Parametric beam-based crashworthiness optimisation for the crush zone of a subway vehicle

This study proposed a method to optimise the crashworthiness for the crush zone structure of a subway vehicle based on the beam element model. In the preliminary conceptual design, a simplified beam element model of the crush zone was established to verify the feasibility of the model. Then, a parameterised modelling method for the mechanical characteristic curves of the energy-absorbing structures and the front-end beam was proposed, and a hybrid-weight prediction model of the mechanical curves was built. Based on the mapping relationship, a database of mechanical and geometric parameters of the crush zone was established. Finally, beam element models of the crush zone with different arrangement schemes were obtained through optimisation based on genetic algorithm. Multiple sets of feasible geometric structure parameters were obtained and the best scheme was determined. The research results showed that the calculation speed for the simplified beam element model of the crush zone structure was 461 times faster than that of the finite element model. The prediction model of the mechanical characteristic curve of the crush zone structure built in this study exhibited sufficient accuracy. The mapping relationship between the geometric structure and the mechanical properties enabled the optimised structure by the discrete beam model to be quickly obtained. The mechanical parameters of the optimised crush zone were obtained with energy absorption of 597.51 kJ, mean crushing force of 2398.38 kN, and crushing displacement of 249.72 mm. The proposed method is expected to provide a convenient guideline for fast optimisation and upgrade of energy-absorbing structures.