X-Ray Stress Analysis of Electrically Damaged Surface on Rolling Bearings

Abstract

This paper experimentally investigates the application of an X-ray stress measurement called “cos α method” to analyze the electrical pitting generated on rolling bearings. First, a small size ball bearing rotation test was conducted in which an electric current passed continuously through the test bearings under various rotating conditions such as current density and electrical conductivities of lubricating greases. Then, the residual stress and full width at half maximum (FWHM) on the electrically damaged bearing raceway were measured. From the correlation between the residual stress and FWHM and the shape of the damage on the raceway surface, it was found that when the bearing was lubricated by the non-conductive grease, the surface was softened by the electric current and the characteristic shape of surface damage occurred. It was also found that lubrication by the conductive grease could reduce the thermal energy during discharge and suppress the surface softening. These findings demonstrate the validity of applying the X-ray stress measurement for electrical pitting analysis.