Crushing analysis for novel bio-inspired hierarchical circular structures subjected to axial load

Hierarchical structures are widely observed in nature, and used in engineering due to superior mechanical properties. In this paper, a novel hierarchical circular tube (HCT) by iteratively adding self-similar sub-circle at the junctions of the primary ribs is proposed to enhance structural crashworthiness performance. The finite element model of HCT is firstly established through LS-DYNA and validated via experiment testing. The energy absorption performance of different hierarchical HCTs is investigated under dynamic load. The hierarchical organization has remarkable potential to improve the crashworthiness behavior of thin-walled structure, especially, the 2nd order HCT exhibits significant advantages for energy absorption efficiency. Then, parametric designs are performed to explore the crashworthiness effect on main geometrical parameters of 2nd order HCT. Furthermore, theoretical model of 2nd order HCT is derived based on super folding element method, and obtain the good prediction accuracy for energy absorption and mean crushing force. To further obtain the optimal design of the 2nd order HCT, multi-objective optimization is performed by employing radial basis function (RBF) neural networks and multi-objective particle swarm optimization (MOPSO) algorithm. The several optimal structures are obtained under different peak crushing force (PCF). The findings of this research offer a new route of designing novel crashworthiness structure with high energy absorption capacity.