This paper describes a numerical model adopted to estimate adhesion coefficient between rail and wheel under wet conditions, by applying the partial Elasto-Hydrodynamic Lubrication (EHL) theory at three-dimensional (3-D) contact. The effects of rolling speed, water temperature, and surface roughness (i.e., the standard deviation of asperity heights and the orientation of asperity on contact surfaces) on the adhesion coefficient are investigated using this model, with the effect of asperity characteristic of contact surfaces focused on in particular. To verify the adequacy of the 3-D numerical model adopted to estimate the adhesion coefficient between rail and wheel, numerical solutions were compared with experimental results that were obtained by a twin-disc rolling contact machine set up at Railway Technical Research Institute in Japan.

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