Impact fragment cloud propagating in a pressure vessel

Abstract

The propagation of fragment clouds in a pressurized steel container with PMMA (polymethylmethacrylate) side-windows was investigated. The fragment clouds were generated by hypervelocity impact of aluminum projectiles on 1 mm thick AlMg3 plates. Projectile diameters ranged from 2.0 mm to 4.4 mm. At impact velocities of around 7 km s −1, kinetic energies varied between 269 J and 2950 J. Container gas pressures were between 0.1 bar and 10 bar N 2. The fragment cloud was photographed employing an image converter camera in a shadowgraph technique with a frame separation of 1 μs. By evaluation of the pictures, fragment cloud velocities were measured and shapes of the fragment clouds could be characterized as a function of projectile diameters and pressures. It has been found that at equal impact and target parameters the average fragment cloud velocity decreases linearly with increasing container pressure. It has been observed that the deceleration of the fragment cloud in the gas is strongly dependent on the bumper plate thickness to projectile diameter ( t d ) ratio. The strongest effect of gas pressure on fragment cloud velocity and shape was observed for the smallest projectile of 2.0 mm diameter. The fragment cloud velocities of projectiles with small t d ratio depended weaker on container pressure. The shapes of the fragment clouds in most pressure container experiments can be divided into two distinct portions: an outer cone and a center part. This effect was observed weakly in the reference cloud shapes under near-vacuum conditions (i.e. 0.1 bar) and was obviously magnified owing to the interaction with the pressure gas.