Understanding Experimental and Computational Gurney Energies

Abstract

It is now common to experimentally reduce Gurney energies associated with detonation products expansions using experimental cylinder expansion tests and the traditional Gurney formula for cylinders. However, this methodology results in Gurney energy values that are inherently geometrically dependent and do not provide quantitative measurements of explosive work output per mass. It is well known that the outside surface of an explosively expanding metal cylinder has a somewhat lower radial velocity than the cylinder inside due to wall thinning. It is also well known that the cylinder wall bends during acceleration resulting in a material motion Lagrangian velocity that is neither perpendicular to the original wall surface nor to the instantaneous wall surface. In addition, the high explosive detonation products have axial flow that is not accounted for using the cylinder Gurney formula. A number of researchers have identified these issues and have used various different methods to address them. One increasingly common methodology is to calculate Gurney energies using an analytic cylinder model along with thermochemical equation of state calculations. This methodology has proven to provide excellent agreement with experimental Gurney energies for a wide variety of high explosives.