Damage response of steel plate to underwater explosion: Effect of shaped charge liner T A G G E D P ABSTRACTA shape of charge liners has a great effect on formation of a metal jet and its penetration into a target. In this paper, three different shapes of a charge liner, namely, conical, hemispherical and spherical-segment, are chosen to investigate their effectondamageresponseofaplatetounderwater explosion. A Smooth Particle Hydrodynamic (SPH) method based on mesh-free Lagrange formulation is applied to simulate an entire process of a shaped-charge detonation, formation of a metal jet as well as penetration on a steel plate. Initially, a SPH model of the shaped charge with a spherical-segment liner is developed, and its results are compared with experimental data to verify the effectiveness of this method. Then, numerical simulations of shaped charges with different liners are performed to study the damage characteristics of a steel plate subjected to underwater-explosion shock loading and the metal jet. It was found that for the shock wave the peak value of the radial pressure is larger than that of the axial pressure during the detonation process; the level of pressure in the spherical-segment case was higher than that of the other two cases. After the detonation, the metal jet was gradually produced under the effect of the detonation wave. Three types of the metal jet -a shaped charge jet (SCJ), a jetting projectile charge (JPC) and an explosive formed projectile (EFP) À were formed corresponding to three cases with conical, hemispherical and spherical-segment liners. The obtained results show that the velocity and length of the SCJ in the conical case are greater than that of the other cases, and it therefore may lead to a larger penetration depth. In addition, the EFP has a better motion stability for a velocity difference in the spherical case is lower than that of the other two cases. Subsequently, the shock wave arrives at the plate earlier than the metal jet, which will cause deformation of the plate. Due to higher pressure, the shock wave in the sphericalsegment case has a stronger damaging effect on the plate than that in the other two cases. Finally, the metal jet reaches the plate causing a hole. Because of a wider jet head, the EFP results in a more serious damage to the plate. The suggested analysis and its results provide a reference for structural design of shaped charge warheads.

No abstract

No abstract

With the improvement of the antiknock performance of warships, shaped charge warheads have been focused on and widely used to design underwater weapons. In order to cause efficient damage to warships, it is of great significance to study the formation of shaped charge projectiles in air and water. This paper uses Euler governing equations to establish numerical models of shaped charges subjected to air and underwater explosions. The formation and the movement of Explosively Formed Projectiles (EFPs) in different media for three cases: air explosion and underwater explosions with and without air cavities are discussed. First, the velocity distributions of EFPs in the formation process are discussed. Then, the empirical coefficient of the maximum head velocity of EFPs in air is obtained by simulations of air explosions of shaped charges with different types of explosives. The obtained results agree well with the practical solution, which validates the numerical model. Further, this empirical coefficient in water is deduced. After that, the evolutions of the head velocity of EFPs in different media for the above three cases are further compared and analyzed. The fitting formulas of velocity attenuation of EFPs, which form and move in different media, are gained. The obtained results can provide a theoretical basis and numerical support for the design of underwater weapons.

This study numerically investigates the underwater explosion bubble dynamics during the process from detonation to bubble jet with a hybrid algorithm based on Runge Kutta Discontinuous Galerkin-Level Set-Direct Ghost Fluid method (RKDG-LS-DGF) and boundary element method (BEM). RKDG-LS-DGF method is used to simulate the physical process from the detonation of a column charge at one end to the formation of a nonspherical initial bubble and the process of bubble jet. And BEM is adopted to simulate bubble pulsing characteristics. In addition, the numerical results are compared with the experimental results to verify the feasibility of the numerical method. It is found that, during the detonation process of a column charge, the detonation product experiences a shape change from an initial ellipsoid into a sphere during expansion. After the detonation, the bubble experiences expansion and contraction and develops a jet. The jet threads through the bubble in the opposite direction to gravity and induces a high-pressure region. Subsequently, the pressure of this region decreases when the bubble reexpands after being penetrated by the jet. The numerical results agree well with the experimental data, which proves that axisymmetric RKDG-LS-DGF method and BEM are successfully combined to simulate the whole process of underwater explosion.