Study On The Dynamic Behaviour Of High-Speed Train/Track Coupling System Composed Of Multiple Vehicles

Nowadays, more and more people consider the high-speed trains as a comfortable, safe, low and clean energy consumption transportation tool with high on-schedule rate. But, increasing train’s running speed posts very high requirements on operation safety, riding comfort, and vibration control in environments, all of which are closely related to the dynamic behavior of train-track coupling system. Therefore, modeling and analysis of train-track coupling system dynamics is important for the rapid developing high-speed railways. Both theoretical and experimental studies on this topic are desired.A nonlinear high speed train-track coupled model based on multi-body system dynamic is developed in the present paper. The traditional single vehicle/track vertical and lateral coupled model was extended to multi-vehicles/track vertical-lateral-longitudinal coupled model. In the simulation model, each vehicle is modeled as a42D.O.F. multi-body system with nonlinear suspension characteristics. The detailed inter-vehicle connection model includes the nonlinear coupler-buffer system, nonlinear inter-vehicle dampers and the tightening vestibule diaphragm. The model of the track is a traditional triple layer model consisting of the rails, the sleepers, and the ballast. Rails are assumed to be Timoshenko beams supported by discrete sleepers. Each sleeper is treated as an Euler-Bernoulli beam. The ballast bed is replaced by equivalent rigid ballast bodies. The train couples with the track through the wheel/rail rolling contact. The wheel/rail contact model includes two basic issues:the geometry relationship and the contact forces between the wheel and the rail. The geometric problem of wheel/rail contact is solved spatially and evaluated on-line using a new wheel/rail contact geometry relationship solution model. The calculation of wheel/rail contact forces includes a normal model and a tangent one. The normal forces of the wheel/rail are calculated using Hertzian contact theory and their creep forces are determined with the nonlinear creep theory by Shen et al. A "Moving Track" model is used to simulate the train/track excitation caused by the periodical discrete sleepers.The dynamic responses, nonlinear hunting stability, dynamic curving behavior, and riding comfort are analyzed by using the coupled train-track dynamic model. In the present analysis, a detailed comparison of dynamic behaviors between results obtained by a single vehicle model and results obtained by the3,5,8vehicles train models are made including random response, nonlinear hunting stability, dynamic curving behavior, and riding comfort. And the nonlinear characteristic of inter-vehicle connections on the train-track system dynamic behavior is investigated.The analysis reveals that the random responses of car body accelerations and wheel/rail contact forces obtained by the single vehicle model are much different from that obtained by the multiple vehicles coupled train model. It is found that the lateral dynamic behavior of high speed train calculated by the single vehicle model would make large mistake, and a multiple vehicles train model is needed. The vertical dynamic behavior obtained by a single vehicle model could represent the long high speed train’s vertical responses well. In addition, the numerical results indicate that the characteristic of inter-vehicle connections have a significant influence on the dynamic behavior of train-track system. Appropriately installed connections between vehicles can improve the critical running speed, riding quality and curving safety of the high-speed train.