Evaluation of velocity interferometry for high energetic materials using a VISAR

Abstract

In this study, a cylinder expansion test was performed using a square prism OFHC copper with a cylindrical extrusion filled with Comp B explosive charge. A Valyn VISAR was used as a measuring tool to record the expansion history of the cylinder by Doppler shift of the light reflected off its surface, which subsequently was used to obtain the velocity history of the square prism cylinder. Quadrature fringe signals obtained from the square prism cylinder test were analysed using the results still showing some traces of fringe jumps. Whereas the hands-on calculations were more precise in correcting the jumps. This introduced some shifts in the velocity results VISAR Push-Pull reduction software and hands-on calculations. The outcome of the two velocity graphs (reduction software and manual) did not correspond. This might be due to the software velocity which caused the variation in the two velocity results. Overall, both software and manual methods resulted in velocity values that were difficult to draw conclusions from. In an attempt to further understand the test results, the displacement curve were also reduced from the velocity graphs. Although the trend of the displacement graph obtained from the reduction software is comparable to the displacement graph published in literature for the same test, the magnitudes of the values are still difficult to explain. The cylinder design used in this study was tested for the first time and numerous challenges rose up during setup and execution and are discussed. It is important for another test to be conducted with an improved setup in order to achieve a reliable interpretation of the cylinder test results.