Simple bearing models commonly used in rotor dynamic analyses cannot explain how the vibratory force and moment are transmitted from the shaft to the casing in rotor systems. This paper develops a lumped parameter model of a single-stage rotor system which includes a new mathematical model for precision rolling element bearings to clarify this issue quantitatively and qualitatively. A comprehensive bearing stiffness matrix [K]{sub}(bm) of dimension six is proposed which clearly demonstrates the coupling between the rotating shaft and casing motion. Eigensolution and forced harmonic solution are obtained numerically. Natural frequencies predicted are found to be in excellent agreement with finite element model. Our proposed model is capable of predicting bearing and mount moment transmissiblllties, in addition to the force transmissiblllties, which are not observed in the simple vibration models.
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