简谐激励频响分析规范

Q/SZJ191001-2017简谐激励频响分析规范HarmonicFrequencyResponseAnalysis20XX20XX-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简谐激励频响分析规范范围本标准规定了术语和定义、简谐的定义、CAE求解方法等方面内容。本标准适用于CAE部门NVH领域简谐激励方面内容。规范性引用文件无。术语和定义本规范涉及到的术语及其定义如下：NVHVibrationNoiseandharshness；简谐激励在频域范围内，激励的幅值和频率为正弦或者余弦。摘要在整车振动和噪声的分析研究中，系统的简谐激励频响分析是一个非常有用的工具，运用频响分析，可以进行问题要因研究、传递路径分析、结构修改的验证以及同试验对标。在上下方向的同相或者异相正弦单位力激励是应用最普遍的情况。一般来说，激励点的位置是前悬或者后悬与车身接附点，或者车辆其他拐角点位置。同相简谐激励一般用在对称为主的工况例如车辆抖动，异相简谐激励则应用在非对称为主的工况例如车辆横向振动。整车静止状态下，对悬架与车身接附点进行激励，这种工况下的试验测试结果是可重复的，并且仿真结果与这种情况下的试验数据得到的对标结果会更好。动刚度分析是一种特殊的频响分析。如果得到的速度响应点即为激励点，则成为动刚度分析，响应的曲线称为动刚度曲线。Theforcedfrequencyresponseanalysisofasystemmodelwithharmonicexcitationisapowerfultoolusedineverystageofavehiclesystemnoiseandvibrationstudy,includingrootcausestudy,transferpathanalysis,structuralmodificationevaluationandcorrelationwithhardwaretest.Themostwidelyusedharmonicforceexcitationsforsystemmodelingareinphaseorout-of-phasesinusoidalunitforcesintheverticaldirection.Oftenthepointofloadapplicationisateitherthefrontorrearsuspensionspindles,orsomeothercornerpointonthevehicle.Thein-phaseloadingtypicallyexcitessymmetricmodedominatedphenomenasuchasvehiclebeamingshake.Theout-of-phaseloadingexcitesnonsymmetricmodedominatedphenomenasuchasvehiclelateralshake.Iftheloadsareappliedatthespindlesofthesuspensionwhilethevehicleisstationary,thevehiclehardwaretestcanbeduplicatedinacontrolledenvironment.Thisallowsforpotentiallybettercorrelationbetweenthehardwaretestandtheanalyticalmodel.Mobilityanalysisisaspecialcaseoftheharmonicforcedfrequencyresponseanalysis.Ittracksthevelocityresponseatthedrivingpoint(referredtoasdrivingpointmobility)oratanyotherpoint(crossmobility)underaunitharmonicforceexcitation.Thesameprocedurediscussedbelowcanbeusedtoperformamobilitystudy.流程图图1流程图Figure1ProcessFlowDiagram工具描述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):HyperGraph建模和分析过程单位Units分析中所用单位制如下所示:Theunitsusedintheanalysisareasfollows:力(Force) N质量(Mass) Mg长度(Length) mm时间(Time) S内容ContentsN/A坐标系CoordinateSystemsN/A建模技巧ModelingTechniquesN/A假设和限制假设Assumptions所分析的系统在模型和响应上为线性的。非线性的悬置以及其他结构非线性往往不容易被理解。模态求解计算中，模态截断需要考虑到，假如不考虑模态截断误差，则高频的模态结果往往不可信。Thismodelingandanalysistechniqueassumesalinearsystem.Non-linearmounts,andotherstructuralnon-linearitiescannoteasilybecomprehended.Formodalsolutions,itisassumedthatmodaltruncationisaccountedfor.Ifmodaltruncationisnotaccountedfor,theresultsathigherfrequencieswillbepotentiallyinvalid.LimitationsN/A载荷和边界条件边界条件模型的约束应该能表现整车实际状态。对于整车分析，只有轮胎的patch节点被约束。其他自由状态即可。