Q/SZJ191001-2017簡(jiǎn)諧激勵(lì)頻響分析規(guī)范HarmonicFrequencyResponseAnalysis20XX20XX-12-31實(shí)施20XX-11-27發(fā)布XXXX汽車工程技術(shù)有限公司發(fā)布Q/SZXX-X-2017簡(jiǎn)諧激勵(lì)頻響分析規(guī)范范圍本標(biāo)準(zhǔn)規(guī)定了術(shù)語(yǔ)和定義、簡(jiǎn)諧的定義、CAE求解方法等方面內(nèi)容。本標(biāo)準(zhǔn)適用于CAE部門NVH領(lǐng)域簡(jiǎn)諧激勵(lì)方面內(nèi)容。規(guī)范性引用文件無(wú)。術(shù)語(yǔ)和定義本規(guī)范涉及到的術(shù)語(yǔ)及其定義如下：NVHVibrationNoiseandharshness；簡(jiǎn)諧激勵(lì)在頻域范圍內(nèi)，激勵(lì)的幅值和頻率為正弦或者余弦。摘要在整車振動(dòng)和噪聲的分析研究中，系統(tǒng)的簡(jiǎn)諧激勵(lì)頻響分析是一個(gè)非常有用的工具，運(yùn)用頻響分析，可以進(jìn)行問題要因研究、傳遞路徑分析、結(jié)構(gòu)修改的驗(yàn)證以及同試驗(yàn)對(duì)標(biāo)。在上下方向的同相或者異相正弦單位力激勵(lì)是應(yīng)用最普遍的情況。一般來說，激勵(lì)點(diǎn)的位置是前懸或者后懸與車身接附點(diǎn)，或者車輛其他拐角點(diǎn)位置。同相簡(jiǎn)諧激勵(lì)一般用在對(duì)稱為主的工況例如車輛抖動(dòng)，異相簡(jiǎn)諧激勵(lì)則應(yīng)用在非對(duì)稱為主的工況例如車輛橫向振動(dòng)。整車靜止?fàn)顟B(tài)下，對(duì)懸架與車身接附點(diǎn)進(jìn)行激勵(lì)，這種工況下的試驗(yàn)測(cè)試結(jié)果是可重復(fù)的，并且仿真結(jié)果與這種情況下的試驗(yàn)數(shù)據(jù)得到的對(duì)標(biāo)結(jié)果會(huì)更好。動(dòng)剛度分析是一種特殊的頻響分析。如果得到的速度響應(yīng)點(diǎn)即為激勵(lì)點(diǎn)，則成為動(dòng)剛度分析，響應(yīng)的曲線稱為動(dòng)剛度曲線。Theforcedfrequencyresponseanalysisofasystemmodelwithharmonicexcitationisapowerfultoolusedineverystageofavehiclesystemnoiseandvibrationstudy,includingrootcausestudy,transferpathanalysis,structuralmodificationevaluationandcorrelationwithhardwaretest.Themostwidelyusedharmonicforceexcitationsforsystemmodelingareinphaseorout-of-phasesinusoidalunitforcesintheverticaldirection.Oftenthepointofloadapplicationisateitherthefrontorrearsuspensionspindles,orsomeothercornerpointonthevehicle.Thein-phaseloadingtypicallyexcitessymmetricmodedominatedphenomenasuchasvehiclebeamingshake.Theout-of-phaseloadingexcitesnonsymmetricmodedominatedphenomenasuchasvehiclelateralshake.Iftheloadsareappliedatthespindlesofthesuspensionwhilethevehicleisstationary,thevehiclehardwaretestcanbeduplicatedinacontrolledenvironment.Thisallowsforpotentiallybettercorrelationbetweenthehardwaretestandtheanalyticalmodel.Mobilityanalysisisaspecialcaseoftheharmonicforcedfrequencyresponseanalysis.Ittracksthevelocityresponseatthedrivingpoint(referredtoasdrivingpointmobility)oratanyotherpoint(crossmobility)underaunitharmonicforceexcitation.Thesameprocedurediscussedbelowcanbeusedtoperformamobilitystudy.流程圖圖1流程圖Figure1ProcessFlowDiagram工具描述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):HyperGraph建模和分析過程單位Units分析中所用單位制如下所示:Theunitsusedintheanalysisareasfollows:力(Force) N質(zhì)量(Mass) Mg長(zhǎng)度(Length) mm時(shí)間(Time) S內(nèi)容ContentsN/A坐標(biāo)系CoordinateSystemsN/A建模技巧ModelingTechniquesN/A假設(shè)和限制假設(shè)Assumptions所分析的系統(tǒng)在模型和響應(yīng)上為線性的。非線性的懸置以及其他結(jié)構(gòu)非線性往往不容易被理解。