Influence of surface topography on friction, film breakdown and running-in in the mixed lubrication regime

Abstract
The influence of surface topography on the lubricant film build-up ability and the friction characteristics of potential rolling bearing surfaces has been investigated by experiments on two-disc rigs. Traction-friction torque measurements were made for a variety of surface combinations, together with measurement of the electrical resistance between the discs as an indication of surface separation. For all disc combinations, running-in of the surfaces under load at any slide-roll ratio led eventually to full film separation. Contrary to results reported in the literature, film breakdown did not always increase with slip but depended on certain aspects of the surface structure. Friction torque measurements in the mixed lubrication regime also confirmed that friction is not determined simply by an Ra value. By suitable modification of the surface topography, keeping Ra constant, friction can be varied by as much as 10 per cent.