Fragment velocity distribution of the bottom part of d-shaped casings under eccentric initiation

In the field of defense technology and public security, asymmetric casings filled with explosive, especially the D-shaped casing, has received considerable attention. However, the effect of eccentric ratio on the fragment velocity distribution of D-shaped casing and its mechanism remain unclear. To obtain the velocity distribution of the fragments in the bottom part of the D-shaped casing, a kind of D-shaped casing with large length-diameter ratio was tested based on the X-ray photography technique. The experimental results show that the fragment velocity distribution of the D-shaped casing is not consistent with the results in existing studies. Then, a series of numerical simulation models were established and validated according to the experimental results, and the acceleration process of the fragments in the bottom part of D-shaped casing was numerically studied. The results indicate that the fragments in the bottom part of D-shaped casing are accelerated not only by the initial detonation wave but the detonation wave reflected from the arc part shell, which causes the inconsistency mentioned above. In addition, an empirical calculation formula was proposed based on the acceleration process of D-shaped casing and it was in a good accordance with numerical results. The findings herein could serve as a foundation for further research on the D-shaped casings and other kinds of asymmetric casings. It can also be a solid reference for engineering design of innovative warheads.