Abstract: A coupling dynamics model of railway vehicle with oval wheels and track is built and a corresponding numerical method is developed. The effect of ovalization of the wheels on the dynamical behavior of the vehicle system is analyzed in details. The numerical results regarding the misalignments of the vehicle and wheelset, the dynamical normal loads of the wheels and the rails and the reduction in the wheelset loading are presented under the conditions in which the wheels are in ovalization and the train speed is from 200 km/h to 350 km/h. The limit of the wheel ovalization is determined according to the traditional criterion of wheelset loading reduction for safely running estimation. The results show that the dynamical behavior of the vehicle are much related to the wheel ovalization status (the difference between the maximum diameter and the minimum diameter of the elliptical wheel), the phase between the elliptical shapes of the two side wheels and the train speed. The wheel ovalization under high speed greatly influences the vehicle behavior. The lateral motion ability and the running quality of the vehicle quickly reduce with an increasing in the wheel ovalization, and the dynamical normal load increases greatly. In such a situation, it is affirmed that the use lives of the parts of the vehicle and the track would be much reduced. And also the risk of derailment is increased largely.

Key words: High speed train, Lateral stability, Safety, Vehicle/track coupling dynamics, Wheel ovalization