Introduction and application of modified surface roughness parameters based on the topographical distributions of peaks and valleys

A set of modified roughness parameters (N%-Rpv's) is introduced based upon the separate distribution of peaks and valleys. These new measures of surface roughness are utilized to quantitatively evaluate the as-rolled and deformation-induced surface roughness of A1 sheets. N%-Rpv is defined as the difference between the average heights of the upper N% of peaks and the lower N% of valleys. As N decreases, the magnitude of N%-Rpv tends to be more sensitive to the contribution from relatively large-wavelength roughness components. The topographical difference between the transverse direction (TD) and the rolling direction (RD) roughness profiles of the as-rolled surface is shown to be characterized more realistically by N%-Rpv than the root-mean-square roughness (Rq). The result from this quantification of deformation-induced surface roughness of the A1 sheet at intermediate and macroscopic scales suggests that the presence of spatially organized macro-roughening patterns can be characterized using the relative magnitudes of 100%-Rpv and 10%-Rpv. This suggests a possible link between the spatial distribution of surface roughness and the magnitude of N%-Rpv. (c) 2006 Elsevier Inc. All rights reserved.