Evaluating Surface Roughness From Contact Vibrations

Abstract

This paper examines the relationship between the contact dynamics and the composite surface roughness of two bodies in planar contact. Measurements of the natural contact frequency are obtained for a range of surface roughness levels and normal loads from an apparatus which isolates the contact dynamics of two steel blocks from all other system dynamics. The normal contact dynamics of the contacting components are modeled with a single-degree-of-freedom system which incorporates the Greenwood and Williamson surface roughness model. Analytical and empirical expressions relating the normal natural contact frequency and roughness parameters, such as the standard deviation of asperity heights and the average roughness value, are developed. Both theory and experiments show that the contact frequency increases with a decrease in the composite roughness and vice versa; a power law relation between the contact frequency and the roughness parameters is found in most cases. The results of this work indicate that it may be possible to use contact vibration as a means for assessing or monitoring composite roughness parameters of surfaces in contact.