Identification of lubrication regime on textured surfaces by multi-scale decomposition

This paper focuses on the analysis of surfaces resulting from thickness reduction of aluminium strips, provided with lubricant reservoirs, and deformed with different lubricant viscosities and drawing velocities, by a specific experimental drawing process. During reduction, the lubricant is pressurized and may escape from its initial cavities and supply the neighbouring ones. The nature of the lubrication regime is thus locally changed and may vary from boundary to hydrodynamic. The deformed surfaces are measured by means of a Vertical Scanning Interferometer then analysed in terms of arithmetic roughness and developed roughness profile length. Since these two parameters are found not accurate enough to identify regions where different lubrication phenomena occurred, a method based on roughness peaks and valleys curvature radii estimation, recently developed by some of the present authors, is applied. The acquired surfaces are assumed as fractal surfaces and a multiscale decomposition of the peaks and valleys curvature radii of roughness profile is performed, for each experimental test. Then the analysis of the deformed surfaces is achieved and the effects of the different testing conditions on the curvature radii are highlighted. During this study, this method has been of great help to qualitatively define the different contacts nature, i.e. severe or not, and to link the different regions to a lubrication regime.