Determination of Detonation Pressure

The VOD may be experimentally determined by any of the methods described in Section 3.3.3 and then approximate Pc, may be calculated using Equation 3.11. 

For the accurate determination of detonation pressure (Pq), a technique of impedance mismatch is applied. The explosive is detonated in contact with water (its equation of state is known and is transparent which facilitates record of shock propagation by shadowgraphy technique). Then, after measuring the transmitted shock velocity in water, detonation pressure is calculated by Equation 3.12  

When water is used as a medium, the Equation 3.12 becomes Equation 3.13  

IJSW is determined experimentally by the Aquarium Technique and then, l/pw is calculated by substituting the values of Usw, a and h in Equation 3.14  

Finally, detonation pressure (transmitted shock pressure in water) is calculated by putting the values of Usw, Upvj and density of water (which is 1) in the Equation 3.13. 

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Detonation, Free Surface Velocity Method for Determination of Detonation Pressure is briefly discussed under Detonation (and Explosion), Pressures of and Their Measurements... 

Accdg to Dunkle (Ref 56), free-surface velocity method (or determination of detonation pressure, developed by R.W. Goranson, was probably first described in then conf Los Alamos Rept No 487(1955) (listed here as Ref 35a). The method seems to be de-... 

Another method for determination of detonation pressure is by the "measurements of the velocity of shock wave set-up by normal impact of the detonation front on the explosive/water interface . It was mentioned by Fauquignon in the same paper as above, but not described. He gave the following refs where the method is described ... 

J.W. Gehring Jr J. Dewey, "An Experimental Determination of Detonation Pressure in Two Solid High Explosives ,... 

Example 2.12 Simplified determination of detonation pressure and velocity for hydrogen... 

A schematic of the measuring system for the determination of detonation pressure is shown in Figure 4.61. 

Determination of Detonation Velocity (71-4) Sensitivity to Impact (Sensibilite/ au choc) (74-5) Sensitivity to Friction (75-6) Sensitivity to Initiation (Sensibilite a 1 amorce) (76) Pressure Measurements by Manometric Bomb, by Crusher Test and by Piezoelectric Manometer (79 97) Density Determination (99-100) Chronographs of Schulze and of Le Boulange (101) Tests for Stability by Methods of Abel, Spica, Vieille at 110°C, German at 135° Bergmann-Junk, Su, Hansen-Grotannelli, Silvered Vessel and Taliani (107-09) Explosion Test (109-10)... 

I. Jaffe et al, "Determination of Shock Pressure Required to Initiate Detonation of an Acceptor in the Shock Sensitivity Test , ARS-J 32, 22-25 (1962). In experiments performed at NOL by Jaffe et al, the assembly shown in Fig 3 was used to measure the attenuation of a shock wave in a Lucite rod. The shock wave was initiated by a... 

AND EXPLOSION), EXPERIMENTAL PROCEDURES . Determination of shock pressure required to initiate detonation of an acceptor in the shock sensitivity test is described in Ref 8 Refs 1) W.C. Holton, "The Detonation Pressure in Explosives as Measured by Transmitted Shocks in Water , NavOrdRept 3968(1954) (Conf) 2) Dunkle s Syllabus (1957-1958), p 175 3) Cook (1958), 68-9... 

In an effort to understand the formidable-appearing output of many computations for a wide variety of C-H-N-O explosives at various initial loading densities, we have investigated interrelationships between such properties as pressure, velocity, density, heat of reaction, etc. These studies have led to a number of interesting observations, important among which were the facts that much simpler semiempirical formulas could be written for desk calculation of detonation velocities and detonation pressures, with about the same reliance on their answers as one could attach to the more complex computer output. These equations require as input information only the explosive s composition and loading density and an estimate of its heat of formation, and, in their comparative simplicity, seem to throw light on the relative importance of the quantities which determine the detonation pressure in particular, and other properties as well. 

The experimental stucfy of the shock wave initiation process is primarily directed to the determination of the pressure of the shock wave front, w ich may cause initiation, and to the determination of the relation between the shock wave pressure and the distance (or time) that the shock wave passes through the explosive before being transformed into a full detonation wave. This distance is known as run-to-detonation distance. 

Various dynamic methods based on different physical principles are used for the experimental determination of the pressure at the CJ point and the duration of the chemical reactions in the chemical reaction zone. A large number of these methods, especially for the determination of the pressure at the CJ point-detonation pressure, were independently developed in the USA and the former USSR in the 1950s. In the years to follow, the detonation parameters of the solid explosives, equation of state, and adiabatic shock (or Hugoniot) equation of detonation products were the subject of numerous experimental and theoretical investigations. But it should be mentioned that different interpretations of the experimental results were frequent. 

The principle of the determination of the detonation pressure by a manganin pressure gauge is based on the fact that under dynamic action of detonation pressure the electrical resistance of the gauge is changed. The resistance change is directly related to the measured detonation pressure. 

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... 

These are the basic equations of the hydrodynamic theory of detonation. If p2 and v2 can be determined, they enable the remaining features of the detonation wave to be calculated. Unfortunately p2 and v, relate to conditions in the detonation wave and not to the lower pressure conditions which the explosion products would reach at equilibrium in, for example, a closed vessel. Therefore, further calculations are needed to determine p2 and v2. 

Belles prediction of the limits of detonability takes the following course. He deals with the hydrogen-oxygen case. Initially, the chemical kinetic conditions for branched-chain explosion in this system are defined in terms of the temperature, pressure, and mixture composition. The standard shock wave equations are used to express, for a given mixture, the temperature and pressure of the shocked gas before reaction is established (condition 1 ). The shock Mach number (M) is determined from the detonation velocity. These results are then combined with the explosion condition in terms of M and the mixture composition in order to specify the critical shock strengths for explosion. The mixtures are then examined to determine whether they can support the shock strength necessary for explosion. Some cannot, and these define the limit. 

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