Experimental Determination of Detonation Velocity

B. Experimental Determination of Detonation Velocity. Historical background for development of methods for exptl determination of deton velocities is already given in Vol 3 of this Encycl (Ref 75), pp C310-R and C311-L, under Chronographs and Other Devices Used for Measuring Detonation Velocities of Explosives. 

Detonation Velocity Tests. See under DETONATION EXPLOSION AND DEFLAGRATION) VELOCITY, Experimental Determination of Detonation Velocity and also under CHRONOGRAPHS in Vol 3 of Eneycl, pp C304-R to C319-L... 

Detonation rate determination 1 X see Experimental determination of detonation velocity 4 D632-D640... 

Experimental determination of detonation velocity 4 D632—D640... 

Andreev Belyaev (I960), 193-210 (Deton in condensed expls theoretical part) 210-222 (Experimental methods for determination of deton velocities, which include Dautriche-, photographies, and oscillographic-methods)... 

Vol 3(1966), pp C304 to C319, (Chronographs and other methods for determination of detonation velocities) 84) R.W. Woolfolk A.B. Amster, "Low-Velocity Detonations Some Experimental Studies and Their Interpretation , 12thSympCombsm (1968) (Pub 1969), pp 731-39 85)M.F. Zimmer, "Similarity Between Wave Structures of Gaseous and Liquid Low Velocity Detonations , Ibid, p 740 (Paper No 73 in Abstracts, pp 133-34). This material is published in Combustion Flame 12, 1-4(1968)... 

Unfortunately, such a more general comparison of calculated detonation pressures with measured detonation pressures is complicated by the fact that experimental determinations of this property are inherently difficult and thus often inexact. The C-J detonation pressure cannot be measured directly at the current state of the art, but rather, it is deduced from experimental determinations of shock velocities and free-surface velocities of metal plates adjacent to the explosive.17... 

Dixon experimentally determined the detonation velocity of an equimo-lecular mixture as 2728 m/sec (1903). In a later paper, Campbell (1922) found a velocity of 2667 m/sec. 

Other experimental determinations of the velocity of detonation yields divergent results from those shown in the table, at least partially due to the variations caused by the granulation of the ammonium nitrate. Amatols have better oxygen balance than TNT producing larger amounts of gaseous explosion products. This accounts for the greater power of the amatols. 

For more detailed description of particle-velocity measurements, see "Detonation, Particle Velocity in and Its Determination Andreev Belyaev (Ref 44, pp 247-49) describe a method of experimental determination of pressure of detonation, using the arrangement shown in Fig B, Here 1 is charge of an explosive enclosed in a metallic container, and 2 is a metallic (usually aluminum) plate, 1-2mm thick, firmly inserted as a cover at the end of cartridge opposite detonator, 3. On initiation of charge, a shock wave will spread to plate 2 and, when the wave reaches the outer surface of the plate, it will start to move with initial velocity VH (here H is nachaT-naya, which means initial). After determining this velocity experimentally, the... 

Three undetermined parameters which appear in the LSZK equation of state are evaluated from the experimental data, and the remaining constants required are evaluated from the experimentally determined dependence of detonation velocity on density... 

Detonation velocity can be either calculated or determined experimentally A. Calculation of Detonation Velocity. Various calcn methods are described in Refs 24, 26, 27,... 

The thermodynamic data as well as the detonation parameters can nowadays be very reliably obtained by using quantum-mechanical computer calculations. On the one hand it is important to check experimental results, and on the other hand and even more importantly - it is important to predict the properties of potential new energetic materials without any prior experimental parameters, for example during the planning of synthetic work. Moreover, such computational methods are ideal for the estimation of the detonation parameters of newly synthesized compounds, which have not been obtained in the 50 100 g quantities which are necessary for the experimental determination of such detonation parameters (e.g. detonation velocity). 

