Complexity of space trajectory and macro-micro failure mechanism of elliptical projectile penetrating concrete at high velocity

This paper studies the oblique penetration behavior of the high-speed elliptical projectile into a concrete target. The complexity of the oblique penetration trajectory is analyzed. For the first time, it is discovered that during the penetration process, the elliptical projectile rotates around its longitudinal axis and exhibits more pronounced three-dimensional ballistic characteristics compared to a circular projectile. Then, the elliptical projectiles' macro deformation and failure mechanism are analyzed. Four typical macroscopic failure modes of the elliptic projectile are identified: overall mass erosion and the surface cutting pit, the crushing at the junction of the head and the shank, the bending near the 1/2 length in the minor axis side, and the collapsed and fractured of wall on the side of the minor axis. Finally, the intrinsic mechanisms of mass erosion and fracture failure of the elliptical projectile are explained through microanalysis, and the relationship between the micro failure mechanisms and the structural characteristics of elliptical projectiles is revealed. It suggests that the major axis side of the elliptical projectile is subjected to a more severe loading environment during the penetration process, and the fracture of its head is mainly attributed to the combined action of composite compression-shear and tensile-shear stress.