模態(tài)求解計(jì)算中，模態(tài)截?cái)嘈枰紤]到，假如不考慮模態(tài)截?cái)嗾`差，則高頻的模態(tài)結(jié)果往往不可信。Thismodelingandanalysistechniqueassumesalinearsystem.Non-linearmounts,andotherstructuralnon-linearitiescannoteasilybecomprehended.Formodalsolutions,itisassumedthatmodaltruncationisaccountedfor.Ifmodaltruncationisnotaccountedfor,theresultsathigherfrequencieswillbepotentiallyinvalid.LimitationsN/A載荷和邊界條件邊界條件模型的約束應(yīng)該能表現(xiàn)整車實(shí)際狀態(tài)。對(duì)于整車分析，只有輪胎的patch節(jié)點(diǎn)被約束。其他自由狀態(tài)即可。Themodelshouldbeconstrainedinamannerthatrepresentsthevehicleinarealoperatingcondition.Thisimpliesthatforatypicalfullvehicleanalysis,thetirepatchgridsshouldbegrounded,andnootherpointsconstrained.動(dòng)剛度模型的頻響分析，單相關(guān)的子系統(tǒng)建模即可。例如，假如計(jì)算車體動(dòng)剛度，首先車體需要建模，其他的懸架、動(dòng)力總成則不需要建出。假如計(jì)算懸架動(dòng)剛度，那么懸架模型需要建出，車體不需要建模。IfthisprocedureisusedtogenerateFRF’sformobilitymodeling,onlythesubsystemofinterestismodeled.Forexample,ifthebodymobilitiesaredesired,onlythebodyshouldbemodeled,andnotthesuspension,powertrain,etc.Ifthesuspensionmobilitiesaredesired,onlythesuspensionshouldbemodeled,andnotthebody.載荷使用Nastran有兩種數(shù)值方法求解簡(jiǎn)諧激勵(lì)的頻響分析：直接法和模態(tài)法。直接法是使用復(fù)雜的矩陣直接組裝每個(gè)頻率下的耦合的動(dòng)力學(xué)方程。模態(tài)法則使用有限數(shù)量的結(jié)構(gòu)模態(tài)陣型來組裝非耦合動(dòng)力學(xué)方程，同時(shí)縮減方程維數(shù)。強(qiáng)迫激勵(lì)的響應(yīng)是通過多數(shù)模態(tài)響應(yīng)的累加得來的。在大多數(shù)實(shí)際的計(jì)算中，模態(tài)法比直接法求解效率更高，因此，應(yīng)用的也更廣泛。TherearetwodifferentnumericalmethodsusedbyNASTRANtosolveharmonicfrequencyresponseproblems:thedirectmethodandthemodalmethod.Thedirectmethodsolvesthecoupleddynamicequationsofmotionateachexcitationfrequencyusingcomplexalgebra.Themodalmethodutilizesafinitenumberofmodeshapesofthestructuretouncouplethedynamicequationsofmotionandatthesametimetoreducethesizeofequations.Theresponseduetoaforcingfrequencyisobtainedthroughthesummationofindividualmodalresponses.Inmostofthepracticalcasesforasystemmodel,themodalmethodisamoreefficientmethodthanthedirectmethod,thereforeitisusedmoreoften.當(dāng)求解的模型尺寸較小，或者求解的模態(tài)頻率是離散的，則選擇用直接法。模態(tài)法使用的情況是模型尺寸巨大或者求解模態(tài)頻率較多。Thedirectmethodshouldbeusedwhenthemodelsizeissmallorthenumberofdiscretefrequenciesforfrequencyresponseanalysisissmall(i.e.lessthanfive)foralargemodel.Themodalmethodshouldbeusedwhenthemodelisverylargeandthenumberofdiscretefrequenciesforfrequencyresponseanalysisislarge.基于模態(tài)的頻響分析ModalFRFAnalysisinNASTRANNastranSOL111是基于模態(tài)的頻響分析求解器。13.1章節(jié)提供了一個(gè)系統(tǒng)垂向加載正弦激勵(lì)的例子，輸出響應(yīng)為加速度。