Effect of yaw and spin motions on the wheel–rail adhesion under wet condition, considering surface roughness and temperature

This paper proposes a three-dimensional numerical model to clarify wheel–rail adhesion characteristics under wet conditions, incorporating wheelset yaw-spin motions, surface roughness, and thermal effects. The adhesion model comprises normal and tangential contact submodels. Normal contact pressure under yaw motion is solved by mixed lubrication theory. An improved non-Hertzian extended creep force model accounting for spin-induced thermal effects determines tangential contact characteristics. The dynamic wheel–rail adhesion coefficient is derived from these normal and tangential solutions. The results show that lateral displacement and yaw angle critically influence normal contact pressure and film thickness distributions. Small lateral displacements maintain uniform normal stress and stable film thickness, while larger displacements generate stress concentration and film thickness fluctuations. Increased yaw angle elevates lateral creepage, inducing asymmetric tangential stress and expanded high-temperature zones. Spin creepage generates significant frictional heat, creating non-uniform temperature fields that alter traction behavior. The traction coefficient initially increases with yaw angle due to enhanced lateral creepage and tangential stress, reaching a maximum at approximately 40 mrad, beyond which it decreases as thermal effects dominate, causing material softening. This research reveals the contact mechanism under complex conditions, which is crucial for ensuring railway transportation safety and enhancing train operation performance.