NVH副车架建模规范

Q/SZJ191001-2017NVH副车架模型建模规范ModelingSpecificationOfCradle/SubframeforNVH20XX20XX-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-2017NVH副车架模型建模规范范围本标准规定了NVH副车架建模方法。本标准适用于CAE部门副车架NVH模型建模。规范性引用文件下列文件对于本文件的应用是必不可少的。凡是注日期的引用文件，仅注日期的版本适用于本文件。凡是不注日期的引用文件，其最新版本（包括所有的修改单）适用于本文件。有限元网格建模规范CAE整车模型命名规范术语和定义无。摘要Abstract底盘副车架是汽车的主要结构部件。准确的副车架模型是获得整车模型验证和响应特性的关键。ThechassisCradleisamajorstructuralcomponentforcars.Anaccurateframemodelisimportantinobtainingfullvehiclemodelvalidationandresponsecharacteristics.汽车在车身下方利用副车架。前副车架支撑电机和前悬架组件和后副车架或扭力梁支撑后悬架。汽车可以使用副车架,以减少汽车重量。Carsutilizeacradle(sometimescalledsubframe)inunibodyapplications.Thefrontcradlesupportsthemotorandfrontsuspensioncomponentsandtherearcradleorcrossmembersupportstherearsuspension.Vehiclesmayusecradlesinanefforttoreducevehicleweight.本文讨论了用于NVH分析的副车架的建模准则。模型可以单独使用，也可以和其他模型组成整车模型使用。Thisdocumentdiscussesmodelingguidelinestobeusedforcradlestobuildmodelstobeusedinnoiseandvibrationanalysis.Themodelswillbeusedbothstand-aloneandincombinationwithothermodelsinafull-vehiclesystemmodel.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):MSC.Nastran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有限元模型的内容应包括结构特征，包括几何和材料属性以及载荷和边界条件。模型的最终用户可以添加载荷和边界条件。Thecontentsofthefiniteelementmodelshouldincludeastructuralrepresentation,composedofthegeometryandmaterialproperties,aswellastheloadsandboundaryconditions.Loadsandboundaryconditionsmaybeaddedbytheenduserofthemodel.结构特征应包括副车架内的每个物理部件，包括但不限于钣金件、螺栓、螺母、焊接螺母、垫片、轴套、焊缝。Thestructuralrepresentationshouldincludeeveryphysicalcomponentofthecradleincluding,butnotlimitedto,sheetmetalcomponents,bolts,nuts,weldnuts,spacers,bushings,welds.结构部件可以被划分成二个种类：一种是即贡献模型刚性又贡献质量的，另一种是只贡献模型质量的。仅贡献于模型质量的部件（如焊接螺母等）可以用集中质量模拟。提供刚度的部件应采用板/壳或实体单元来模拟。所有部件都需要建模，以准确地表示结构的质量分布。一般情况下，工程师需要判断哪些部件可以用集中质量模拟，哪些必须详细建模。如果对特定部件的建模方式存在不确定性，则建模者应在保守建模，使用板/壳或实体单元对部件建模。Thecomponentsofthestructurecanbedividedintotwogroups:thosethatcontributetothemodelstiffnessandmass,andthosethatcontributeonlytomodelmass.Componentssuchasweldnutsthatcontributeonlytomodelmasscanberepresentedbylumped(concentrated)massmodelingtechniques.Componentsthatcontributetostructuralstiffnessshouldbemodeledusingplate/shellorsolidelements.Allcomponentsneedtobemodeledtoaccuratelyrepresentthedistributedmassofthestructure.Generally,engineeringjudgmentcanbeusedtodecidewhethertomodelacomponentusinglumpedmassordetailedfiniteelements.Ifthereisuncertaintyabouthowaparticularcomponentshouldbemodeled,themodelershoulderrontheconservativesideandmodelthecomponentusingplate/shellorsolidelements.坐标系CoordinateSystems整车全局坐标系。GlobalVehicleCoordinate.材料属性MaterialProperties材料规格应从CAD零件文件中获得,但应准确验证。MaterialspecificationsshouldbeobtainedfromtheCAD(ComputerAidedDesign)partfile,butshouldbeverifiedforaccuracy.