Influence of Sliding Speed and Glass Bead Concentration on 3D Roughness Parameters

This paper presents an analysis of 3D amplitude and functional parameters for worn surfaces of composites with polyamide 6 as matrix and different glass bead concentrations (0%, 2.5%, 5%, 10%, 20%, 30% and 50%wt). The worn surfaces after dry sliding of a steel pin on a disk, for 10 km, at constant velocity (0.5 m/s, 1 m/s and 1.5 m/s) and under an average pressure of 1 MPa. There were done two tests under the same conditions. On each worn track, there were investigated three surfaces of 500 mu m x 500 mu m with a contact profilometer. The number of points on the scan line was 200 points and the step between lines was 5 mu m. The following amplitude parameters were measured and calculated for assessed surfaces: the arithmetic mean deviation, Sa, the root mean square deviation, Sq, the maximum height of surface prominence, Sp, the maximum surface depth, Sv, the maximum height, St, the skewness factor, Ssk and the kurtosis, Sku. The discussed functional parameters are the reduced peak height, Spk, the height of the core of the surface, Sk and the depth of the valley zone, Svk. The comparison of their values makes posible to evaluate if the worn surface could function in a new running or the replacement of the component is recommended. Considering that machine components have intermittent operation, these worn surfaces becoming initial surfaces for the following cycle of contact operation. Based on the average values of amplitude and functional parameters, it was found that a relatively good surface quality is preserved for concentrations of 10...30%wt glass beads, for v=0.5...1 m/s (Sa and Sq having similar trend); for lower concentrations and for 50% glass beads, the parameter values increase but without identifying a distinct relationship with the working regime, especially for 2.5 and 5% glass beads.