In Chapter 4.2.2 we already discussed methods for the theoretical calculation of the detonation velocity and detonation pressure. In this chapter we now want to focus on the experimental determination of the detonation velocity. Bearing in mind that detonation velocities of known high explosives may reach up to 10,000 m s the experimental determination of the detonation velocity is not easily achieved. There are several methods which are suitable to measure the detonation velocity [38], Most of these methods are based on the fact that the detonation process is accompanied by the emission of light (autoluminous process). Depending on the measuring equipment selected, the methods for the detonation velocity determination can be divided into,... 

It is difficult to achieve an entirely reliable experimental determination of the detonation parameters due to their extreme values detonation velocity reaches 10 mm/ps, detonation pressure goes as far as 400 kbar, detonation temperature ranges from 2000 to 5000 K, duration time of the chemical reactions in the reaction zone is in a microsecond region, and the width of the chemical reaction zone ranges from tenths of a micrometer to several millimetres. 

Characterization of the explosive requires experimental determination of the detonation pressure and velocity. If the experimental state is near the ideal BKW detonation product Hugoniot, the isentrope of the detonation products can be determined by displacing the isentrope through the experimental state. Otherwise, the ideal detonation product Hugoniot must be displaced so that it intersects the observed detonation pressure and velocity by decreasing the energy available to the detonation products. This results in a weak detonation with a flat top Taylor wave. 

In this type of representation, all combustion events are collapsed into a discontinuity (the wave). Thus, the unknowns are uu u2, p2, T2, and P2. Since there are four equations and five unknowns, an eigenvalue cannot be obtained. Experimentally it is found that the detonation velocity is uniquely constant for a given mixture. In order to determine all unknowns, one must know something about the internal structure (rate of reaction), or one must obtain another necessary condition, which is the case for the detonation velocity determination. 

In the next section of Addnl Ref O, Evaluation of Parameters , it is stated that the parameters, y, a, and B/Q, which appear in the LSZK equation of state, must be evaluated by using experimental data and it is explained how this is done on pp 9 10. As an example, compressed TNT of various densities was investigated. Detonation velocities determined by LSZK expression (34) proved to be in good agreement with those detd by the empirical formula ... 

Detonation, Ideal and Nonideal. Accdg to Cook (Ref 2, p 44), an ideal detonation corresponds to the theoretical maximum or hydrodynamic value D. This maximum velocity D is subject to direct experimental determination it is the steady value attained at a sufficiently long distance from the initiator in a tube or charge of diameter sufficiently large that further in-... 

For determination of critical diameters, the test s described under Detonation Velocity-Charge Diameter and Density Relationships, Experimental Procedures can be used... 

Kast s values for many expls are given in Refs 1,2,3,4,5,5a,6,7,8,9,10,11,13,14,15 17. They are listed in the appended table in conjunction with detonation velocities and brisance values determined experimentally by several methods evolved on deton and D the detonation velocity. However, practical tests do not confirm the idea that B is proportional to the square of the deton velocity but that simple proportionality(as in the formula of Kast) agrees better with the facts(see Ref 2,p 476). Friederich(Ref 10a) introduced the term "specific brisance" and proposed to calc it from the formula (D2maJt A)/100 kg/cm2, where max is maximum detonation velocity and A specific gravity in g/cc. The following table compares "specific brisance with Kast s brisance values ... 

Comparison of Brisance Values Calculated by Kast s Formula, Relative Brisance Values Obtained by Various Experimental Procedures Detonation Velocities and Power Determined by Various Methods for Principal Explosives... 

Determination of the detonation velocity offers a number of advantages, both practical and fundamental, over measurement of the pressure of explosion the equipment is simpler, no mechanical system is required and the experimental accuracy is higher. 

Detonotion Rate Determination ar Velocity of Detonation Tsst(Mesures de vitesse de detonation, in Fr) (Detonationsgesdhwindigkeit Probe, in Ger) (Medida de la velocidad de detonacion,in Span) (Determinazione della velocita di detonazione, in Ital), con be approx ealed, but more reliable results are obtained experimentally by one of the following methods s)Mettegang b)Dautriche c)Rotating Drum Streak Cameras... 

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