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1、外文原文EXTENDINGBEARINGLIFEAbstract：Natureworkshardtodestroybearings,buttheirchancesofsurvivalcanbeimprovedbyfollowingafewsimpleguidelines.Extremeneglectinabearingleadstooverheatingandpossiblyseizureor,atworst,anexplosion.Butevenafailedbearingleavescluesastowhatwentw
2、rong.Afteralittledetectivework,actioncanbetakentoavoidarepeatperformance.Keywords:bearingsfailureslifeBearingsfailforanumberofreasons，butthemostcommonaremisapplication，contamination，improperlubricant，shippingorhandlingdamage，andmisalignment.Theproblemisoftennotdif
3、ficulttodiagnosebecauseafailedbearingusuallyleavestelltalesignsaboutwhatwentwrong．However，whileapostmortemyieldsgoodinformation，itisbettertoavoidtheprocessaltogetherbyspecifyingthebearingcorrectlyinThefirstplace．Todothis，itisusefultoreviewthemanufacturerssizinggui
4、delinesandoperatingcharacteristicsfortheselectedbearing.Equallycriticalisastudyofrequirementsfornoise,torque,andrunout,aswellaspossibleexposuretocontaminants,hostileliquids,andtemperatureextremes.Thiscanprovidefurthercluesastowhetherabearingisrightforajob.1Whybear
5、ingsfailAbout40%ofballbearingfailuresarecausedbycontaminationfromdust,dirt,shavings,andcorrosion.Contaminationalsocausestorqueandnoiseproblems,andisoftentheresultofimproperhandlingortheapplicationenvironment．Fortunately,abearingfailurecausedbyenvironmentorhandling
6、contaminationispreventable，andasimplevisualexaminationcaneasilyidentifythecause．Conductingapostmortemil1ustrateswhattolookforonafailedorfailingbearing．Then，understandingthemechanismbehindthefailure,suchasbrinellingorfatigue,helpseliminatethesourceoftheproblem.Brin
7、ellingisonetypeofbearingfailureeasilyavoidedbyproperhandingandassembly.Itischaracterizedbyindentationsinthebearingracewaycausedbyshockloading－suchaswhenabearingisdropped-orincorrectassembly.Brinellingusuallyoccurswhenloadsexceedthematerialyieldpoint(350,000psiinSA
8、E52100chromesteel)．Itmayalsobecausedbyimproperassembly,Whichplacesaloadacrosstheraces．Racewaydentsalsoproducenoise，vibration，andincreasedtorque.Asimilar
