Using an ultra-high speed camera to capture a tube expansion test

Abstract

Computational analyses of explosive events became commonplace over the last twenty years or so. The input parameters used by these computational tools to calculate the material response requires extensive testing in most cases. One set of such parameters is for the JWL equation of state that models the detonation of an explosive. Tube or cylinder expansion tests are a standard way to determine the JWL parameters of such an explosive. A streak camera normally captures the copper tube expansion as the explosive detonates, resulting in a high-resolution continuous expansion at a fixed position. This paper discusses the test set-up and the use of the Cordin ultra-high-speed camera for capturing the results of the expanding copper tube. The camera captured the expansion of the cylinder at a frame rate of one million frames per second and produced 32 digital images. Firstly, the velocity of detonation is approximated by noting the onset of swelling of the tube on each of the 32 images. Secondly, the expansion of the tube was estimated by viewing each image and extracts the expansion position in terms of pixels at specific locations, using the PFV software from Photron. Fifteen of the 32 images were used for this exercise.