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Cavity Collapse in Energetic Materials.
ARMY BALLISTIC RESEARCH LAB ABERDEEN PROVING GROUND MD
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The mechanics of cavity collapse is studied in an energetic material. During cavity collapse, several mechanisms can act individually or collectively to produce high temperature hot spots. Our goal is to understand how pressurization rate, cavity size and material parameters affect hot spot formation. For this purpose we have considered the collapse of spherical cavities using a modified form of the model of Carroll and Holt. This analysis is used to consider hot spots produced by inviscid plastic work, viscoplastic work, gas phase heating, or solid phase compression which occurs as the result of high pressures produced when material collides at the center of the cavity. Under the proper conditions, each of these mechanisms may be dominant, but viscous heating is the most efficient mechanism and is dominant when the rise time of the pressure is short, viscosity is high, andor yield stress is low. The conditions under which the other mechanisms are dominant and the dependence of the hot spot temperatures on the pressurization rate, cavity size, and material properties are discussed. Cavity size and melt point have an interesting effect on the computed temperatures. Melting is significantly desensitizing when the cavities are small but can be sensitizing for larger cavities.
APPROVED FOR PUBLIC RELEASE