Behaviour of expansion tubes under impact load: Deformation mode and mechanical response

Abstract

The expansion tube is a promising energy absorption structure in spacecraft and airplanes, where it is often exposed to impact stress. Despite prior studies on the deformation mode of expansion tubes have been conducted, the majority of them have relied on quasi-static load. This research has utilized theoretical, computational, and experimental approaches to concentrate on the behaviors of expansion tubes exposed to dynamic impacts. The experimental results show that the strain-rate effect and the downward velocity discrepancy could even cause the deformation mode transition of the expansion tube. The dynamic theoretical model of steady-state expansion force is derived and used to predict the normalized compressive force. A normalized compressive force more than 0.85 would promote buckling deformation of the expansion tube. The normalized compressive force is then used to predict the deformation mode diagrams of the expansion tube for a range of geometric parameters; this analysis reveals that the semi-angle, expansion rate, and radius/wall-thickness of the tube all play a role in determining the deformation mode, while the effect of length/radius is less evident. The expansion tube's buckling resistance is enhanced by the parent material's strain rate sensitivity and diminished by the strain hardening effect.