>> P.68
1-4BearingSelection(15)VibrationduetoforcedrotationBearingsbasicallyperformtheirfunctionbyrotating,buttheirrotationalsogeneratesvibration.Vibrationwhichchangesfrequencydependingontherotationspeediscalledvibrationduetoforcedrotation.CalculationofvibrationduetoforcedrotationinrollingballbearingsVibrationisgeneratedinthreedirections:axial,radial,androtation.Theseformsofvibrationseriouslyaffectperformance,dependingontheproductinwhichthebearingisused.Aswell,theseformsofvibration,asvibrationenergy,mayalsoexciteinherentvibrationinthecomponentsaroundtheshaft.Understandtheproductpropertieswhenselectingthebearingtypeanddecidingonitsspecifications.DwDpwα0Z:Balldiameter(mm):Pitchcirclediameter(mm):Nominalcontactangle(°):NumberofballsnfrFr:Integernumber:Innerringrotationspeed(Hz):Outerringrotationspeed(Hz)-DwDpwcos2α0frSameasfaDpwDw21ZfaZ(fr-fa)cosα0fr1-DwDpw21Ballorbitalvibration(fa)Retainerrotationvibration(fb)Ballrotationvibration(fc)Ballpassagevibration(fd)•FormulaforinnerringrotationVibrationduetoinnerringracewaygroovewavemotion(fe)Asasimplifiedcalculation,cosα0=1isalsoacceptable.Axialdirectionvibration(Radialdirectionvibration(fet)fer)Vibrationduetoouterringracewaygroovewavemotion(Vibrationduetoballsurfacewavemotion(fg)ff)Axialdirectionvibration(Radialdirectionvibration(fgt)fgr)fr-fa)nZ(fet±frnZfa2nfcfgt±fa68
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