A Mixed Numerical Approach to Evaluate the Dynamic Behavior of Long Trains

Abstract The evaluation of the longitudinal forces exchanged between the wagons composing a long train is very complex due to the large number of d.o.fs to be considered and due to the non linearities introduced by the coupling elements. The most common approach to simulate long trains is the use of simplified wagon models realized considering only the longitudinal d.o.f. In this way the number of d.o.fs used for the full vehicle model is equal or a little greater than the number of the connected cars. The efficiency of this approach, in calculating the in train forces during traction and braking operations, has been demonstrated by several authors in the literature. In particular the long train simulators have been developed with the aim to evaluate the longitudinal forces during the braking operations in order to optimize the braking strategy and the mass distribution along the train. This method is efficient to optimize the train configuration in order to minimize the in train forces, but it does not allow to evaluate the vehicle safety indexes (such as derailment, wheel unload and lateral force) because the wheel-rail contact forces are completely neglected. This work shows a novel approach where the long train numerical model, realized using the Simpack multibody code, is developed considering both simplified wagon models, with few d.o.fs and no contact module, and detailed wagon models, which include several d.o.fs and the algorithm for the contact forces evaluation. In particular this mixed technique allows to evaluate both the longitudinal train dynamic and the behavior of some of the wagons when the train is running on curve. The position of the detailed wagon models along the train combination can be selected by the user in order to evaluate the influence of a particular wagon position on the vehicle safety.