The effects of yield stress and casing thickness on blast impulse and fragment velocity

Abstract

A previous paper by the author [1] showed how his equation [2], based on the model first proposed by Gurney [3] for the blast impulse from cased munitions, can be modified to allow for the yield stress of the casing metal. This paper [1] also provided validation for this further equation from available experimental data. Further issues regarding the many smaller but significant interactions between the fracturing casing and the expanding gases need to be investigated before it can be said that a complete theory of blast impulse and fragment initial velocity is in place. In this paper, an approximate evaluation will be made of the potential effect and significance of kinetic energy losses, due to dissipation by means of casing strain energy dissipation. As expected, these losses are found to be most significant for thick, low density, high yield stress casings. The effect of finite casing thickness, also not previously considered, has been found to be small.