這些卡片的詳細(xì)含義和使用方法可以參考Nastran的幫助文檔，其他一些重要的要點(diǎn)如下：NASTRANsol111isthemodalfrequencyresponsesolution.Section13.1showsasampleinputdeckforasystemmodelwithverticalsinusoidalforcesappliedatapoint.Accelerationresponseatallpointsisoutput.WhiledetailedrulesontheusageofthesecardscanbefoundintheNASTRANusers’manuals,afewimportantissuesarehighlightedasfollows.模態(tài)截?cái)郙odaltruncation可以使用EIGRL卡片提取自然頻率。即使計(jì)算的模態(tài)頻率范圍很小，也會(huì)產(chǎn)生模態(tài)截?cái)嗾`差。為了避免累積的模態(tài)截?cái)嗾`差，求解的模態(tài)頻率應(yīng)該為頻響分析上限的2~3倍。低于頻響分析頻率2倍，則不適用與模態(tài)發(fā)求解，應(yīng)該使用直接法。TheEIGRLcardspecifiesthenumberofnormalmodesbeingextractedformodalreduction.Usingasmallnumberofmodesyieldsafastersolution,howeveritalsoincreasesmodaltruncationerror.Toavoidexcessivemodaltruncationerror,themodesupto2to3timesthefrequencyofinterestedshouldbeextracted.Ifthemodestoatleast2timesthedesiredfrequencyarenotavailable,thedirectmethodshouldbeused.阻尼Damping使用卡片TABDMP1來定義模態(tài)阻尼值。模態(tài)阻尼的定義相對(duì)于頻率是獨(dú)立的。一般來說，2%到4%之間的臨界阻尼可以應(yīng)用在系統(tǒng)中。當(dāng)然，直接來自于整車模態(tài)試驗(yàn)測(cè)試的模態(tài)阻尼也可以運(yùn)用。同時(shí)，可以直接修改模態(tài)阻尼值，使仿真結(jié)果能更好的對(duì)標(biāo)試驗(yàn)結(jié)果。TheTABDMP1cardcanprovidemodaldampingvaluesforasystemmodel.Modaldampingvaluesforthiscardcanbefrequencydependent.Typically2%to4%ofcriticaldampingisusedforasystemmodel.Themodaldampingvaluesfromavehiclemodaltestcanalsobeused.Modaldampingallowthemodelertotunethemodeltobettercorrelatethefrequencyresponsetoavailabletestdata.響求解Frequencyresolution求解的頻率步長(zhǎng)有一定的規(guī)則。當(dāng)求解頻響上限為50Hz時(shí)，頻響步長(zhǎng)定義為0.25Hz，當(dāng)求解頻響上限為100Hz時(shí)，頻響步長(zhǎng)定義為0.5Hz。Afrequencyintervalof0.25Hzisrecommendedforlowfrequencystudyupto50Hzand0.5Hzforupto100Hz.直接頻響分析DirectFRFAnalysisinNASTRAN直接法的頻響分析使用NastranSOL108求解器完成。13.2章節(jié)提供了一個(gè)直接法求解的案例。直接法求解卡片設(shè)置類似于模態(tài)法，但直接法不適用卡片EIGRL和TABDMP1。但是，一個(gè)全局結(jié)構(gòu)阻尼需要通過卡片PARAM,G,0.04定義。同樣，也可以修正這個(gè)參數(shù)，來對(duì)標(biāo)試驗(yàn)測(cè)試數(shù)據(jù)。NASTRANsol108isusedfordirectfrequencyresponseanalysis.Template13.2showsasampleinputdeckfordirectfrequencyresponseanalysisforasystemmodel.ItissimilartothemodalFRFfileexcepttherearenoEIGRLorTABDMP1card.Instead,aglobalstructuraldampingvalueisspecifiedbyaPARAM,G,0.04card.Similarly,themodelercanusethisdampingvaluetotunethemodelaccordingtotestinformation.性能要求N/A分析要求時(shí)間歷程節(jié)點(diǎn)TimeHistoryNodesN/A輸出文件OutputFilesN/A分析時(shí)長(zhǎng)AnalysisDurationN/A結(jié)果結(jié)果格式ResultsFormatsN/A相關(guān)測(cè)試CorrelationTestsN/A參考文件N/A聯(lián)系人N/A例子模態(tài)法頻響分析求解例子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直接法頻響分析求解例子SampleinputfilefordirectfrequencyresponseanalysisIDSYNTH,MODALFREQUENCYRESPONSESOL108TIME999999CENDTITLE=PowertrainCheck,LS1/4L60EACCELERATION(PUNCH)=ALLDLOAD=10