EFFECTS OF SURFACE-ROUGHNESS IN ELASTOHYDRODYNAMIC LUBRICATION

The nominal film thickness in the elastohydrodynamic lubrication (EHL) regime is of the same order of magnitude as the surface roughness of contacting bodies. Since the breakdown of EHL films seems to be associated with asperity interactions, a detailed description of local fluctuations of EHL films and pressures caused by asperity interactions provides an important basis for a clearer understanding of the working performance of machine elements, the causes of surface failures and methods for their prevention. In this review, why and how EHL films are influenced by the surface kinematic conditions and the orientation and shape of surface irregularities are discussed based mainly on the experimental facts using model asperities. The results described will provide a clue to solving EHL problems in the mixed regime between full fluid film and boundary lubrication.