Crushing characteristics and multi-objective optimisation of a novel bionic frog leg tube

Recently, the demands for structural impact protection in automobile, train, aerospace and other fields have become increasingly intense, and the bionic energy absorption structures have attracted widespread attention for their excellent structural properties and crushing characteristics. In this study, inspired by the great impact resistance of the frog legs, a novel bionic frog leg tube was proposed and investigated by numerical simulation and parametric study. Firstly, according to the structural forms of the legs for frogs, humans and pigs, three types of bionic leg tubes were designed, and the energy absorption characteristics of these tubes subjected to axial loading were investigated, it was found that the peaking crushing force (PCF) and undulation of load-carrying capacity (ULC) seem to have a strong relationship with the jumping ability for animals, lower PCF and ULC could decrease the injury transmitted to the body. Then, the parametric studies were conducted to investigate the effects of structural parameters on the crushing behaviour of the bionic tubes, the results indicated that a bionic frog leg tube with smaller L1 tends to present the concertina deformation mode, and a larger L1 will lead to the diamond mode or mixed mode. Lastly, the multi-objective optimisation of the bionic frog leg tube was carried out to simultaneously improve specific energy absorption (SEA), crushing force efficiency (CFE), and reduce ULC, based on the NSGA-II algorithm. The optimal configuration of the structural parameters of the bionic tube was obtained, and the bionic tubes present better crashworthiness characteristics than initial structures under the axial loading. The findings of this study provide new insights into the transformation of natural biological inspiration into engineering applications for protective structures.