Fault Diagnosis of Dynamically Loaded Bearing with Localized Defect Based on Defect-Induced Excitation

Abstract

The defect-induced excitations causing the bearing to vibrate have significant contribution in vibration generated from rolling element bearings. Therefore, in this work an investigation has been made to estimate the excitations caused by localized defects on different elements of a bearing, viz., inner race, rolling element and outer race, subjected to load. The applied load on a radially loaded bearing is often not of pure static nature but has a dynamic component associated with it. The dynamic load on bearing has been considered to be composed of a static and a dynamic component. The dynamic component has been considered to be either harmonic or random in nature. The spectra of excitations have been obtained to correlate with the significant spectral components of respective response. The amplitudes of harmonic and variance of random loading have been varied to investigate the effects of dynamic loading on excitation spectra. Numerical results have been obtained for NJ305 bearing with normal clearance. For harmonic load, a new spectral component has been noticed in frequency spectrum of excitation for the defects on outer race and rolling element, whereas there is no new component for inner race defect. In the case of random loading, noise in the spectrum has been noticed. The rise in noise level and coefficients of spectral components also perceived with the increase in variance of random load. The rise in noise level with increment in dispersion of random loading is significant so that few spectral components have been masked under the noise for non-stationary defect, whereas for stationary defect the spectral components are clearly detected in spite of rise in noise level. The numerical procedure explained can be extended for different kinds of loading which may be due to the defects in mating components supported by shaft and bearing system.