Q/SZJ191001-2017整車瞬態(tài)響應分析規(guī)范SpecificationofTransientResponseAnalysis20XX20XX-12-31實施20XX-11-27發(fā)布XXXX汽車工程技術有限公司發(fā)布Q/SZXX-X-2017整車瞬態(tài)響應分析規(guī)范范圍本標準規(guī)定了整車瞬態(tài)響應分析的方法。本標準適用于CAE部門整車瞬態(tài)響應分析。規(guī)范性引用文件無。術語和定義無。摘要Abstract整車瞬態(tài)響應分析用于計算整車上特定激勵輸入的短暫響應。典型的激勵有一個緩沖塊凸起、一個路面凹坑、一段伸縮縫或其它不規(guī)則路面，這些將導致對整車的沖擊作用。響應點包括方向盤、座椅導軌和車廂內(nèi)噪聲等。瞬態(tài)響應分析是指模擬對緩沖塊激勵的響應來對比試驗和分析的結果，特別是懸架左右側同時過緩沖塊對懸架跳躍模態(tài)和左右側不同時過緩沖塊對懸架踏步模態(tài)兩種情況。本規(guī)范討論了使用NASTRAN并使用超單元進行整車瞬態(tài)響應分析方法，也可用于不采用超單元的情況。進行瞬態(tài)響應分析可以使用直接法和模態(tài)法兩種。在直接法中，整車響應通過直接數(shù)值積分求解一系列耦合方程。直接法支持線性和非線性模型。瞬態(tài)響應分析不支持復數(shù)系數(shù)，因此結構阻尼必須轉換成等價的粘性阻尼。這種轉換方法局限在于結構阻尼和等效粘性阻尼僅在某一頻率下相等，使用者必須提供這些數(shù)據(jù)。如果小于這個頻率時，阻尼減少；如果高于這個頻率時，阻尼增大。結構阻尼和單元結構阻尼都會出現(xiàn)這種情況。當進行模態(tài)瞬態(tài)響應分析時，結構模態(tài)振型用來減少計算規(guī)模，使數(shù)值積分更有效率來求解（當使用模態(tài)阻尼時）。這種方法通過匯總單獨的模態(tài)響應結果來求解總的響應。如果阻尼矩陣存在，則系統(tǒng)矩陣不能對角化。因此如果使用粘性阻尼（包括結構阻尼轉換而來的），模態(tài)瞬態(tài)分析方法求解解耦問題數(shù)值積分問題和直接法一樣。在模態(tài)空間中求解與在物理空間類似，但是求解的模態(tài)數(shù)目要遠遠少于物理空間，在模態(tài)空間進行直接積分效率更高。但模態(tài)求解方法的缺點是由于模態(tài)數(shù)目的縮減導致誤差，但可以通過殘余向量來減少。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.流程圖收集模型收集模型CollectDetailedFiniteElementModels創(chuàng)建計算卡片SetuptheDataDeckwithFileManagement,ExecutiveControl,CaseControl&BulkDataSections模型檢查ChecktheModelwithGroundcheck&WeightCheck求解RunthemodelwithSOL112(ModalTransient)orSOL109(DirectTransient)繪制響應曲線（加速度/時間）PlottheResponse(Accelerationsvs.Time)圖1流程圖工具描述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):Nastran后處理(Postprocessors):Hypergraph建模和分析過程Modeling/AnalysisProcedure為了得到更高的精確度，相關頻率范圍內(nèi)的整車模態(tài)要準確。特別是前后懸架，包括襯套剛度、阻尼和質量等值。默認使用頻率相關的襯套屬性線性值。襯套和安裝點的非線性值在加載發(fā)生改變時優(yōu)先使用。Toachievehigherlevelsofaccuracy,accuraterepresentationofthevehiclemodesisrequiredforthefrequencyregionofinterest.Thefrontchassisandsuspensionareofspecialinterest,inadditiontotheaccuratebushingstiffness,damping,mass,andsuspensionproperties.Linearfrequencydependentcharacteristicsofkeybushingpropertiesarepreferred(e.g.,frontsuspensionlowercontrolarmridebushing).Non-linearcharacteristicsofkeybushingsandmountsarealsopreferredwhentravelduringloadingresultsinratechanges.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(nèi)容Contents無。坐標系CoordinateSystems無。建模技巧ModelingTechniques無。假設和限制Assumptions/Limitations無。載荷和邊界條件Loads/BoundaryConditions約束無。載荷兩種不同的方法來描述緩沖塊的形狀。半正弦波形狀的緩沖塊用TLOAD2卡片描述，AES緩沖塊用TLOAD1和TABLED1卡片描述。在NASTRAN中，通過不同時間點緩沖塊高度來描述運動，這意味著加載隨時間改變。時間段等于緩沖塊長度除以整車速度。在測試中，使用1/512=1.953125E-03秒。分析中需要更好的方法，推薦使用2.0E-04秒，總時間為2秒，則總步長為10000。每隔10步輸出結果。Twodifferentmethodsfordescribingtheshapeofabumpwillbedescribedintheexamplesthatfollow.AbumpwiththeshapeofahalfsinepulseisdescribedwithananalyticalfunctionusingaTLOAD2cardwhileanAESimpactbumpisdescribedwithdiscreetpointsusingaTLOAD1andTABLED1cards.ToenforcethemotionspecifiedbythebumpinNASTRAN,theshapeofthebumpisdescribedasbumpheightversustime,whichmeanstheloadingconditionsarevelocitydependent.Thetimevaluesforthebumparedeterminedbydividingthebumplengthbythevehiclespeed.Inthetestdata,theresolutionusedis1/512=1.953125E-03seconds.Thefiniteelementanalysisrequiresfinerresolutionthanthetest.Therecommendedtimeincrement(t)is2.0E-4seconds;totaltimeis2seconds;andthetotaltimestepwillbe10,000.Printtheoutputatevery10steps.圖2兩種不同的方法描述緩沖塊形狀結果Results無。相關測試CorrelationTests無。性能要求PerformanceRequirements如下設計優(yōu)化方向可以提高瞬態(tài)振動性能：懸架的垂向和縱向阻尼（減振器、液壓襯套、副車架安裝點）；減少彈簧下質量或增加彈簧上質量；懸置阻尼；高的動力總成垂向表現(xiàn)質量（加速度導納）。調(diào)整液壓懸置在車輪跳躍模態(tài)時最大表現(xiàn)質量（包括摩擦）；對于非液壓動力總成懸置，考慮將動力總成在接地狀態(tài)下的跳動模態(tài)頻率高于車輪跳躍模態(tài)頻率；Designchangedthatcanimprovetransientvibration:Verticalandlongitudinaldampinginsuspension(e.g.,shocks,hydraulicridebushing&sub-framemounts)Reduceunspringmassorincreasesprungmass.Dampinginpowertrainmounts.Highverticalapparentmassofthepowertrain.Tunehydraulicstoachievemaximummassatdynamicwheelhopfrequency(inclusiveoffrictioneffects)Fornon-hydraulicpowertrainmounts,considerplacingpowertrain-to-groundbouncemodeabovedynamicwheelhopfrequency.分析要求ANALYSISREQUIREMENTS無。參考文件DOCUMENTATION無。聯(lián)系人CONTACTS無。例子EXAMPLES帶線性輪胎的整車瞬態(tài)響應分析例子：$SOL112CEND$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