Unbalance Response Prediction for Rotors on Ball Bearings Using Speed- and Load-Dependent Nonlinear Bearing Stiffness

[摘要] Rolling-element bearing forces vary nonlinearly withbearing deflection. Thus, an accurate rotordynamic analysisrequires that bearing forces corresponding to the actual bearingdeflection be utilized. For this work, bearing forces werecalculated by COBRA-AHS, a recently developed rolling-elementbearing analysis code. Bearing stiffness was found to be a strongfunction of bearing deflection, with higher deflection producingmarkedly higher stiffness. Curves fitted to the bearing data for arange of speeds and loads were supplied to a flexible rotorunbalance response analysis. The rotordynamic analysis showed thatvibration response varied nonlinearly with the amount of rotorimbalance. Moreover, the increase in stiffness as critical speedswere approached caused a large increase in rotor and bearingvibration amplitude over part of the speed range compared to thecase of constant-stiffness bearings. Regions of bistable operationwere possible, in which the amplitude at a given speed was muchlarger during rotor acceleration than during deceleration. Amoderate amount of damping will eliminate the bistable region, butthis damping is not inherent in ball bearings.

[学科分类] 力学，机械学