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外文文献翻译(含：英文原文及中文译文)英文原文EXTENDINGBEARINGLIFEAbstractNatureworkshardtodestroybearings,buttheirchancesofsurvivalcanbeimprovedbyfollowingafewsimpleguidelines.Extremeneglectinabearingleadstooverheatingandpossiblyseizureor,atworst,anexplosion.Butevenafailedbearingleavescluesastowhatwentwrong.Afteralittledetectivework,actioncanbetakentoavoidarepeatperformance.Keywords:bearingsfailureslifeTherearemanycausesofbearingfailure,butcommononesareimproperuse,contamination,improperuseoflubricants,damageduringinstallationorhandling,andmountingerrors.Itisnotdifficulttodiagnosethecauseofthefailurebecausethetracesleftonthebearingscandeterminethecauseofthebearingfailure.However,whenpost-hocinvestigationsprovidevaluableinformation,itisbesttoavoidfailurescompletelybyproperlyselectingthebearingsfirst.Inordertodothis,itisimportanttoreviewthemanufacturer'sdimensionalpositioningguidelinesandtheusecharacteristicsoftheselectedbearings.1CauseofbearingfailureAbout40%ofballbearingfailuresarecausedbydust,dirt,debris,andcorrosion.Contaminationisusuallycausedbyincorrectuseandpooruseoftheenvironment.Italsocausesproblemswithtorqueandnoise.Bearingfailurescausedbytheenvironmentandcontaminationarepreventable,andsimplevisualinspectioncandeterminethecauseofsuchfailures.Throughpost-failureanalysis,youcanfindoutwhataspectsofbearingsthathavefailedorareabouttofailshouldbeviewed.Understandingthemechanismsoffailuresuchaserosionandfatiguefailurecanhelpeliminatetherootcauseoftheproblem.Aslongasitisusedandinstalledproperly,erosionofthebearingiseasilyavoided.Erosionischaracterizedbythepresenceofindentationsontheracewaysofthebearingringcausedbyimpactloadsorincorrectinstallation.Erosionusuallyoccurswhentheloadexceedstheyieldlimitofthematerial.Iftheinstallationisincorrectsothataloadtraversingthebearingringcanalsoproduceerosion.Thepitsonthebearingringsalsoproducenoise,vibrationandadditionaltorque.Asimilardefectistheellipticalindentationthatoccurswhenthebearingdoesnotrotateduetotheballoscillatingbetweenthebearingrings.Thiskindofdamageiscalledlowerosion.Thistypeofdamageoccursinboththeequipmentintransitandtheequipmentthatisstillvibratingwhennotinuse.Inaddition,thedebrisgeneratedbylow-frequencychatteringactlikeabrasiveparticlesandfurtherdamagethebearing.Unlikedenudation,lowchargeerosionisoftencharacterizedbyfrettingcorrosionthatproducesareddishcolorinthelubricant.Eliminatingthesourceofvibrationandmaintaininggoodbearinglubricationcanpreventlowloadchatter.Isolatingthedeviceorisolatingthebasecanreducethevibrationoftheenvironment.Inaddition,addingasmallpreloadonthebearingnotonlyhelpstheballandthebearingringtomaintainclosecontact,butalsohelpstopreventthelowloaderodinggeneratedduringthetransportationoftheequipment.Causesofbearingseizuresareduetolackofinternalclearance,improperlubricationandexcessiveloads.Beforeitgetsstuck,excessivefrictionandheatsoftenthebearingsteel.Overheatedbearingsusuallychangecolorandgenerallyturnblue-blackoryellowish.Frictionalsoforcesthecage,whichcandamagethesupportframeandacceleratebearingfailure.Prematurefatiguefailureofmaterialsiscausedbyexcessivepreloadafterheavyload.Iftheseconditionsareunavoidable,thebearinglifeshouldbecarefullycalculatedtodevelopamaintenanceplan.Anothersolutionistochangethematerial.Ifstandardbearingmaterialsdonotguaranteeadequatebearinglife,specialmaterialsshouldbeused.Inaddition,ifthisproblemiscausedbyexcessiveloads,bearingswithstrongerloadcarryingcapacityorotherstructuresshouldbeused.Creepisnotascommonasprematurefatigue.Thecreepofthebearingiscausedbytheexcessiveclearancebetweentheshaftandtheinnerring.Theharmcausedbycreepisverylarge.Itnotonlydamagesthebearingsbutalsodestroysotherparts.Theobviousfeaturesofperistalticmotionarescratches,scratches,orchangesinthecoloroftheshaftandtheinnerring.Inordertopreventcreep,thecomponentsofthebearinghousingandtheshaftshouldbevisuallyinspectedfirst.Creepisrelatedtoimproperinstallation.Ifthebearingringisnotcorrectortilted,theballwillmovealonganon-circularorbit.Thisproblemiscausedbyincorrectinstallationorincorrecttolerancesorinsufficientverticalityatthebearinginstallationsite.Ifthedeflectionismorethan0.25°,thebearingwillprematurelyfail.Itismuchmoredifficulttocheckthecontaminationofthelubricantthantocheckforimproperassemblyorcreep.Contaminationischaracterizedbyprematurebearingwear.Solidimpuritiesinlubricantsactlikeabrasiveparticles.Poorlubricationbetweentheballandcagecanalsowearandweakenthecage.Inthiscase,lubricationiscriticaltoafullyprocessedformofcage.Incontrast,ribbonorcrowncagesmakeiteasiertogetthelubricanttotheentiresurface.Rustisaformofmoisturepollution,anditspresenceoftenindicatesthatthematerialisnotproperlyselected.Ifamaterialistestedtomeettherequirementsofthejob,theeasiestwaytopreventrustistopackagethebearingsuntilthepackageopens.2methodstoavoidfailureThebestwaytosolvethebearingfailureproblemistoavoidfailure.Thiscanbeachievedbyconsideringkeyperformancefeaturesduringtheselectionprocess.Thesecharacteristicsincludenoise,startingandrunningtorque,stiffness,non-repetitiverunout,andradialandax