文件管理Documentation建议将每个零件或焊接与CAD零件名称、编号、描述、质量、厚度、有限元模型部件名称、杨氏模量、剪切模量、泊松比、质量密度和材料名称等进行列出，以记录该模型。文件应包括质量检查，模态和静态分析结果。ItisrecommendedthatthemodelbedocumentedbylistingeachpartorweldalongwiththeCADpartname,number,description,mass,thickness,finiteelementmodelcomponentname,Young’smodulus,shearmodulus,Poisson’sratio,massdensityandmaterialname.Resultsfromthequalitycheck,modalandstaticanalysesshouldbeincludedinthedocumentation.模型编号ModelNumbering参考文档《NVH整车模型编号规范》。零件名管理PartNamingConventionandOrganization分析模型应按设计数据的组织方式分解为组件和零件。应该对模型零件进行命名，以防误解这么做的原因。模型中的组件和部件应尽可能与相应的设计组件和部件号具有相同的名称。焊接应根据焊接设计数据的命名或编号组织成集。用于加载，约束或外部连接外在附件的蛛网状的刚性单元应该放在一个Comp里。Theanalysismodelshouldbebrokendownintocomponentsandpartsinthesamewaythatthedesigndataareorganized.Namingofmodelpartsshouldbedonesothatnomisunderstandingoftheirpurposecanbemade.Thecomponentsandpartsinthemodelshould,whereverpossible,haveidenticalnamestothecorrespondingdesigncomponentsandpartnumbers.Weldsshouldbeorganizedintocollectorsaccordingtothenamingornumberingofthewelddesigndata.Rigidspidersforloadapplication,constraintsorexternalattachmentsshouldbeorganizedintocollectors.建模技巧ModelingTechniques简化模型建模技巧SimplifiedModelingTechniques虽然使用BEAM单元或其他单元创建简化副车架模型可能是可取的,但目前没有提供这样做的指南。Whileitmaybedesirabletocreateasimplifiedcradlemodelusingbeamorotherelements,guidelinesfordoingsoarenotcurrentlyavailable.详细模型建模技巧DetailedModelingTechniques参考《Q/SZC1-001-2015有限元网格建模规范》.网格类型ElementType参考《Q/SZC1-001-2015有限元网格建模规范》网格尺寸ElementSize建议单元尺寸4mm至8mm的精细/中等网格密度的板/壳单元。Therecommendedplate/shellelementsizeis4mmto8mm,orfine/mediumdensity.集中质量和非结构质量ConcentratedandNon-StructuralMass那些不提供结构刚度的零件可以用集中质量建模。在正确的位置（通常是这些组件的质心位置）用CMASS或CONM单元+蛛网状的RBE3单元建立。RBE3单元应附着在用集中质量建模的组件相同的安装位置上。如果一个硬角靠近附件的位置，由于增加了刚性，RBE3节点连接到硬角上是有好处的。连接到RBE3的集中质量应该连接到1-6自由度的RBE3的从点，RBE3主点连接到结构件上，自由度为1-3。Thosecomponentsofthestructurethatdonotcontributetostructuralstiffnesscanbemodeledwithlumped(concentrated)masses.CMASSorCONM2elementsshouldbeaddedtoRBE3elementspidersbuiltspecificallytolocatetheconcentratedmassatthecorrectlocation,usuallythecenterofgravityofthecomponentwhosemassisbeingmodeled.RBE3elementsshouldattachtothevehiclestructureatthesamelocationsasthecomponentattachmentswhosemassisbeingmodeled.Ifahardcornerisneartheattachmentlocation,thenitmaybebeneficialtoattachtheRBE3elementtoagridonthiscornerduetotheaddedrigidity.AttachmentoftheRBE3tothelumpedmassshouldbemadeattheRBE3dependentGRIDwithDOF1through6,whileattachmentoftheRBE3tothestructureshouldbemadeatRBE3independentGRIDswithDOF1through3.图1集中质量建模钣金件厚度SheetMetalComponentThickness如果实际厚度与CAD公称厚度不一致，那么有限元模型应模拟实际钣金件厚度，而不是CAD公称厚度。FiniteelementmodelsshouldbebuilttoactualhardwarenominalsheetmetalthicknessratherthanCADnominalthicknessifhardwarenominaldiffersfromCADnominal.螺栓连接BoltedConnections对螺栓连接建模的综合评估尚不具备。