Experimental Characterization of Explosives

As we have seen in the previous chapter, energetic materials are often initiated using thermal processes. However, the explosion stimuli could also come from mechanical or electrostatic sources. Therefore, it is important to know the exact sensitivities for explosive compounds. The important values that have to be determined are  

Testing the response of solid, liquid or pasty substances to impact, friction and thermal stimuli is required in various standards such as EEC, Official Journal of the European Communities as well as UN Recommendations on the Transport of Dangerous Goods, 13.4.2 Test 3(a)(ii) BAM drop hammer. 

In order to determine the friction sensitivity according to the BAM regulations, the sample is placed onto a rough porcelain plate (25 X 25 x 5 mm). This plate is 

This is a particularly important test for the safe handling of explosives since the human body can be electrically charged (depending on the type of elothing worn and humidity etc.) which on discharge can cause spark formation. Typical values for the human body are  

In accordance with the UN guidelines for the transport of dangerous/hazardous goods, the substances in Table 6.2 have been classified based on their impact and friction sensitivities. 

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Proper experimental characterization of flammable and explosive materials... 

The experimental apparatus used to characterize the explosive nature of dusts is shown in Figure 6-17. The device is similar to the vapor explosion apparatus, with the exception of a... 

Of course such observables only yield a rather indirect information on the nuclear equation of state. Early investigations of the supernova required a soft equation of state characterized by a compressibility as low as K 140 MeV. A stiffer EOS would not allow sufficient energy to be stored during the collapse such that the subsequent explosion would not reach the surface. Taking into account additional features like effects of neutron heating, a different composition or a rotation of the progenitor star may allow for a supernova even with a stiffer EOS. On the other hand it turned out that also the comparison of experimental data of relativistic heavy ion collisions with corresponding results of computer simulations does not provide a unique answer for the properties of the EOS. Early calculations seemed to show a preference for a stiff EOS with a compressibility as... 

Brossard, J., Desbordes, D. Gamier, J.L., Hendrickx, S., Lannoy, A., Leyer, J.C., Perrot, J. Saint Cloud, J.P.,"Experimental analysis of Unconfined Explosions of Air-Hydrocarbon Mixtures - Characterization of the Pressure Field," Loss Prevention and Safety Promotion in the Process Industries, Harrogate, Sept. 1983... 

The studies of shock sensitivity were based on the detonation velocities, D, calculated by the Kamlet and Jacobs method [156], and in some cases they also were determined experimentally. The heat of explosion, Qreai, was calculated by means of the semi-empirical relationships by Pepekin et al. [ 157]. Both these quantities characterize the shock wave due to chemical transformation of EM, i.e. the detonation wave. 

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. 

The relative shock sensitivities of explosive compositions are commonly assessed by means of gap tests. In these tests, the shock from a standard donor explosive is transmitted to the test explosive through an inert barrier (the so called gap ). The shock sensitivity of the test explosive is characterized by the gap thickness for which the probability of detonation is 50%. In reference 26, the Los Alamos standard gap test and the Naval Ordnance Laboratory (NOL) large scale gap test were modeled using the 2DE code with Forest Fire burn rates. The Los Alamos gap test uses Dural for the inert barrier while the NOL gap test uses Plexiglas. The test explosive is unconflned in the Los Alamos gap test. In the NOL gap test the test explosive is confined with steel. The model showed good agreement between the calculated and experimental gap test values for PBX-9404, PBX-9502, Pentolite, Composition B, and an HMX based propellant, VTQ-2. 

Thomal augmentation of firagmentation kinetics has been found experimentally under conditions relevant to steam explosions (sustained pressure). Characterization of these fragmentation rates and related microinteractions zone is possible through the use of flash X rays. 

Highly energetic compounds with potential use in explosive devices must be characterized completely and safely, particularly as the explosive character may be linked directly to vibrational modes in the molecular structure, hence the application of computational methods to complement experimental observations. ANTA 5 has been the subject of various studies and, as an adjunct to one of these and to confirm the results of an inelastic neutron scattering experiment, an isolated molecule calculation was carried out using the 6-311G basis set <2005CPL(403)329>. 

The degree to which the amount of nitric oxide obtained after the explosion approximates the equilibrium quantity characterizes the rate and time of the reaction in the explosion. By making the natural assumption that under similar conditions (volume of the vessel, initial pressure) the time of the reaction is the same, the influence of the explosion temperature on the reaction rate could be studied. The reaction 2NO + 02 = 2N02 in mixtures containing additional nitric oxide gave rise to some complications in the experimental technique and in the treatment of the results. 

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