This study investigates the onset of electrically induced damage in rolling element bearings (REBs). An Electric Discharge Test Rig (EDTR) was designed and developed to investigate the effects of load, speed, lubricant, and electrical power on bearing damage. In the EDTR, one race of a thrust ball bearing is used to control the motion of the balls, while the counter raceway was replaced by a polished bearing steel flat. This configuration allows for examination of the flat specimen for the extent and nature of damage, as well as re-polishing and subsequent use. The test bearings were comprised of a single steel ball and five ceramic balls to control the flow of electrical current. Key parameters, including lubricant film thickness, supply power, and applied thrust load, were systematically varied to evaluate their influence on the damage. The effect of electrical power was also investigated by applying both direct current (DC) and alternating current (AC). Surface profilometry was conducted along the running track to measure the damage morphology, followed by a statistical analysis of the pits created due to electric discharge. Surface analysis revealed two characteristic forms of EIBD: discrete surface pitting along the running track and an indented surface profile in the central contact region, resulting from thermal softening and localized plastic deformation. The results show that electrical damage at the contact is a strong function of the lubricant film thickness. Thin films promote frequent discharge events and high pit density, whereas thick films limit discharge frequency but produce deeper pits when breakdown occurs. Increasing electrical power and load intensifies damage severity, increasing both pit density and surface indentation. Statistical analysis confirmed lubricant film thickness as the dominant factor governing EIBD, followed by electrical power.
Park et al. (2026) studied this question.