Proposition of a finite element-based approach to compute the size effect in fretting fatigue

The aim of this paper is to propose a finite element (FE)-based methodology capable to predict the pad size effect on specimen life. This phenomenom has been observed in a number of available fretting fatigue tests, which will be considered to validate the analysis. The proposed methodology differs from conventional FE analysis as (i) it provides a direct evaluation of the fatigue strength at nodal points, besides the traditional stress/strain results and (ii) it proposes that, for problems involving the presence of severe stress gradients, as it is the case in many mechanical assemblies subjected to fretting, the size of the FE should be defined so that it characterizes the stress state in a process zone rather in a point. A discussion of how to define a priori the size of such FE is also conducted. Multiaxial stress-based criteria incorporated into the code are considered to carry out the fatigue analysis. The results obtained show that there is not a single range of FE sizes capable to correctly predict the fretting fatigue limit for all tests considered.