentonthestiffnessperformanceofitsbodyandchassissystems.TheCAEprocessdocumentedhereprovidesasimple,generic,andrealisticmethodologytoevaluatethestiffnessatcriticallocationsonastructure.Itprovidessimplestaticlikestiffnessvaluesthataredirectlycomparabletotestandbushingstiffness,takesintoaccountlocal,global,andmasseffects,andisindependentofboundaryconditions.WhenthisprocedureisusedtogetherwiththeAttachmentPointStiffnessStrategyitprovidesanupfrontdesigntooltosettargets,providestiffnessmeasurements,diagnosticcapabilities,andaprocesstosetmeaningfulstiffnesstargetstomeetNVHandvehicledynamicsgoalswhileoptimizingdesignsforweightandcost.Thetraditionalmethodofdynamicstiffnessdeterminationinvolvestakingadisplacementfrequencyresponsefunctioninunitsofmm/NandinvertingthemagnitudetogetfrequencydependentstiffnessinN/mm.Comparisonofstructuralstiffnessderivedfromdisplacementpointmobilitiestodynamicbushingstiffnessarecommon.Acertainstiffnessratiotargetisthenset.Forexample,theratioofstructuretobushingstiffnessof5:1.AttachmentpointstiffnesstakesthisdisplacementFRFwhereitinterceptsthestaticaxis(0.0Hz)andinvertstogenerateasinglescalarnumber.Forfree-bodyanalysis,thedisplacementpointmobilityincreasesasymptoticallyat0.0Hz.Inordertoobtainafinitenumberfortheintercept,therigidbodymotionmustberemoved.Thefollowingfigureillustratesthedifferenceindrivingpointresponseswithandwithoutrigidbodymodesincluded.图1位移频响曲线Fig1DisplacementFrequencyResponse流程图ProcessFlowDiagram建模建模Modeling结果是否满足要求Istheresultok?定义边界条件DefineBoundary定义载荷Defineloads分析计算Calculation结束ENDYESNO优化Optimization图2流程图Fig2ProcessFlowDiagram工具描述ToolDescription仿真分析过程中需要用到的如下软件:Thefollowingsoftwarefacilitatestheanalyticalsimulationprocess:求解器(AnalysisCode):NASTRANSOL111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分析模型包括整备车架、整备车身和副车架。Modelcontentsincludetrimmedframe,trimmedbodyandsubframe.输入数据类型InputDataType输入文件是nastran格式的包含整备车身或整备车架的批量数据。对于将整备车身装配到整备车架的情况，也需要静态车身安装速率的数据。ForaNASTRANrun,theinputdataisabulkdatadeckofthetrimmedbodyortrimmedframe.ForTrimmedBodyassembledtoTrimmedFrame,thestaticbodymountratesarealsoneeded.坐标系CoordinateSystems全局坐标系。Theglobalstandardcoordinationsystem.建模技巧ModelingTechniques参考车架、整备车身和副车架的建模规范。适当的质量表示很重要。虽然求解的是刚度值，但惯性边界条件使刚度与质量相关。Refertothefollowingprocedures:Modelingaframe.Modelingatrimmedbody.Modelingasubframe.Itisimportanttohavepropermassrepresentation.Eventhoughweareafterstiffnessvalues,wearesimulatinganinertialboundaryconditionsothismakesthestiffnessvaluesmassdependent.假设和限制Assumptions/Limitations假设AssumptionsN/A限制LimitationsN/A载荷和边界条件Loads/BoundaryConditions约束和边界条件Constraints/BoundrayConditions除了副车架刚度分析外，所有的刚度分析使用自由边界条件。需要设置残余柔性向量，需要用到NASTRAN中的SUPPORT卡片，用于设置虚拟几何支撑。副车架分析要将车身附着在地面上。Inallcasesexceptsubframestiffnessanalysis,weareusingfree-freeboundaryconditions.Upperresidualflexibilityvectorsarerequiredthatneedvirtualgeometricsupports(SUPORTcardinNASTRAN).Subframeanalysisrequiresbodymountsattachedtoground.载荷Loads沿XYZ方向在结构接附点上作用单位载荷。副车架分析只需在底盘接附点上作用载荷。UnitloadsareappliedatthestructureattachmentpointsinXYZdirections.Forsubframeanalysis,onlythechassisattachmentpointsareloaded.结果Results输出数据类型OutputDataType输出包含接附点和方向数据的刚度列表，单位为N/mm。出于诊断目的，将接附点刚度的模态贡献量以优先级顺序列出表格，同时也列出关键接附点的信息。出于诊断目的，并考虑优先级，生成关键接附点的应变能动画。