On penetration characteristics of three typical shaped chargesinto double-layer spaced targets in water

To select the shaped charge structure suitable for large-distance non-contact penetration damage in water, three typical shaped-charge structures, explosively formed projectile (EFP), jetting projectile charge (JPC), and shaped charge jet (SCJ), were selected. The velocity tests of different penetrators before entering water, before hitting the target, and after penetrating the target were carried out, and the penetration tests of double-layer spaced targets in water were conducted. Firstly, a comparative test of penetration of three types of shaped charges in the air was carried out to verify the rationality of the structure of shaped charges. The air explosion height of 35 cm was selected to meet the penetration requirements of the three shaped charges. At the same time, the velocity of the shaped charges before penetrating water was measured, which provides the basis for the underwater penetration test. Secondly, the penetration test of three types of shaped charges on an underwater double-layer spaced target was carried out when the air height was 35 cm, and the length of the water medium in front of the target was 20, 45, and 100 cm. The reflected pressures were measured by the wall pressure sensor and PVDF sensor. The velocities of the penetrator at the time of water entry, before the target, and after the target were measured by double-layer on-off net targets.The damage performance of three shaped charge structures on the double-layer spaced target plate was respectively obtained when the water medium in front of the target was at short range, medium range and long range.Based on the projectile-target structure used in the experiment, a two-dimensional finite element model of shaped charge penetrating a double-layer spaced target in water was established using ANSYS/LS-DYNA finite element software. The measured velocity values of the shaped charge penetrator before entering the water, before hitting the target, and after passing through the target were compared with the numerical simulation results to verify the accuracy of the model. The error rate is about 3%. Based on the verified finite element model, the time series characteristics of the underwater damage element of the shaped charge, the peak characteristics of the forward shock wave in the water, the variation law of the penetration velocity in the water, and the penetration performance of the shaped charge against the double-layer spaced target in the water were studied. The results show that the forward shock wave reaches the target plate before the penetrator. As the length of the water medium increases, the peak pressure of the forward shock wave at the front target plate decreases linearly, and the peak pressure of the forward shock wave at the rear target plate decreases nonlinearly. The velocities of EFP, JPC, and SCJ decrease nonlinearly with the increase of water medium, and the velocity in front of the SCJ target is about twice that of JPC. When the length of the water medium in front of the target is not more than 25 cm, the maximum perforation diameter formed by EFP on the front target plate reaches 5 cm, which is 1.3 times the perforation diameter of JPC and 3 times the perforation diameter of SCJ. When the length of the water medium in front of the target is not more than 100 cm, JPC and SCJ have better penetration effect on the double-layer spacer target, and the penetration performance of JPC is better than that of SCJ.