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Metal Angle Correction in the Cylinder Test

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Abstract

Cylinder test data show that the copper wall angle increases with time in a given shot and becomes much larger if the wall is at half-thickness. The true velocity is suggested to be that perpendicular to the wall, and this brings full- and half-wall data in closer agreement. The previously published Gurney-type equation for calculating the detonation energy density at each relative volume is modified by the angle of the wall and the angle of the measuring probe. This provides a unique solution to the energy density that does not require empirical coefficients or standards. We derive the length of the cone perpendicular to the cylinder surface and we use this as a description of the constant relative volume, creating a unified model for the first time. As a standard for full-wall cylinders, we obtain relative volumes of 2.4, 4.4, and 7.0 at the scaled wall displacements of 6, 12.5, and 19 mm. For a full-wall copper cylinder at the three points, the wall angles average 10.0, 11.0, and 11.6°. Besides Cylinder test data on copper, previously unpublished framing camera pictures also measure angles for eight different metals. The angles are a function of wall thickness and relative volume but of nothing else, including the type of metal. For modeling, our simulation code calculates the wall velocity as seen along a particular probe direction, as this is a more realistic comparison to measurements than a zone particle velocity.

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