The evaluation of such interactions is an important task for designers who have to evaluate the energy absorbed at the coach interfaces and then the consequent deceleration profiles. It is clear that for trains with a large number of coaches, this aspect is a very difficult one to be approached by analytical calculations or physical evaluations, but in these circumstances also finite element simulations would appear infeasible as they can be very time-consuming. On the other hand, the recourse to simplified numerical analyses, as those based on multi-body techniques [1,2,3,4], can result in a lack of accuracy if non-linear and strain rate properties of interface components are not adequately modelled.

In fact, the interface elements between coaches are made up of complex energy absorbing and coupling systems, whose global load-displacement paths are non-linear or even inelastic in compression. In this paper those paths have been evaluated through explicit dynamic finite element simulations of the collision of the frontal and back substructures of the coach under opportunely selected boundary condition, according to design specifications.

Then, the paths obtained have been applied to characterize the stiffness of the one-dimensional elements which constitute the interface between the coaches in a complete multi-body model. Full finite element simulations of the same impact scenarios have been developed to compare the results obtained with the reference ones.

The general agreement between the results of multi-body and finite element analyses is good, but it has to be stressed that the runtimes which are required to work out the finite element model of the simplest among the train configurations considered are at of least two orders of magnitude longer than those corresponding to the use of multi-body models.

1

W. Schiehlen, N. Guse, R. Seifried, "Multibody dynamics in computational mechanics and engineering applications", Comput. Methods Appl. Mech. Engrg, 195, 5509, 2006. doi:10.1016/j.cma.2005.04.024

2

P. Drazetic, P. Level, D. Cornette, P. Mongenie, Y. Ravalard, "One-Dimensional modelling of contact impact problem in guided transport vehicle crash", Int. J. Impact Engng, 16(3), 467-478, 1995. doi:10.1016/0734-743X(94)00056-3

3

J.A.C. Ambrosio, "Dynamics of structures undergoing gross motion and non linear deformations: a multibody approaches", Comp. & Structures, 59(6), 1001-1012, 1996. doi:10.1016/0045-7949(95)00349-5

4

J.P. Dias, M.S. Pereira, "Optimization methods for crashworthiness design using multibody models", Comp. & Structures, 82, 1371-1380, 2004. doi:10.1016/j.compstruc.2004.03.032

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