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The large-distance penetration capability of an annular-shaped charge under multipoint synchronous initiation was experimentally investigated. For different annular charge structures and different multipoint initiation settings, incident angle, collision type of detonation waves, and overpressure on the shaped charge’s liner at adjacent initiation points were analyzed using the detonation wave propagation theory. Furthermore, the shaped charge’s penetration capability at a standoff distance of 1–15 m from a 20 mm thick 45# steel plate (the target) was determined through penetration experiments. It was found that the annular cutter formed by the 500 mm diameter annular shaped charge (charge width: 100 mm) completely penetrated the target for a large distance, namely a distance of 150 times the charge width. The ratio of the width of the ring gap penetrated by the annular cutter to the liner’s initial radial width was about 1.07; this indicated that the annular cutter’s width was equivalent to the liner’s radial width for the above flight distance, which in turn implied that the annular cutter had superior circular degree. The annular cutter formed in the case of Mach reflection had better circular degree, integrity, and penetration capability than that formed by regular reflection.

Dynamic recrystallization (DRX) is a widely observed phenomenon in metals and alloys during hot deformation. However, a comprehensive understanding of the mechanisms and microstructural evolution of DRX at extremely high strain rates is still lacking. In this study, we present a new mechanism, termed planar fault-assisted dynamic recrystallization (pfDRX), which was identified by simulating the cold spray of copper (Cu) at high strain rates using molecular dynamics. Our findings indicate that planar faults, such as nanotwins, stacking faults, hexagonal close-packed martensites, and local slip, play a dominant role in the initial deformation of Cu during high velocity impacts in columnar-like quasi-two-dimensional samples where deformations are primarily limited to in-plane slip. Furthermore, subsequent slip events interact with pre-existing planar faults, triggering the formation of new grains via a common interaction-amorphization-nucleation-growth pfDRX mechanism. We systematically varied temperature and strain rates to determine the optimal conditions for pfDRX. This study offers valuable insights into novel DRX mechanisms in face-centered cubic metals at high strain rates and provides guidance for future experimental research. [ABSTRACT FROM AUTHOR]

The finite element model of oblique penetration of short-rod projectile into a thin metal target was established and the effectiveness of the model was verified to study the oblique penetration law of short-rod projectile into a thin metal target. The simulation calculation of short-rod projectile penetrating thin metal targets with different obliquities at different impact velocities was carried out. The simulation results show that the critical ricochet velocity of the projectile increased with the increase of the obliquity of the target plate, as well as the increment of the critical ricochet velocity of the projectile. With the increase in the obliquity of the target plate, the ultimate penetration velocity of the projectile increases exponentially, and when the obliquity is large, the ultimate penetration velocity increases sharply. When the projectile ricocheted without invading the target, the velocity attenuation of the projectile increased with the increase of the impact velocity, whereas the mass of the residual projectile decreased. However, when the impact velocity exceeds the ultimate penetration velocity of the projectile to the target plate, the velocity attenuation of the projectile decreased and the mass of the residual projectile increased with the increase of the impact velocity. With the increase of impact velocity, the included angle decreased gradually, and the decreasing trend also slowed down. When the impact velocity was just greater than the ultimate penetration velocity, the included angle was the largest. At the same impact velocity, the greater the obliquity of the target plate, the greater the included angle. This study is of great significance to reveal the critical ricochet and ultimate penetration of projectile, the velocity, mass, and trajectory change in the process of penetration, as well as the damage of projectile to the target plate. [ABSTRACT FROM AUTHOR]