Dynamic response and microstructure evolution of the finite steel target subjected to high velocity impact by copper explosively formed projectile

Abstract

The dynamic deformation of the finite steel target subjected to high velocity impact of copper explosively formed projectile is investigated by optical, scanning, and transmission electron microscopy. Morphology analysis of fracture surfaces indicates that the copper remainder plated to the crater wall shows extremely plastic deformation, which consists of elongated parabolic dimples, and the mild carbon steel target exhibits excellent brittle features that material fails mainly along the cleavage facets on the rear surface of target under strong impact of explosively formed projectile. In the surface of crater, the whole part of copper remainder and partial material of steel target undergoes completely dynamic recrystallization. The layer thickness of dynamic recrystallization zone, which displays an extreme plastic flow in solid state, is about 21.3 μm in steel target, and the average size of the refined grains significantly decreases to approximately 200 nm. Theoretically calculated results indicate that the temperature increase is associated with shock wave and plastic deformation of steel target and can reach 1352 K, which is 0.75Tm (where Tm is the melting temperature of steel target). The change in microhardness from the crater wall to the matrix of target is consistent with micro‐deformation of grains, and maximum microhardness is observed on the interface between dynamic recrystallization and severe plastic deformation zones of steel target.

Ballistic performance study on the finite steel target subjected to normal and oblique impact by copper explosively formed projectile

“…However, as a chemical energy projectile, which is one of the most common weapons used to defeat the armors in the military applications (Weickert and Gallagher, 1993; Wu et al, 2007; Yu et al, 1999), EFP (explosively formed projectile) will experience essentially plastic strains up to 300%, at strain rates of the order of 10 4 s −1 (Pappu, 2000; Sui and Wang, 2000) during the formation and penetration process and the projectile cannot be treated as a rigid body anymore (Senthil and Iqbal, 2013; Sui and Wang, 2000). Actually, the main body of EFP will be fragmented or eroded during the penetration process of semi-infinite or infinite targets (with thickness orders of magnitude greater than the projectile dimensions) at high-velocity impact, only leaving some fractional mass in the crater wall (Li et al, 2010; Liu et al, 2017) and crater bottom. As the appearance of projectile is stable, the EFP is in a long rod-shaped with a high kinetic energy (Cardoso and Teixeira-Dias, 2016; Wu et al, 2007).…”