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1、EXTENDINGBEARINGLIFEBearingsfoilforanumberofreasons,butthemostcommonaremisapplication,contamination,improperlubricant,shippingorhandlingdamage,andmisalignment.Theproblemisoftennotdifficulttodiagnosebecauseafailedbearingusuallyleavestelltalesignsaboutwhatwentwrong.However,whileapostmortemyieldsg
2、oodinformation,itisbettertoavoidtheprocessaltogetherbyspecifyingthebearingcorrectlyinThefirstplace.Todothis,itisusefultoreviewthemanufacturerssizingguidelinesandoperatingcharacteristicsfortheselectedbearing.Equallycriticalisastudyofrequirementsfornoise,torque,andrunout,aswellaspossibleexposuret
3、ocontaminants,hostileliquids,andtemperatureextremes.Thiscanprovidefiirthercluesastowhetherabearingisrightforajob.1.WhybearingsfailAbout40%ofballbearingfailuresarecausedbycontaminationfromdust,dirt,shavings,andcorrosion.Contaminationalsocausestorqueandnoiseproblems,andisoftentheresultofimproperh
4、andlingortheapplicationenvironment.Fortunately,abearingfailurecausedbyenvironmentorhandlingcontaminationispreventable,andasimplevisualexaminationcaneasilyidentifythecause.Conductingapostmortemillustrateswhattolookforonafoiledorfoilingbearing.Then,understandingthemechanismbehindthefailure,suchas
5、brinellingorfatigue,helpseliminatethesourceoftheproblem.Brinellingisonetypeofbearingfailureeasilyavoidedbyproperhandingandassembly.Itischaracterizedbyindentationsinthebearingracewaycausedbyshockloading—suchaswhenabearingisdi^opped-orincorrectassembly.Brinellingusuallyoccurswhenloadsexceedthemat
6、erialyieldpoint(350,000psiinSAE52100chromesteel).Itmayalsobecausedbyimproperassembly,Whichplacesaloadacrosstheraces.Racewaydentsalsoproducenoise,vibration,andincreasedtorque・Asimilardefectisapatternofellipticaldentscausedbyballsvibratingbetweenracewayswhilethebearingisnotturning.Thisproblemisca
7、lledfalsebrinelling.Itoccursonequipmentintransitorthatvibrateswhennotinoperation.Inaddition,debriscreatedbyfalsebrinellingactslikeanabrasive,furthercontaminatingthebearing.Unlikebrinelling,falsebinellingisoftenindicatedbyareddishc
