The steady state sliding of rough surfaces

Abstract

The changes in surface topography which take place when two rough surfaces of different hardnesses are in continuous sliding have been analysed. It is shown that the surfaces “shake down” to a steady state which is perfectly elastic only if the nominal contact pressure is below a critical limit. This shakedown limit is shown to be dependent upon the roughness characteristics of the hard surface, the hardness of the soft surface, the contact modulus and the coefficient of friction between them. Continuous sliding under conditions in which the shakedown limit is exceeded leads to the accumulation of plastic strain and hence to an increase in wear. Tests on a copper specimen in lubricated sliding contact with a hard steel surface of varying roughness showed that the wear rate decreased to a negligible value when the nominal pressure was reduced to values within the shakedown limit.