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Simple Calculation Methods for Munitions Cookoff times and temperatures
Author(s) -
Victor Andrew C.
Publication year - 1995
Publication title -
propellants, explosives, pyrotechnics
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.56
H-Index - 65
eISSN - 1521-4087
pISSN - 0721-3115
DOI - 10.1002/prep.19950200506
Subject(s) - thermal conductivity , ignition system , simple (philosophy) , thermal conduction , opacity , thermal , mechanics , materials science , heat flux , propane , boundary value problem , heat transfer , thermodynamics , composite material , physics , epistemology , optics , quantum mechanics , philosophy
Simple one‐dimensional quasi‐static heat transfer calculations can be used to estimate fast cookoff times of cylindrical munitions with metal cases. The most critical parameter for the thermal analysis is the heat flux to the ordnance from the fire. One must remain aware that heating will be different for transparent flames of propane or methane test fires than they are for the opaque smoky flames of wood and jet‐fuel fires. Good values for material thermal conductivities and energetic material ignition behavior are also needed. Low‐conductivity composite cases cannot be analyzed in the same way because case mechanical failure is the primary initial failure path, rather than thermal conduction leading directly to ignition of the energetic material. Reaction violence cannot be calculated in a simple way with the present state of the art. Simple hand analysis of slow cookoff problems is limited to simple symmetric shapes of the type that were published over 30 years ago involving constant boundary temperatures. Modern computers, using finite‐difference codes can be used to readily solve problems with varying boundary temperatures to predict time to cookoff. However, as this paper shows, quasi‐static solutions of symmetric shapes (slabs, cylinders and spheres) can be obtained with desktop computer spreadsheets that give the same results as the finite‐difference codes. There are no a priori methods for predicting the violence of the slow cookoff reaction. These same comments apply as well to intermediate cookoff heating rates (greater than 3.3 K/h). Calculations by the methods of this paper place tools for designing experiments to explore cookoff behavior and for designing ordnance to meet insensitive munitions requirements on virtually every desktop.