The Effect of Surface Depressions on Conformal and Nonconformal Contact Pressure Distributions

This paper presents a numerical method for analyzing the stress concentration around one or several shallow longitudinal surface depressions. The modified iterative method and modified influence function are used in conjunction with an automatic mesh generation technique to avoid solving the ill-condition of the large scale linear system and therefore a wide range of contact problems having multiply-connected regions can be solved. The effect of the blending radius and the pit size on the stress concentration for a pitted copper cylinder contacting an elastic half space are examined. The conformal pressure distributions for a smooth steel journal contacting a self-lubricated bearing with various radial clearances and material properties are also determined. The numerical results show that the smaller the blend radii, the higher the stress concentration for a given pit size. A large deviation from the Hertzian solution is observed for a surface with large pits because of the loss of pressure supporting area. The results of the analysis provides a design tool for predicting the magnitude and location of the peak stress for the rolling and sliding contact elements.