Crashing performance and multi-objective optimization of honeycomb-filled thin-walled energy absorber with axisymmetric thickness

Improving the crashing performance of energy-absorbing structure is of vital significance for the safety of subways. To this end, a new type of honeycomb-filled thin-walled energy absorber with axisymmetric thickness (HTEA-AT) was proposed. Unlike the honeycomb-filled thin-walled energy absorber with uniform thickness (HTEA-UT), the thicknesses of adjacent tube walls of HTEA-AT were defined as independent variables, while the thicknesses of the opposite walls remained identical. Numerical, theoretical and experimental methods were adopted to systematically investigate the crushing mechanics of the honeycomb-filled thin-walled energy absorber (HTEA). To improve the crashworthiness of HTEA-AT and HTEA-UT, a multi-objective optimization design (MOD) was carried out. The results revealed that HTEA-AT has a lower peak force and higher energy absorption than HTEA-UT, achieving superior crashworthiness performance. In addition, a multi-criteria decision-making method combining integrated entropy and gray relational analysis (GRA) was introduced to seek the ideal balance between the energy absorption (EA) and initial peak crushing force (IPCF) in the Pareto front. The optimized results indicated that the gray correlation was the largest at optimal point C, where EA and IPCF reached a balance (EA = 177.82 kJ, IPCF = 430.03 kN). This means that the optimized configuration can provide insightful information for the crashworthiness design of the energy-absorbing structure at the end of subways.