Experimental and theoretical study on crashworthiness of star-shaped tubes under axial compression

Thin-walled tubes play a very important role in energy absorbing for car crash. Current studies mainly focus on the design theory and performance improvement by proposing different structures. However, the practical performances might be influenced by manufacturing process, but few studies on this aspect could be found. In this paper, the crashworthiness of several star-shaped tubes, i.e., the hexagonal, octagonal and twelve corners, which were made with different material and fabrication methods, are compared through the experimental analysis. It is found that the energy absorption of octagonal star-shaped tubes is the best and that of the twelve corners star-shaped tubes is the lowest. Under quasi-static compression, the Pm of the octagonal star-shaped tubes increases by 7.94% with respect to the hexagonal star-shaped tubes, while the Pm of star-shaped tubes with twelve corners decreases by 15.75% with respect to the octagonal star-shaped tubes. The star-shaped tubes manufactured by different processing methods have some influence on the deformation mode, but the effect on overall crashworthiness is limited. Finally, the axial mean crushing force of the star-shaped tubes was analyzed theoretically based on the simplified Super Folding Element theory. A theoretical solution for the mean crushing force of the star-shaped tubes was derived, and the theoretical solutions show an excellent agreement with the experimental results.