A model of mixed lubrication with capillary effects

When sufficiently smooth surfaces slide in the presence of a small quantity of liquid, there is a tendency for adhesive forces to develop in the interface because of highly curved menisci within the contact. In the present work, a model is developed to account for the effect of an intervening capillary film on the friction force between a rigid, nominally flat, rough surface and an elastic flat. A simple contact analysis is employed to account for the elastic deformation of the surfaces, and an average Reynolds equation is solved to determine the hydrodynamic load and viscous friction forces. For the operating conditions under consideration, it is found that the adhesive load increases with decreasing surface roughness and increasing sliding speed. The adhesive load is also found to increase with increasing external load, but the dependence is weak. In addition, it is found that the viscous contribution to the friction force is small.