Tolerable longitudinal forces for freight trains in tight S-curves using three-dimensional multi-body simulations

With the need for increasing length of freight trains, the longitudinal train dynamics and its influence on the running safety become a key issue. Longitudinal train dynamics is a complex issue with contributions from both the vehicle and the operating conditions such as infrastructure design, braking regimes, etc. Standards such as the UIC Code 530-2 and EN-15839 detail the procedure for on-track propelling tests that should be conducted to determine the running safety of a single wagon. Also, it only considers a single S-curve and specifies neighbouring wagons and buffers. Hence, the resulting longitudinal train dynamics would not be able to judge the effects of various heterogeneities in the train formation such as the adjacent wagons, buffer types, carbody torsional stiffnesses, curvatures, etc. Here, there is a potential of using three-dimensional multi-body simulations to develop a methodology to judge the running safety of a train with regard to its longitudinal dynamic behaviour, subjected to various heterogeneities. In this study, a tool based on three-dimensional multi-body simulations has been developed to provide longitudinal compressive force limits and tolerable longitudinal compressive force for wagon combinations passing through S-curves of varying curvatures, and the sensitivities of the various heterogeneities present in the train are assessed. The methodology is applied to open wagons of the 'Falns' type on tight S-curves by calculating the corresponding tolerable longitudinal compressive force, and the effect of various parameters on the same is discussed.