AN EXPERIMENTAL-STUDY OF THE EFFECTS OF SURFACE LAY ORIENTATIONS ON INITIAL SURFACE DAMAGE IN POINT CONTACTS

An experimental investigation to determine the effects of surface roughness lay direction relative to the direction of motion on initial surface damage was conducted using a four-ball machine under both simple sliding and pure rolling point contact conditions. Surface topographies ranging from 0.11 mum (4.45 muin.) to 0.73 mum (28.61 muin.) RMS roughness and 31.5 mum (1239 muin.) to 59.6 mum (2345 muin.) in wavelength were utilized in the experimental program. A lithium complex grease was used as the lubricant for all tests. The experimental results indicate that surfaces with transverse lay orientations cause more initial surface damage than surfaces with longitudinal lay orientations for relatively low ratios of film thickness-to-composite surface roughness, and low ratios of surface wavelength-to-contact radius.