Themodelshouldbeconstrainedinamannerthatrepresentsthevehicleinarealoperatingcondition.Thisimpliesthatforatypicalfullvehicleanalysis,thetirepatchgridsshouldbegrounded,andnootherpointsconstrained.动刚度模型的频响分析，单相关的子系统建模即可。例如，假如计算车体动刚度，首先车体需要建模，其他的悬架、动力总成则不需要建出。假如计算悬架动刚度，那么悬架模型需要建出，车体不需要建模。IfthisprocedureisusedtogenerateFRF’sformobilitymodeling,onlythesubsystemofinterestismodeled.Forexample,ifthebodymobilitiesaredesired,onlythebodyshouldbemodeled,andnotthesuspension,powertrain,etc.Ifthesuspensionmobilitiesaredesired,onlythesuspensionshouldbemodeled,andnotthebody.载荷使用Nastran有两种数值方法求解简谐激励的频响分析：直接法和模态法。直接法是使用复杂的矩阵直接组装每个频率下的耦合的动力学方程。模态法则使用有限数量的结构模态阵型来组装非耦合动力学方程，同时缩减方程维数。强迫激励的响应是通过多数模态响应的累加得来的。在大多数实际的计算中，模态法比直接法求解效率更高，因此，应用的也更广泛。TherearetwodifferentnumericalmethodsusedbyNASTRANtosolveharmonicfrequencyresponseproblems:thedirectmethodandthemodalmethod.Thedirectmethodsolvesthecoupleddynamicequationsofmotionateachexcitationfrequencyusingcomplexalgebra.Themodalmethodutilizesafinitenumberofmodeshapesofthestructuretouncouplethedynamicequationsofmotionandatthesametimetoreducethesizeofequations.Theresponseduetoaforcingfrequencyisobtainedthroughthesummationofindividualmodalresponses.Inmostofthepracticalcasesforasystemmodel,themodalmethodisamoreefficientmethodthanthedirectmethod,thereforeitisusedmoreoften.当求解的模型尺寸较小，或者求解的模态频率是离散的，则选择用直接法。模态法使用的情况是模型尺寸巨大或者求解模态频率较多。Thedirectmethodshouldbeusedwhenthemodelsizeissmallorthenumberofdiscretefrequenciesforfrequencyresponseanalysisissmall(i.e.lessthanfive)foralargemodel.Themodalmethodshouldbeusedwhenthemodelisverylargeandthenumberofdiscretefrequenciesforfrequencyresponseanalysisislarge.基于模态的频响分析ModalFRFAnalysisinNASTRANNastranSOL111是基于模态的频响分析求解器。13.1章节提供了一个系统垂向加载正弦激励的例子，输出响应为加速度。这些卡片的详细含义和使用方法可以参考Nastran的帮助文档，其他一些重要的要点如下：NASTRANsol111isthemodalfrequencyresponsesolution.Section13.1showsasampleinputdeckforasystemmodelwithverticalsinusoidalforcesappliedatapoint.Accelerationresponseatallpointsisoutput.WhiledetailedrulesontheusageofthesecardscanbefoundintheNASTRANusers’manuals,afewimportantissuesarehighlightedasfollows.模态截断Modaltruncation可以使用EIGRL卡片提取自然频率。即使计算的模态频率范围很小，也会产生模态截断误差。为了避免累积的模态截断误差，求解的模态频率应该为频响分析上限的2~3倍。低于频响分析频率2倍，则不适用与模态发求解，应该使用直接法。TheEIGRLcardspecifiesthenumberofnormalmodesbeingextractedformodalreduction.Usingasmallnumberofmodesyieldsafastersolution,howeveritalsoincreasesmodaltruncationerror.Toavoidexcessivemodaltruncationerror,themodesupto2to3timesthefrequencyofinterestedshouldbeextracted.Ifthemodestoatleast2timesthedesiredfrequencyarenotavailable,thedirectmethodshouldbeused.阻尼Damping使用卡片TABDMP1来定义模态阻尼值。模态阻尼的定义相对于频率是独立的。一般来说，2%到4%之间的临界阻尼可以应用在系统中。当然，直接来自于整车模态试验测试的模态阻尼也可以运用。同时，可以直接修改模态阻尼值，使仿真结果能更好的对标试验结果。