Hurling of shells by hollow charges

Results of the numerical solution of the problem of one-dimensional hurling of shells by hollow explosive charges are elucidated. The results of the numerical solution are compared with asymptotic formulas. Numerous domestic and foreign papers have been devoted to the question of hurling shells by explosive charges. A numerical solution of the problem of convergence of a ring to the center under the effect of detonation products is presented in [1–3]. The problem of hurling a shell by a hollow explosive charge with an internal lining is considered in [4]; the solution of the problem of hurling a shell by a hollow explosive charge without the cavity lining is presented in [5] on the basis of the energy-balance equations; however, the complete picture of the processes occurring in the detonation products is not considered.Translated from Zhurnal Prikladnoi Mekhaniki i Tekhnicheskoi Fiziki, No. 3, pp. 161–166, May–June, 1976.     

Numerical solution of the two-dimensional unsteady-state problem of the motion of a shell under the action of the products of an axial detonation

A numerical solution is obtained to the problem of the motion of an incompressible cylindrical shell with a charge of explosive, with excitation of the detonation simultaneously along the whole axis of the charge. The strength of the shell is not taken into consideration. A three-term equation of state is adopted for the products of the detonation. In [1] a numerical solution is obtained to the problem of the one-dimensional motion of a shell with the axial detonation of a charge of explosive.     

Motion of the detonation products of a point-ignited charge in a cylindrical shell

A numerical solution is obtained for the two-dimensional nonsteady problem of the motion of detonation products from a cylindrical high-explosive charge enclosed in a shell with the initiation of detonation at a central point in the end of the charge. The detonation products propagate in vacuum. The strength of the shell is not considered. A three-term equation of state is used for the detonation products.     

Effect of the casing on the initial parameters of the underwater explosion of a cylindrical charge of explosive

An experimental determination was made of the initial parameters of shock waves in water with the explosion of cylindrical charges of TNT in casings. It is shown that these parameters depend mainly on the dynamic rigidity of the material and the relative weight of the shell. It is established that during the process of the expansion of the casing of the charge with an explosion in limited volumes of water there is formed a region of extremely rapid expansion, whose boundary can be identified with the boundary between the detonation products and the water after destruction of the casing, coinciding in time with the arrival of the cavitation front.Translated from Zhurnal Prikladnoi Mekhaniki i Tekhnicheskoi Fiziki, No. 1, pp. 165–168, January–February, 1973.     

Gasdynamics of the scattering of the detonation products of a cylindrical explosive charge with inert metal particles

A mathematical model of the scattering of the detonation products of a condensed explosive with inert metal particles when the wave travels along the axis of a cylindrical charge is proposed and numerical calculations are carried out. Detonation product scattering is simulated by a two-phase nonequilibrium axisymmetric jet flow in a supersonic external airstream. A technique for calculating the product gas-suspension behind the detonation wave is developed. The optimal values of the difference scheme parameters ensuring the required calculation accuracy are found. The gasdynamic properties of the process associated with the particles and the lateral spread are investigated.Moscow. Translated from Izvestiya Rossiiskoi Akademii Nauk, Mekhanika Zhidkosti i Gaza, No. 5, pp. 101–111, September–October, 1995.     

The nature of the electrical impulse in an explosion

The mechanism for the formation of an electric impulse on the explosion of ordinary explosive substances is analyzed. A double electrical layer with voltage of the order kT 0.2–0.6 V is formed in the detonation wave. When the detonation wave passes to the outer surface of the charge, electrons adhere to molecules of air and explosion products. As the charged explosion products fly apart, the distance between the positive and negative charge s increases and the voltage increases to a magnitude of the order of a kilovolt. The asymmetric separation of the charged explosion products is the cause of the impulse. Theoretical estimates are compared with experiments [1].Translated from Zhurnal Prikladnoi Mekhaniki i Tekhnicheskoi Fiziki, Vol. 11, No. 2, pp. 72–75, March–April, 1970.The authors are grateful to Ya. B. Zel'dovich and Yu. P. Raizer for useful discussions.     

Container for Localization of an Explosion of a Compact High–Explosive Charge with an Inert Shell

Results of an experimental study of fragmentation effects in the explosion and the piercing power of the fragments of inert masses in the form of hemispherical aluminum and soft–steel shells enclosing the spherical charge of a high explosive under their action on flat steel, aluminum, steel–net, and claydite—concrete barriers are given. A design of the lightest spherical explosion–proof container with a load–carrying steel or glass–reinforced plastic shell protected by a splinter–proof layer capable of withstanding an explosion of a high–explosive charge (with a twofold safety factor) with an inert steel shell is proposed.     

