Contact conditions and stresses induced during fretting fatigue

This paper analyses the contact conditions and stresses induced during fretting fatigue tests of uniaxial specimens using fretting bridges with spherical-tip contact pads. This analysis considers the displacement of the stick zone induced by the variable bulk stress applied to the specimen. It describes an approach to, analytically, calculate the eccentricity of the stick zone and the stress tensor under the contact zone including this stick zone displacement. Two different situations have been considered in the specimen, plane stress and plane strain. The error in the calculation of the stresses using this approach has been estimated and has been found to be very small. A comparison to the results obtained experimentally is presented. Finally, the analytically calculated stresses are compared to those obtained using the classical Mindlin-Cattaneo approach which does not consider the bulk stress. It has been found that stresses calculated using the classical approach may be underestimated even by 10%, which is a very critical quantity for a fatigue analysis.