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Pulsed X-ray photography is a usual method for determining the radial distribution of the fragment velocity of a thin-walled structure under explosion loading, in which two X-ray tubes are used to photo the charge specimen at different instants. Because of the inevitable distance between the two X-ray tubes in the test configuration, the radial distribution of the fragment velocity of a long charge could not be obtained because of the shadowing problem. Consequently, short charges are typically used in this scenario. However, the radial velocity distribution of the one-line asymmetrical initiation was found to be significantly influenced by the end rarefaction waves. This means that the fragment velocity distribution measured using short charges cannot reflect the real influence of the initiation styles or warhead designs. New test methods are demanded.

This study uses SPH modeling to propose a new method for measuring the radial velocity distribution using X-ray photography while eliminating the effect of end-rarefaction waves. First, based on the SPH modeling, the radial distributions of the fragment velocity of two-line asymmetrically initiated warheads with different length–diameter ratios were investigated. The influence of rarefaction waves on the radial distribution of the fragment velocity was also discovered in the two-line asymmetrical initiation. Subsequently, based on the different velocity distribution results, new mechanisms were revealed, and based on these three methods for determining the actual fragment velocity distribution were proposed. Finally, the conclusions were validated through X-ray experiments using a multi-anode X-ray tube. The proposed methods apply also to other initiation styles, warhead materials, and warhead structures. This study provides important references for related X-ray test methods and the development of high-lethality warheads.