>> P.36
1-4BearingSelection(6)RatingloadandlifeBasicratinglifeL10Definedas"ratinglifewhenreliabilityis90%undernormaloperatingconditions."Thismeansthe"totalnumberofrotationspossiblewithoutmaterialpeelingfor90%ofagroupofthesamebearingsoperatedunderthesameconditions."BasedonJISB1518:2013,itiscalculatedwiththefollowingformula.L10=CrPrL10CrPr:Basicratinglife(106rotations):Basicdynamicradialloadrating(N):Dynamicequivalentradialload(N)Thegivennumberofrotationsisnormallyexpressedastime.Basicratinglifeandlifetimehavethefollowingrelationship.L10=100ࢫnCrPrL10n:Time(h):Numberofrotations(min-1)ModifiedratinglifeLnmBasicratinglifeL10hasbeenusedastheevaluationstandardforbearingperformanceovermanyyears;inrecentyears,however,inadditiontolifecalculationatvariousreliabilitylevels,therehasbeenanincreasingdemandforlifecalculationreflectingactualstatustosomeextent,takingintoconsiderationlubricationperformance,contaminationstatus,etc.Modernhigh-qualitybearingsareknowntoachieveextremelylonglivescomparedtothebasicratinglifewheningoodoperatingstatusnotexceedingcertainconditions;ontheotherhand,pooroperatingconditionsareknowntoshortenlife.ISO281:2007andJISB1518:2013definelifecalculationformodifiedratinglifetakingintoaccountthefluctuationsandmutualeffectsofthefactorsthatinfluencebearinglife.Themodifiedratinglifedamageprobabilityn%isexpressedwiththefollowingformula.Lnm=α1αisoL10α1αisoL10:Reliabilitycoefficient:Modifiedlifecoefficient:Basicratinglife36
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