| Heavy-haul railway transportation as an advanced and effective technical means, has been widely adopted and developed across the world, which would be helpful to solve the problem of the supply and demand on cargo transport. However, an extension of train marshalling and an increase of axle-load cause various problems, such as severe wheel-rail wear, coupler fracture, derailment, which would greatly threaten to the safety of train and cargo. To ensure healthy and rapid development of railway transportation, a large number of field survey, test and theoretical research should be undertaken eagerly.Taking the freedom of degree of the longitudinal and the couper buffer into account, the typical single vehicle-track vertical-lateral coupled dynamics model, is extended to a three-dimensional train-track coupled dynamics model. As the basic unit of heavy-haul train, the vehicle is modelled as a 52 degree of freedom multi-body system. The nonlinear characteristic of Vehicle’s components is considered in detail. Coupler draft gears are used to connect feightcars unit, and transfer the longitudinal traction and braking forces. The model of coupler draft gears considers the hysteresis characteristics in the process of its loading and unloading with the test data. A traditional ballasted track is modelled as a three layers lump-spring-damper model. The rail is treated as Timoshenko beam supported by continuous elastic discrete sleepers, which is simplified as a mass block. The ballast is modelled as several discrete rigid masses. In order to improve the calculation efficiency of train dynamics, a lumped parameter track model is established. In addition, a numerical algorithm based on arbitrary profiles of wheel and rail is used to calculate the wheel/rail contact geometry. The normal force is solved by Hertz nonlinear contact theory and creep forces are calculated by Shen-Hedrick-Elkins nonlinear creep theory or Polach creep theory according to different research object. The validity and reliability of model is verified in several respects by using the commercial software-SIMPACK.With the established model above, the dynamic responses of vehicle passing through plane and vertical curve are calculated, and further the influence of key geometric parameters of railwayline can be investigated deeply on the wheel-rail forces, safety indexes, and stability of the vehicle. Next, based on the measured wheel/rail profiles, wheel/rail wear characteristics is summarized for tracks with different curve radius and operation distances. With the testing data, the wheel-rail contact geometry and dynamic behaviors of curve negotiating are studied. Finally, the research focuses on the dynamic response of locomotive passing through straight or curve line at varing velocity and the longitudinal impulse mechanism of train system under the condition of traction and braking.The simulation results reveal that when the train runs on a complex railway line, plane curve mainly affects the vehicle dynamic performance. During the design of line geometric parameters, small radius curve should be avoided as far as possible. A certain curve cant deficiency should be set up, and transition curves should have enough length. Wheel/rail wear is serious on small radius curves, which will deteriorate vehicle dynamics behaviors, especially the lateral ride quality of car body. In the process of locomotive traction and braking, the axle load may transfer between wheelsets. Different braking mode, coupler gap, line condition, buffer dynamic behavior, and formation form of combined heavy-haul train may give rise to different longitudinal impact features. Therefore, according to simulation results, little coupler gap and reasonable group organization can effectively reduce the longitudinal impulse. Meanwhile, the train should not brake in curve or ramp, which may lead to some vehicles to be in poor state. |
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