Real-time monitoring of wear debris using electrostatic sensing techniques

Abstract

In this article, electrostatic charge sensing technology has been used to monitor adhesive wear in oil-lubricated contacts. Previous work in this area using FZG gear wear rig and pin-on-disc tribometers demonstrated that ‘precursor’ charge events may be detected prior to the onset of scuffing. Possible charging mechanisms associated with the precursor events were identified as tribocharging, surface charge variation, exo-emissions, and debris generation. This article details tests carried out to investigate the contribution of wear debris. Tests were carried out on a modified pin-on-disc rig using a sliding point contact and fitted with electrostatic sensors, one of which monitored the disc wear track and the other the disc surface just outside the wear track. Baseline tests used mild wear conditions with no seeded particles added to the entrained lubricant, whereas the high wear tests entrained seeded steel particles into the contact to promote wear. The wear debris produced dynamic charge features and the overall charging activities are directly related to the wear rate (i.e. charging levels increase with increasing wear rate). There appears to be a link between the net volume loss and the charge levels, relating charge directly to the increasing rate of debris production. Wear debris due to natural wear produced positive dynamic charge features, whereas debris from the seeded tests produced negative dynamic charge features. The polarity of the charge on debris is thought to depend on which charging and wear mechanism is predominant.