Q/SZJ191001-2017NVH副車架模型建模規(guī)范ModelingSpecificationOfCradle/SubframeforNVH20XX20XX-XX-XX實施20XX-XX-XX發(fā)布XXXX汽車工程技術有限公司發(fā)布Q/SZXX-X-2017NVH副車架模型建模規(guī)范范圍本標準規(guī)定了NVH副車架建模方法。本標準適用于CAE部門副車架NVH模型建模。規(guī)范性引用文件下列文件對于本文件的應用是必不可少的。凡是注日期的引用文件，僅注日期的版本適用于本文件。凡是不注日期的引用文件，其最新版本（包括所有的修改單）適用于本文件。有限元網格建模規(guī)范CAE整車模型命名規(guī)范術語和定義無。摘要Abstract底盤副車架是汽車的主要結構部件。準確的副車架模型是獲得整車模型驗證和響應特性的關鍵。ThechassisCradleisamajorstructuralcomponentforcars.Anaccurateframemodelisimportantinobtainingfullvehiclemodelvalidationandresponsecharacteristics.汽車在車身下方利用副車架。前副車架支撐電機和前懸架組件和后副車架或扭力梁支撐后懸架。汽車可以使用副車架,以減少汽車重量。Carsutilizeacradle(sometimescalledsubframe)inunibodyapplications.Thefrontcradlesupportsthemotorandfrontsuspensioncomponentsandtherearcradleorcrossmembersupportstherearsuspension.Vehiclesmayusecradlesinanefforttoreducevehicleweight.本文討論了用于NVH分析的副車架的建模準則。模型可以單獨使用，也可以和其他模型組成整車模型使用。Thisdocumentdiscussesmodelingguidelinestobeusedforcradlestobuildmodelstobeusedinnoiseandvibrationanalysis.Themodelswillbeusedbothstand-aloneandincombinationwithothermodelsinafull-vehiclesystemmodel.工具描述ToolDescription仿真分析過程中需要用到的如下軟件:Thefollowingsoftwarefacilitatestheanalyticalsimulationprocess:前處理(Preprocessors):Hypermesh求解器(AnalysisCode):MSC.Nastran后處理(Postprocessors):HyperView建模和分析過程Modeling/AnalysisProcedure單位Units分析中所用單位制如下所示:Theunitsusedintheanalysisareasfollows:力(Force) 牛頓(N)質量(Mass) 噸(Ton)長度(Length) 毫米(mm)時間(Time) 秒(Second)內容Contents有限元模型的內容應包括結構特征，包括幾何和材料屬性以及載荷和邊界條件。模型的最終用戶可以添加載荷和邊界條件。Thecontentsofthefiniteelementmodelshouldincludeastructuralrepresentation,composedofthegeometryandmaterialproperties,aswellastheloadsandboundaryconditions.Loadsandboundaryconditionsmaybeaddedbytheenduserofthemodel.結構特征應包括副車架內的每個物理部件，包括但不限于鈑金件、螺栓、螺母、焊接螺母、墊片、軸套、焊縫。Thestructuralrepresentationshouldincludeeveryphysicalcomponentofthecradleincluding,butnotlimitedto,sheetmetalcomponents,bolts,nuts,weldnuts,spacers,bushings,welds.結構部件可以被劃分成二個種類：一種是即貢獻模型剛性又貢獻質量的，另一種是只貢獻模型質量的。僅貢獻于模型質量的部件（如焊接螺母等）可以用集中質量模擬。提供剛度的部件應采用板/殼或實體單元來模擬。所有部件都需要建模，以準確地表示結構的質量分布。一般情況下，工程師需要判斷哪些部件可以用集中質量模擬，哪些必須詳細建模。如果對特定部件的建模方式存在不確定性，則建模者應在保守建模，使用板/殼或實體單元對部件建模。Thecomponentsofthestructurecanbedividedintotwogroups:thosethatcontributetothemodelstiffnessandmass,andthosethatcontributeonlytomodelmass.Componentssuchasweldnutsthatcontributeonlytomodelmasscanberepresentedbylumped(concentrated)massmodelingtechniques.Componentsthatcontributetostructuralstiffnessshouldbemodeledusingplate/shellorsolidelements.Allcomponentsneedtobemodeledtoaccuratelyrepresentthedistributedmassofthestructure.Generally,engineeringjudgmentcanbeusedtodecidewhethertomodelacomponentusinglumpedmassordetailedfiniteelements.Ifthereisuncertaintyabouthowaparticularcomponentshouldbemodeled,themodelershoulderrontheconservativesideandmodelthecomponentusingplate/shellorsolidelements.坐標系CoordinateSystems整車全局坐標系。GlobalVehicleCoordinate.