Study on the wheel/rail adhesion characteristic under water and oil conditions by using mixed lubrication model

Abstract

During train operation, water, oil, or oil-water mixtures may adhere to the wheel/rail contact interface, thereby altering the adhesion between the wheel and the rail. In order to study the adhesion characteristics of wheel/rail under wet conditions, a deterministic mixed lubrication model considering surface roughness and transient state is established in this paper, in which the quasi-system numerical and finite difference method are used for numerical solution. The results show that the influence of speed on the wheel-rail adhesion characteristics is more obvious, with the increase of train speed, the fluid dynamic pressure effect between the wheel-rail contact interface is enhanced, the contact pressure of the wheel-rail carried by the fluid film increases, the wheel-rail contact area accounts for the direct contact area of the proportion of the wheel-rail contact area continues to decrease, the thickness of the fluid film between the wheel-railcontinues to increase, and the coefficient of the wheel-rail adhesion decreases. Under the same working condition, with the increase of axle weight, the wheel-rail attachment coefficient increases, and when the axle weight reaches 22t, the attachment coefficient becomes obviously smaller; with the increase of creep-slip rate, the wheel-rail attachment coefficient increases obviously, and then stays relatively stable; with the increase of the wheel-rail surface roughness, the wheel-rail attachment coefficient also increases. Different wetting conditions between wheel/rail interfaces have more obvious effects on wheel/rail adhesion characteristics. In particular, under the same working conditions, the film thickness between the wheel/rail is the largest and the wheel/rail adhesion coefficient is the smallest when the wheel/rail interface is lubricated by oil. It is worth noting that when oil lubrication occurs on the surface of the wheel -rail, the thickness of the fluid film between the wheel-rail is the largest, and the coefficient of adhesion of the wheel-rail is the smallest, which brings safety hazards to the train operation. Therefore, it is necessary to regularly check and clean up the wheel-rail surface, especially the oil contaminants.