The Influence of Surface Roughness on the Capacitive Measurement of Film Thickness in Elastohydrodynamic Contacts

Abstract

Measurements of oil film thickness according to the capacitive method as carried out on a disc machine with discs having a surface roughness of 10 μin c.l.a. showed marked deviations from the theoretical values predicted by Dowson and Higginson (1)^†, especially in the region of small film thickness, i.e. smaller than 0–6 μm (23·6 [μin). In this paper the authors show that surface roughness is the cause of this discrepancy.