Analysis of adhesion under wet conditions for three-dimensional contact considering surface roughness

This paper describes a numerical model to estimate the adhesion coefficient between rail and wheel under wet conditions, by applying the partial elasto-hydrodynamic lubrication (EHL) theory at three-dimensional (3D) contact considering surface roughness. The effect of the characteristics of surface roughness on the adhesion coefficient is particularly focused on in this study. Based upon numerical solutions obtained by the 3D numerical model, the effects of rolling speed, water temperature, surface roughness amplitude (i.e., standard deviation of roughness height) and parameter of roughness orientation on asperity contact pressure, which has important influence on the adhesion coefficient, are investigated under wet conditions. Furthermore, to verify the adequacy of the 3D numerical model adapted to estimate the adhesion coefficient between rail and wheel, the numerical solutions are compared with the experimental values that were obtained by a twin-disc rolling contact machine.