Pressure, detonation

Table 5. Calculated and Experimental Detonation Pressures and Rates of Explosives...

Explosive Detonation pressure, GPa Bulk specific gravity Detonation velocity, km/s Contains high explosives Heat of detonation kj /g Excavated vol relative to equal wt of TNT... 

The Chapman-Jongnet (CJ) theory is a one-dimensional model that treats the detonation shock wave as a discontinnity with infinite reaction rate. The conservation equations for mass, momentum, and energy across the one-dimensional wave gives a unique solution for the detonation velocity (CJ velocity) and the state of combustion products immediately behind the detonation wave. Based on the CJ theory it is possible to calculate detonation velocity, detonation pressure, etc. if the gas mixtnre composition is known. The CJ theory does not require any information about the chemical reaction rate (i.e., chemical kinetics). 

The pressure behind the nonreactive shock is much higher than the CJ detonation pressure, which is not attained until the reaction is complete. The duration of the... 

The best shaped charge results are obtained with expl compns having the highest detonation pressure HE as illustrated (Ref 20) ... 

Low-detonation pressure composites consisting of PETN (and other expls) in a low-density (foam) plastic matrix (eg polyurethanes) are described by Abegg et al (Ref 33)... 

Density (g/cc) Dimensions of PETN Diameter x Length. (inches) Fitted Detonation Velocity (mm/p sec) (Eqs 1,2 3) Detonation Pressure pCJ (kbar)... 

The PETN Detonation Pressure, P (also called the CJ Pressure), is shown as a function of packing density in Table 7 and in Fig 4. Note that the measured P values in Fig 4 lie quite close to the theoretical curve developed by Lee Homig (Ref 72), which is based on a Wilkin s type equation of state (see Vol 4, D294-L) with a Grueneisen ratio, r, for the detonation products, that is solely a function of specific volume. Shea et al obtained an effective T = 8.077 p-12.288 (Ref 74)... 

Solid particle-gaseous oxidizer systems have been studied because of applications to propints and expls (Refs 5 14), and hazards due to dust explns (Refs 1,3, 4, 6, 7, 10 15). Strauss (Ref 9) reported on a heterogeneous detonation in a solid particle and gaseous oxidizer mixt the study concerned A1 powder and pure oxygen in a tube. Detonations initiated, by a weak source were obtained in mixts contg 45-60% fuel by mass. Measured characteristics of the detonations agreed with theoretical calcns within about 10%, and detonation pressures of up to 31 atms were observed. With regard to solid particle-air mixts, detonations have not been reported only conditions for expln have been studied (Ref 2)... 

Lu, Vyn, Sandus and Slagg (Ref 17) conducted ignition delay time and initiation studies on solid fuel powder-air mixts in an attempt to determine the feasibility of solid-air detonations. The materials investigated included Al, Mg, Mg-Al alloy, C and PETN. Ignition delay time was used as a method of screening the candidate fuels for further work in initiation studies which determined detonation wave speed, detonation pressure, detonation limits, initiation requirements, and the effect of particle size and confinement. The testing showed the importance of large surface area per unit mass, since the most... 

References to detonation pressure are scattered thruout Vol 4, eg, D230—35, D265, D463—64, and D483—93. The present article is primarily an up-date of the Vol 4 entries. However, its additional purpose is to bring together ina single article pertinent information on detonation pressure... 

Detonation pressure may be computed theoretically or measured exptly. Both approaches are beset with formidable obstacles. Theoretical computations depend strongly on the choice of the equation of state (EOS) for the detonation products. Many forms of the EOS have been proposed (see Vol 4, D269—98). So.far none has proved to be unequivocally acceptable. Probably the EOS most commonly, used for pressure calcns are the polytropic EOS (Vol 4, D290-91) and the BKW EOS (Vol 4, D272-74 Ref 1). A modern variant of the Lennard Jones-Devonshire EOS, called JCZ-3, is now gaining some popularity (Refs -11. 14). Since there is uncertainty about the correct form of the detonation product EOS there is obviously uncertainty in the pressures computed via the various types of EOS ... 

Explosive Density (g/cc) Det Vel (cm /, p sec) Tran smitted Shock Vel, Us cm/p sec) Measured Detonation Pressure, Pdet (kbar) LLL Values ... 

Values determined by the LLL Standard Test for Detonation Pressure Measurement ... 

The preceding paragraphs have been primarily devoted to a brief description of the methods of measuring detonation pressure and the presentation of selected measurement data. We have emphasized that both theory and measurements entail considerable uncertainty. Thus comparison between theory and observation is at best rather risky. Nevertheless, the P j vs loading... 

Except for 02 (a product in oxygen-rich expls), equilibria (1) thru (6) account for all, major detonation products of condensed CHNO expls. In gas detonations (ie, at low detonation pressures) such species as OH, H etc may also exist. In experimental measurements of detonation products (to be discussed later) HCN frequently appears as a minor product... 

Propellant Density (g/cc) Diameter (cm) Critical Diameter (cm) Detonation Velocity (km/sec) Detonation Pressure (kbar) Ref... 

The constants a and p were first chosen to give the best fit to experimental detonation velocity measurements for a wide variety of materials. They have more recently been revised by Cowan and Fickett to give better agreement with experimentally measured detonation pressures. For numerous other approaches to the problem of the equation of state under detonation conditions, readers are referred to the book by Cook and a paper by Jacobs. 

Tables 2.1 and 2.2 show that theory enables detonation velocities to be calculated in close agreement with those observed experimentally. This, unfortunately, is not a critical test of the theory as velocities when calculated are rather insensitive to the nature of the equation of state used. A better test would be to calculate the peak pressures, densities and temperatures encountered in detonation, and compare these with experimental results. The major difficulties here are experimental. Attempts to measure temperatures in the detonation zone have not been very successful, but better results have been obtained in the measurement of densities and pressures. Schall introduced density measurement by very short X-ray flash radiography and showed that TNT at an initial density of 1 -50 increased 22% in density in the detonation wave. More recently detonation pressures have been measured by Duff and Houston using a method (introduced by Goranson) in which the pressure is deduced from the velocity imparted to a metal plate placed at the end of the column of explosive. Using this method, for example, Deal obtains the detonation pressures for some military explosives recorded in Table 2.3. More...

Explosive Density (g ml 1) Detonation velocity (ms 1) Streaming velocity (ms1) Detonation pressure (10 Pa)... 

TABLE 2.4 Detonation Pressures of Commercial Explosives (3-18 cmdiam.)... 

The penetrating power of a shaped charge is approximately proportional to the cube of its diameter, but also very dependent on maintenance of exact axial symmetry during construction. It is also proportional to the detonation pressure of the explosive used, so that suitable fillings are cast Pentolite or RDX/TNT. Well-known applications of shaped charges are in the British PIAT and American bazooka. 

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