On the cumulative microslip phenomenon

Abstract

The cumulative microslip phenomenon is the accumulation of relative slips in a tangential direction on the contact interface of two solids under cyclic loadings. This leads to significant global relative displacement between components and can account for the failure of some assembly parts in mechanical structures. Practical examples from the automotive industry are presented in this paper to describe cumulative microslip effects in real situations. The phenomenon is then characterized from a theoretical point of view as an asymptotic behaviour for the contact interface under cyclic loads, by analogy with Ratcheting effects in elasto-plasticity. Accommodation and slip-shakedown are introduced in the same light. These various behaviours are illustrated with a reference discrete example that includes an original friction dissymmetry. Then we investigate the phenomenon's occurrence in various models. The existence of a dissymmetry in the assembly turns out to be a necessary condition for the phenomenon to occur. However, this condition proves not sufficient and the additional characteristics required to reproduce it are analysed. As dissymmetries are bound to exist in some assemblies because of the prescribed environment at work, a theoretical analysis of the phenomenon is performed and a slip-shakedown theorem is proposed. It leads to the introduction of a safety coefficient with respect to slips when a standard friction law is assumed. The safety coefficient can be computed from two static and kinematic approaches in min–max duality, which are illustrated on the reference discrete example.