The coordinated design and optimisation of combined energy-absorbing structure with multi-level thin-walled tapered square tubes

To solve the problem of high peak force and large load fluctuation of combined energy-absorbing structures, a coordinated design strategy based on staggered compensation of load curves was proposed. First, an energy-absorbing unit of metal thin-walled tapered square tube was designed, and its crashworthiness was verified by experiment and simulation, and the peak force was reduced by introducing a groove inducing structure. Then, a combined structure with multi-level energy-absorbing units was proposed through layout arrangement and dimensional design. The parameter analysis was performed using a validated surrogate model. It is found that the thickness of the outer tube of the energy-absorbing units has a significant effect on peak crushing force (PCF), crushing force uniformity (CFU) and specific energy absorption (SEA). To improve the crashworthiness of the combined structure, a multi-objective optimisation was applied to achieve the maximum CFU and SEA values, and weight factors were introduced to select design schemes. The results show that the optimised combined structure reduces PCF by 44.48% and increases CFU by 50.78%, while improving the SEA.