reaches6000 rpm,thetemperaturerisewillexceed25 °Cwhilethepreloadisreducedtoalowerlevel.Fromtherollingbearinganalysistheory[1]T.A.Harris,RollingBearingAnalysis(thirded.),JohnWileyandSons,NewYork(1991).[1],thespin–rollratioisincreasedbydecreasingthepreload.Asthespin–rollratioincreases,thebearingproducesmorefrictionandhenceheatgeneration.Meanwhile,itisobservedfromourexperimentthatthepreloadlessthan1000 Ncannoteliminateclearanceeffectivelyandthusdecreasetherigidityandincreasethefrictionandwearresultingfromexcessivesliding.Therefore,thepreloadof1000 Ncanbedeterminedforhighspeedrangeover6000 rpm.Thevariablepreloadswiththerotationspeedduringhighspeedrange(3000–7000 rpm)canbeobtained,aslistedinTable8.Speed(rpm)Variablepreload(N)≤40002000≤50001000≤60001000≤70001000Variablepreloadsforhighspeedrange.
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