As one of the common forms of wheel tread defects, wheel flat can induce a great wheel-rail impact, seriously affecting train running stability and safety. A 3D wheel-rail rolling contact finite element model was established to study wheel-rail impact responses caused by the wheel flat using an explicit finite element method. The change of wheel-rail contact state during the whole process of wheel flat impacting rail was described, and the influences of initial fatigue damage and strain rate effect of wheel/rail materials on wheel-rail impact responses were emphatically analyzed. Besides, the influences of train speed, flat length and axle load were also discussed. The results indicate that the maximum wheel-rail vertical contact force induced by the wheel flat is about 2. 6-4. 3 times of the quasi-static wheel-rail vertical contact force. Within the scope of the study, it is shown that the initial fatigue damage and strain rate effect of wheel/rail materials exert no influence on the wheel-rail vertical contact force, contact patch and contact pressure, but significantly affect von Mises equivalent stress, longitudinal stress, vertical stress, lateral stress and equivalent plastic strain. Furthermore, the train speed, flat length and axle load all have great effect on wheel-rail impact responses. The obtained results provide a technical support to the optimal design of wheel-rail systems and the safety of train operation. © 2022, Editorial Office of Journal of Vibration and Shock. All right reserved.
