The expansion tube is normally used in impact-resistant components, owing to the stable expansion force, and high specific energy-absorption capacity. This paper reports the deformation mechanism and energy absorption characteristics of expansion tube subject to impact velocity ranging from 0.083 m/s to 48.84 m/s. The effects of cone piston semi angle, tube wall thickness, and impact velocity on expansion tube performance were studied via experimental measurements and numerical modeling. The mechanical responses of the expansion tube were measured using a universal gas gun setup. The energy absorption capacity of the expansion tube absorber was identified to be different under quasi-static and dynamic compressions. The dynamic expansion force is lower than the quasi-static expansion force, which is about 62.2%-76.6% of the static expansion force, but the deformation mechanisms of the tube under quasi-static loading and dynamic impact are same. A finite element numerical model was built and validated with the experimental data. The finite element predictions were in good agreement with the experimental measurements. It was shown that the decrease in the friction coefficient is the main reason for the dynamic expansion force lower than the quasi-static expansion force. The influence of cone piston semi angle and tube wall thickness are significant on the energy absorption capacity of the tube. The dynamic expansion response does not change significantly when the impact velocity is less than 50 m/s. Under dynamic impact, the change of energy absorption efficiency is negligible, and the plastic deformation energy is about 64%-71.5% of the total kinetic energy of striker. INDEX TERMS Dynamic impact, energy absorption characteristics, expansion response, expansion tubes, friction coefficient.

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An expansion tube is an ideal energy absorber which dissipates kinetic energy through plastic deformation and friction. There is an urgent need to understand the influence of key parameters such as the semi-angle, tube material, and friction coefficient on the mechanical characteristics of expansion tubes. In the present work, the material properties of expansion tubes were tested under quasi-static loading conditions, and numerical simulations were carried out using a commercial software ABAQUS. The validated finite element simulations revealed that the energy absorption capacity of an expansion tube is significantly affected by the semi-angle, tube material, and friction coefficient. An expansion tube with a parent material of high tensile stress and high tensile stress/density has high energy absorption capacity and high specific energy absorption, respectively. This work would serve as guidance to the structural design and parent material selection for expansion tubes.

Expansion tube absorber is a kind of excellent energy absorption devices owing to its good mechanical characteristics. In this study, the two-dimensional axisymmetric finite element models of expansion tube were established to simulate the influence of length of cone area and radius of cylindrical area on the mechanical properties of expansion tube. It is found that the expansion force increases significantly with the decrease of length of cone area in axial direction. Then, the expansion force reaches a stable value when the semi angle of cone area reaches 45°. The expansion force increases significantly when the radius of cylindrical area increases, but the trend of expansion force-displacement curves does not change. The influence of length of cone area and radius of cylindrical area on the mechanical properties of expansion tube is very regular. The mechanical properties of the expansion tube as absorber are very controllable and versatile, demonstrating that the performance of expansion tube as energy absorber is very reliable.