Friction Model of Elastic-plastic Line Contact in Mixed Lubrication Regime with Non-Newtonian Lubricant

The friction characteristics of the lubricated rough surfaces are of great significance for the lubrication design of mechanical structures. To study the behaviour of friction coefficient in the rolling-sliding coexisting line contact rough surfaces under mixed lubrication regime, the Kogut-Etsion elastic-plastic model and the Carreau rheological model are utilized to describe the dry rough contact and the non-Newtonian characteristics of the lubricant film, respectively. A mixed lubrication model for predicting friction coefficient is proposed based on the load-sharing concept at which the normal load is shared by the lubricant film and the asperity component. The effects of normal load, surface roughness and lubricant inlet viscosity on hydrodynamic scaling factor, film thickness parameter and the coefficient of friction were analyzed. The dimensionless predictive expression for the critical sliding velocity is derived by nonlinear regression. The research results provide theoretical guidance for the lubrication design and optimization of mechanical structures.