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Stretching and breaking of shaped-charge jets and the behavior of the strained metal are studied with the use of dislocation mechanisms of plastic straining and with due allowance for shock wave processes at the stage of liner collapse and jet stretching. Regular features of shaped-charge jet stretching and breaking are found. Equations are derived for analyzing the influence of the strength and plastic properties of the material, its microstructure, geometric parameters, and kinematic characteristics on jet stretching and breaking. [ABSTRACT FROM AUTHOR]

This paper is a review of the series of investigations carried out at the S. A. Khristianovich Institute of Theoretical and Applied Mechanics (ITAM, Siberian Branch of the Russian Academy of Sciences (RAS)) aimed at solving the sonic boom problem. It has been shown, with the example of flow over a body of revolution at Mach number M = 2, that a decrease in the flow temperature near the body leads to a change in the flow structure in the region of the formation of a hanging shock wave and a decrease (by 12%) in the sonic boom intensity on the ground. The results are presented of investigations of the influence of the relative position and geometrical shape of configuration elements of a supersonic passenger airplane on the sonic boom parameters at long distances from the disturbance source. The prospective aspect of the supersonic passenger airplane providing the minimum level of sonic boom in cruising flight has been determined. The scheme (IZS method) for measuring in the experiment disturbed pressure profiles at a given distance from the investigated model has been described. [ABSTRACT FROM AUTHOR]

An approach for molecular dynamics simulation of the formation of polycrystalline materials from a melt during its cooling is proposed. Atomic configurations of copper corresponding to polycrystals with the mean grain size from 2 to 16 nm are obtained. Isothermal uniaxial tension and compression of these polycrystals is studied by the molecular dynamics method. For the mean grain size of polycrystalline copper being smaller than 10 nm, it is shown that Young's modulus and yield stress decrease as the grain size decreases. Shock adiabats for polycrystalline copper are constructed. For a material with the grain size approximately equal to 2 nm, the temperature behind the shock wave front is demonstrated to be 10% higher than that in a polycrystal with the grain size greater than 10 nm. Molecular dynamics calculations predict the presence of copper with a body-centered cubic lattice behind the shock wave front at pressures ranging from 100 to 200 GPa. [ABSTRACT FROM AUTHOR]

The article presents a study on phase transition behind a shock front in polycrystalline copper. Topics discussed include effect of the structural state of polycrystalline metals and alloys on their thermomechanical metals, method of molecular dynamics (MD), and calculation of the interaction between copper atoms.

The article presents a study on the numerical simulation of a supersonic flow around the system of an immobile body beyond a transmitted shock wave. The study investigates a grid of cylinders, which are transversely located in a two-dimensional setup, using the mathematical model for Favr-averaged Navier-Stokes equations. The results of the study show that the transitions between the different flow type are described by the mode maps for flows around the cylinders or spheres.

The influence of the basic factors of cryogenic forcing on formation of the middle zone on the sonic boom and aerodynamic characteristics of the flying vehicle is studied by experimental and numerical methods. Experimental data obtained with alcohol or liquid nitrogen as an injected liquid are used for comparisons; as a result, the total effect of temperature and coolant evaporation can be determined. The influence of temperature is studied by means of numerical simulations of the cryogenic action of distributed injection of air. A comparison of numerical and experimental data reveals the effect of the coolant evaporation process on perturbed flow formation. It is demonstrated that evaporation of the coolant outgoing onto the vehicle surface should be intensified to increase the efficiency of cryogenic forcing (to decrease the coolant flow rate). [ABSTRACT FROM AUTHOR]

The evolution of the initially disturbed mixing layer of two gases of different densities under the action of an incident shock wave, shock waves reflected from the end face, compression and expansion waves is studied in a two-dimensional unsteady approximation on the basis of the previously formulated mathematical model of mechanics of a two-velocity two-temperature mixture of gases. Problems of wave interaction with a sinusoidally disturbed diffusion layer are solved numerically. It is shown that the calculated width of the mixing region is in good agreement with experimental data. [ABSTRACT FROM AUTHOR]

