汽车差速器英文版原件

FailureanalysisofanautomobiledifferentialpinionshaftH.Bayrakceken*AfyonKocatepeUniversity,TechnicalEducationFaculty,03200Afyon,TurkeyReceived8July2005;accepted14July2005Availableonline2September2005AbstractDifferentialisusedtodecreasethespeedandtoprovidemomentincreasefortransmittingthemovementcomingfromtheenginetothewheelsbyturningitaccordingtothesuitableangleinvehiclesandtoprovidethatinnerandouterwheelsturndifferently.Piniongearandshaftattheentrancearemanufacturedasasinglepartwhereastheyareindifferentformsaccordingtoautomobiletypes.Mirrorgearwhichwillworkwiththisgearshouldbecomefamiliarbeforetheassembly.Incaseofanybreakdown,theyshouldbechangedasapair.Generally,inthesesystemsthereareweardamagesingears.Thegearinspectedinthisstudyhasdamageasaformofshaftfracture.Inthisstudy,failureanalysisofthedifferentialpinionshaftiscarriedout.Mechanicalcharacteristicsofthematerialareobtainedfirst.Then,themicrostructureandchemicalcompositionsaredetermined.Somefractographicstudiesarecarriedouttoassesthefatigueandfractureconditions.2005ElsevierLtd.Allrightsreserved.Keywords:Differential;Fracture;Powertransfer;Pinionshaft1.IntroductionThefinal-drivegearsmaybedirectlyorindirectlydrivenfromtheoutputgearingofthegearbox.Di-rectlydrivenfinaldrivesareusedwhentheengineandtransmissionunitsarecombinedtogethertoformanintegralconstruction.Indirectlydrivenfinaldrivesareusedattherearofthevehiclebeingeithersprungandattachedtothebodystructureorunsprungandincorporatedintherear-axlecasing.Thefinal-drivegearsareusedinthetransmissionsystemforthefollowingreasons[1]:(a)toredirectthedrivefromthegearboxorpropellershaftthrough90and,(b)toprovideapermanentgearreductionbetweentheengineandthedrivingroad-wheels.1350-6307/$-seefrontmatter2005ElsevierLtd.Allrightsreserved.doi:10.1016/j.engfailanal.2005.07.019*Tel.:[phone];fax:[phone].E-mailaddress:[e-mail]is13(2006)1422–1428fferentialisthemainpartwhichtransmitsthemovementcomingfromtheenginetothewheels.Onasmoothroad,themovementcomestobothwheelsevenly.Theinnerwheelshouldturnlessandtheouterwheelshouldturnmoretodotheturningwithoutlateralslippingandbeingflung.Differen-tial,whichisgenerallyplacedinthemiddlepartoftherearbridge,consistsofpiniongear,mirrorgear,differentialbox,twoaxlegearandtwopinionspidergears.AschematicillustrationofadifferentialisgiveninFig.1.ThetechnicaldrawingofthefracturedpinionshaftisalsogiveninFig.2.Fig.3showsthephotographofthefracturedpinionshaftandthefracturesec-tionisindicated.Indifferentials,mirrorandpiniongeararemadetogetusedtoeachotherduringmanufacturingandthesameserialnumberisgiven.Bothofthemarechangedonconditionthatthereareanyproblems.Inthesesystems,thecommondamageisthewearofgears[2–4].Inthisstudy,thepinionshaftofthedifferentialofaminibushasbeeninspected.Theminibusisadieselvehicledrivenattherearaxleandhasapassengercapacityof15people.Maximumenginepoweris90/4000HP/rpm,andmaximumtorqueis205/1600Nm/rpm.Itstransmissionboxhasmanualsystem(5forward,1back).Thedamagewascausedbystoppingandstartingtheminibusatatrafficlights.Inthisdifferential,entranceshaftwhichcarriesthepiniongearwasbroken.Variousstudieshavebeenmadetodeterminethetypeandpossiblereasonsofthedamage.Theseare:studiescarriedouttodeterminethematerialoftheshaft;studiescarriedouttodeterminethemicro-structure;studiesrelatedtothefracturesurface.ThereisacloserphotographofthefracturedsurfacesandfractureareainFig.4.Thefracturewascausedbytakingoutcircularmarkgearseeninthemiddleofsurfaces.Fig.1.Schematicoftheanalyseddifferential.H.Bayrakceken/EngineeringFailureAnalysis13(2006)1422–14281423Fig.2.Technicaldrawingoftheanalysedpinionshaft.Fig.3.Thepictureoftheundamageddifferentialpinionanalysedinthestudy.Fig.4.Photographsoffailedshaftandfracturesurfaces.1424H.Bayrakceken/EngineeringFailureAnalysis13(2006)1422–14282.ExperimentalprocedureSpecimensextractedfromtheshaftweresubjectedtovarioustestsincludinghardnesstestsandmetal-lographicandscanningelectronmicroscopyaswellasthedeterminationofchemicalcomposition.Alltestswerecarriedoutatroomtemperature.2.1.ChemicalandmetallurgicalanalysisChemicalanalysisofthefractureddifferentialmaterialwascarriedoutusingaspectrometer.Thechem-icalcompositionofthematerialisgiveninTable1.ChemicalcompositionshowsthatthematerialisalowalloycarburisingsteeloftheAISI8620type.Hardenabilityofthissteelisverylowbecauseoflowcarbonproportion.Therefore,surfaceareabe-comeshardandhighlyenduring,andinnerareasbecomestoughbyincreasingcarbonproportiononthesurfaceareawithcementationoperation.Thisisthekindofsteelwhichisgenerallyusedinmechanicalpartssubjecteddotorsionandbending.Highresistanceisobtainedonthesurfaceandhighfatigueendur-ancevaluecanbeobtainedwithcompressiveresidualstressbymakingthesurfaceharder[5–7].Inwhichalloyelementsdistributethemselvesincarbonsteelsdependsprimarilyonthecompound-andcarbide-formingtendenciesofeachelement.Nickeldissolvesintheaferriteofthesteelsinceithaslessten-dencytoformcarbidesthaniron.Siliconcombinestoalimitedextentwiththeoxygenpresentinthe