Issue 33

C. Montebello et alii, Frattura ed Integrità Strutturale, 33 (2015) 159-166; DOI: 10.3221/IGF-ESIS.33.20 159 Focussed on characterization of crack tip fields Multi-scale approach for the analysis of the stress fields at a contact edge in fretting fatigue conditions with a crack analogue approach C. Montebello, S. Pommier LMT (ENS Cachan / CNRS / Université Paris Saclay) Claudio.Montebello@ens-cachan.fr , Sylvie.Pommier@ens-cachan.fr K. Demmou, J. Leroux, J. Mériaux Snecma Villaroche Karim.Demmou@snecma.fr , Julien.Leroux@snecma.fr, Jean.Meriaux@snecma.fr A BSTRACT . This paper describes a novel method to model the stress gradient effect in fretting-fatigue. The analysis of the mechanical fields in the proximity of the contact edges allows 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, Is, Ia, Ic, depending on the macroscopic loads applied to the mechanical assembly, and spatial reference fields, ds, da, dc, 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. By using as input the macroscopic load, the procedure consists in computing a set of nonlocal stress intensity factors, which are an index of the severity of the stress field in the proximity of the contact edges. This description has two main advantages. First, the nonlocal stress intensity factors are independent from the geometry used. Secondly, the procedure is easily applicable to industrial scale FE model.. K EYWORDS . Fretting fatigue; Contact; Fatigue. I NTRODUCTION omputational models for fatigue damage analysis in presence of a steep stress gradient still remain poorly effective. This is the case of fretting-fatigue where a local stress concentration is introduced by contacting components experiencing small amplitude relative motion. This phenomenon is a major concern for the aerospace industry, in particular for aircraft engine applications where there are several components that may suffer fretting-fatigue failure like the dovetail blade-root connections. In the last years several fatigue criteria have been developed aiming at improving the accuracy of the fatigue life prediction in the presence of a severe stress gradient. Almost all of them can be divided into two major families. On the one hand, the nonlocal stress fatigue models [1, 2] employ an averaged quantity as input for the prediction criterion in order to C