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1-4BearingSelection(6)RatingloadandlifeModernhigh-qualitybearings,manufacturedwithhigh-qualitybearingsteel,havearatinglifewhichcanbecalculatedbasedonISO281:2007andJISB1518:2013.BearinglifeTheliferequiredofbearingsvariessignificantlydependingonthedevicepurposeandrequiredcontent.Thisisbecausedeviceusageishighlydiverse,andthemeasurementscalefor"life"varieswidely.Therefore,asuitablelifemustbesetwithconsiderationforthepurposeandrequiredcontent.Evenwhenbearingsareusedundernormalconditions,repetitivecompressionstressisgeneratedontheracewaysurfaceoftheouterandinnerringsandontherollingsurfaceoftherollingelements,leadingtoflaking*duetomaterialfatigueandthusfailuretomeetspecifications.Bearingratinglifeisdefinedasthetotalnumberofrotationsuntilflakingisgenerated,expressedasapredictedvaluebasedonthebasicdynamicradialloadrating.Aswellasratinglife,otherdefinitionsoflifeincludenoiselife,lubricationlife,andfunctionallife.Noiselifereferstothetimeuntilthenoiselevelrequiredfortheapplicationorproductisexceeded,lubricationlifetothetimeuntilthelubricantdeterioratesenoughtofailtoperformitsfunction,andfunctionallifetothetimeuntilfunctionssuchasrotationspeedandrunoutexceedtheirsettingsandnolongermeetrequirements.InthebearingsmanufacturedbyMinebeaMitsumi,thesedefinitionsoflifearesometimesevenmoreimportantthantheratinglife.Thissectionprovidesanoverviewofthe"basicratinglife"and"modifiedratinglife"of"radialballbearings"asregulatedinJISB1518:2013andISO281:2007,onwhichtheJISdefinitionisbased.*Peelingordamageduetometalfatigue.Seep.83forphotographs.BasicdynamicradialloadratingCrDefinedas"agivenstationaryradialloadwhichthebearingcantheoreticallywithstandatthebasicratinglifeof1millionrotations."ThecalculationmethodisprovidedinJISB1518:2013.Thebasicdynamicradialloadratingisindicatedinthedimensiontables.34
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