小螺栓只能用刚性连接进行建模,但螺栓和螺母质量必须用集中质量模拟。大型螺栓应采用BAR单元+RBE2模拟。螺栓头的中心是蛛网状的RBE2的主点。Acomprehensiveassessmentofmodelingofboltedconnectionsisnotyetavailable.Smallboltscouldbemodeledwithrigidconnectionsonly,buttheboltandnutmassmustbeaccountedforusingconcentrated-massmodelingtechniques(describedinthesectiononconcentratedmass).LargeboltsshouldbemodeledwithabarelementandRBE2endattachments.Thecenteroftheboltheadistheindependentnodefortherigidspiderconnection.焊接Welds副车架通常使用连续焊缝,如电弧焊或MIG焊。有几种方法可用于对连续焊缝进行建模。可用的方法是直接刚性连接使用RBE2单元、弹性单元、壳单元或实体单元+刚性单元、CWELD连接。Cradlesgenerallyusecontinuouswelds,suchasarcorMIGwelds.Severalmethodsareavailabletomodelcontinuouswelds.SomeoftheavailablemethodsaredirectrigidconnectionsusingRBE2elements,mesh-independent-weldsusingelastic,shellorsolidelementsthatjoinpartsbymeansofrigidattachments,orCWELDconnections.假设和限制Assumptions/Limitations假设Assumptions这种建模方法假定所有组件的行为都是线性的。不模拟非线性行为。Thismethodofmodelingassumesallcomponentsbehaveinalinearfashion.Nonlinearbehaviorisnotsimulated.限制Limitations它已经显示在在频率范围到300Hz，通过该程序建立的副车架模型的自然频率预测比实际测试频率高5.7%以内。Ithasbeenshownthatoverafrequencyrangeto300Hz,mathmodelnaturalfrequencypredictionswerewithin5.7%greaterthanthemeasuredhardwaremeanofmultiplesamples,usingacradlemodelbuiltaccordingtothedescribedprocedures.应该注意的是,在这个的研究中,都仔细地测量了多个生产零件样本,并与根据本文件所述的指南建立的模型进行分析预测进行比较。自然频率预测是与测试样品平均值误差在±6%。Itshouldbenotedthatintheabove-mentionedstudies,multipleproductionhardwaresampleswerecarefullymeasuredandcomparedtoanalysispredictionsfrommodelsbuiltaccordingtotheguidelinesdescribedinthisdocument.Naturalfrequencypredictionswerewithinabout±6%ofthemeanofnaturalfrequencymeasurementsofmultipleproductionhardwaresamples.载荷和边界条件Loads/BoundaryConditions在应用孤立约束时，应运用工程判断，这会导致应力集中和局部变形。通过使用蛛网状刚性单元，或者通过对套管零件的有限元建模,将约束分布在表示实际接触面积的相邻节点上,可以避免这种情况。Engineeringjudgmentshouldbeexercisedinapplyingisolatedconstraints,whichtendtoaccentuatestresssingularitiesandproduceexcessivelocaldeformations.Thissituationcanbeavoidedbydistributingtheconstraintsoveradjacentnodesthatrepresenttheactualcontactareabyusingspider-websofrigidelements,orbyemployingfiniteelementmodelingofthebushingparts.一个车身安装支架可以建模通过一个刚性的蛛网状的RBE3，安装支架中心点为从点，支架周围一圈为主点。如果实际套管用有限元网格建模，这种方法可能会导致局部刚性偏小。Abodymountattachmentcanbemodeledviaarigidspider-webofRBE3sthatconnectcenter-ofbody-mountlocationtonodesaroundthebodymountbracketopening.Thismethodmayresultinasofterlocalstructurethanwouldresultiftheactualbushingpartsweremodeledusingfiniteelements.图2约束点或加载点建模结果Results无。性能要求PerformanceRequirements应运行自由模态分析来检查模型，应验证以下内容：质量、质心和惯性值是合理的。存在六阶小于0.1Hz的刚体模态。在所有刚体模态中,网格应变能接近于零。所有的模型应该有6阶刚体模态，代表在X、Y、Z方向单独存在或线性组合三个平移模态和三个旋转模态。前10阶结构模态频率应该在75Hz-400Hz之间。无可疑的局部模式。所有警告信息都应进行检查和验证。应根据需要更正模型。Free-freenormalmodesanalysisshouldberuntocheckthemodel.Thefollowingshouldbever