Q/SZJ191001-2017車輪疲勞分析規(guī)范SpecificationofFatigueAnalysisforWheel20XX20XX-XX-XX實(shí)施20XX-XX-XX發(fā)布XXXX汽車工程技術(shù)有限公司發(fā)布Q/SZXX-X-2017車輪疲勞分析規(guī)范范圍本標(biāo)準(zhǔn)規(guī)定了汽車車輪疲勞分析的方法及要求。本標(biāo)準(zhǔn)適用于CAE部門車輪疲勞分析。規(guī)范性引用文件無。術(shù)語和定義無。摘要Abstract本流程基于車輪的耐久評(píng)估試驗(yàn)，提供了車輪彎曲和徑向疲勞的有限元分析方法。Thisprocedureprovidestheanalysismethodforwheelbendingandradiatingfatiguebasedonsimulationtestsusedtoassesswheeldurability.以下給出了流程圖并闡述部件疲勞分析的典型方法。Theprocessflowdiagramisgivenbelowandrepresentsatypicalwaytoanalysisacomponentconcerningtofatiguelife.流程圖ProcessFlowDiagramGatherinputforstrengthanalysisTargetReached?PreparatoryworkonmodelGatherinputforstrengthanalysisTargetReached?PreparatoryworkonmodelPreparatoryworkonmaterialPreparatoryworkonloadingDocumentandreportRunfatigueanalysisPreparefiniteelementmodelaccordingthegeneralmodellingguidelines.Editinputfileforfatigueanalysis.Carryoutalinearelasticstressfiniteelementanalysis.根據(jù)通用的建模指南，準(zhǔn)備有限元分析模型，編輯疲勞分析輸入文件。完成線彈性有限元應(yīng)力分析Ifnecessary,addcyclicmaterialpropertiesintomaterialdatabase.如有必要，增加循環(huán)材料屬性在材料數(shù)據(jù)庫(kù)中。Importhistoriesintoloadingdatabase.將載荷歷程導(dǎo)入到載荷數(shù)據(jù)庫(kù)中。Associatematerialaccordingtothedifferentmaterialsinthestructure.根據(jù)結(jié)構(gòu)中不同的材料關(guān)聯(lián)材料。Associatethefiniteelementloadswiththeirtimevariations.Customizeloadingunits,scalingandoffset.關(guān)聯(lián)有限元載荷時(shí)間的歷程。適配單位載荷，縮放偏移。Ifdesired,createspecialelementgroupsofinterest.如果期望，可以創(chuàng)建感興趣的特殊單元組。Selectstrain-lifefatigueanalysis.UseSmith-Watson-Toppermeanstresscorrection.SelectNeuberplasticitycorrection.Activateabiaxialitycheck.Performfatigueanalysisonelementsusingaveragingformaximumabsoluteprincipals。選擇應(yīng)變-壽命疲勞分析，使用SWT平均應(yīng)力修正。選擇Neuber塑性修正，激活二軸率檢查。使用單元平均絕對(duì)值最大主應(yīng)力開展疲勞分析。Checkdamagemodelatthecriticalareas.Ascertainservicelife.Modifymodel,ifnecessary.檢查模型危險(xiǎn)區(qū)域的損傷值。確定服役壽命。如有必要，修改模型Reportonanalysis.Documentwithdamagecontourplot.編寫報(bào)告，記錄損傷云圖。圖1流程圖Fig1ProcessFlowDiagram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/nCode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(N)質(zhì)量(Mass) 噸(Ton)長(zhǎng)度(Length) 毫米(mm)時(shí)間(Time) 秒(Second)內(nèi)容Contents本流程用線彈性分析疊加有限元模型，用E-N方法計(jì)算疲勞。載荷本身的獲取不是本流程的主題。當(dāng)物理模型處于線彈性區(qū)域，普遍認(rèn)為創(chuàng)建好的有限元模型能夠準(zhǔn)確的預(yù)測(cè)應(yīng)力。為了得到準(zhǔn)確的應(yīng)力水平，應(yīng)該注意模型網(wǎng)格的建模，應(yīng)用正確的載荷和邊界條件，并且確保材料屬性的準(zhǔn)確。識(shí)別模型中線性理論和圣維南假設(shè)理論失效的區(qū)域也是非常重要的。在車輪中這些假設(shè)沒有失效的地方，用本流程產(chǎn)生的應(yīng)力結(jié)果來精確評(píng)估絕對(duì)性能（不是相對(duì)性能）期望是合理的。