Abstract
AbstractThe object of this paper is to develop a 3‐dimensional numerical model to estimate the wheel and rail adhesion coefficient considering surface roughness under wet condition. The water film thickness formed between wheel and rail plays an important role on the adhesion coefficient. Firstly, the full isothermal elasto‐hydrodynamic lubrication (EHL) theory of elliptical contact is used to obtain more than 20 different film thickness cases using Bett and Cappi's viscosity equation of water. Based on the numerical solutions, empirical formulas for the central and minimum film thickness are obtained relating to rolling speed, wheel and rail contact force, and material parameters and compared with results obtained by previous studies. Secondly, taking the surface roughness into consideration, the EHL theory is used to obtain the load carried by water, and the statistical elastic‐plastic mico‐contact model presented by Lee et al. was applied to calculate the load carried by asperities. Meanwhile, the thermal influencing reduction factor is used to consider the inlet heating effects on the film thickness, and the change of water viscosity is also taken into consideration due to the flash temperature generated between the moving rough surfaces. Furthermore, the present work investigates the dependence of the wheel/rail adhesion coefficient on train speed and surface roughness amplitude under wet condition.
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