弹体斜侵彻双层钢板的结构响应和失效研究

In order to investigate the structural response and failure of projectiles obliquely penetrating into a multi-layered steel plate target, oblique penetration tests were conducted, in which three kinds of projectiles with circular, elliptical, and asymmetric elliptical cross-sections were employed while the ballistic trajectory and structural failure of projectiles were recorded. With the photographs captured by high-speed camera, a pixel measuring method was used to obtain the velocity and attitude deflection angle of projectiles. Based on the test results, the ballistic characteristics, dynamic loads and structural response of projectiles are analyzed by using FEM code ABAQUS/explicit, focusing on the oblique penetration at initial speed of 480 m/s and attack angle within 2°. Then, based on the free-free beam theory and the dynamic loads obtained by numerical simulation, the distributions of axial force, shear force and bending moment within projectiles are calculated, and an analytical method for structural strength and dynamic failure of projectiles is developed. The results show that when the projectile horizontally penetrates a multi-layered steel plate target with positive inclined angle, there exists a critical attack angle. If the attack angle is smaller than this critical value, the projectile will head drop and its trajectory turns downwards; when the attack angle is larger than the critical value, the projectile will be raised and its trajectory turns upwards. In addition, the critical attack angle increases as the thickness of the target plate decreases. For the projectiles with high strength and low ductility, the failure mode is brittle fracture and the distances between the fracture position and the projectile nose is 0.72−0.81 times of its length, which is mainly due to the lateral impact load at the rear part of projectile. Moreover, by means of the dynamic model of the projectile based on the free-free beam theory, the fracture position of projectile during oblique penetration process could be well predicted. Also, among the three types of projectiles with the same length and cross-sectional area, the projectile with asymmetric elliptical cross-section is easier to fracture and the position is even closer to the projectile nose.