Double casing warhead with sandwiched charge: The axial distribution of fragments velocities

The double casing warhead with sandwiched charge is a novel fragmentation warhead that can produce two groups of fragments with different velocity, and the previous work has presented a calculation formula to determine the maximum fragment velocity. The current work builds on the published formula to further develop a formula for calculating the axial distribution characteristics of the fragment velocity. For this type of warhead, the simulation of the dispersion characteristics of the detonation products at different positions shows that the detonation products at the ends have a much larger axial velocity than those in the middle, and the detonation products have a greater axial dispersion velocity when they are closer to the central axis. The loading process and the fragment velocity vary with the axial position for both casing layers, and the total velocity of the fragments is the vector sum of the radial velocity and the axial velocity. At the same axial position, the acceleration time of the inner casing is greater than that of the outer casing. For the same casing, the fragments generated at the ends have a longer acceleration time than the fragments from the middle. The proposed formula is validated with the X-ray radiography results of the four warheads previously tested experimentally and the 3D smoothed-particle hydrodynamics numerical simulation results of several series of new warheads with different configurations. The formula can accurately and reliably calculate the fragment velocity when the length-to-diameter ratio of the charge is greater than 1.5 and the thickness of the casing is less than 20% its inner radius. This work thus provides a key reference for the theoretical analysis and the design of warheads with multiple casings.