Effect of the method used to detonate the borehole charges on the breakdown characteristics

Conclusions The change in the method of detonation is an effective means of controlling the energy of the explosion.By choosing an appropriate method of detonating it is possible not only to concentrate the explosive energy in a specified direction but also to increase the total effect of the explosion in various media.Using the bilateral cord detonation it is possible to achieve a 10–40% increase in the work-effectiveness of the charge depending on the type of rock by comparison with detonation from the end; effectiveness can also be increased 17–80% by comparison with detonation along the charge. This will enable the parameters of drilling and explosive work to be changed and make it possible to have a 30% reduction in costs as has been shown in preliminary analysis.Translated from Ogneupory, No. 6, pp. 28–32, June, 1984.     

Spin wave and attenuation of liquid explosive detonation

The detonation of nitromethane and a dinitrotoluene solution in bistrinitroxyethylnitramine when the diameter of the cylindrical charge is close to the critical was investigated with the aid of high-speed photography of the luminosity of the lateral and end cylinder surfaces and the recording of the spin wave surface using sampling plates with an air gap. It was discovered that the appearance of penetrating spinning absence-of-reaction waves, which are responsible for the attenuation of liquid explosive detonation, is closely related to the spread of detonation spin waves over the charge surface (or immediately below it). The spin waves, which are instrumental in the propagation of a normal detonation in weakly heterogeneous cast charges consisting of trotyl-hexogene and trotyl-PETN, in the case of liquid explosives probably inhibit the detonation process by inducing the formation of penetrating absence-of-reaction spin waves. It is shown that the spin wave velocity corresponds to the degree of material compression in the near-surface layer, as calculated according to the Dremin-Trofimov model (it can be only slightly above it.)Moscow. Translated from Fizika Goreniya i Vzryva, Vol. 28, No. 2, pp. 93–98, March–April, 1992.     

Effect of a porous interlayer on the strengthening of low-carbon steel by contact explosion

We have studied the effect on strengthening and microstructural changes from a powder interlayer positioned between an explosive charge and a low-carbon steel surface. It has been established that the use of such interlayers leads to a greater increase in hardness and change in microstructure than comes about through direct contact of the charge with the surface being hardened. The effect increases as the acoustic impedance of the interlayer and the detonation characteristics of the explosive are increased.Novosibirsk. Translated from Fizika Goreniya i Vzryva, No. 2, pp. 130–137, March–April, 1991.     

Interactions of Impact Shock Waves in a Thin-Walled Explosive Container. I. Impact by a Flat-Ended Projectile

Interaction of impact shock waves that could detonate an explosive (Composition B) confined in a thin-walled container impacted by a cylindrical projectile is numerically studied, based on the Forest Fire explosive reaction rate model. After the impact, rarefaction waves from projectile periphery and front cover–explosive interface catch up the forward-moving shock fronts in the explosive as well as in the projectile. At a high impact velocity, the transmitted shock front induces detonation at the front cover–explosive interface. At an intermediate velocity, the rate of energy release from the shock-compressed volume in the explosive is such that the associated effects prevail over the effects caused by rarefaction waves, leading to detonation after the shock wave travels a certain distance in the explosive. There is a range of minimum impact velocities at which the effect of rarefaction waves prevails over the energy release; hence, the detonation is excited not behind the shock-wave front moving over the explosive but only after shock-wave reflection from the high-impedance back plate. It is suggested that, in interpreting the detonation behavior of an explosive confined by a high-impedance container, one should take into account the effects of shock-wave interaction with container walls.     

Seismic, Hydroacoustic, and Acoustic Action of Underwater Explosions

Results of a fullscale study of hydroacoustic, seismic, and acoustic effects of an underwater explosion of charges of a chemical high explosive are described. The study had a comprehensive character and included video filming of surface phenomena at the explosion epicenter, registration of hydroacoustic waves in water, seismic waves on the ground, and acoustic waves in air at distances of 0.08–30 km from the explosion epicenter. Parameters of these waves and the character of their decay with distance were obtained, and the wave spectra were analyzed. It is shown that the main specific feature of the wave shapes of hydroacoustic, seismic, and acoustic signals is caused by oscillations of the cavity filled by detonation products, which can be used to identify underwater explosions.     

The formation of smooth spalls in steel during the interaction of glancing detonation waves

A study is made of the formation of smooth spalls in steel specimens when their surfaces are blasted by explosive charges via a glancing detonation wave. When a steel specimen is blasted with an explosive, behind the front of glancing shock waves of compression two glancing shock waves of rarefaction, propagating toward each other, form, the interaction of which produces in the steel a smooth spall in the form of a dihedral angle. It is shown that a variation of the composition of the explosive (TNT, plastic explosive, TG 50/50 alloy) of a given thickness changes the distance from the vertex of the dihedral angle to the surface at which the charge was placed.VNIIÉF, Arzamas-16 607200. Translated from Fizika Goreniya i Vzryva, Vol. 30, No. 4, pp. 138–140, July–August, 1994.     