Thisprocedureuseslinearelasticstressanalysisforsuperpositiononthefiniteelementsideandthestrain-lifeapproachforfatiguecalculations.Theloadingacquisitionitselfisnotatopicofthisprocedure.Itiswidelyacceptedthatwell-constructedfiniteelementmodelscanpredictstresswithverygoodaccuracywhenthephysicalstructurebeingmodeledremainsinthelinearelasticrange.Toachievethis,levelofaccuracy,however,caremustbetakenincreatingthemodelmesh,applyingthecorrectloadingandboundaryconditions,andinsuringaccuratematerialproperties.ItisalsoveryimportanttoidentifyregionsofthemodelwherelinearityandSaint-Venant'sprincipleassumptionsbreakdown.Itisreasonabletoexpectthatstressresultsfoundfollowingthisprocedurecouldbeaccurateenoughtobeusedtoestimateabsoluteasopposedtocomparativeperformanceinregionsofawheelwhereassumptionsdonotbreakdown.坐標(biāo)系CoordinateSystems有限元單元坐標(biāo)系和載荷坐標(biāo)系都是全局坐標(biāo)系：+X：整車縱向從前到后；+Y:側(cè)向從駕駛員到副駕駛；+Z：垂向從底部到頂部。Thefiniteelementcoordinatesystemandtheloadingcoordinatesystemareboththeglobalonewith:+X:longitudinallyfromfronttorearofthevehicle;+Y:laterallyfromdrivertopassenger(forlefthanddrive);+Z:verticallyfrombottomtotop.建模技巧ModelingTechniques7.4.1各車輪分析模型由輪轂、輪輞、輪輻及連接單元（焊縫）組成，其中鋁合金車輪和鋼車輪分析模型分別見圖2和圖3。圖2鋁合金車輪分析模型圖3鋼車輪分析模型Fig2TheModelofAluminumWheelFig3TheModelofSteelWheel7.4.2車輪用殼單元模擬。如用一階四邊形單元，推薦關(guān)注區(qū)域2-4mm范圍，如用二階四邊形單元，推薦單元尺寸5-6mm范圍。對(duì)于鍛造，鑄造的車輪，用實(shí)體單元建模。用一階四面體單元，推薦關(guān)注區(qū)域單元尺寸在1-2mm范圍，如用二階四面體單元，推薦單元尺寸2-4mm范圍。對(duì)于二階六面體單元，推薦范圍是5-6mm。模型中應(yīng)力公認(rèn)為不準(zhǔn)確的區(qū)域，比如螺栓孔或者是應(yīng)力和應(yīng)力梯度低的地方，可以降低有限元建模指南中四面體失效的標(biāo)準(zhǔn)，這樣能簡(jiǎn)化建模任務(wù)。當(dāng)對(duì)實(shí)體網(wǎng)格車輪進(jìn)行耐久分析時(shí)，為了得到準(zhǔn)確的大應(yīng)力，推薦實(shí)體網(wǎng)格表面包一層殼單元。確保存在的二維單元對(duì)車輪剛度沒大的影響，推薦賦予殼單元一個(gè)小的厚度（例如0.001mm）。Forstampedwheelsuseameshofshellelements.Whenusingfirstorderquadrilateralelements,itisrecommendedthattheelementsizesinregionsofinterestareinthe2to4-millimeterrange.Forsecondorder,quadrilateralelements,itisrecommendedthatelementsizesareinthe5to6-millimeterrange.Forwrought,cast,orforgedwheels,useameshofsolidelements.Whenusinglineartetrahedralelements,itisrecommendedthatelementsizesareinthe1to2-millimeterrangeforregionsofinterestinthemodel.Forsecondordertetrahedrons,therecommendedrangeis2to4millimeters.Forsecondorder,hexahedralelements,therecommendedrangeis5to6millimeters.Inregionsofthemodelwherethestressesareknowntobeinaccurate,suchasnearthelugboltcircleorinareaswhereitcanbedemonstratedthatstressesandstressgradientsarelow,itisreasonabletorelaxthetetrahedralelementcollapsecriterionoftheFiniteElementModelingGuidelinestosimplifythemodelingtask.Whenperformingadurabilityanalysisofawheelmeshedwithsolidelements,itisrecommendedto"skin"(cover)thecompletedsolidelementmodelwithappropriateshellelementstoattaingreaterstressaccuracy.Toensurethatthepresenceofthetwo-dimensionalelementsdoesnothaveasignificanteffectonthestiffnessofthewheelmodel,itisrecommendedthataverysmallthickness(forexample0.001millimeters)beassignedtothem.