Research On The Entry Of Truncated-oval Projectiles Into Water And Their Penetration Effects On Typical Targets

With the enhancement of the protection capability of underwater targets,higher requirements were put forward for the attack and penetration capability of underwater weapons.The underwater semi-armor-piercing projectiles can explode after intruding into the target,which greatly enhance the lethality of projectiles.However,the current research on the underwater semi-armor-piercing projectile mainly focused on the damage part of the explosion,while ignoring the process of the projectile entering the water and penetrating.In this paper,the water entry and penetration process of the projectile were divided into two parts,and the scaled model after the counterweight was used to simulate the water entry and penetration characteristics of the truncated-oval notch projectile structure.Used the ALE fluid-structure coupling calculation method in ANSYS/LS-DYNA,a quarter simulation model of the projectile entering the water vertically and a half simulation model of the projectile entering the water were established to simulate the projectile entering the water at different angles,through the analysis of ballistic characteristics such as cavitation and underwater velocity decay after the truncatedoval notch was thrown into the water,and the following conclusions were obtained:The velocity decayed very fast,and the decay law was similar when entering the water at different initial velocities;The projectile body was subjected to a large inclination angle into the water stability test;The 107 mm experimental bomb entered the water at 300m/s and sailed for 20 m underwater,the average residual velocity was185.19m/s,and the relative error between the theoretical residual velocity and the experimental residual velocity was less than 22%,and the calculation method was reliable.Established a half model of the projectile penetrating the thin steel plate underwater and in the air to simulated the projectile penetrating the target plate at different angles and different target speeds.The post-processing software was used to analyze the damage mode of the target and the velocity attenuation characteristics of the projectiles,and the following conclusions were obtained:The damage mode of the target plate when the projectile penetrates at a medium and high speed in water was similar to that when the projectile penetrates at a low speed in the air;When penetrating in water,the speed of the projectile had begun to decay rapidly before hitting the target plate,the speed decay was faster than in the air,and the remaining speed was small;When the projectile penetrated the target plate at 365m/s and 15° in two environments,the relative error of the projectile’s residual velocity was 1.55%,and the residual velocity of the projectile in water was small.According to the test requirements,the calculation model of the whole projectile that the projectile body penetrated the reinforced aluminum target plate underwater was established.The four positions of the large rib midpoint,the junction point of the large rib and the small rib,the midpoint of the small rib and the homogeneous target plate without reinforcing ribs were simulated,and the following conclusions were obtained:The relative error of the remaining velocity of the projectile obtained by theoretical calculation and simulation was less than 0.47%;The failure mode of part of the structural target plate was petal-shaped failure accompanied by the dish-shaped deformation of the target plate,and the part of the reinforcing rib was punching failure and petal-shaped failure;The shape of the bullet hole was a perfect circle,the large stiffener had a strong hindering effect on the stress propagation of the target plate.The above experiments and simulation results showed that,the structure of the truncated-oval notch projectile has good water entry stability and underwater penetration ability.The theoretical and experimental results can provide a reference for the research of underwater weapons.