材料屬性MaterialProperties材料規(guī)格應從CAD零件文件中獲得,但應準確驗證。MaterialspecificationsshouldbeobtainedfromtheCAD(ComputerAidedDesign)partfile,butshouldbeverifiedforaccuracy.文件管理Documentation建議將每個零件或焊接與CAD零件名稱、編號、描述、質量、厚度、有限元模型部件名稱、楊氏模量、剪切模量、泊松比、質量密度和材料名稱等進行列出，以記錄該模型。文件應包括質量檢查，模態(tài)和靜態(tài)分析結果。ItisrecommendedthatthemodelbedocumentedbylistingeachpartorweldalongwiththeCADpartname,number,description,mass,thickness,finiteelementmodelcomponentname,Young’smodulus,shearmodulus,Poisson’sratio,massdensityandmaterialname.Resultsfromthequalitycheck,modalandstaticanalysesshouldbeincludedinthedocumentation.模型編號ModelNumbering參考文檔《NVH整車模型編號規(guī)范》。零件名管理PartNamingConventionandOrganization分析模型應按設計數據的組織方式分解為組件和零件。應該對模型零件進行命名，以防誤解這么做的原因。模型中的組件和部件應盡可能與相應的設計組件和部件號具有相同的名稱。焊接應根據焊接設計數據的命名或編號組織成集。用于加載，約束或外部連接外在附件的蛛網狀的剛性單元應該放在一個Comp里。Theanalysismodelshouldbebrokendownintocomponentsandpartsinthesamewaythatthedesigndataareorganized.Namingofmodelpartsshouldbedonesothatnomisunderstandingoftheirpurposecanbemade.Thecomponentsandpartsinthemodelshould,whereverpossible,haveidenticalnamestothecorrespondingdesigncomponentsandpartnumbers.Weldsshouldbeorganizedintocollectorsaccordingtothenamingornumberingofthewelddesigndata.Rigidspidersforloadapplication,constraintsorexternalattachmentsshouldbeorganizedintocollectors.建模技巧ModelingTechniques簡化模型建模技巧SimplifiedModelingTechniques雖然使用BEAM單元或其他單元創(chuàng)建簡化副車架模型可能是可取的,但目前沒有提供這樣做的指南。Whileitmaybedesirabletocreateasimplifiedcradlemodelusingbeamorotherelements,guidelinesfordoingsoarenotcurrentlyavailable.詳細模型建模技巧DetailedModelingTechniques參考《Q/SZC1-001-2015有限元網格建模規(guī)范》.網格類型ElementType參考《Q/SZC1-001-2015有限元網格建模規(guī)范》網格尺寸ElementSize建議單元尺寸4mm至8mm的精細/中等網格密度的板/殼單元。Therecommendedplate/shellelementsizeis4mmto8mm,orfine/mediumdensity.集中質量和非結構質量ConcentratedandNon-StructuralMass那些不提供結構剛度的零件可以用集中質量建模。在正確的位置（通常是這些組件的質心位置）用CMASS或CONM單元+蛛網狀的RBE3單元建立。RBE3單元應附著在用集中質量建模的組件相同的安裝位置上。如果一個硬角靠近附件的位置，由于增加了剛性，RBE3節(jié)點連接到硬角上是有好處的。連接到RBE3的集中質量應該連接到1-6自由度的RBE3的從點，RBE3主點連接到結構件上，自由度為1-3。Thosecomponentsofthestructurethatdonotcontributetostructuralstiffnesscanbemodeledwithlumped(concentrated)masses.CMASSorCONM2elementsshouldbeaddedtoRBE3elementspidersbuiltspecificallytolocatetheconcentratedmassatthecorrectlocation,usuallythecenterofgravityofthecomponentwhosemassisbeingmodeled.RBE3elementsshouldattachtothevehiclestructureatthesamelocationsasthecomponentattachmentswhosemassisbeingmodeled.Ifahardcornerisneartheattachmentlocation,thenitmaybebeneficialtoattachtheRBE3elementtoagridonthiscornerduetotheaddedrigidity.AttachmentoftheRBE3tothelumpedmassshouldbemadeattheRBE3dependentGRIDwithDOF1through6,whileattachmentoftheRBE3tothestructureshouldbemadeatRBE3independentGRIDswithDOF1through3.圖1集中質量建模鈑金件厚度SheetMetalComponentThickness如果實際厚度與CAD公稱厚度不一致，那么有限元模型應模擬實際鈑金件厚度，而不是CAD公稱厚度。FiniteelementmodelsshouldbebuilttoactualhardwarenominalsheetmetalthicknessratherthanCADnominalthicknessifhardwarenominaldiffersfromCADnominal.