Coupling effects of spin and temperature on transient wheel–rail adhesion under mixed lubrication

Wheel–rail adhesion is not a singular physical process but a dynamic response system arising from the complex interplay of spin, rolling–sliding motion, thermal effects, surface roughness, and environmental media. Understanding these interacting mechanisms is essential for train operational safety. This paper proposes a novel three-dimensional dynamic numerical model aimed at elucidating the adhesion mechanism under thermal mixed lubrication conditions, with a focus on the strong coupling among fluid, thermal, and roughness effects. The model consists of three key modules: a vehicle-track coupled dynamics model (VTDM) considering water lubrication, a kinematic model of the wheel–rail contact interface, and a dynamic wheel–rail adhesion model. Time-varying rolling contact parameters are obtained using the VTDM and fed into the kinematic model to determine the velocity field within the contact patch, followed by the solution of the dynamic adhesion model under thermal mixed lubrication conditions. Simulation results reveal that the lateral velocity component induced by spin and lateral creepage generates an asymmetric temperature distribution within the fluid-filled contact patch, with heat concentrated in the lateral direction, leading to localized attenuation of the fluid film. This effect is particularly pronounced at the trailing edge of the contact patch, where concentrated thermal stress renders it a primary location for fatigue crack initiation. The proposed three-dimensional model integrates fluid medium characteristics, spin motion, thermal effects, and surface roughness into a unified framework, providing a more comprehensive and mechanism-driven analytical tool for predicting wheel–rail adhesion behavior under complex operating conditions.