Some aspects of the crashworthiness of rail vehicles

This thesis describes the studies carried out by the author on two aspects of the crashworthiness of rail vehicles : (1) The behaviour of rakes of vehicles during collisions; (2) Interior crashworthiness for occupants (passengers) during secondary collisions. The investigation of the behaviour of vehicles in rakes aims to study how the initial kinetic energy is partitioned amongst the vehicles after impact. Head-on collisions between two rakes of up to seven coaches were simulated using two non-linear Finite Element codes. The model, which correlates well with British Rail's full scale test results, assumes that a rake of coaches may be represented by a series of masses connected by non-linear springs. Important parameters that governed the rake behaviour have been identified. The effects of inter-vehicular distances, velocity-sensitive couplers, number of coaches, initial impact velocities and spring characteristics (e. g. constant collapse force, softening, hardening etc. ) on energy distribution along colliding rakes have been studied and discussed. In order to study the behaviour of passengers in the vehicle interior during the collision, acceleration pulses generated by the above rake models were used as input to Finite Element models of the vehicle interior which included dummies, placed in various seating arrangements. The investigation of interior crashworthiness of occupants began by `tuning' some selected input parameters of the non-linear Finite Element dummy model so that its behaviour matched that found in an actual sled test. The effects of various pulses on the occupant have also be investigated. These pulses contain the parametric effects caused by couplers, damping forces, spring characteristics, initial impact velocities and inter-vehicular distances. Assessments of the injury potential of occupants are based on comparing the selected output forces/moments from the dummy models to well-established human injury criteria. Another major aspect of this crashworthiness study included an investigation into the collapse behaviour of simple components (e. g. tubes and beams) in order to gain an insight as to how energy is absorbed during structural collapse. It is also important to study how recycled energy absorbers function and how much energy absorbing capacity has been lost after the recycling process. Studies of this nature are included in the Appendices of this thesis for tubes made from High Density Polyethylene (HDPE).