Effects of charge strength on ignition parameters for solids on impact

A model has been used for thermoplastic failure and ignition in a thin layer of viscoplastic material on impact with the normal law for the strength distribution in an explosive charge in order to perform numerical calculations on the initiation parameters and explosion curves as functions of charge dimensions and impact energy.Moscow. Translated from Fizika Goreniya i Vzryva, Vol. 27, N. 4, pp. 99–104, July–August, 1991.     

Reaction of a real explosion chamber to internal pulsed loading

Results are given for strain measurements of an actual explosion chamber intended for explosive hardening of railway points with an explosive charge weight up to 20 kg. It is shown that with an increase in explosive weight within the working range average stresses increase linearly. A special point of the construction is the pole of the chamber bottom. Use of a plane stressed state model for treating measured results leads to an increase in maximum stresses by 10–30%. Frequencies of the main modes of the construction at 84–1040 Hz are determined by spectral analysis of the deformation profiles. The damping decrement of the main harmonics is 5–30%.Institute of Hydrology and Hydrotechnology, Siberian Branch, Russian Academy of Sciences, 630090 Novosibirsk. Translated from Fizika Goreniya i Vzryva, Vol. 30, No. 2, pp. 95–102, March–April, 1994.     

Explosion resistance of welded cylindrical titanium shells

Results are provided for an experimental study of the reaction to internal explosive loading of titanium alloy PT-3V welded cylindrical shells filled with air or water. It is established that shell failure develops a strong scale effect in the form of a sharp reduction in explosion resistance with an increase in dimensions. Recommendations are made for weakening the effect of the scale factor and increasing shell explosion resistance. Semi-empirical equations are obtained which are recommended for evaluating explosion deformation parameters for the shell of a cylindrical explosion protection chamber made of titanium alloy.VNIIÉF, Arzamas-16 607200. Translated from Fizika Goreniya i Vzryva, Vol. 30, No. 4, pp. 148–156, July–August, 1994.     

Dispersion of explosion products in a shaped-gas charge

The phenomenon of energy focusing in the detonation of an explosive has found wide application in industry. Examples are shaped charges for geophysical investigations [1] and for crushing rock masses under conditions of back pressure [2], charges for crushing bulky pieces of rock [3, 4], directed well-drilling and pressure charges [5, 6], shaped-gas charges for accelerating solids [7] and for supersonic focusing [8].Dnepropetrovsk. Translated from Fizika Goreniya i Vzryva, Vol. 27, No. 6, pp. 127–131, November–December, 1991     

Dynamic strength of spherical fiberglass shells under internal explosive loading

In this article, we determined experimentally the response and made an estimate of the strength of fiberglass spherical shells,500 mm in diameter of two types of winding under radial-symmetric internal explosive loading. The advantage of shells with a more uniform thickness (15–20mm) of the load-carrying fiberglass layer is shown. On explosion of a charge involving an energy equivalent to1.4 kg ofTNT, this layer has an approximately twofold strength factor. It is established that the change from uniaxial (cylindrical shells) to biaxial strain in spherical shells does not change the magnitude of total strain at failure.Scientific Research Institute of Experimental Physics, Kremlev 607200. Translated from Fizika Goreniya i Vzryva, Vol. 31, No. 4, pp. 93–99, July–August, 1995.     

Explosive combustion of a gas mixture in radial annular chambers

Experimental results are described for continuous explosive ignition of compressed gases in flat annular chambers. The basis of the process is B. V. Voitsekhovskii's transverse-detonation method. Two types of tests were done: 1. The fuel components were fed through the cylindrical walls at the outer radius and the combustion products flowed out through the free surface at the inner radius. 2. The radial flow was reversed and the products flowed out with no wall at the outer radius. In both cases conditions were found where transverse detonation-like waves rotated around the annulus.Lavrent'ev Institute of Hydrodynamics, Siberian Branch, Russian Academy of Sciences, Novosibirsk 630090. Translated from Fizika Goreniya i Vzryva, Vol. 30, No. 4, pp. 111–119, July–August, 1994.     

Pulsed Loading of Objects during Intense Expansion of Products of Explosion of Solid Explosives (Review)

Specific features of pulsed loading of objects during intense expansion of explosion products of solid explosives are considered. Parameters of the semi-empirical equation of state of explosion products in the density range that has not been adequately considered are given. Results of experimental investigations of reflection of unsteady shock waves from a rigid wall and their effect on thin targets are summarized. Processes that occur under moderate-intensity dynamic impacts on solid and porous media are described: multiple collisions of solids with rigid targets, shock-induced coalescence of nanodiamonds, and emission effects due to expansion of explosion products into an evacuated volume, air, and inert gas.__________Translated from Fizika Goreniya i Vzryva, Vol. 41, No. 3, pp. 3–28, May–June, 2005.     

