Expansion and Fracture of Fragmenting Warhead Shells of Various Materials under a Cl-20 Explosive Charge

To study the effect of the warhead material characteristics upon warhead expansion and fracture and upon the formation of fragments under a high-power explosive charge, four different warhead materials; 30CrMnSiNi2A steel, 40CrMnSiB steel, 50SiMnVB steel and 82 steel; are examined. This paper builds a analytical modeling to theoretically analyze the expansion and fracture processes for the different material warheads. In addition, the AUTODYN-3D finite element software is used to numerically simulate the expansion and fracture processes of the four materials, and high-speed photography technology and a tinfoil target velocity test system are used to verify the simulation results. It is found that, for the “ φ 62mm” aperture warhead under the explosive CL-20 charge, the expansion and fracture processes of the four materials all require ~60 μs, and the shell expansion velocity in the whole process can be divided into three stages called libration, acceleration and stabilized. The initial velocities of the fragments along the warhead axis for the different warhead materials are consistent with each other, though the expansion velocity and the maximum initial velocity of the fragments are largest for the 30CrMnSiNi2A steel warhead. It is found that the warhead expansion velocity and the initial velocity of the fragments decrease gradually as the ultimate tensile strength of the warhead material decreases and as its dynamic fracture toughness increases. This study introduces the coefficient of radial warhead expansion and acquires the function for the distance of the radial warhead expansion over time, which is influenced by the warhead material characteristics. The results of this study will provide a reference for fragmenting warhead shell material selection and design.