To obtain the ballistic characteristics of the oblique penetration of an elliptical cross-section projectile into concrete, a systematic study was carried out using numerical simulation. A reliable finite element numerical simulation model was constructed. The oblique angle, attack angle and axis spin angle that affect the ballistic deflection were decoupling. Numerical simulations of the oblique penetration of an elliptical cross-section projectile into concrete under different drop angles were carried out. The evolution laws of ballistic deflection and spin were deeply analyzed, and the mechanisms of ballistic deflection and spin were explained. The results show that the oblique angle and attack angle lead to the asymmetry of the force-bearing areas on the upper and lower surfaces of the projectile, and the attack angle also leads to the asymmetry of the surface stress of the projectile, eventually generating a deflection torque that prompts the deflection of the projectile. The angular velocity, attitude angle and ballistic offset of the projectile increase with the increases of the oblique angle and attack angle. In the case of oblique penetration with an oblique angle, the projectile in the upright position (γ=0°) deflects slowly and for a long time, while the projectile in the lying position (γ=90°) deflects quickly and for a short time. There is no absolute superiority or inferiority between the two positions in terms of ballistic stability. In the case of oblique penetration with an attack angle, the ballistic stability of the projectile in the upright position is better than that of the projectile in the lying position. The combined effects of the axis spin angle and oblique angle lead to the asymmetry of the projectile-target intersection. Besides offset and deflection, the projectile also has a self-rotating motion around the axis. When the axis spin angle increases from 0° to 90°, the projectile-target intersection condition undergoes a transformation from symmetry to asymmetry and then back to symmetry. The offset in the horizontal direction and the axis spin angle increment of the projectile first increase and then decrease. The research results provide important references for the practical engineering application of the elliptical cross-section projectile.

As a novel reactive damage material, high-entropy alloys (HEAs) have garnered widespread attention in the field of reactive damage in recent years due to their excellent mechanical properties and favorable energy release characteristics. Not only do HEAs possess high strength, high hardness, outstanding plasticity, and energy release capabilities, but their material compositions and performance parameters are also tailorable, enabling them to meet the material requirements of various application scenarios. Furthermore, HEAs have demonstrated potential application advantages in several aspects, such as processing and forming, mechanical strength, and impact-induced energy release. In particular, Ti-Zr-based systems have become a research hotspot due to their penetration-energy release coupling effect, and a growing body of experimental results has confirmed the application potential of HEAs in the field of reactive damage. Currently, reactive high-entropy alloys hold broad application prospects in areas such as projectile casings, reactive fragments, shaped charge liners, and armor-piercing projectiles. This paper introduces the definition and characteristics of reactive high-entropy alloys, summarizes existing reactive HEA systems, and reviews the current research status regarding the dynamic mechanical behavior and impact-induced energy release characteristics of reactive HEAs. It also outlines the potential application fields of HEAs and provides a preliminary outlook on the future directions of high-entropy alloys in the reactive damage domain.

Two kinds of structural projectiles made of two different materials were designed in this paper. An experimental study of 11 kg projectiles penetrating the reinforced concrete target at 1400 m/s was carried out using a 203 mm Davis gun. Based on the experimental results, the structural response, penetration capability and related engineering issues of the projectile are discussed. The results show that when the reinforced concrete target is penetrated at a velocity of 1400 m/s, the heads of projectiles made of two different materials experienced erosion and were mushroomed. This was caused by high temperatures resulting from friction between the projectile and the concrete during penetration, which significantly softened the surface of the projectile. Furthermore, the contact pressure between the projectile and the target exceeded the yield strength of the projectile material near the surface, causing the material to enter a state of plastic flow and ultimately leading to the erosion and mushrooming of the projectile head. Additionally, the surface material of the projectile was stripped due to the cutting action of the hard aggregates in the concrete, resulting in severe abrasion of the projectile body. When comparing the structural responses of projectiles made of different materials, it was evident that material properties influenced their behavior. Compared to 30CrMnSiNi2MoVE, DT1900, known for its higher strength, hardness and better resistance to impact compression, showed less erosion at the projectile head. However, the inferior shear resistance and wear resistance of DT1900 led to severe abrasion on the projectile body. The mass loss pattern of a conical projectile is different from that of a solid long-rod projectile, with the latter concentrated mainly in the projectile body. The conical flared tail design, while suppressing ballistic deflection, increased the contact area between the projectile body and the target, enhancing the abrasive and cutting actions of aggregates and steel. Moreover, under high-speed penetration conditions, the erosion and mushrooming of the projectile head could reduce the penetration depth; the less erosion at the head, the greater the penetration depth. In experiments, the maximum penetration depth of DT1900 projectiles could reach up to nine times the length of the projectile.