On how to determine surface roughness power spectra

TL;DR

This paper evaluates experimental methods for measuring surface roughness power spectra, highlighting the reliability of stylus and AFM techniques over optical methods, and discusses deriving 2D spectra from 1D data for isotropic surfaces.

Contribution

It systematically compares experimental techniques for surface roughness measurement and proposes methods to derive 2D spectra from 1D data for isotropic surfaces.

Findings

Optical methods often lack accuracy for roughness power spectra.

Stylus instruments and AFM provide reliable and consistent results.

Methods to derive 2D spectra from 1D data for isotropic surfaces are explored.

Abstract

Analytical contact mechanics theories depend on surface roughness through the surface roughness power spectrum. In the present study, we evaluated the usability of various experimental methods for studying surface roughness. Our findings indicated that height data obtained from optical methods often lack accuracy and should not be utilized for calculating surface roughness power spectra. Conversely, engineering stylus instruments and atomic force microscopy (AFM) typically yield reliable results that are consistent across the overlapping roughness length scale region. For surfaces with isotropic roughness, the two-dimensional (2D) power spectrum can be derived from the one-dimensional (1D) power spectrum using several approaches, which we explored in this paper.