Rapid analysis of the effects of surface and sub-surface defects in elastohydrodynamic contacts

Surface and sub-surface defects alter the stress distribution in the material and tend to significantly reduce the life of elastohydrodnamic (EHL) contacts. Where the defects lie well below the surface their effect may be obtained by taking the EHL pressures from standard analyses and using these to determine the stress distribution. However, defects lying closer to the surface can produce significant local displacements and alter the EHL pressures. Analysis is difficult because these displacements change as the defect passes under the conjunction and calculation tends to be extremely time consuming. This paper presents an extension to the perturbation technique used for the rapid analysis of surface roughness. This extension enables solutions for both two and three dimensional defects to be obtained rapidly. The procedure is outlined and a number of examples given.