Blast wave propagation in air from a gaseous charge

In the point explosion problem it is assumed that an instantaneous release of finite energy causing shock wave propagation in the ambient gas occurs at a space point. The results of the solution of the problem of such blasts are contained in [1–4]. This point model is applied for the determination of shock wave parameters when the initial pressure in a sphere of finite radius exceeds the ambient air pressure by 2–3 orders of magnitude. The possibility of such a flow simulation at a certain distance from the charge is shown in papers [4, 5] as applied to the blast of a charge of condensed explosive and in [6, 8] as applied to the expansion of a finite volume of strongly compressed hot gas. In certain practical problems the initial pressure in a volume of finite dimensions exceeds atmospheric pressure by a factor 10–15 only. Such cases arise, for example, in the detonation of gaseous fuel-air mixtures. The present paper considers the problem of shock wave propagation in air, caused by explosion of gaseous charge of spherical or cylindrical shape. A numerical solution is obtained in a range of values of the specific energy of the charge characteristic for fuel-air detonation mixtures by means of the method of characteristics without secondary shock wave separation. The influence of the initial conditions of the gas charge explosion (specific energy, nature of initiation, and others) is investigated and compared with the point case with respect to the pressure difference across the shock wave and the positive overpressure pulse.Translated from Izvestiya Akademii Nauk SSSR, Mekhanika Zhidkosti i Gaza, No. 3, pp. 110–118, May–June, 1986.     

Intensification of a detonation wave in the zone of secondary reactions in a two-phase medium

A method is proposed for the numerical calculation of one-dimensional nonsteady-state flows of a mixture of a gas with particles, based on the separation of a system of differential equations for a two-phase medium into two subsystems. The problem is solved concerning the propagation of a plane detonation wave in a mixture of a detonating gas with particles, behind the front of which secondary chemical reactions are taking place between the vapors of the particle material and the detonation products. The velocity profiles of the gas and of the thermodynamic functions behind the detonation wave front are determined, and also the dependence of the detonation velocity on the distance to the point of initiation. The conditions for intensification of the detonation wave are obtained in the zone of secondary reactions.Leningrad. Translated from Izvestiya Akademii Nauk SSSR, Mekhanika Zhidkosti i Gaza, No. 5, pp. 92–96, September–October, 1972.     

杆式弹对厚壁壳体装药冲击起爆机制模拟分析

为研究高速杆式弹冲击厚壁壳体装药的起爆机制,运用冲击物理显式欧拉型动力学SPEED软件,开展了不同弹径和弹长的钨合金杆式弹与厚壁壳体Comp-B装药相互作用过程的数值模拟,采用升降法获得弹体起爆装药临界着速及装药起爆位置变化。研究结果表明:弹体起爆装药临界着速随弹径增大而显著降低,随弹长增大呈先降低后平缓变化的规律;弹体以临界着速起爆装药时,存在2种装药起爆机制,即弹体贯穿壳体后的宏观剪切起爆和未贯穿壳体的低速冲击起爆,且其机制随弹体着速在临界着速以上继续提高会发生转变,最终均会转变为高速冲击起爆机制;装药起爆位置均发生在炸药壳体交界面后一定距离处,相同机制下此距离随弹体着速提高而减小。     

The detonation burning of a fuel mixture resulting from a double explosion

A study is made of the propagation of a multifront detonation burning in a fuel mixture consisting of a gaseous fuel and an oxidant with additions of combustible solid or liquid particles arising as a result of a double point explosion. In such combustible media it is possible for there to be propagation of several detonation or burning fronts following one after the other. The easily igniting gaseous fuel burns in the first detonation wave, which propagates in the gaseous mixture with particles which are heated by the products of the explosion, ignite and burn in the second detonation wave or in the flame front. Self-similar regimes of propagation of such waves in an idealized formulation were studied in [1].Translated from Izvestiya Akademii Nauk SSSR, Mekhanika Zhidkosti i Gaza, No. 2, pp. 126–131, March–April, 1985.     

Structure of detonation waves in gas suspensions of fuel containing the oxidant

The structure of detonation waves in air suspensions of unitary fuels (fuels containing an oxidant such as gunpowder and high explosives) is investigated. In such systems, complete combustion of the particles is possible at a high mass concentration of the fuel. As a result, the structure of detonation differs from that in gas-drop [1–3] and gas [4, 5] mixtures. The shock adiabats characteristic for air suspensions [6, 7] are used to investigate the field of integral curves which describe the structure of detonation waves in disperse media. Calculated distributions of the parameters which characterize the gas and particles in the detonation front are given. The influence of the rate of combustion of the particles and the intensity of interphase friction on the structure of the detonation is investigated. Results of the calculation of the structure of relaxation shock waves in gas suspensions of the solid fuel of rockets are given in [8]. Unsteady problems of convective combustion and the transition of combustion of air suspensions into detonation are analyzed in [9, 10].Translated from Izvestiya Akademii Nauk SSSR, Mekhanika Zhidkosti i Gaza, No. 5, pp. 47–53, September–October, 1981.     

Numerical Stress–Strain Analysis of Shells Including the Nonlinear and Shear Properties of Composites

A presentation is made of the numerical results obtained in a stress–strain analysis of thin and nonthin orthotropic shells with due regard for the physical nonlinearity and small and nonsmall shear stiffness of composites. A spherical shell with a circular hole is used as an example to analyze how the above-mentioned factors affect the distribution of stresses and strains depending on the shell thickness for adopted deformation models (the Kirchhoff–Love and Timoshenko hypotheses). Generalized conclusions are drawn from which it is possible to decide which of the composite properties and shell models should be given more priority.     

