Comparing texture characterization parameters on their ability to differentiate ground polyethylene ski bases

Abstract

The objective of this work is to compare the ability of three texture analysis methods—conventional, FFT, and scale-sensitive fractal analysis—to differentiate measurements of polyethylene ski bases (i.e., sliding interfaces) that were stone-ground under different conditions. Ski base grinds allegedly influence the gliding of skis on snow, which is a complex and poorly understood tribilogical interaction. No sufficiently sophisticated models exist on which to optimize the design of a ski base texture. In this study, five polyethylene ski bases were ground, using different conditions, and were then measured multiple times with a scanning laser microscope at three different sampling intervals. The scales that could be used for differentiation of the respective base grinds were determined from F-tests of significance applied to the results of area-scale analysis. Anisotropy of the grinds was characterized as a function of scale, using length-scale fractal analyses in transverse and longitudinal directions. Comparison of the resulting length-scale plots in the two directions shows that anisotropy is most evident at scales below 1.5 mm. Area-scale analysis can differentiate textures when conventional and 2-D FFT cannot and indicates the scales over which the differentiation takes place. Only relative areas can differentiate any of the measurements at the finest scales, 0.2 mm × 0.2 mm with at 1 μm sampling interval, and then only in a limited sense. This indicates greatest similarity between the textures may be at the finest scales, where the texture is formed by the interaction of an abrasive grit with the polyethylene. This also indicates that the surface textures at the finest scales tend to be the most independent of the dressing and grinding conditions.