Dynamic embedding behavior of thin-wall expansion tube loaded by explosive shock wave

Abstract

Expansion tubes have been considered to be promising impact-resistant structures due to their lightweight and high specific energy absorption capacity. The mechanical behaviors of expansion tubes subjected to a quasi-static loading or a dynamic loading have been widely studied; however, no previous study was reported regarding a blast loading. In this paper, the dynamic embedding responses of expansion tubes considering the effects of shock wave properties, structural parameters, and scaled distance were first investigated through orchestrated explosion experiments. The explosion results show that the embedding displacement is affected by the overpressure and impulse simultaneously. A finite element method was then proposed and verified by comparing the numerical solutions with the experimental results, based on which the effects of loading condition, scaled distance, and semi-angle of expansion tube were revealed. Finally, metallic foam impact tests were conducted to reveal the effect of the shell on the embedding displacement. The numerical solutions indicate that the expansion force increases by 22.9% when the quasi-static loading is replaced with a blast loading. The expansion tube can efficiently reduce the maximum shock stress acting on the baseboard and prolong the buffering process in the time domain. Due to the effect of the blast wave with a quasi-triangular stress-time curve, there exists a negative correlation between the effective impulse and the stress threshold of the expansion tube. In addition, the shell shows an insignificant effect on the embedding displacement of expansion tube. The results in this paper provide useful guidance for the application of expansion tubes in practice for improving the blast-resistant of a structure.