Table5.Advanced Bearing Analysis Results LoadCondition Load Applied [N]Max.Mean Hertzian Stress [MPa] A.B. JonesCABARET CABARETMax. PeakuHertzian Stress [MPa] A.B.Jones X-axis Radial 13.022235.34 1135.57 3353 1703.35Axial 397.2 Z_axise Radial 70.69 2048.00 1794.91 3072 2692.4 Axial 206.5 Allofthecasesstudied predict stresses belowtheconservative guideline forquietoperation 15,with margin. Failure Discussion andPractical Solution oftheProblem Facts Thebearings failed(according tothemechanism described) duringvibrations ontheout-of-plane axis(Zaxis).Thecalculated loadsonthebearings arelowerthantheload-carrying capacity ofthebearings and themaximum meanstresses arewithinthespecified limitsbyMIL-A-83577B, Para.3.2.3.1.2. The calculated natural frequency ofthefree-body motionofthemobilepackage is123Hzfarawayfromthe 600Hzinputcomponent. However thestructural analysis showed thatZ-axisisthesecond moreloaded vibration caseandisthecasewiththemaximum radialloads.Thebearings advanced analysis showed thatthecalculated axialdeflections are21.71x10.3mmforX-axisand14.81x10.3mmforZ-axisinput andthecalculated radialdeflections are0.96x10.3mmforX-axisand6.96x10.3mmfortheZ-axis.This isanincrease ofmorethan7timesoftheradialdeflections fortheZ-axiscase.Thisisbecause a transversal resonance islocated between 600and700Hzandinaddition, thecoupling steady-state transmissibility function hasapeakinthesameregion.Asaresulttheaxialresponse onZ-axisvibrations (figure16)alsoshowshigheroverallgrmsdrivenbyahigherPSDinthe600Hzregion,highereventhan thePSDcorresponding tothe100Hzregion(thefree-body motionnaturalfrequency region). Discussion Itseemsthatthefailureistherefore related toacombination ofhighradialdeflections andhighoverall vibration levelsduetothe600HzmodesonZ-axis. Astructural analysis ofthebearing itselfwascarried outtodetermine thestructural deformations modesshapes ofthebearing. Themodelconsisted inasolid inner-race (thisistroughbecause oftheincrease inthestiffness oftheinner-race duetotheshaft)witha centered protrusion thatensured thattheoverallcenterofmasscoincides withtheofthecenterofmassof theassembly mobilepackage. Thesupplementary massidealization element addedthenecessary mass sothemodelbehaves similartotheassembly mobilepackage. Theouter-race wasconsidered supported onthefacethatinrealitytouches thesnap-ring. Duetothehighstiffness ofthesnap-ring thiswas considered totallyrigid.Theentirecompliance ofthebearing waslocated intheballs,whichweremodeled assprings oriented onallthreeaxes.Eachofthespringwaslocated between twopointsoneonthe inner-race groove andtheotherontheouterrace-groove withthestiffness derived fromtable3.The outer-race wasnotconstrained ontheouter-diameter inordertosimulate theassembly clearance. A standard modalanalysis wasdonetodetermine allmodes insidethefrequency interval from20Hzto 2000Hz.Theanalysis found6modes insidethisinterval: 451.2Hz,622.9Hz,736.0Hz,1082.0 Hz, 1164.5 Hzand1721.7 Hz.Thereisgoodcorrelation between thesemodes andtheexperimental data uMax.PeakHertzian Stressisconsidered 1.5Max.MeanHertzian Stress-elliptical stressdistribution assumption. aCalculated usingA.B.JonesBearing Analysis Software Version. 5.4.3 152309MPa(335ksi)formeanHertzian stresses basedonthespecification MIL-A-83577B, Para.3.2.3.1.2 formechanisms requiring quietoperation andlowtorqueripple. NASA/CP--2002-211506 302