IMPACT FRAGMENT CLOUD PROPAGATING IN A PRESSURE-VESSEL

The propagation of fragment clouds in a pressurized steel container wi th PMMA (polymethylmethacrylate) side-windows was investigated. The fr agment clouds were generated by hypervelocity impact of aluminum proje ctiles 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 ene rgies varied between 269 J and 2950 J. Container gas pressures were be tween 0.1 bar and 10 bar N-2. The fragment cloud was photographed empl oying an image converter camera in a shadowgraph technique with a fram e separation of 1 mu s. By evaluation of the pictures, fragment cloud Velocities were measured and shapes of the fragment clouds could be ch aracterized as a function of projectile diameters and pressures. It ha s been found that at equal impact and target parameters the average fr agment cloud velocity decreases linearly with increasing container pre ssure. It has been observed that the deceleration of the fragment clou d in the gas is strongly dependent on the bumper plate thickness to pr ojectile diameter (t/d) ratio. The strongest effect of gas pressure on fragment cloud velocity and shape was observed for the smallest proje ctile of 2.0 mm diameter. The fragment cloud velocities of projectiles with small t/d ratio depended weaker on container pressure. The shape s 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 ne ar-vacuum conditions (i.e. 0.1 bar) and was obviously magnified owing to the interaction with the pressure gas. Copyright (C) 1997 Elsevier Science Ltd.