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Cite this article as: K. Pereira, T. Yue and M. Abdel Wahab, Multiscale analysis of the effect of roughness on fretting wear, Tribiology International, http://dx.doi.org/10. 1016/j.triboint.2017.02.024 This is a PDF file of an unedited manuscript that has been accepted for publication. As a service to our customers we are providing this early version of the manuscript. The manuscript will undergo copyediting, typesetting, and review of the resulting galley proof before it is published in its final citable form. Please note that during the production process errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain. Abstract: Fretting occurs when two loaded contacting surfaces are exposed to oscillatory relative movement of small amplitude. Depending on conditions such as surface finishing, coefficient of friction, normal load and slip amplitude, fretting may reduce the service life of a component by fretting wear. The effect of surface roughness on the fretting wear profile is still uncertain and may be significant. However, most of the finite element (FE) models that are used to predict fretting wear do not take it into consideration. In this paper, we propose a multiscale procedure to study roughness effect on fretting wear using FE models. In order to do that, we treat the problem in two scales: a) micro scale to analyse the effect of roughness on the contact pressure for frictionless conditions, and b) macro scale to estimate the wear profile evolution for a cylinder on plane contact configuration.

Fretting wear is the material damage of two contact surfaces caused by micro relative displacement. Its characteristic is that debris is trapped on the contact surfaces. Depending on the material properties, the shapes of the debris, and the dominant wear mechanisms, debris can play different roles that either protect or harm interfaces. Due to the micro scale of the debris, it is difficult to obtain instantaneous information and investigate debris behavior in experiments. The Finite Element Method (FEM) has been used to model the process of fretting wear and calculate contact variables, such as contact stress and relative slip during the fretting wear process. In this research, a 2D fretting wear model with a debris layer was developed to investigate the influence of debris on fretting wear. Effects of different factors such as thickness of the debris layer, Young’s modulus of the debris layer, and the time of importing the layer into the FE model were considered in this study. Based on FE results, here we report that: (a) the effect of Young’s modulus of the debris layer on the contact pressure is not significant; (b) the contact pressure between the debris layer and the flat specimen decreases with increasing thickness of the layer and (c) by importing the debris layer in different fretting wear cycles, the debris layer shows different roles in the wear process. At the beginning of the wear cycle, the debris layer protects the contact surfaces of the first bodies (cylindrical pad and flat specimen). However, in the final cycle, the wear volumes of the debris layers exhibit slightly higher damage compared to the model without the debris layer in all considered cases.