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

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 wheelrail 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 wheelrail 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.