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.

The influence of contact conditions on surface reaction layers formed between steel surfaces lubricated by an aviation oil

“…Electrostatic sensing is especially sensitive to the tribo-charge generated from wear debris [16], contact potential difference (CPD) [17,18] and chemical interactions within the lubricant [19]. The CPD effect arises from subtle differences in surface work functions especially when surface phase transformation or tribo-film formation or stripping occurs.…”

Electrostatic Sensor Application for On-Line Monitoring of Wind Turbine Gearboxes

“…To develop this new debris monitoring technology, a series of experiments were conducted to explain the mechanism of charge generation in the lubrication system. Through experiments, Harvey found the debris produced by adhesive wear to be positively charged and the magnitude of charge was directly related to the total volume loss; the higher the total volume loss, the larger the charge [ 19 ]. Wood presented an experimental investigation into the effect of lubricating oil quality on tribo-charging, indicating that the oil flow would also carry some charge [ 20 ].…”

A study of white etching crack bearing failure detection using electrostatic sensing in wind turbine gearboxes

“…The electrostatic (ES) sensing technique has shown promising results when identifying charges associated with surface and lubricant degradation mechanisms, such as contact potential difference (CPD) [17][18][19][20] , triboemission [21][22][23] and debris formation [24,25] , as well as identifying charges associated with the double layer effect [26] (lubricant-surface interaction). ES sensors have also shown to be able to detect bearing failures in advance of vibration monitoring techniques [27][28][29] .…”