Dynamic deformation and fragmentation of exploding metal cylinders

In this paper, an explosive loading technique is applied to study the uniform expansion of smooth wall cylinder specimen (low-carbon steel and 304 stainless steel; Do-t-L: 34-3-100 mm) at high strain rate. A column of high explosive PETN is installed coaxially inside a cylinder specimen and initiated at the central axis by exploding fine copper wires using an impulsive discharge current from a capacitor bank. The streak and framing camera photos indicate radially symmetrical and axially almost uniform expansion of cylinders with the average strain rate of over 104s-1 and the wall velocity of 3-7×102m&middots-1, representing rather earlier fracture for 304SS cylinders. The initial time-histories of surface velocity are measured to monitor the spall damage of cylinder wall, and the experimental average wall velocities are compared with those calculated using the simple equation on energy consumption. Hydro codes have been applied to simulate the experimental behavior of the cylinders, examining the constitutive equations and the fracture criteria. A steel chamber filled with wasted clothe-pieces for cushioning is provided inside the explosion pit, and 84-99% of the fragments of the exploded cylinder installed at the center are recovered successfully. The sizes of every fragment are measured, and in this study the circumferential fracture spacing is investigated using the Grady's fragmentation model.