The possibility of improving the efficiency of cryogenic forcing on the parameters of the hanging shock determining the length of the region of minimization of the sonic boom (middle zone) generated by a modified power-law body is studied. The effect of distributed injection of the coolant from the body surface on the formation of a perturbed flow near the body and at large distances from the body is considered. The scheme of distributed injection and the regime of coolant exhaustion are demonstrated to exert a significant effect on the length of the middle zone of the sonic boom. A scheme of cryogenic forcing is determined, which ensures reduction of bow shock wave intensity by more than 40% at distances corresponding to 7000 body diameters. The mechanism of cryogenic forcing on the flow structure near the body is discussed. [ABSTRACT FROM AUTHOR]

The possibility of controlling the sonic boom level by means of cooling the surface of a flying vehicle is discussed. The effect of surface cooling on the formation of the perturbed flow structure at large distances from the vehicle is demonstrated by an example of a modified power-law body of revolution. The intensity of the intermediate shock wave and the perturbed pressure pulse near the body are seen to decrease, which expands the altitude range of the region where the sonic boom is reduced (down to 50%). At larger distances from the body, cryogenic forcing ensures a 12% decrease in the bow shock wave intensity. The possibility of controlling the process of formation of wave structures near the surface, such as barrel shock waves, is demonstrated. An explanation of the cryogenic forcing mechanism is offered. [ABSTRACT FROM AUTHOR]

Some analytical and numerical results obtained by the authors in the field of mechanics of reactive heterogeneous media at the Institute of Theoretical and Applied Mechanics of the Siberian Division of the Russian Academy of Sciences during several years are summarized. [ABSTRACT FROM AUTHOR]

A mathematical model of mechanics of a two‐velocity two‐temperature mixture of gases is developed. Based on this model, evolution of the mixing layer of two gases with different densities under the action of shock and compression waves is considered by methods of mathematical simulation in the one‐dimensional unsteady approximation. In the asymptotic approximation of the full model, a solution of an initial‐boundary problem is obtained, which describes the formation of a diffusion layer between two gases. Problems of interaction of shock and compression waves with the diffusion layer are solved numerically in the full formulation. It is shown that the layer is compressed as the shock wave traverses it; the magnitude of compression depends on shock‐wave intensity. As the shock wave passes from the heavy gas to the light gas, the mixing layer becomes overcompressed and expands after shock‐wave transition. The wave pattern of the flow is described in detail. The calculated evolution of the mixing‐layer width is in good agreement with experimental data. [ABSTRACT FROM AUTHOR]

Results of numerical simulation of the shock wave passing along a dusty layer are presented; the simulation was performed under the one‐temperature, one‐velocity assumption. It is shown that a system of compression and expansion waves is formed inside the layer, and these waves are successively reflected from the external boundary and solid wall. Regular and irregular reflections of the leading shock wave from the solid wall with different scenarios of instability evolution on the layer edge are described. Possible mechanisms of particle lifting from the surface are described. [ABSTRACT FROM AUTHOR]

Asymptotic solutions are constructed for the problem of the shock‐wave structure in mixtures of gases with disparate molecular masses. The effect of emergence of a plateau on the density profile of the light component and nonmonotonicity of the temperature profile of the heavy component is described. Based on a comparison with calculations of the full model, the range of applicability of asymptotic solutions is determined. [ABSTRACT FROM AUTHOR]

It is experimentally established that intensive self-oscillations of shock wave fronts, which arise in a supersonic jet impinging onto a solid or permeable obstacle of finite dimensions, can be suppressed under the action of an electric discharge operating at the periphery of the jet. [ABSTRACT FROM AUTHOR]

The article offers analysis on the developmental processes of the Richtmeyer-Meshkov instability during the interaction of the incident shock wave with the perturbed mixing layer. It says that such interaction will allow for further repeated interaction of the layer with the waves reflected from the end. In this analysis, researchers considered the incidence of the shock wave on the mixing layer with the reflection angle in a one-dimensional approximation.

The phenomenon of rebounding of a shaped-charge jet from the armour surface with small angles between the jet axis and the target surface is considered. Rebounding angles as a function of jet velocity are obtained in experiments for a copper shaped-charge jet. An engineering calculation technique is developed. The results calculated with the use of this technique are in reasonable agreement with experimental data. [ABSTRACT FROM AUTHOR]