外文翻译--无级变速器中摩擦环的应力分析 英文版.pdf

FiniteElementsinAnalysisandDesign352000213}225StressanalysisoftheringincontinuouslyvariabletransmissionmechanismSerdarTumkorDesignandManufacturingInstitute,StevensInstituteofTechnology,CastlePointonHudson,Hoboken,NJ07030,USAAbstractDuringtheserviceperformanceofafrictionringinacontinuouslyvariabletransmissionCVTmechanism,themostcommonlyobservedfailuremodeisfatiguefailure.Themainpurposeofthisstudyistodeterminethereasonofthisfailureandtoimprovetheshapeofthering.TheringismodeledbytheniteelementmethodFEMandalsocheckedbyanalyticalformulasgeneratedforcircularrings.Thecalculationsshowthathighinteriorstressesarepresentonthecontactsurfaces.Theshapeoftheringismodiedtondtheoptimumshapeanddimensionsofthering.Byturningagrooveinsideofthering,thesurfacestressisdecreased,butthestressesnearthegrooveisincreasedbasedonaFEManalysisdependingonthegrooveradii.Afteranalysisandoptimizationofthegrooveradius,thedimensionR1.95mmiscalculatedandtested.Fatiguefailureisobservedtodecreasebytestingthemodiedring.2000ElsevierScienceB.V.Allrightsreserved.KeywordsContinuouslyvariabletransmissionShapeoptimizationParametricniteelementmodel1.IntroductionInIndustrycontinuouslyvaryingspeedsareneededformanyapplicationsconcerningmechanisms.Thesetypesofmechanisms,whichhaveavariablevelocityandtorqueratio,arecalledcontinuouslyvariabletransmissionCVTmechanisms.DierenttypesofCVTdriveshavebeensuccessfullyusedindierentindustrialapplicationsformanyyears.Variablemetalbeltandchaindrivesareverywellknown.Inthescopeofthisstudy,aconicalandsteelringassembledtractiondriveisinvestigated.ACVTdrivewithasteelringisinexpensivebecauseofthelowcostsimpleringpartused.Buthightorquecannotbetransmittedbyfrictionaldrives.Dependingontime,atypeoffatiguefailurecalledpittingcanbeobservedduetothenormalforce,whichisneededforthefrictionalboundbetweentheconesandring.TheliteratureonCVTisveryscarce.AperformancecharacteristicofavariablemetalVbeltdrive,whichhasasimilarassemblyandperformancecharacteristic,isgivenbySun1.Speed0168874X/00/seefrontmatter2000ElsevierScienceB.V.Allrightsreserved.PIIS0168874X99000657NomenclatureAareaofthecrosssectionmm2b1widthmmddiametermmEmodulusofelasticityYoungsmodulusPaFNnormalforceNhdistancefromthecentroidalmmkconstantMbendingmomentNmmRgrooveradiusmmrradiusmm,radialpositionofthestressrnneutralaxisradiusmmRrcentroidalaxisradiusmmx,y,zcoordinateskcoecientoffrictionlpoissonratiop.9maximumstressMPaphcircumferentialnormalstressMParatio,transmittedtorque,andfrictioncoecienteectforthevariablemetalVbeltdriveareanalyzedbyKaram2.TheCVTmechanismofpowertransmittinghasbeenstudiedbyKuwabaraetal.3,4.Dynamicofthefrictionalchaindrivesissimulatedtogetrealisticpredictionsaboutthesystembehavior5,6.ThenonlineardynamicsofthechaindriveCVTarealsostudiedbyPauschandPfeier7inautomotivedrivetrainsystems.AnotherstudyonCVTisperformedbyTakemotoetal.8aboutthenoiseproblemcausedbymetaltometalcontactscheme.BasedontheniteelementmethodFEM,newoptimizationprocedureshavebeendevelopedtotransferbiologicaloptimizationmechanismstomechanicalengineering9.Itmeansthatanybiologicalloadcarriertendstoachieveaconstantstressatleastinatimeaverage.Unacceptablehighstressesduetostressconcentrationswouldcausefailure,whiletheunderloadedzonesarewastedmaterials.Therefore,theprincipleoflightweightdesignisthemaincriterionfortheshapeofnaturalstructures.Insomecasesthegeometricalconstraintsshouldbeconsideredforthefunctioningofthemechanisms,thereforethegeometrybecomesmorecriticalthantheweightconsiderations.InthosecasesprinciplesofthecomputeraidedoptimizationCAOMethodcanbeusedhowever,certaingeometricconstraintsmustbeconsidered.ThismethodwasdevelopedbyMattheckandBurkhardt10toimprovetheshapeofhighlyloadedcomponentswithrespecttoareductionandhomogenizationofstressesonthesurface.IntherstFEMrunthestressesarecalculatedwithaniteelementmodel,inwhichactualloadcasesandboundaryconditionsareused.Thisstressdistributionwillleadtoimprovetheshape.AfteranotherFEMrunofimprovedstructurethestresspeakswillbereducedandhomogenized.KasperdiscussessomeoptimizationmethodsincombinationwithgeneralnumericeldcomputationmethodslikeFEM11.214S.Tumkor/FiniteElementsinAnalysisandDesign352000213}225Fig.1.TheassemblyofCVTmechanism.InthispaperaCVTmechanismisreported,whichhasafatiguedamageproblembecauseofthehighstressonitsmetalring.Anapproximateanalyticalsolutionforthecircumferentialstressiscalculated.Tondoutthestressdistribution,FEManalysisisdone.ModicationsoftheringdesignareachievedusingahybridoftheCAOandcurvettingprocedurestogether.Themodiedcasesaretestedandthefatiguefailureisseentodecrease.2.DescriptionofthemechanismInFig.1therearetwofrictionconesonthemotorshaftofthemechanismformingapulley.b1conesarexedandb2conesarefreeintheaxialdirection.b2conesareallowedtomovewithintheprescribedrange.Bothoftheseconesmovethesamedistancesincetheyareconnectedtoeachother.AnIsometricviewandthepictureoftheCVTmechanismareshowninFigs.2and3,respectively.Velocityratiovariesbetweentheminimumandmaximumvaluesdependingonthelocationoftheringrelativetothepulley.Torqueistransmittedthroughlinecontactsbetweenthepulleyformedbytheconesandthesteelring.Frictioninterfaceissatisedbytheappliednormalforceduetogivenprestresstoconnectionpointsofthesteelringandcones.Forrollingwithoutsliding,thenormalforceandthefrictionforcearerelatedbytheCoulombsmodelasfollowsFNF/k,1wherethecoecientoffrictionl0.1}0.13isassumed12.OtherfrictionmodelsbesidetheCoulombsarereviewedbyOlssonetal.13.Forasimilarmechanism,themetalVbeltbehaviorofaVbeltCVTwasinvestigatedanalyticallyandexperimentallybyKimandLee14.InthisS.Tumkor/FiniteElementsinAnalysisandDesign352000213}225215Fig.2.Isometricviewofthecvtmechanism.Fig.3.ThePictureoftheCVTMechanism.Table1DamageobservedoncontactsurfaceoftheringWorkperiodhNumberofpitting80211204516080216S.Tumkor/FiniteElementsinAnalysisandDesign352000213}225