The dependence of wear rate on wear scar size in fretting; the role of debris (third body) expulsion from the contact

Abstract

The paper ‘The third-body approach: a mechanical view of wear’ by Maurice Godet (Wear, 100 (1984), pp 437–452) was perhaps the first to articulate clearly the key role of the rate of debris expulsion from a fretting contact in controlling the overall rate of wear. Whilst subsequent research over the past four decades has acknowledged this, the issue is generally addressed qualitatively rather than quantitatively. There are many parameters which will affect the rate of debris expulsion from a fretting contact, and amongst them is the physical size of the fretting contact. In this paper, for the first time, a physically-based relationship is proposed between the debris-expulsion-limited wear rate and the contact size. This relationship is able to account for differences in wear rates observed in tests conducted with different (and evolving) contact geometries (non-conforming contacts) over a range of durations, thus clearly demonstrating the validity of the approach.