Investigation of Copper Spall in Cylinder Test Experiments

Cylinder test experiments (CYLEX) are used to measure performance and calibrate a products equation of state for High Explosives (HE). The experiment measures the wall velocities of the copper cylinder as it expands. While this is considered a standard test, the measurements of the HE are of an indirect nature. When an isentrope is fit to the results, any other physical phenomena that affects the copper wall velocities modify the isentrope fitting. One such phenomena is spall. As the detonation wave transmits a shock into the copper wall, the shock moves to the free surface then reflects off as a rarefaction wave. If the wave's pressure difference is strong enough the copper metal can rip apart internally thus disconnecting the copper wall from the time dependant detonation physics of the HE. Experiments involving different geometric scales of the CYLEX test revealed interfering spall in the larger scales but negligible spall in the smaller scales. This work will present replicated experiments through simulations in a Lagrangian code with a spall model. Preliminary simulation results have shown the range of spall effects in a half-scale and full-scale CYLEX experiment. An analysis will also be presented of the shock dynamics in the copper wall of the varying geometric scales to provide better insight into the spall mechanisms to better inform experiments.