Home – Home – Jornals – Advanced Search

Instability of a conical liner during shaped-charge jet formation has been studied. To establish the metal flow pattern during shaped-charge jet formation, we fabricated three-layer copper-copper-constantan liners consisting of a solid copper conical funnel with an cone angle of 45^oC, a wall thickness 1.5 mm, and a funnel pressed into it and rolled from a copper sheet 1.0 mm thick clad by explosion welding with constantan 0.2 mm thick. Liner implosion was carried out by an RDX charge 20 mm thick. The jet formation process was recorded by flash radiography, and the metal flow pattern was determined by micro sections of recovered slugs. Since the boundary of explosion welded metals is clearly distinguishable on the sections, the residual deformation in different sections of the slug shows the occurrence of instability of the liner during the implosion, which manifests itself in the form of folds oriented along the generatrix of the cone. However, the general flow pattern described in terms of the theory of an ideal incompressible fluid is not disturbed, which follows from radiographs of the shaped-charge jet formation process.

Experiments on the explosive welding of low-plasticity steels through thin plastic layers show that, aside from the geometric features of collision (thickness and angle of collision of plates and contact point velocity), the dimensions of waves arising in the junction region are also highly affected by the mechanical properties of welded materials (hardness, density, and sound velocity). It is determined that waves of different dimensions can be formed under the same conditions, but their length lies in a certain range of values. On the basis of the resulting experimental data and with involvement of the Landau model, which describes the instability of a steady flow of viscous fluid, expressions for estimating the top and bottom boundaries of wavelengths are constructed with allowance for geometric parameters of collision and mechanical properties of colliding metal plates.

This paper describes the structural studies of hollow cylindrical shells made of D16 and AMts aluminum alloys, loaded by sliding detonation. Explosive loading conditions for the complete convergence and closure of shells are established. Light optics scanning electron microscopy, and transmission electron microscopy are applied to study the structural and phase transformations in shells under shock-wave loading. The relation of composition, structure, and mechanical characteristics of alloys with their behavior under the action of shock loading is shown. There are several scenarios of convergence of shells, depending on their composition and loading conditions - from complete and steady convergence to multiple spalling.

The structural mechanisms of buckling and the deformation behavior of copper and steel cylindrical shells (pipes) during convergence under the action of an explosion are studied. The dependence of deformation behavior on the transverse dimensions of the shell and properties of the loaded material is described. It is established that the stability of radial convergence depends on absolute dimensions of the shell rather than relative dimensions, with the convergence of large-diameter shells occurring more stably. It is demonstrated that the convergence stability is violated due to the formation of a characteristic pattern of localized deformation in the sample, consisting of homogeneous, orderly arranged structural elements whose dimension depends little on the material properties and experimental conditions. A criterion for stable radial convergence that relates the characteristic dimensions of the structural element of localized deformation and the shell radius is proposed.

Numerical simulation studies of shaped charges with hemispherical liners of degressive thickness (decreasing from the top to the bottom) have been continued. The possibility of increasing not only the velocity but also the mass of the head sections of the formed shaped-charge jets to the level provided by conical liners of progressive thickness has been analyzed. For this purpose, liners of degressive thickness in the form of a truncated sphere and a semi-ellipsoid slightly elongated along the charge axis have been additionally studied.

The results of numerical simulation of the blast impulse of explosive charges on structural elements are presented. The numerical method was validated against available experimental data describing the blast effect in the near zone of explosion. Additional experiments on explosive acceleration of steel discs were performed. The effect of explosion conditions (the presence or absence of air, additional reflecting surfaces) on the blast impulse was studied.

An X-ray pulse video recording method is used to study the projecting ability of coaxial combined explosive charges containing dispersed aluminum in a thin peripheral layer as compared with charges containing a uniformly distributed aluminum additive and charges with no additives. The significant influence of the burnout of detonation products on the projecting ability of explosive charges containing dispersed aluminum is confirmed. It is shown that aluminum in a composition with explosive charges burns out because of reacting both with detonation products and ambient air, including in a rarefied environment.

Experiments on detonation spraying of ceramic coatings are carried out by feeding a powder as part of a suspension into a barrel for the first time. Spraying of Al₂O₃ and TiO₂ nanopowders and hydroxyapatite shows that the new method for obtaining coatings (suspension detonation spraying) can be implemented on a CCDS2000 detonation device. Unlike conventional detonation spraying technologies using micron-sized powders, suspension spraying makes it possible to work with powders whose particle size is smaller than 1  m, serving as a basis for a suspension fed into the projector barrel during spraying.

Fundamental features of explosive packing of powder mixtures containing refractory metal carbides and metal bonds are under consideration. The effect of acoustic rigidity of metal bonds on the residual porosity of samples after explosive treatment is revealed. It is shown that the degree of packing of mixtures of carbide powders with metals under explosive pressing is determined by the possibility of arrival of shock waves in the metal bond particles at their surfaces free of contacts with other particles and with a mass velocity acquired by the metal bond at these surfaces due to unloading.

A number of modern scientific and practical problems in design of multifunctional safety systems for coal mines and requirements to such systems are discussed. The reasons and the dynamics of accidents in mines are analyzed; examples of approaches to preventing such accidents are given. Available and promising directions of the development of engineering tools and systems for ensuring miners' safety are considered. The efficiency of using the scanning gas monitoring technology is demonstrated. Combining this technology with the automatic system of fire quenching allows the fire to be suppressed at the initial stage of ignition of the methane-air mixture.