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This paper outlines a five degrees of freedom model of a rotating spindle supported by a pair of lubricated angular contact ball bearings. The ball to raceway contacts are simulated by non-linear contact springs, representing the elastic deformation of the mating rolling members and nonlinear spring/dampers, corresponding to the contact elastohydrodynamic oil film thickness. A regression formula is used to model the latter and includes the damping contributed by the squeeze film effect caused by the mutual convergence of bearing rings. Some results of simulation studies with the model are also presented, in both the time and frequency domains. They include the overall system response, when subjected to varying spindle mass or the number of balls in the support bearings. Furthermore, comparisons are made between the simulated response of the dry and lubricated models. The overall contribution to damping of the elastohydrodynamic oil films between the rolling elements and their raceways is shown to be slight.

This paper describes experiments carried out to investigate the frequency response of a grinding machine tool spindle supported by preloaded angular-contact ball bearings. The experimental apparatus includes a loading device to simulate grinding head radial loads. The frequency spectra obtained show bands of requencies associated with the ball passage frequency. The spectra also include bounce Good correlation of the dominant frequencies was obtained with the results of the theoretical models published elsewhere. and rocking vibration modes of the assembly, w l ere the supporting bearings act as non-linear springs.