螺栓連接BoltedConnections對螺栓連接建模的綜合評估尚不具備。小螺栓只能用剛性連接進行建模,但螺栓和螺母質量必須用集中質量模擬。大型螺栓應采用BAR單元+RBE2模擬。螺栓頭的中心是蛛網狀的RBE2的主點。Acomprehensiveassessmentofmodelingofboltedconnectionsisnotyetavailable.Smallboltscouldbemodeledwithrigidconnectionsonly,buttheboltandnutmassmustbeaccountedforusingconcentrated-massmodelingtechniques(describedinthesectiononconcentratedmass).LargeboltsshouldbemodeledwithabarelementandRBE2endattachments.Thecenteroftheboltheadistheindependentnodefortherigidspiderconnection.焊接Welds副車架通常使用連續(xù)焊縫,如電弧焊或MIG焊。有幾種方法可用于對連續(xù)焊縫進行建模?？捎玫姆椒ㄊ侵苯觿傂赃B接使用RBE2單元、彈性單元、殼單元或實體單元+剛性單元、CWELD連接。Cradlesgenerallyusecontinuouswelds,suchasarcorMIGwelds.Severalmethodsareavailabletomodelcontinuouswelds.SomeoftheavailablemethodsaredirectrigidconnectionsusingRBE2elements,mesh-independent-weldsusingelastic,shellorsolidelementsthatjoinpartsbymeansofrigidattachments,orCWELDconnections.假設和限制Assumptions/Limitations假設Assumptions這種建模方法假定所有組件的行為都是線性的。不模擬非線性行為。Thismethodofmodelingassumesallcomponentsbehaveinalinearfashion.Nonlinearbehaviorisnotsimulated.限制Limitations它已經顯示在在頻率范圍到300Hz，通過該程序建立的副車架模型的自然頻率預測比實際測試頻率高5.7%以內。Ithasbeenshownthatoverafrequencyrangeto300Hz,mathmodelnaturalfrequencypredictionswerewithin5.7%greaterthanthemeasuredhardwaremeanofmultiplesamples,usingacradlemodelbuiltaccordingtothedescribedprocedures.應該注意的是,在這個的研究中,都仔細地測量了多個生產零件樣本,并與根據本文件所述的指南建立的模型進行分析預測進行比較。自然頻率預測是與測試樣品平均值誤差在±6%。Itshouldbenotedthatintheabove-mentionedstudies,multipleproductionhardwaresampleswerecarefullymeasuredandcomparedtoanalysispredictionsfrommodelsbuiltaccordingtotheguidelinesdescribedinthisdocument.Naturalfrequencypredictionswerewithinabout±6%ofthemeanofnaturalfrequencymeasurementsofmultipleproductionhardwaresamples.載荷和邊界條件Loads/BoundaryConditions在應用孤立約束時，應運用工程判斷，這會導致應力集中和局部變形。通過使用蛛網狀剛性單元，或者通過對套管零件的有限元建模,將約束分布在表示實際接觸面積的相鄰節(jié)點上,可以避免這種情況。Engineeringjudgmentshouldbeexercisedinapplyingisolatedconstraints,whichtendtoaccentuatestresssingularitiesandproduceexcessivelocaldeformations.Thissituationcanbeavoidedbydistributingtheconstraintsoveradjacentnodesthatrepresenttheactualcontactareabyusingspider-websofrigidelements,orbyemployingfiniteelementmodelingofthebushingparts.一個車身安裝支架可以建模通過一個剛性的蛛網狀的RBE3，安裝支架中心點為從點，支架周圍一圈為主點。如果實際套管用有限元網格建模，這種方法可能會導致局部剛性偏小。Abodymountattachmentcanbemodeledviaarigidspider-webofRBE3sthatconnectcenter-ofbody-mountlocationtonodesaroundthebodymountbracketopening.Thismethodmayresultinasofterlocalstructurethanwouldresultiftheactualbushingpartsweremodeledusingfiniteelements.圖2約束點或加載點建模結果Results無。性能要求PerformanceRequirements應運行自由模態(tài)分析來檢查模型，應驗證以下內容：質量、質心和慣性值是合理的。存在六階小于0.1Hz的剛體模態(tài)。在所有剛體模態(tài)中,網格應變能接近于零。所有的模型應該有6階剛體模態(tài)，代表在X、Y、Z方向單獨存在或線性組合三個平移模態(tài)和三個旋轉模態(tài)。前10階結構模態(tài)頻率應該在75Hz-400Hz之間。無可疑的局部模式。所有警告信息都應進行檢查和驗證。應根據需要更正模型。Free-freenormalmodesanalysisshouldberuntocheckthemodel.Thefollowingshouldbever