Prediction of Sliding Friction Force of Rough Surfaces in Lubricated Point Contacts

A mixed lubrication model, based on an unified Reynolds equation in all lubrication regimes including elastohydrodynamic, mixed and boundary lubrication, for prediction of the sliding friction between rough surfaces in point contacts, was developed. In the calculation, the fluid traction in the lubrication region was determined in terms of rheology model for the lubricant, while the friction from asperity contact was calculated by limiting shear stress model of boundary film. Thus the total friction was obtained by summing up the two components. Then, the effects of roughn ess amplitude and texture on friction coefficient were investigated. The magnitude of fluid friction coefficient from the different non-Newtonian fluid models with limiting shear show that a rougher surface would give rise to higher friction coefficient in stress was also compared. The results mixed lubrication regime, and higher critical speed of transition from full-film elastohydrodynamic to mixed lubrication. But roughness amplitude has less effect in hydrodynamic and boundary lubrication. Cross texture is more beneficial to lubrication than the transverse if the operating conditions are the same. Different rheology models with limiting shear strength have little effect on prediction of fluid traction under the same operating conditions.