Explosive generation of heterogeneous detonation waves in aerocolloids of a unitary fuel

The process of explosive initiation of spherical, heterogeneous detonation waves in monodisperse, homogeneous aerocolloids of a unitary fuel is modeled mathematically. It is shown that regimes of decaying and detonating combustion of the reacting disperse mixtures are possible, depending on the initial mass concentration and initial particle size in the mixture. It is established that the laws governing the mass transfer of burning particles have a significant influence on the patterns of explosive generation and propagation of detonation waves in unitary fuel aerocolloids. The critical (maximum) diameter of the unitary fuel particles, below which the shock initiation of heterogeneous combustion is possible, is determined as a function of the particular value of their relative mass concentration in the mixture.Institute of Mechanics of Multiphase Systems, Siberian Branch of the Russian Academy of Sciences. Translated from Fizika Goreniya i Vzryva, Vol. 31, No. 3, pp. 83–91, May–June, 1995.     

Attenuation of Blast Overpressures from Liquid in an Elastic Shell

Parameters of air blast waves produced by a ground explosion of explosive charges of mass G=0.1 – 1 kg placed in a liquid bounded by an elastic shell were measured experimentally. Encapsulation of the liquid in the elastic shell leads to an increase in the compressibility of the medium which transfers the energy of explosion products to the air and contributes to a significant decrease in airblast amplitude at a reduced distance R/G ^1/3 = 0.63 – 6.8 m/kg^1/3. The efficiency of attenuation of overpressures by immersing an explosive in a liquid bounded by an elastic shell is comparable to efficiency of damping blast waves by gasfilled twophase systems. It is shown that the main parameter of blastwave attenuation is the ratio of the mass of the liquid to the mass of the explosive charge rather than the viscosity and density of the liquid.     

Reaction Zones of Detonating Solid Explosives

The reaction zones of normal and overdriven detonation waves in a number of solid HE were studied by recording the shock–wave luminosity in chloroform placed at the end of a high–explosive (HE) charge. The data obtained have led to some conclusions on the regularities of HE decomposition in a detonation wave. Thus, in a powerful solid HE, the heterogeneity of the charge plays a decisive role in the formation of a chemical spike. In this case, the time of reaction of heterogeneous HE correlates with the Jouguet pressure rather than with the sensitivity of the HE. The experimental parameters of the chemical spike are in good agreement with calculations on an extrapolated shock adiabat of the HE. This, however, does not indicate that the fraction of the HE decomposed directly at the detonation front is small but only shows that it depends smoothly on the front parameters. In overdriven detonation waves, an increase in the overcompression pressure is accompanied by an increase in the fraction of the HE decomposed directly at the front, and with a relatively large increase in pressure, the chemical spike completely disappears. In TATB and TATB–based HE, this occurs at a pressure of 40 GPa.     

A method of modeling large cratering explosions

Summary Modeling a cratering explosion has made it possible to investigate the dependence of the crater radius on the depth of the charge and the energy of the gas in the cavity. The empirical formula thus obtained is in satisfactory agreement with the results of test explosions in alluvium and loam over a broad interval of charge weights (from 80 kg to 450 t). The model and full-scale experiments are also in agreement with respect to their kinematic characteristics.The role of the gravity field in the cratering process has been clearly established and a corresponding method of calculating the energy of the explosion at different charge depths is proposed.The possibility of modeling a cratering explosion with respect to its kinematic parameters suggests new means of solving a whole series of engineering problems involving the explosive displacement of soil masses.Fizika Goreniya i Vzryva, Vol. 3, No. 1, pp. 119–127, 1967     

The load on an obstacle from a sliding detonation in a thin layer of explosive

Loading by a sliding detonation in a thin layer of explosive is considered. The loading parameters have been related to the acoustic impedance by numerical calculation. Measurements have been made on how the surface size and explosive thickness affect the momentum transferred to aluminum and Tufnol. The pulse distribution is considered for a two-layer Tufnol-aluminum system. The measurements are explained in terms of considerable length in the loading pulse.Moscow. Translated from Fizika Goreniya i Vzryva, Vol. 27, No. 4, pp. 94–99, July–August, 1991.     

Brisance of mixed explosives in standardized cylinders

The use of standardized cylinders in tests of the brisance of explosives has made it possible to obrain a rather detailed picture of the variation in brisance with the properties of the metal and explosive material [1–4]. A wide class of steels (low-, medium-, and high-carbon) has been used with basically only three types of explosive: TNT, stabilized hexogen—aluminum, and stabilized octogen. The brisance of mixed compositions containing and explosive material, oxidant (potassium perchlorate), and fuel (aluminum powder) is studied in this article.N. É. Bauman Moscow State Technical University, 107005 Moscow. Translated from Fizika Goreniya i Vzryva, Vol. 30, No. 3, pp. 147–150, May–June, 1994.     

Plane initiation of a detonation

The conditions for exciting a plane detonation wave were experimentally observed to be independent of the initial [gas] pressure. The explanation is based on the concept that impacts of transverse waves play a leading role in initiating and propagating the detonation. The dimension of the effective zone which is responsible for initiating the detonation is close to the dimension of the chemical [energy] peak. Formulas are presented for estimating the energy equivalent of the initiator, based on the concept of transforming the plane detonation wave into a spherical, cylindrical, or plane detonation by diffracting the initial wave by convex angle. The basic analytical conclusions of the concept are confirmed by experiment.Novosibirsk. Translated from Fizika Goreniya i Vzryva, Vol. 29, No. 3, pp. 164–170, May–June, 1993.