Analysis of the stress gradient effect in fretting-fatigue through nonlocal intensity factors

This paper proposes a new method to describe the stress gradient effect in fretting-fatigue. Through the analysis of the mechanical fields in the proximity of the contact edges, it has been possible to extract nonlocal intensity factors that take into account the stress gradient evolution. For this purpose, the kinetic field around the contact ends is partitioned into a summation of multiple terms, each one expressed as the product between nonlocal intensity factors, I-s, I-a,I-c,depending on the macroscopic loads applied to the mechanical assembly, and spatial reference fields, d(s), d(a), d(c), depending on the local geometry of the part. This description is obtained through nonintrusive post-processing of FE computation and is conceived in order to be easily implementable in the industrial context. As a matter of fact, for any given macroscopic load and geometry, a set of nonlocal intensity factors is computed that permits to characterize the mechanical fields close to the contact edges. Such nonlocal description has the advantage of being (i) geometry independent so that the nonlocal intensity factors can be used to compare laboratory test with real-scale industrial assembly, (ii) applicable to industrial FE models usually characterized by rougher meshes compared to the ones used to describe fretting-fatigue in the academic context. An extensive validation is carried out through the comparison with experimental data for plain fretting and fretting-fatigue tests on different materials. (C) 2015 Elsevier Ltd. All rights reserved.