### Sharp contact corners, fretting and cracks

#### Abstract

Contacts with sharp edges subject to oscillatory loading are likely to nucleate cracks from the

corners, if the loading is sufficiently severe. To a first approximation, the corners behave like notches, where the

local elastic behaviour is relieved by plasticity, and which in turn causes irreversibilities that give rise to crack

nucleation, but also by frictional slip. One question we aim to answer here is; when is the frictional slip

enveloped by plastic slip, so that the corner is effectively a notch in a monolithic material? We do this by

employing the classical Williams asymptotic solution to model the contact corner, and, in doing so, we render

the solution completely general in the sense that it is independent of the overall geometry of the components.

We then re-define the independent parameters describing the properties of the Williams solution by using the

inherent length scale, a procedure that was described at the first IJFatigue and FFEMS joint workshop [1]. By

proceeding in this way, we can provide a self-contained solution that can be ‘pasted in’ to any complete contact

problem, and hence the likelihood of crack nucleation, and the circumstances under which it might occur, can

be classified. Further, this reformulation of Williams' solution provides a clear means of obtaining the strength

(defined by crack nucleation conditions) of a material pair with a particular contact angle. This means that the

results from a test carried out using a laboratory specimen may easily be carried over to any complicated contact

problem found in engineering practice, and a mechanical test of the prototypical geometry, which may often be

quite difficult, is avoided.

#### Full Text:

PDFDOI: http://dx.doi.org/10.3221%2FIGF-ESIS.25.05