Progress in the application of notch asymptotics to the understanding of complete contacts subject to fretting fatigue

Abstract

This paper describes progress in the interpretation of notch fatigue data by re‐working the Williams solution to bring out the effects of mode mixity and the limits of small scale yielding. The results are displayed in KI versus KII space. Experimental results from complete fretting fatigue tests using a high strength steel alloy known as “super CMV” are then plotted out on this diagram and it is shown that the fretting damage does not significantly reduce fatigue life, while the stress localisation effects of adhered pad edges does.

A discussion of: Development of a complete contact fretting test device by J Juoksukangas et al.

“…This is an assumption that can be investigated by determining the relative contributions of the mode I and mode II terms throughout the load cycle. 5,6 Also, given that slip and separation are implied by the asymptotic analysis, further investigation of their extent of could be performed. 7 This will form part of a more extensive investigation beyond the scope of this discussion paper.…”

Fretting in complete contacts - the use of Williams’ solution

“…This can sometimes be quite a complicated process, as the stress intensity contributions from mode I and mode II loading may change sign, giving rise to local separation, and there are the competing non-linear local effects of slip (giving rise to fretting damage) and plasticity (giving rise to crack nucleation) [2,3]. For background material, these two papers should be consulted.…”

“…So, in general terms, normal loading drives the state of A stress into the (KI<0,KII>0) quadrant, implying, as intuitively expected, firm closure of the contact corner, whereas the application of a shear force or tension drives the state of stress into either the (KI>0,KII>0) or (KI<0,KII<0) quadrants. These imply some degree of local opening [2,3].…”

Contact around a Sharp Corner with Small Scale Plasticity

“…We can normalize the length and stress field of the system with the scales defined based on the solution of an infinite large wedge [51,52] to make the results general. In such a case the detailed loading and geometry of the model are not important; what matters are the stress-intensity factors.…”