假設(shè)和限制Assumptions/Limitations假設(shè)Assumptions正確的應(yīng)力和壽命結(jié)果取決于許多要考慮的因素。假設(shè)模型按建模指南建模，按照上面的要求施加載荷，邊界條件是合理的，正確的材料特性被應(yīng)用，比如彈性模量和泊松比。另外假設(shè)模型中線性和S-V理論假設(shè)失效的區(qū)域被正確區(qū)分。Theaccuracyofstressandliferesultsdependonavarietyofconsiderations.ItisassumedthatthemodelusedhasameshasdescribedinModelingGuidelines,theappliedloadresultantsarecorrectasnotedabove,thatboundaryconditionsareappropriate,andthataccuratematerialpropertiessuchasmodulusofelasticityandPoisson'sRatioareused.ItisalsoassumedthatregionsofthemodelwherelinearityandSaint-Venant'sprincipleassumptionsbreakdown(regionswhereresultsmustbeignored)arecorrectlyidentified.限制Limitations在車輪表面螺栓接觸車輪，車輪接觸連接器或輪轂固定裝置處，當(dāng)用線彈性FEA處理，應(yīng)力結(jié)果是不準(zhǔn)確的。同樣的限制應(yīng)力準(zhǔn)確性發(fā)生在旋轉(zhuǎn)試驗(yàn)中輪緣約束處附近。類似的限制應(yīng)力準(zhǔn)確性也發(fā)生在徑向載荷中輪緣施加分布載荷的輪緣處。用E-N和線性疊加計(jì)算疲勞結(jié)果也許會(huì)偏離的，由于許多重要的次序。Stressresultswillbeinaccuratenearandincludingthewheelsurfaceswherethelugnutscontactthewheeland/orthewheelcontactstheadapter(rotarytest)orhubfixture(radialtest)whenlinearelasticFEAisperformed.Thesamelimitationsinstressaccuracyoccurneartheconstraintsattherimflangeintherotarytest.Similarlimitationsinstressaccuracyoccurneartheappliedloaddistributionsontherimflangesintheradialtest.Fatigueresultscalculatedusingstrain-lifeandlinearsuperpositionasdescribedinthisproceduremaybeoffbyasmuchasanorderofmagnitude.載荷和邊界條件Loads/BoundaryConditions彎曲疲勞分析約束按照試驗(yàn)臺(tái)架夾具裝夾位置，將輪緣均分成6份，按照每間隔60°約束60mm寬下部輪緣單元節(jié)點(diǎn)DOF123456，約束示意圖見下寬度60mmDOF123456寬度60mmDOF123456相隔60°圖4彎曲疲勞約束邊界Fig4TheSPCofBendingFatigue徑向疲勞分析約束鋁合金車輪約束車輪螺栓安裝孔周圍一層單元節(jié)點(diǎn)DOF123456，鋼車輪約束車輪螺栓安裝孔周圍兩層單元節(jié)點(diǎn)DOF123456,示意圖見下圖。圖5徑向疲勞約束邊界Fig5TheSPCofRadialFatigue彎曲疲勞載荷整體坐標(biāo)系下，沿X軸、Z軸分別按照公式（1）、公式（2）加載周期性變化集中力。試驗(yàn)載荷以18°間隔沿圓周方向旋轉(zhuǎn)一周，分20步得到1個(gè)靜力結(jié)果，如下圖（1）（2）FORCEFORCE（Z）FORCE（X）圖6彎曲載荷Fig6BendingLoading徑向疲勞載荷123在車輪任意中心角72°范圍內(nèi)按照公式(3)在局部坐標(biāo)系下加載徑向疲勞試驗(yàn)載荷，加載區(qū)域?yàn)檩嗇y內(nèi)外胎圈座。載荷及局部坐標(biāo)系以36°間隔沿圓周方向旋轉(zhuǎn)一周，完成10次加載，得到10個(gè)靜力結(jié)果。輪胎胎壓均布在車輪輪輞單元上，大小取試驗(yàn)中輪胎充氣胎壓值。（3）式中：Wr——與軸線成角處車輪徑向分布力；——最大徑向分布力；——徑向載荷作用的最大偏轉(zhuǎn)角，在本規(guī)范中取等于36°。對(duì)公式（3）在-到范圍內(nèi)定積分可得到計(jì)算公式如下：（4）式中：R——輪胎座半徑