Surface Topography Changes in Polymer-Metal Sliding - I

Abstract

The adhesive wear of polymers, sliding against smooth metal surfaces, is influenced by the manner in which the surface topography of sliding surfaces is modified. The variation in the surface topographical parameters with sliding between a ground steel disc and a poly(methyl methacrylate) pin was, therefore, investigated for both the unsteady state and steady state wear conditions. The surface profiles of the unrubbed and rubbed metal disc were recorded, using a profilometer, both along and perpendicular to the direction of sliding. From the profile ordinate data read at 10 μm intervals, the surface roughness parameters, namely, the rms and c.l.a. roughness, asperity radius of curvature, asperity density, and average asperity slope were calculated using a computer program. Three point analysis was used to define a peak and compute the asperity slope and radius of curvature. The distributions of surface parameters were determined using a Weibull distribution approach. The analysis showed that the surface parameters have a large initial variation followed by more or less stable conditions, which explains the transition of unsteady state wear to steady state wear. The changes on the disc surface perpendicular to the sliding direction are minimal. The rms roughness and the average asperity slope were found to have a linear relationship.