To further improve the strike accuracy and penetration power of explosively-formed projectile (EFP) after long-distance flight, a polygonal charge capable of forming EFP with tail fins was designed during the study. A model for calculating the EFP velocity was derived from the effective charge and detonation projection theories with the integration of calculus. The circumferential velocity distributions of EFP formed using polygonal charges were obtained using this model, and the mechanisms underlying the formation of tail fins were elucidated. The feasibility of using this polygonal charge to form tail fin EFP was verified by conducting multi-media soft recovery tests and numerical simulations. Furthermore, the feasibility of forming tail fin EFP using polygonal charges with different numbers of sides and the effects of the structural parameters of a hexagonal charge on the formation of tail fin EFP were investigated by simulation. The ranges of optimal values for the structural parameters of a hexagonal charge capable of forming high-performance tail fin EFPs were determined.

The dispersion distribution characteristics of prefabricated fragments from an improvised explosive device (IED) are essential in defense technology development. To improve warhead design, it is essential to predict a fragments velocity and dispersion distribution accurately. This paper investigates a fragments flying angle from a detonated warhead with a cylindrical charge under a one-end central detonation. A modified formula for calculating the fragment dispersion distribution at each axial position of the warhead was obtained based on experimental data and model analysis. The impacts of the following parameters on the flying angle were considered in the formula: ratio of charge mass to shell mass, charge diameter, axial sparse effect, and relative axial shell position. The formula was verified by experimentation to be suitable for wide applications using different validation samples. Theoretical calculations with the formula show good accuracy in predicting the flying angle of cylindrical-shell fragments, agreeing with experimental data. The proposed model meets the error requirements of engineering applications. This work provides a theoretical foundation for subsequent research on damage effectiveness and IED damage assessment.

In urban combat, sub-millimeter inert metal powder is used to replace fragments in explosive bombs, which can effectively reduce collateral damage. In order to investigate the damage effect of high-speed metal particles on the human body, a particle ring filled with a charge was designed to create an explosion-driven particle cloud for the penetration ballistic gelatin. The particle ring was made of polytetrafluoroethylene (PTFE) and sub-millimeter tungsten powder. The dispersion properties of the particle cloud driven by the explosion were studied with high-speed photography and ballistic gelatin. Furthermore, the numerical simulation models of particle-penetrating gelatin based on the experimental results were established with the finite element method. The influences of the particle size and velocity on the penetration depth and cavity diameter was obtained. The relationship between the critical interference distance of the cavity and the distance between particles was determined. This paper provides references and theoretical support for the design of low collateral damage ammunition based on inert metal powder.

Dynamic spatial distribution and killing characteristics of warhead fragments are important topics in the field of weapon effectiveness and protection. However, there is little research on the fragment distribution formed by continuous dynamic attacks of multiple projectiles that explode above the ground. This study analyzes spatial distributions of warhead fragments using witness boards in a rectangular target test. The results show that the fragment distribution of multiple projectiles in continuous dynamic attacks demonstrates a spatial superposition characteristic. The superimposed distribution is the sum of the distributions of two independent fragment distributions. The distribution characteristics are consistent with fragment scattering behavior. Therefore, they can be used to analyze the killing effects of multiple projectiles conveniently. The effects of falling speed, falling angle, and explosion height on the damage range of fragments were explored by a fragment spatial distribution model obtained from experiments. Analysis indicates that the prefabricated fragment distribution conformed to a spatial superposition relationship under dynamic multiprojectile continuous attacks, and the superposition obeyed fragment scattering characteristics. As the projectile falling angle increased at the explosion center, or as the falling height decreased, the positive pressure duration increased gradually. The falling speed had the greatest impact on the specific impulse of overpressure. The falling angle had the greatest impact on the peak value of overpressure. Both the falling angle and the explosion height had the greatest impact on the positive pressure acting time.

Silicon carbide (SiC) ceramics have been widely used in lightweight armor protection due to their combination of high compressive strength, high hardness, and low density. The mechanical properties and penetration resistance of SiC ceramics are of significant importance for armor protection design. To investigate the mechanical response and fragment penetration resistance of SiC ceramics, this study systematically carried out plate impact tests, dynamic and quasi-static uniaxial compression tests, as well as ballistic penetration tests. Based on the experimental data, the parameters of the Johnson-Holmquist II (JH-2) constitutive model for the SiC ceramic were calibrated. Subsequently, a numerical simulation model of tungsten alloy fragment penetration into SiC ceramic composite targets was established. The model was validated using tungsten alloy fragment penetration tests on SiC/6061-T6 composite targets, and the penetration characteristics of fragments into SiC/6061-T6 composite targets were systematically compared with those into monolithic 6061-T6 aluminum alloy targets. The error between the experimental and simulation results of the composite target penetration tests is less than 9%, verifying the accuracy of the calibrated JH-2 model parameters. For monolithic 6061-T6 aluminum alloy targets, the penetration depth of spherical fragments is significantly greater than that of cubic and cylindrical fragments. In contrast, for the ceramic composite targets, the residual penetration depth of spherical fragments is markedly lower, indicating that SiC ceramic exhibits substantially better resistance to spherical fragments than to the other two fragment shapes. This study can provide a theoretical basis and data support for the design and performance evaluation of lightweight armor protection.

The radius of jetting projectile charge (JPC) varies significantly from the head to the tail, resulting in the crater formed with a large and uniform radius when penetrating steel target. Current methods for calculating crater radius typically use the average radius without considering JPC radius distribution, leading to large errors in the calculation. Therefore, it is necessary to introduce JPC radius distribution when predicting JPC penetration and cratering. By incorporating the radius distribution in the calculation of JPC break-up time, the modified break-up time model was used to obtain the prediction model for penetration depth. Based on the current jet (JET) cratering theory, JPC radius distribution was introduced to derive the prediction model for crater radius of JPC penetration. The X-ray tests and numerical simulations were used to obtain the radius and velocity distribution of JPC. Finally, the prediction model was verified using data from static penetration tests and literature. The results show that the penetration depth calculated using the modified model had a small error compared to the test results, therefore, the modified model could predict the variation of the crater radius with the penetration depth. And the variation of crater radius was in good agreement with the tests, and accorded with the characteristics of uniform crater radius of JPC penetration. The findings have important guiding significance for JPC design and evaluation.