Crashworthiness design and multi-objective optimization of bionic gradient circular multi-cell structure

As bionic design principles have been widely used in the design of energy-absorbing structures in recent years, this paper proposes a new bionic gradient circular multi-cell structure (BGCM) combining gradient and micro-circular features inspired by nature, such as bamboo and beetles, to enhance crashworthiness in energy-absorbing structures. A finite element model of the BGCM is developed and validated against experimental data, showing a maximum error of 7%. Comparative analysis between the bionic gradient multi-cell round tube (BGM) and BGCM demonstrates that the combination of gradient and micro-circular structures improves energy absorption capacity and load stability, yielding a 50% average increase in specific absorbed energy (SEA). The optimal cross-sectional structure of the bionic thin-walled tube was also selected using the E-TOPSIS method, and the BGCM structure exhibited excellent crashworthiness when the number of cell elements was 8. Additionally, the BGCM-8 has been optimized using the Non-dominated Sorting Genetic Algorithm-II (NSGA-II) for SEA and Initial Peak Force (IPF) with emphasis on wall thickness t and radius r. The comparison between the prediction model and the finite element model shows a maximum error of 0.4%, confirming the model's high accuracy in predicting BGCM mechanical behavior.