Cylinder expansion test wall velocity

An example of the cylinder test data cylinder expansion curve, wall velocity-time curve, acceleration-time curve, and JWL isentropic expansion curve for Comp B are given in Figures 5.19 and 5.20. 

We describe herein the first analysis of copper cylinder expansion tests with pressed ETN. We discuss the detonation behavior for the material, along with wall velocity and diameter effect information. All data is compared to PETN tested under similar conditions. 

Figure 5.23 C-J pressure as a function of cylinder test wall velocity at 6 and 19 mm wall expansion.

Although the cylinder test appears to be a simple method, the treatment of the data provides a lot of important information regarding the tested explosive. It gives us the Gurney energy (from cylinder wall velocity) and the equation of the detonation products isentropic expansion. 

As described in Chapter 5, section 5.4, the cylinder test consists of detonating a cylinder of explosive confined by copper and measuring the velocity of the expanding copper wall until it fractures. The cylinder test is commonly used to evaluate explosive performance using the JWL fitting form. The numerical model required to interpret cylinder wall expansion experiments must include a realistic description of build-up of detonation, Forest Fire burn and resulting wave curvature. That first became possible with the development of the NOBEL code. All previous calibrations of the JWL equation of state from cylinder test expansion data used explosive models without the essential detonation build-up to and of detonation. 

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