OnthemechanismsofvariousfrettingwearmodesM.H.Zhu,Z.R.ZhounTribologyResearchInstitute,TractionPowerStateKeyLaboratory,SouthwestJiaotongUniversity,Chengdu610031,PRChinaarticleinfoArticlehistory:Received30May2010Receivedinrevisedform31January2011Accepted17February2011Availableonline9March2011Keywords:FrettingwearRadialfrettingTorsionalfrettingRotationalfrettingabstractAccordingtorelativemotiondirectionsforaball-on-flatcontact,therearefourfundamentalfrettingwearmodes,e.g.,tangential,radial,torsionalandrotationalmodes.Inthispaper,themechanismsofthesefourfundamentalfrettingwearmodes,particularlyforthelaterthreemodes,havebeenreviewedfromresultsobtainedbytheauthorsincombinationwithresultsfromliterature.Somegeneralfeatureshavebeenreported.Differencesbothinrunninganddegradationbehaviorhavebeendiscussedindetail.Resultsshowedthatsomesimilarlawsforthreefrettingregimes(partialslipregime,mixedregimeandslipregime),frettingmaps(runningconditionfrettingmapandmaterialresponsefrettingmap),wearandcrackingmechanismsobtainedfromtheclassicmode(i.e.tangentialfretting)werealsoidentifiedandusefultocharacterizetheothermodes.Nevertheless,theoccurrenceofrelativeslipfortheradialfretting,theformationofmixedregimeforthetorsionalfretting,theevolutionofsurfacemorphologyfortherotationalfrettingwerequitedifferentcomparedtothatoftheclassicalfrettingmode.&2011ElsevierLtd.Allrightsreserved.1.IntroductionFrettingphenomenonwasfirstreportedintheopenliteratureinnearonecenturyago[1].Itiscausedbytherelativeoscillatorymovementofsmallamplitudewhichmayoccurbetweencontact-ingsurfacessubjectedtosuchasmechanicalvibration,cyclicloads,electromagneticshocks,andthermalcycling[2,3].Thefrettingmayresultincontactwearbydetachmentofparticlesandcontactfatiguebyrapidcracknucleationandpropagation[2–4].Ingeneral,accordingtotherelativemotiondirections,foracontactofball-on-flat,thefrettingwearmodesarecomposedofthetangential,radial,torsionalandrotationalmodes,asnotedinFig.1[5].Infact,alotofexperimentaltestsofthetangentialortheclassicalfrettingwearhavebeenfrequentlyreportedinliteraturewhiletheotherthreemodeshavebeenrarelyinvestigatedduetosomedifficultiesinrealizationofexperimentalrigs.Forradialfretting(Fig.1(b)),itismainlyinducedbyvaryingnormalloadorthermalcycling,thetwosurfacesremainincontactandnoimpacteffectoccurs[6].Torsionalfrettingcanbedefinedastherelativemotionwhichisinducedbyreciprocatingtorsionundertheoscillatoryvibratoryenvironment[7],asseeninFig.1(c).Simi-larly,therotationalfretting(Fig.1(d))istherelativemotionofreciprocatingrotationundertheoscillatoryvibratoryenvironment[8].Recently,thefrettingweartestsofthelaterthreemodeshavebeendevelopedinourlaboratory.Inthispaper,asareference,theclassicalfrettingwear(i.e.tangentialfrettingwear)behaviorshavebeenreviewedinbrief,andthemainbehavioroftheotherthreemodeshasbeendiscussedindetail.Generalfeaturesanddifferencesinbothrunninganddegradationmechanismsforthevariousmodeshavebeensummarized.Thispaperwillnotonlyofferanoverviewofallsimplefrettingmodes,butalsobeveryusefultobetterunderstandthebehaviorofdualandmulti-directionalfrettingmodesinpractice.2.FrettingweartestersFrettingwearexperimentsofthefourmodeshavebeeninvesti-gatedwithacontactconfigurationofball-on-flat.Thetestrigshavebeen,respectively,describedindetailinpreviousworks[6–8].Fortheallfrettingmodes,theprecisecontrolandrealizationindis...
