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A20Lifeadjustmentfactorforoperatingconditionsa3Thisfactorhelpstakeintoaccounttheeffectsofoper-atingconditions,especiallylubricationonthebearing.Thebearinglifeislimitedbythephenomenonoffatiguewhichoccurs,ingeneral,beneathsurfacessubjectedtorepeatedstresses.Undergoodlubrica-tionconditionswheretherollingelementandracewaysurfacesarecompletelyseparatedbyanoilfilmandsurfacedamagecanbedisregarded,a3issettobe1.However,whenconditionsoflubricationarenotgood,namely,whentheviscosityofthelubricatingoilislowortheperipheralspeedoftherollingelementsisespeciallylow,andsoon,a3<1isused.Ontheotherhand,whenlubricationisespeciallygood,avalueofa3>1canbeused.Whenlubrica-tionisnotgoodanda3<1isused,thelifeadjustmentfactora2cannotgenerallyexceed1.Whenselectingabearingaccordingtothebasicdynamicloadrating,itisrecommendedthatasuitablevalueforreliabilityfactora1ischosenforeachappli-cation.Theselectionshouldbemadeusingthe(C/P)orfhvaluesdeterminedbymachinetypeandbasedupontheactualconditionsoflubrication,tem-perature,mounting,etc.,whichhavealreadybeenexperiencedandobservedinthesametypeofmachines.LimitingconditionsThesebearinglifeequationsareapplicableonlywhenthebearingismountedandlubricatednormallywith-outintrusionofforeignmaterialsandnotusedunderextremeoperatingconditions.Unlesstheseconditionsaresatisfied,thelifemaybeshortened.Forexample,itisnecessarytoseparatelyconsidertheeffectsofbearingmountingerrors,exces-sivedeformationofhousingandshaft,centrifugalforceactingonrollingelementsathigh-speedrevolu-tion,excessivepreload,especiallylargeradialinternalclearanceofradialbearings,etc.Whenthedynamicequivalentloadexceeds1/2ofthebasicdynamicloadrating,thelifeequationsmaynotbeapplicable.CorrectionofbasicdynamicloadratingfortemperatureandhardnessTemperaturefactorTheoperatingtemperatureforeachbearingisdeter-minedaccordingtoitsmaterialandstructure.Ifspe-cialheattreatmentisperformed,bearingscanbeusedattemperatureshigherthan+150°C.Astheallowablecontactstressgraduallydecreaseswhenthebearingtemperatureexceeds150°C,thebasicdynamicloadratingisloweredandcanbeobtainedbythefollowingequation:Ct= ftC…………………………………… (7)where,Ct: Basicdynamicloadratingconsideringtemperaturerise, N ft: Temperaturefactor(SeeFig.4.) C: Basicdynamicloadrating,NTemperature°C1502002500.750.80.850.90.951.0ftFig.4TemperaturefactorFurther,ifthebearingisusedathightemperature,i.e.120°Corabove,theamountofdimensionaldisplace-mentgetslarger.Sospecialheattreatmentisneces-sary.Ifneeded,pleasecontactIKO.HardnessfactorWhentheshaftorhousingisusedastheracewaysur-faceinsteadoftheinnerorouterring,thesurfacehardnessofthepartusedastheracewaysurfaceshouldbe58〜64HRC.Ifitislessthan58HRC,thebasicdynamicloadratingisloweredandcanbeobtainedbythefollowingequation:CH= fHC…………………………………… (8)where, CH: Basicdynamicloadratingconsideringhardness, N fH: Hardnessfactor(SeeFig.5.) C: BasicdynamicloadratingNHardnessofracewaysurfaceHRC60504030200.10.20.410.80.6fHFig.5HardnessfactorABCDEFGHIJKLM
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