Effect of bearing preloads on the modal characteristics of a shaft-bearing assembly: Experiments on double row angular contact ball bearings

This article investigates the role of bearing preloads on the modal characteristics of a shaft-bearing assembly with a double row angular contact ball bearing. First, an analytical model is developed to comparatively evaluate the effects of axial bearing preloads on the vibratory responses of alternate double row configurations. The analytical model includes bearings via a five dimensional stiffness matrix. Changes in the resonant amplitudes with respect to the bearing preloads are examined for preload-independent and preload-dependent viscous damping models. The bearing preloads significantly affect the vibration characteristics of the shaft-bearing assembly due to major changes in both diagonal and off-diagonal elements of the stiffness matrix, and such effects depend on the bearing configuration. Second, a new experiment consisting of a vehicle wheel bearing assembly with a double row angular contact ball bearing in a back-to-back arrangement is designed. The bearing is subjected to axial or radial preloads in a controlled manner. Experiments with two preloading mechanisms show that the nature and extent of the bearing preloads considerably affect the natural frequencies and resonant amplitudes, thus influencing the vibration behavior of the bearing assembly. Finally, the new bearing stiffness model is validated using measurements from the modal experiment. Suggestions for further work are briefly discussed. (C) 2012 Elsevier Ltd. All rights reserved.