The design of circular tubes with stepped varying thicknesses and their synergistic multi-tube combination

Abstract

A stepped wall circular tube with varying thickness (STVT) and its multi-tube synergistic combination energy absorption structure were developed to address the shortcomings of the high initial peak force of thin-walled metal tubes and the significant load fluctuation of conventional multi-tube combination structures. The STVT was designed with different thickness variations, and its crashworthiness was evaluated numerically and experimentally. An analysis was done on the influences of various characteristics, such as the number of steps and thickness variation, on the crashworthiness of STVTs. Research shows that the STVT with three and four steps has improved crashworthiness. The phase of the curve is significantly influenced by the initial thickness, and for each 0.6 mm difference in step thickness, the peak phase shifts by about 5.5%. In comparison to the combination of four equal-thickness tubes of the same mass, the optimal combination structure optimizes smoothness by 10.67%, energy absorption by 19.52%, crushing force efficiency by 15.30%, and initial crushing force by 20.70%.