5. Roughness

Roughness refers to the roughness and indentations of a surface measured in relation to the average surface, which is locally assimilated to a plane. The geometric characterization of this parameter is tricky because it is a statistical parameter that cannot be defined by a single measurement, and because it is a two-dimensional variable, usually analyzed along a single dimension.

As with any statistical parameter, its evaluation will be all the more reliable if it is carried out over a wide area, but it then comes up against surface shape defects that no longer allow the average surface to be assimilated to a plane. The international standard ISO 4287, currently undergoing probationary investigation, defines the various parameters for characterizing surface roughness. Without being exhaustive, it should be remembered that the heights of protrusions and the depths...