Energy absorption characteristics and crashworthiness of rhombic hierarchical gradient multicellular hexagonal tubes

In order to further improve the crashworthiness, this paper introduces hierarchies and gradients into thin-walled structures, and designs a new type of rhombic hierarchical gradient multicellular hexagonal tube (RHGMHT), which has the characteristics of hierarchies and gradients in structure. Experimental analysis showed that the mean crashing force (MCF) of 2nd order RHGMHT is greatly improved, and its crushing force efficiency (CFE) is increased by 104.91% compared with 0th order hexagonal tube (HT). The finite element model validated by the experiment is simulated to analyze its deformation mechanism and crashworthiness. Compared with other structures at the same mass, RHGMHT has higher specific energy absorption (SEA) and no increase in initial peak force (IPF). The parametric analysis shows that the SEA of 2nd order RHGMHT is 57.89% higher than that of the 0th order HT. In addition, increasing the mass of the structure can further improve the plateau force, but the IPF also increases with the mass. By comparing the thickness ratios of different rib plates, the analysis shows that different rib plate thicknesses significantly affect the deformation mode and thus the crashworthiness of the structure. Finally, according to the simplified super folded element (SSFE) theory, the MCF theoretical prediction model is established. The results show that the MCF predicted by theory is in good agreement with the MCF obtained by numerical simulation. The hierarchical gradient design proposed in this paper provides a certain guiding significance for the design of new energy absorbers.