Crashworthiness performance of conical tubes with nonlinear thickness distribution

•Conical tubes with linear and quadratic thickness distributions are fabricated.•Axial loading of the conical tubes are tested and simulated.•Material hardening overweighs thickness variation in increasing energy absorption.•Numerical simulation of conical tubes is in good agreement with experiment.•Nonlinear thickness distribution outperforms linear thickness distribution.

Crashworthiness performance of conical tubes with various thickness distributions are investigated in the present work. Specimens are fabricated by tube shrinking process and axial crushing tests are carried out to study their energy absorption characteristics. The potential and benefit of tube shrinking to improve crashworthiness performance of tubes are analyzed. Both thickness increase and material hardening during tube shrinking lead to up to 120% increase in energy absorption with even less structural mass. Although the peak force of tubes is increased after shrinking, the load uniformity is still improved due to larger increase in mean crushing force. Numerical simulations are also conducted for tubes with quadratic thickness distributions. The material hardening during fabrication is included and the numerical results compare well with experiment. In addition, crashworthiness optimization of conical tubes with nonlinear thickness distribution is performed by surrogate method. Influences of relevant thickness parameters on performance of the structure are analyzed.