Modelling and defect size estimation of a defective bearing

Abstract

Rolling element bearings eventually become worn and fail by developing surface defects, such as spalls, dents, and pits. Previous researchers have tested bearings with defects that have sharp 90° rectangular edges that were used to develop analytical models of a defective bearing and defect size estimation methods. These models have limitations that require smooth surfaces and constant curvature of the bearing components; as well as assuming the defect profile. An analytical model has been developed for a rolling element bearing that uses a measured defect profile and removes the limitations of previous analytical models that use analytical expressions for contact area and force. The predicted vibration response of a bearing with a defect on the outer raceway was compared with experimental results. It was found that the new analytical model was able to predict the vibration response of a defective bearing. Current defect size estimation methods that use time-series data to estimate the size; these methods do have an aliasing issue when the defect is larger than the separation angle of the rolling elements. In this paper a method for determining if the length of a spall defect is greater than the separation angle of the rolling elements using the varying stiffness of the bearing assembly is presented. The developed model and experimental data have been made publicly available.