Impact of fretting parameters on contact degradation

Two previously developed models, dealing with contact resistance and oxide build-up under fretting conditions, were refined and combined into a single analytical model. This model was used to predict the average effects of contact force and fretting amplitude on contact degradation. The results from fretting tests on specially prepared tin plated contacts were explained within the framework of this model. It was found that decreasing contact force or increasing fretting amplitude produced increased degradation; This is explained in terms of an increase in oxide build-up due to either less asperity deformation (lower forces) or an increase in the number of asperity deformations per cycle (longer fretting amplitude). In addition, thermal shock experiments were conducted on tin plated connector contacts for two widely different temperature swings (i.e. /spl Delta/T=-40 to 105/spl deg/C and 25 to 70/spl deg/C). This data was analyzed to determine the relation between /spl Delta/T and acceleration factor. It was found that the assumed connection between /spl Delta/T and fretting amplitude was consistent with both the fretting probe data and the thermal shock tests. These results provide a basis to model degradation rate in terms of fretting cycles and /spl Delta/T. Consequently, a model was developed to estimate the acceleration factor for a given set of laboratory test parameters to simulate field degradation.