TheTABDMP1cardcanprovidemodaldampingvaluesforasystemmodel.Modaldampingvaluesforthiscardcanbefrequencydependent.Typically2%to4%ofcriticaldampingisusedforasystemmodel.Themodaldampingvaluesfromavehiclemodaltestcanalsobeused.Modaldampingallowthemodelertotunethemodeltobettercorrelatethefrequencyresponsetoavailabletestdata.响求解Frequencyresolution求解的频率步长有一定的规则。当求解频响上限为50Hz时，频响步长定义为0.25Hz，当求解频响上限为100Hz时，频响步长定义为0.5Hz。Afrequencyintervalof0.25Hzisrecommendedforlowfrequencystudyupto50Hzand0.5Hzforupto100Hz.直接频响分析DirectFRFAnalysisinNASTRAN直接法的频响分析使用NastranSOL108求解器完成。13.2章节提供了一个直接法求解的案例。直接法求解卡片设置类似于模态法，但直接法不适用卡片EIGRL和TABDMP1。但是，一个全局结构阻尼需要通过卡片PARAM,G,0.04定义。同样，也可以修正这个参数，来对标试验测试数据。NASTRANsol108isusedfordirectfrequencyresponseanalysis.Template13.2showsasampleinputdeckfordirectfrequencyresponseanalysisforasystemmodel.ItissimilartothemodalFRFfileexcepttherearenoEIGRLorTABDMP1card.Instead,aglobalstructuraldampingvalueisspecifiedbyaPARAM,G,0.04card.Similarly,themodelercanusethisdampingvaluetotunethemodelaccordingtotestinformation.性能要求N/A分析要求时间历程节点TimeHistoryNodesN/A输出文件OutputFilesN/A分析时长AnalysisDurationN/A结果结果格式ResultsFormatsN/A相关测试CorrelationTestsN/A参考文件N/A联系人N/A例子模态法频响分析求解例子SampleinputfileformodalfrequencyresponseIDSYNTH,MODALFREQUENCYRESPONSESOL111TIME999999CENDTITLE=PowertrainCheck,LS1/4L60E$$SolutionwillbereturnedasaPUNCHfile$ACCELERATION(PUNCH)=ALLMETHOD=1DLOAD=100FREQUENCY=100SPC=100$BEGINBULKPARAMGRDPNT0PARAMMAXRATIO1E10PARAMWTMASS1.0PARAMAUTOSPCYESPARAMNEWSEQ6PARAMK6ROT1000.PARAMPRGPSTYESPARAMEPZERO1.0E-5$$TheEIGRLCardbelowsetstherangeoffrequenciestofindmodes$Inthiscase,allmodesbetween0.0-100.0Hzwillbefound$ItwascalledbytheMETHODcardincasecontrolabove$EIGRL,1,0.0,100.0,,,15,.1$$TheFREQ1cardbelowspecifiesthefrequencyrangetosolveover.$Inthecase,thefrequencyresponsewillbecomputedfor$.5-50Hzinincrementsof.5Hz,or100incrementsof.5Hz$ItwascalledbytheFREQcardincasecontrol.$FREQ1,100,0.5,0.5,100$$TheDLOADcardiscalledbytheDLOAD=100incasecontrolsection.$TheDLOADcardspecifiesthemagnitudeoftheloadandreferencesRLOAD.$TheRLOADcardsetsloadphasingandreferencesDAREAandTABLED1.$TheDAREAcardsetsthegridnumberforloadingandthedirection.$TheTABLED1cardsetstheamplitudeoftheloadingoverthefrequency$ desired.$Thereareotherwaysofloadingthestructure.SeeNASTRANreferences.$DLOAD,100,.00102,1.0,200RLOAD1,200,300,0,0,0,400DAREA,300,70500,3,1.00TABLED1400+400A+400A0.01.060.01.0ENDT$INCLUDE'/home/guest/powertrain_model.bdf’$ENDDATA直接法频响分析求解例子SampleinputfilefordirectfrequencyresponseanalysisIDSYNTH,MODALFREQUENCYRESPONSESOL108TIME999999CENDTITLE=PowertrainCheck,LS1/4L60EACCELERATION(PUNCH)=ALLDLOAD=10