Fracture behavior of explosively loaded spherical molded steel shells

Experimental and numerical works are made to study the fracture of explosively loaded spherical molded steel shells. The first series of experiments included three sawdust recovery shots to save fragments for examination. In this series, detonation was initiated from the center of the sphere. Results of the experiments show that two types of fractures are observed in spherical shells: radial and shear as in cylindrical shells. Spall fracture is also observed in spherical shells. To assist understanding of the experimental results, a computer simulation of expanding shells is performed to provide information on the stress, strain, strain rate and position of each element of the shell wall as a function of time after detonation. For t=7.5 μs after detonation, triaxial non-uniform strain prevails in the middle of the thickness of the wall. The peak of the stress equals to 6.5 GPa and exceeds the spall strength of carbon steel. In the second series of experiments, spall fracture is suppressed by displacing the point of detonation initiation from the center to periphery of HE charge.     

Similarity motions of a gas in the case of local supply of mass and energy in a fuel mixture

One-dimensional nonstationary similarity motions of a gas with exothermic reactions behind shock waves are analyzed. The thickness of the region of chemical reactions is ignored. New solutions are obtained for the problems of flows of a chemically active gas with the formation of shock and detonation waves. In particular, it is shown that in the framework of the adopted schemes of the combustion process a solution with five strong-discontinuity surfaces can be constructed. The results are given of numerical solutions for supercompression detonation and Chapman-Jouguet detonation.Translated from Izvestiya Akademii Nauk SSSR, Mekhanika Zhidkosti i Gaza, No. 4, pp. 70–77, July–August, 1979.     

Detonation Wave Propagation in Rotational Gas Flows

This paper studies the propagation of detonation and shock waves in vortex gas flows, in which the initial pressure, density, and velocity are generally functions of the coordinate — the distance from the symmetry axis. Rotational axisymmetric flow having a transverse velocity component in addition to a nonuniform longitudinal velocity is considered. The possibility of propagation of Chapman–Jouguet detonation waves in rotating flows is analyzed. A necessary conditions for the existence of a Chapman–Jouguet wave is obtained.     

Nonstationary problems of the combustion of aerosuspensions in fuel that contains the oxidant

A study is made of one-dimensional nonstationary problems of the combustion and detonation of aerosuspensions of unitary fuels or propellants, which contain the oxidant as well as the combustible material (gunpowder, high explosives). A numerical analysis is made of the damping of the convective combustion which occurs at relatively low mass concentrations of the fuel; the critical concentration dividing the damped and the detonation regimes is determined. It is shown that the realization of the damped or detonation regime of convective combustion at a given concentration is completely determined by the gas dynamics of the relative motion of the gas and the particles (two-velocity effect), this being governed by the coefficient of friction.Translated from Izvestiya Akademii Nauk SSSR, Mekhanika Zhidkosti i Gaza, No. 1, pp. 22–27, January–February, 1981.     

Direct initiation of detonation in a hydrogen-oxygen mixture diluted with nitrogen

The direct initiation of plane and cylindrical detonation waves in a hydrogen-oxygen mixture diluted with nitrogen using an exploding copper wire and a moving piston is investigated.Translated from Izvestiya Rossiiskoi Akademii Nauk, Mekhanika Zhidkosti i Gaza, No.6, pp. 151–156, November–December, 1992.The authors are grateful to G. D. Smekhov for calculating the Chapman-Jouguet detonation parameters and to V. V. Mitrofanov, who reviewed the article, for his useful comments.     

On the origin and part played by pulsations of a detonation front

Arguments are given which show that the occurrence of pulsations is independent of the part they play in self-sustained detonation. It is shown that the perturbations which generate kinks in the detonation front are not formed in the region of shock compression but in the burning gas. It is suggested that the primary cause of the perturbations could be strong fluctuations associated with intense chemical transformations.Translated from Izvestiya Akademii Nauk SSSR, Mekhanika Zhidkosti i Gaza, No. 5, pp. 190–194, September–October, 1979.I am grateful to V. A. Levin and G. G. Chernii for discussions and valuable comments and to Ya. K. Troshin for support.     

Errors in stress measurements in soils under short-term loads

The results of experimental investigations of systemic errors in stress measurements in sandy soils by strain gauges under short-term loads produced by detonation of a plane charge are presented. The effect of rigidity of sensitive elements of the gauges and the effects of stress concentrations around the gauge body on the stress field measured are analyzed. A comparison of the experimental results with the theoretical calculations of [1, 2] is offered. It is shown that the systemic errors will not exceed ± 3–7% if certain easily achieved requirements with respect to the gauges are fulfilled. The question of evaluating systemic error in stress measurement in soils under low intensity static loads has been examined in [3–6].Translated from Zhurnal Prikladnoi Mekhaniki i Tekhnicheskoi Fiziki, No. 4, pp. 146–154, July–August, 1972.In conclusion, the authors thank N. V. Zvolinskii and A. M. Skobeev for their valuable advice and evaluation of the study, and A. I. Kotov, V. P. Sutyrin, and L. G. Romanov for participation in the conduct of the experiments and processing of the results.