Crashworthiness study of double square gradient hierarchical tubes

A new type of bi-double square gradient hierarchical tube (DSGHT) is proposed, and its crashworthiness under consistent wall thickness is analyzed. The results show that the energy absorption (EA), specific energy absorption (SEA), and crush force efficiency (CFE) of DSGHT3 are increased by 1305.14%, 430.14%, and 469.50%, respectively, compared to DSGHT0. The combination of double square tubes and gradient laminar design effectively enhances the crashworthiness of the structure. A parametric study indicates that increasing wall thickness significantly improves crashworthiness, with EA, SEA, and CFE improvements of 805.75%, 125.83%, and 126.83%, respectively, at a wall thickness of 0.8 mm compared to 0.2 mm. However, the effect of wall thickness gradient distribution on structural crashworthiness is minimal. Conversely, the ratio of the inner to outer square tube edge length (δ) significantly impacts crashworthiness; SEA and CFE increase by 37.77% and 37.35%, respectively, when δ is 6/12 compared to 8/12. Finally, DSGHT3 was compared to other hierarchical, tree-shaped fractal structures, and it demonstrated superior crashworthiness. Specifically, DSGHT3 has 35.32% and 34.29% higher SEA and CFE, respectively, compared with MSTL2-2.