>> P.24
StaticsafetyfactorThebasicstaticloadratinggivesthetheoreticalallow-ablelimitofthestaticequivalentload.Normally,thislimitiscorrectedbyconsideringtheoperatingcondi-tionsandtherequirementsforthebearing.Thecor-rectionfactor,namely,thestaticsafetyfactorfsisdefinedasinthefollowingequationanditsgeneralvaluesareshowninTable4.fs= ………………………………………(9)C0P0C0: Basicstaticloadrating,NP0: Staticequivalentload,Nwhere, Table4StaticsafetyfactorOperatingconditionsofthebearingWhenhighrotationalaccuracyisrequiredForordinaryoperationconditionsForordinaryoperationconditionsnotrequiringverysmoothrotationWhenthereisalmostnorotationfs≧3≧1.5≧1IncaseofShellTypeNeedleRollerBearingsofwhichouterringisdrawnfromathinsteelplateandthencarburizedandquenched,itisnecessarytouseasta-ticsafetyfactorof3ormore.BasicStaticLoadRatingandStaticSafetyFactorBasicstaticloadratingintheracewaysorload,therotatingperformance.Whenabearingatrestsustainsaheavyloadorabearingrotatingatarelativelylowspeedreceivesaheavyshockthecontactstressmayexceedalimitingvalue,producingalocalpermanentcertaindeformationtherollingelements,andsubsequentlycausingnoiseorvibrationorlower-ingThebasicstaticloadratingis,therefore,determinedasaguidelineforthemaximumallowableloadforthebearingatrest,underwhichthepermanentdeformationwillnotexceedaloweringoftherotatingcertainlimitvalue,andtheperformancewillnotoccur.Itsdefinitionisgivenasfollows.ThebasicstaticloadratingisthestaticloadthatgivesthecontactstressshowninTable3atthecenterofthecontactareaoftherollingelementandtherace-wayreceivingthemaximumload.Aradialloadcon-stantindirectionandmagnitudeisusedinthecaseofradialbearings,whileanaxialloadconstantinmagni-tudeactingalongthebearingcentralaxisisusedinthecaseofthrustbearings.Table3TypeofbearingContactstress MPaRollerbearingsSelf-aligningballbearingsOtherballbearings400046004200A21
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