Damage of a multi-layer Q345 target under hypervelocity impact of a rod-shaped 93W projectile

Abstract

In order to research the penetration characteristics and damage mechanism of multi-layer targets under hypervelocity impact, experiments and numerical simulations were carried out on a rod-shaped 93W projectile impacting a multi-layer Q345 steel target. A gram-order rod-shaped 93W projectile together with a sabot was launched by a 57/10 mm two-stage light gas gun to penetrate into a ten-layer Q345 target. The damage photos of the target after penetration were transformed into binary images by a Matlab processing software. The equivalent diameter of the center hole, the number and total areas of the holes, the diameters of damage circles of the ten-layer target were summed up and analyzed. The AUTODYN software was used to perform the smoothed particle hydrodynamics simulation. Then the microscopical data of the target plates were obtained by scanning electron microscopy (SEM) and optical microscopy to analyze the microstructure and element composition. Results show that a rod-shaped 93W projectile could penetrate 8 or 9 layers of a ten-layer Q345 target under different initial impact velocities. Perforated lips, petal-shaped plastic deformation, tearing, cratering and bulging were formed in target plates. These failure modes are attributed to plastic expanding failure and shear tearing under shear stress. The damage mode of the first three layers of the target is dominated by hypervelocity perforation due to the high impact velocity, with many holes but small area, while the holes in the later layers are few, but the diameter increases first and then decreases as the masses and velocities of fragments decrease. The simulation results were verified by the experimental results. They are in good agreement with the experimental results. Micro analysis shows that the materials of the target and projectile are melt, while the grains are broken up, refined, melt and recrystallized in the target plates. There are aggregated micropores and microcracks formed during the penetration process. The micro analysis results show that the damage failure is mainly caused by the combined effects of thermal stress during the cooling process of the molten mixture and shear tearing under the shear stress, which is consistent with the macro-scopical results.