The analysis of profile strata for surface texture specification

Abstract Surface are created by a series of one or more processes and each process in the series leaves its signature on the surface. For many common manufacturing processes the height distribution of a surface profile is known to be essentially Gaussian, and if such a distribution is plotted on normal probability coordinates the resulting curve closely approximates a straight line whose slope is proportional to the rms average of the height distribution. If the cumulative height distribution of a surface profile obtained from a surface created by a series of processes is plotted on normal probability coordinates, it can generally be represented by a series of straight line segments each of which corresponds to one of the various processes involved in creating the surface. These straight line segments can be used to define strata within the surface profile and the intersections among the lines are the heights at which the transitions between the strata occur. Within any of the strata, the surface texture is very different from adjacent strata, or else the existence of the strata would not be apparent from the plotted curve. The concepts of stratified surfaces are discussed using both theoretical and experimental examples. A classification system for stratified surfaces is proposed and methods for analysis are presented. It is shown that these data analysis techniques are far more useful for the specification of engineering surfaces than is the usual technique of reporting parameters obtained from analysis of the surface profiles as a whole.