Measured friction between hardened steel surfaces in nominal elastic or plastic contact

Published values of friction coefficients seldom mention the role of surface roughness and it is generally thought not to be an important factor. This is at variance with modern friction theories. The objective of this work is to study the dependence of the friction coefficient on surface roughness. The well known Greenwood and Williamson model for the contact of rough surfaces suggest that the friction coefficient in the elastic contact range should be proportional to ss/Rs ; where sigmas is the standard deviation of the asperity summit heights, and Ra is the average asperity tip radius.; While this concept isn't new, the relationship has never been shown experimentally. This study will consist of a friction tests wherein the surface roughness will be altered with other parameters nominally unchanged. The goal is to determine if the qualitative and quantitative relationship to the surface roughness parameters, described above will be observed in experiments.