轴承中英文对照外文翻译文献.docx

轴承中英文对照外文翻译文献.docx

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轴承中英文对照外文翻译文献

中英文资料翻译

（文档含英文原文和中文翻译）

EXTENDINGBEARINGLIFE

Abstract：

Natureworkshardtodestroybearings,buttheirchancesofsurvivalcanbeimprovedbyfollowingafewsimpleguidelines.Extremeneglectinabearingleadstooverheatingandpossiblyseizureor,atworst,anexplosion.Butevenafailedbearingleavescluesastowhatwentwrong.Afteralittledetectivework,actioncanbetakentoavoidarepeatperformance.

Keywords:

bearingsfailureslife

Bearingsfailforanumberofreasons，butthemostcommonaremisapplication，contamination，improperlubricant，shippingorhandlingdamage，andmisalignment.Theproblemisoftennotdifficulttodiagnosebecauseafailedbearingusuallyleavestelltalesignsaboutwhatwentwrong．

However，whileapostmortemyieldsgoodinformation，itisbettertoavoidtheprocessaltogetherbyspecifyingthebearingcorrectlyinThefirstplace．Todothis，itisusefultoreviewthemanufacturerssizingguidelinesandoperatingcharacteristicsfortheselectedbearing.

Equallycriticalisastudyofrequirementsfornoise,torque,andrunout,aswellaspossibleexposuretocontaminants,hostileliquids,andtemperatureextremes.Thiscanprovidefurthercluesastowhetherabearingisrightforajob.

1Whybearingsfail

About40%ofballbearingfailuresarecausedbycontaminationfromdust,dirt,shavings,andcorrosion.Contaminationalsocausestorqueandnoiseproblems,andisoftentheresultofimproperhandlingortheapplicationenvironment．Fortunately,abearingfailurecausedbyenvironmentorhandlingcontaminationispreventable，andasimplevisualexaminationcaneasilyidentifythecause．

Conductingapostmortemil1ustrateswhattolookforonafailedorfailingbearing．Then，understandingthemechanismbehindthefailure,suchasbrinellingorfatigue,helpseliminatethesourceoftheproblem.

Brinellingisonetypeofbearingfailureeasilyavoidedbyproperhandingandassembly.Itischaracterizedbyindentationsinthebearingracewaycausedbyshockloading－suchaswhenabearingisdropped-orincorrectassembly.Brinellingusuallyoccurswhenloadsexceedthematerialyieldpoint（350,000psiinSAE52100chromesteel）．Itmayalsobecausedbyimproperassembly,Whichplacesaloadacrosstheraces．Racewaydentsalsoproducenoise，vibration，andincreasedtorque.

Asimilardefectisapatternofellipticaldentscausedbyballsvibratingbetweenracewayswhilethebearingisnotturning．Thisproblemiscalledfalsebrinelling.Itoccursonequipmentintransitorthatvibrateswhennotinoperation.Inaddition,debriscreatedbyfalsebrinellingactslikeanabrasive,furthercontaminatingthebearing.Unlikebrinelling,falsebinellingisoftenindicatedbyareddishcolorfromfrettingcorrosioninthelubricant.

Falsebrinellingispreventedbyeliminatingvibrationsourcesandkeepingthebearingwelllubricated.Isolationpadsontheequipmentoraseparatefoundationmayberequiredtoreduceenvironmentalvibration.Alsoalightpreloadonthebearinghelpskeeptheballsandracewayintightcontact.Preloadingalsohelpspreventfalsebrinellingduringtransit.

Seizurescanbecausedbyalackofinternalclearance,improperlubrication,orexcessiveloading.Beforeseizing,excessive,frictionandheatsoftensthebearingsteel.Overheatedbearingsoftenchangecolor，usuallytoblue-blackorstrawcolored．Frictionalsocausesstressintheretainer，whichcanbreakandhastenbearingfailure．

Prematurematerialfatigueiscausedbyahighloadorexcessivepreload．Whentheseconditionsareunavoidable，bearinglifeshouldbecarefullycalculatedsothatamaintenanceschemecanbeworkedout．

Anothersolutionforfightingprematurefatigueischangingmaterial．Whenstandardbearingmaterials，suchas440CorSAE52100，donotguaranteesufficientlife，specialtymaterialscanberecommended.Inaddition，whentheproblemistracedbacktoexcessiveloading，ahighercapacitybearingordifferentconfigurationmaybeused．

Creepislesscommonthanprematurefatigue．Inbearings．itiscausedbyexcessiveclearancebetweenboreandshaftthatallowstheboretorotateontheshaft．Creepcanbeexpensivebecauseitcausesdamagetoothercomponentsinadditiontothebearing．

0thermorelikelycreepindicatorsarescratches，scuffmarks，ordiscolorationtoshaftandbore．Topreventcreepdamage，thebearinghousingandshaftfittingsshouldbevisuallychecked．

Misalignmentisrelatedtocreepinthatitismountingrelated．Ifracesaremisalignedorcocked．Theballstrackinanoncircumferencialpath．Theproblemisincorrectmountingortolerancing，orinsufficientsquarenessofthebearingmountingsite．Misalignmentofmorethan1/4·cancauseanearlyfailure．

