Theoretical development and multi-objective optimisation of a double-tapered rectangular tube with diaphragms

A double-tapered rectangular tube with diaphragms (DTRTD) for energy absorbance in railway vehicles is proposed. The mean crushing force (MCF) of DTRTD was derived. The code LS-DYNA3D (971) was used to build a finite element model, validated using a quasi-static test. The experiment results and numerical simulation indicate the accuracy of the theoretical prediction for the MCF of DTRTD and the regularity and stability of the collapse pattern of this energy-absorbing structure (EAS). To explore the effects of the thickness of different EAS parts on the crashworthiness indexes and obtain the optimal designs, the design of experiment (DOE) and a surrogate model were employed for a parameter study and multi-objective optimisation (MOO). The specific energy absorption (SEA) and crush force efficiency (CFE) cannot reach the optimal values concurrently. Nonetheless, all designs from the Pareto front of MOO significantly improve the crashworthiness of EAS because of the larger SEA and CFE.