>> P.299
Ⅲ-5LoadRatingandLifeLifeoflinearmotionrollingguidesEveninnormaloperationalstatus,alinearmotionrollingguidewillreachtheendofitslifeafteracertainperiodofoperations.Asrepeatedloadisconstantlyappliedontoaracewayandrollingelementsofthelinearmotionrollingguide,thisleadstoleprousdamage(scale-likewearfragments)calledfatigueflakingduetorollingcontactfatigueofmaterials,itwillbeunusableattheend.Totaltravelingdistancebeforeoccurrenceofthisfatigueflakingonaracewayorrollingelementsiscalledthelifeoflinearmotionrollingguide.Asthelifeoflinearmotionrollingguidemayvarydependingonmaterialfatiguephenomenon,ratinglifebasedonstatisticcalculationisused.RatinglifeRatinglifeoflinearmotionrollingguidereferstothetotaltravelingdistance90%ofagroupofthesamelinearmotionrollingguidecanoperatewithoutlinearmotionrollingguidematerialdamagesduetorollingcontactfatiguewhentheyareoperatedindividuallyunderthesameconditions.Fig.1DirectionofloadratingC,C0BasicdynamicloadratingCComplyingwithISO14728-1Basicdynamicloadratingreferstoloadwithcertaindirectionandsizethatislogicallyendurableforratinglifeof50×103mwhenagroupofthesamelinearmotionrollingguidesisoperatedindividuallyunderthesameconditions.BasicstaticloadratingC0ComplyingwithISO14728-2Basicstaticloadratingreferstostaticloadgeneratingacertaincontactstressatthecenterofcontactpartoftherollingelementsandaracewayundermaximumload,whichistheloadattheallowablelimitfornormalrollingmotion.Generally,itisusedconsideringstaticsafetyfactor.StaticmomentratingT0,TX,TYStaticmomentratingreferstostaticmomentloadgeneratingacertaincontactstressatthecenterofcontactpartsofrollingelementsandaracewayunderthemaximumloadwhenthemomentloadshowninFig.2isloaded,whichisthemomentloadattheallowablelimitfornormalrollingmotion.Generally,itisusedconsideringstaticsafetyfactor.Fig.2DirectionofstaticmomentratingT0TXTY
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