A Novel Approach to Study Electrically Induced Damage in an Isolated Bearing Contact

Prof. Farshid Sadeghi

Summary

This fundamental study focuses on the electrically induced damage at an isolated contact between two bearing surfaces subject to an electric current. In order to achieve the objectives, the novel Electric Arcing Rig for Isolated Contact (EARIC) was designed and developed to enable sub-micron positioning of a steel ball and a micron diameter needle against a flat steel specimen, using a piezo-actuated stage with 25 nm resolution. The rig also incorporates a high-magnification visualization setup for in-situ observation of electrical discharge and resulting damage, enabling precise alignment of the bearing surfaces and ensuring repeatable testing. In order to study discharge behavior at a single asperity, a fine 1-micron diameter needle tip was employed in addition to the ball geometry. Experiments were conducted using both direct current (DC) and alternating current (AC) power supplies across various voltage and current settings, along with different lubricants and positioned distances. An optical surface profilometer was used to measure and characterize the resulting damage. Surface damage was consistently observed above 3 VA apparent bearing power, with both the affected area and depth increasing proportionally with power input. The presence of lubricant significantly reduced discharge damage, particularly at higher film thicknesses. Contact geometry influenced both the distribution and severity of damage. The ball tip produced larger, more irregular pits, whereas the needle tip generated smaller, more concentrated craters with greater penetration. With AC power, several shallow pits formed at the contact due to repeated discharge events corresponding to the switching frequency of the signal, in contrast to a single large pit typically generated with DC input.