Axial crushing of tapered circular tubes with graded thickness

• Tapered circular tubes with graded thickness are fabricated by tube tapering machine.
• The responses of straight and tapered tubes under axial loading are compared.
• Numerical simulations of the tests are conducted and agree well with experiment.
• Forming effects during fabrication on energy absorption of tubes are investigated.
• A theory is proposed to predict the mean force of tapered tubes with graded thickness.

This paper aims to investigate the energy absorption characteristics of tapered circular tubes with graded thickness (TCTGT) under axial loading. TCTGT specimens were fabricated by a tube tapering machine and the forming effects on crush response were investigated. Both the original straight circular tube and the fabricated TCTGT were tested and compared to analyze the relative merits of TCTGT. Numerical simulations of the tests were conducted by using nonlinear finite element code LS-DYNA and a simplified fabrication process was also simulated. The energy absorption efficiency of the fabricated TCTGTs was found to be considerably higher than that of straight tubes and the forming effects showed important influence on the increase of efficiency. In addition, a novel approach was proposed to predict the mean crushing force of circular and tapered tubes with and without forming effects. The outcomes of the present study will facilitate the design of TCTGT structures with better crashworthiness performance.

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