Paper IV (iii) Analysis of the Influence of Indentations on Contact Life

Abstract

Applying the relation between stresses and contact fatigue as postulated by Ioannides & Harris, an investigation is carried out to determine the influence of dent geometry on contact life. This analysis is performed using line contact and point contact models. The stresses are calculated using a dry contact model and the elastic half-space assumption. Results from calculations using the line contact assumption are compared with the results of elliptical contact calculations, which model the dents more exactly. The difference in contact pressure between the line and point contact case is analysed in detail. The dent geometry has been obtained from an FEM analysis of an indentation process and the dent is scaled with respect to depth and width to obtain a family of dents. The FEM calculations were compared to experimentally obtained dent profiles. As was done previously for the line contact analysis, the influence of the residual stress field from the plastic indentation process was investigated for the calculated dent geometry (without scaling). The life reduction compared to the smooth contact case has been obtained for three different load cases for a large number of different dent sizes and dent slopes, employing the point contact analysis. The life reductions are compared to the results of an extended line contact analysis and the influence of the position of the dent on life reduction is investigated. This analysis is aimed at establishing the reduction of contact life caused by indentations stemming from handling damage and the overrolling of debris.