Contaminatedlubricantisoftenmoredifficulttodetectthanmisalignmentorcreep．Contaminationshowsasprematurewear．Solidcontaminantsbecomeanabrasiveinthelubricant．Inaddition。

insufficientlubricationbetweenballandretainerwearsandweakenstheretainer．Inthissituation，lubricationiscriticaliftheretainerisafullymachinedtype．Ribbonorcrownretainers，incontrast，allowlubricantstomoreeasilyreachallsurfaces．

Rustisaformofmoisturecontaminationandoftenindicatesthewrongmaterialfortheapplication．Ifthematerialchecksoutforthejob，theeasiestwaytopreventrustistokeepbearingsintheirpackaging，untiljustbeforeinstallation．

2Avoidingfailures

Thebestwaytohandlebearingfailuresistoavoidthem．Thiscanbedoneintheselectionprocessbyrecognizingcriticalperformancecharacteristics．Theseincludenoise，startingandrunningtorque，stiffness，nonrepetitiverunout，andradialandaxialplay．Insomeapplications,theseitemsaresocriticalthatspecifyinganABEClevelaloneisnotsufficient．

Torquerequirementsaredeterminedbythelubricant，retainer，racewayquality（roundnesscrosscurvatureandsurfacefinish），andwhethersealsorshieldsareused．Lubricantviscositymustbeselectedcarefullybecauseinappropriatelubricant，especiallyinminiaturebearings，causesexcessivetorque．Also，differentlubricantshavevaryingnoisecharacteristicsthatshouldbematchedtotheapplication.Forexample，greasesproducemorenoisethanoil．

Nonrepetitiverunout（NRR）occursduringrotationasarandomeccentricitybetweentheinnerandouterraces，muchlikeacamaction．NRRcanbecausedbyretainertoleranceoreccentricitiesoftheracewaysandballs．Unlikerepetitiverunout,nocompensationcanbemadeforNRR.

NRRisreflectedinthecostofthebearing．Itiscommonintheindustrytoprovidedifferentbearingtypesandgradesforspecificapplications．Forexample，abearingwithanNRRoflessthan0.3umisusedwhenminimalrunoutisneeded，suchasindisk—drivespindlemotors．Similarly，machine—toolspindlestolerateonlyminimaldeflectionstomaintainprecisioncuts．Consequently,bearingsaremanufacturedwithlowNRRjustformachine-toolapplications．

Contaminationisunavoidableinmanyindustrialproducts，andshieldsandsealsarecommonlyusedtoprotectbearingsfromdustanddirt．However，aperfectbearingsealisnotpossiblebecauseofthemovementbetweeninnerandouterraces．Consequently，lubricationmigrationandcontaminationarealwaysproblems．

Onceabearingiscontaminated,itslubricantdeterioratesandoperationbecomesnoisier．Ifitoverheats，thebearingcanseize．Attheveryleast，contaminationcauseswearasitworksbetweenballsandtheraceway，becomingimbeddedintheracesandactingasanabrasivebetweenmetalsurfaces．Fendingoffdirtwithsealsandshieldsillustratessomemethodsforcontrollingcontamination．

Noiseisasanindicatorofbearingquality．Variousnoisegradeshavebeendevelopedtoclassifybearingperformancecapabilities．

NoiseanalysisisdonewithanAnderonmeter,whichisusedforqualitycontrolinbearingproductionandalsowhenfailedbearingsarereturnedforanalysis.Atransducerisattachedtotheouterringandtheinnerraceisturnedat1,800rpmonanairspindle.Noiseismeasuredinandirons,whichrepresentballdisplacementinμm/rad.

Withexperience,inspectorscanidentifythesmallestflawfromtheirsound.Dust,forexample,makesanirregularcrackling.Ballscratchesmakeaconsistentpoppingandarethemostdifficulttoidentify.Inner-racedamageisnormallyaconstanthigh-pitchednoise,whileadamagedouterracemakesanintermittentsoundasitrotates.

Bearingdefectsarefurtheridentifiedbytheirfrequencies.Generally,defectsareseparatedintolow,medium,andhighwavelengths.Defectsarealsoreferencedtothenumberofirregularitiesperrevolution.

Low-bandnoiseistheeffectoflong-wavelengthirregularitiesthatoccurabout1.6to10timesperrevolution.Thesearecausedbyavarietyofinconsistencies,suchaspocketsintherace.Detectablepocketsaremanufacturingflawsandresultwhentheraceismountedtootightlyinmultiplejawchucks.

Medium-handnoiseischaracterizedbyirregularitiesthatoccur10to60timesperrevolution.Itiscausedbyvibrationinthegrindingoperationthatproducesballsandraceways.High-handirregularitiesoccurat60to300timesperrevolutionandindicatecloselyspacedchattermarksorwidelyspaced,roughirregularities.

ClassifyingbearingsbytheirnoisecharacteristicsallowsuserstospecifyanoisegradeinadditiontotheABECstandardsusedbymostmanufacturers.ABECdefinesphysicaltolerancessuchasbore,outerdiameter,andrunout.AstheABECclassnumberincrease（from3to9）,tolerancesaretightened.ABECclass,however,doesnotspecifyotherbearingcharacteristicssuchasracewayquality,finish,ornoise.Hence,anoiseclassificationhelpsimproveontheindustrystandard.

GEARANDSHAFTINTRODUCTION

Abstract:

Theimportantpositio