Fragment characteristics of cylinder with discontinuous charge

Abstract

In real applications of warheads, not all charges are continuous. For specific purposes, such as power control and intermittent initiation, non-explosive materials are filled into the casing, which caused the charge to be discontinuous. In addition, detonators and control devices are often used with non-explosive materials. The effect of axial discontinuity of the charge on the fragment was not considered. In this study, we assumed that the non-explosive material was air, and divided the cylinder axially into charge and air parts axially. Existing formulae can neither accurately forecast fragment velocity from the charge part, nor predict that from the air part because of the non-existence of explosives. A cylinder with a discontinuous charge was investigated using a numerical method, and two charge parts were detonated from the air part because the initiator was usually in the non-explosive material to save space. It was found that the explosive products from the two charges were superimposed in the middle of the air part, forming a superimposed high-pressure zone, which accelerated the air part and the charge part casings near the air part. The influence distance of the superimposed high-pressure zone on the charge parts is 2R, where R is the charge radius. A formula was established to predict the fragment velocity distribution. The simulation results were verified by X-ray radiography, where the circumferential half casing of each specimen was semi-preformed and the other half was natural. It was found that the project angle and axial density of the fragments were related to the axial-driven energy gradient but not to the shear stress exceeding the dynamic shear strength. The air part of the semi-preformed shell overlapped and formed a dense zone, whereas that of the natural shell broke at three abrupt axial-driven energy gradients and formed two fragments with greater mass and kinetic energy. The experimental data showed that the average relative error of the proposed formula was less than 4.5%, indicating that the proposed formula can predict the fragment velocity distribution from such a cylinder with sufficient accuracy. This study provides a basis and reference for the study of cylinders with discontinuous charges.