Energy absorption properties of multi-cell thin-walled tubes with a double surface gradient

Abstract Multi-cell design and graded thickness are two efficient strategies for improving the mechanical behaviors of metallic thin-walled tubes. This paper combines these two strategies to present a novel multi-cell structure with a double surface gradient (DSG) and to address the energy absorption characteristics of the new tube subjected to axial compression. A mathematical formulation for the mean load was derived through theoretical analysis of the multi-cell structure's folding mechanism, and two vital parameters were proposed. Afterwards, comprehensive numerical simulations were conducted to validate the formulation and to investigate effects of the DSG on the mechanical properties. The results demonstrated that the combination of the DSG strategy and the multi-cell structure led to a greater energy absorption capacity. Finally, the key factor of the DSG design in promoting the energy absorption efficiency was analyzed. To achieve a higher promotion, an approach of rationalizing the sectional material distribution of the DSG tube was attempted and proven valid. All these achievements shed a light on the multi-cell and graded thickness effects on mechanical properties.