The Mechanism of Lubrication in Low Speed Rolling Contacts

Abstract

The mechanism of lubrication in low speed rolling and sliding contacts was investigated. It was found to be a combination of the following three effects: the chemical formation of boundary lubrication films on the surfaces, the creation of hydrostatic pressure in the lubricant trapped by the surface topography, and the squeeze effect of lubricant in grooves formed by the surface topography. The three different effects were recognized by friction measurements in a four-disk machine. The results indicate that the way in which the surface topography forms dents and grooves influences the flow behavior of the lubricant in the contact. Thus both the surface topography and the viscosity of the lubricant are important parameters affecting friction and wear even in low speed rolling contacts where no hydrodynamic wedge effect is expected to occur.