Wear monitoring of bearing steel using electrostatic and acoustic emission techniques

Both acoustic emission (AE) and electrostatic (ES) wear monitoring are emerging as useful real-time condition monitoring techniques. These techniques are believed to be sensitive to different aspects of the physics of contact and surface degradation prior to the onset of severe wear. Thus, if both systems are used to monitor tribo-contacts, the physics of early contact degradation could be elucidated and the potential of the systems to detect precursors to severe wear could be investigated. This paper uses AE and ES charge signals generated by a bearing steel contact under dry sliding conditions to monitor the various phases of delamination wear. Tests were undertaken using an instrumented pin-on-disc (PoD) tribometer, which enabled continuous measurement of friction, surface temperature, linear wear, AE and ES signals. The AE and ES results were found to correlate with friction levels and wear rates. From the friction level, three distinct regions were identified and the wear mechanisms within each region were found (by SEM and EDS analysis) to be running-in, delamination/oxidation and oxidation.