Dynamic wheel–rail adhesion characteristics on wet curved tracks considering surface roughness

Wheel–rail rolling contact is a complex tribological issue, especially the existence of a thin water film on the rail surface, which leads to low adhesion problems for the traction and braking performance of the railway trains. The objective of this paper is to propose a non-Hertzian dynamic wheel–rail adhesion model for trains passing through wet curved tracks considering wheel–rail surface roughness. A vehicle-track coupling dynamics model was first developed to output the wheel–rail dynamic contact parameters under wet conditions. These parameters were subsequently utilized as dynamic inputs for the present wheel–rail adhesion model to simulate dynamic curve passing. The present numerical model includes the normal contact model and tangential model. For the normal contact issue, an elastohydrodynamic lubrication model was used to accurately determine the normal contact stress within the contact patch along the contact traces. Based on the normal contact characteristics, the advanced extended creep force model was used to compute the tangential stress. Finally, the dynamic wheel–rail adhesion coefficient can be obtained. This model considers the effects of time variation and changes in contact geometry, resulting in sudden increases or decreases in the adhesion coefficient at certain locations. At a speed of 400 km/h, a higher spin creepage occurs, leading to an increased displacement of the third-body layer and causing the maximum tangential stress to shift from one side of the contact patch to the other. Under the combined influence of the creepages, the maximum tangential stress occurs at the trailing edge of the contact patch.