AtableofstiffnessesbyattachmentpointanddirectioninunitsofN/mm.Fordiagnosticspurposes,modalcontributionstoattachmentpointstiffnessforpriorityorcriticalattachmentpointsarelistedintableformat.Fordiagnosticspurposes,astrainenergyanimationisgeneratedforpriorityorcriticalattachmentpoints.输出内容OutputContents接附点的刚度值Stiffnessvaluesatattachmentpoints对于承载式车身结构，输出底盘和动力系统所有接附点在局部坐标下或全局坐标下XYZ方向的刚度（参照下面的刚度值注释）。对于非承载式车身结构，输出所有整备车身与车架的接附点在局部坐标下或全局坐标下XYZ方向的刚度（参照下面的刚度值注释）。对于整备车架，输出所有车身、底盘和动力系统的接附点在局部坐标下或全局坐标下XYZ方向的刚度（参照下面的刚度值注释）。对于整备车身装配到整备车架，输出所有底盘和动力系统的接附点在局部坐标下或全局坐标下XYZ方向的刚度（参照下面的刚度值注释）。对于副车架，输出所有底盘和动力系统的接附点在局部坐标下或全局坐标下XYZ方向的刚度（参照下面的刚度值注释）。注：为了得到衬套和结构的刚度比，必须确保在局部衬套坐标系下进行刚度值计算。不必一定使用全局坐标系，但它能提供一个一致的参考，便于不同车型的结果进行对比。Stiffnessvaluesatattachmentpoints(seeStiffnessNOTEbelow):Foruni-bodyconstruction,outputallofthechassisandpowertrainattachmentpointsineitherlocalorglobalXYZcoordinates(seeNOTEbelow).Forbody-on-frameconstruction,outputalltrimmedbodyattachmentpointstotheframeineitherlocalorglobalXYZcoordinates(seeNOTEbelow).Fortrimmedframe,outputallbody,chassis,andpowertrainattachmentpointsineitherlocalorglobalXYZcoordinates(seeNOTEbelow).Fortrimmedbodyassembledtotrimmedframe,outputallchassisandpowertrainattachmentpointsineitherlocalorglobalXYZcoordinates(seeNOTEbelow).Forsub-frames,outputallchassisandanypowertrainattachmentpointsineitherlocalorglobalXYZcoordinates(seeNOTEbelow).NOTE:Tocomputethestiffnessratiobetweenbushingandstructure,caremustbetakentoensurethestiffnessvaluesaredeterminedusinglocalbushingcoordinatesystems.Globalbodycoordinatesdonothavetobeusedbuttheydoprovideaconsistentframeofreferenceandfacilitatecomparisonsbetweenresultsorwithothervehicles.接附点刚度的模态贡献量Modalcontributionstoattachmentpointstiffness基于NPA、隔离状况、历史数据和测试结果，判断哪些点具有较高的优先级。只输出这些具有较高优先级的接附点。输出接附点刚度的模态贡献量。当模态以残余向量形式表示，这些模态可能集中到一起。输出具有最小贡献量的模态排名。OutputonlyaprioritizedsetofattachmentpointdirectionsbasedonNPA,isolationdeficiencies,historicaldata,ortestresultsthatindicatewhichpointsarehighpriority.Recoverallrealmodalcontributionstoattachmentpointstiffness.Modesthatareresidualvectorsmaybelumpedtogetherifdesiredintoasinglerowlabeled"Local".Showthelowestcontributionrank.应变能动画Strainenergyanimations只运行需要优化的接附点的加载工况。得到以壳单元和实体单元表示的结构的有限元分析动画，除了开闭件或整备件的动画，如油箱。Runloadcasesonlyforthoseattachmentpointsthataretargetedforimprovement.RecoverdetailedFEAanimationoutputforthoseshellandsolidelementsthatrepresentstructure.Closuresortrimitemssuchasfueltanksneednotberecovered.结果处理ResultsProcessing刚度计算StiffnessCalculation接附点在某个方向的刚度等于该受力点在2.0Hz时的频率响应的倒数。例如，该点的频响大小为0.000249609mm/N，则刚度值为4006N/mm。Calculatethestiffnessofeachattachmentpointineachdirectionbyinvertingeachdrivingpointfrequencyresponsefunctionat2.0Hz.Forexample,ifthedrivingpointFRFmagnitudeis0.000249609mm/Nthenthestiffnessvaluewouldbe4,006N/mm.动画和应变能AnimationandStrainEnergy将NASTRANSOL111的结算结果用动画形式呈现，利用任何可以同时显示应变能和动画的后处理软件。AnimateyourNASTRANSOL111resultsusinganypostprocessingsoftwarecapableofshowingstrainenergyandanimationsimultaneously.接附点的模态贡献量ModalContributionstoAttachmentPointStiffness只列出接附点的模态贡献量是为了判断对于多个接附点而言，哪些模态是常见的影响大的。下面这个例子表1）可以看出，地板bumping和车身前端金属板垂向和侧向弯曲模态对车身安装点的刚度影响大。表1中的数字表示贡献量的大小排名，它指出在单位载荷作用下的某一接附点，哪些模态对其刚度值的贡献量大。Modalcontributionstoattachmentpointstiffnessareusedtoidentifywhatmodesarecommonamongmultipleattachmentpoints.Thefollowingexample(Table1)showsthattheFloorPumpingandFESMVert/LatBendingarecommoncontributorstobodymountattachmentpointstiffness.Thenumbersarearankorderoftopcontributorstopotentialenergyfora