S. P. Kiselev

Numerical simulation of wave formation in an oblique impact of plates by the method of molecular dynamics

Results of numerical simulations of wave formation in an oblique symmetric impact of metal plates by the method of molecular dynamics are presented. In this case, the impacting plates experience the same loading conditions as in explosive welding. It is demonstrated that the evolution of waves on the interface between the welded plates is caused by self-induced oscillations in the vicinity of the contact point. A mechanism of building-up and sustaining of self-induced oscillations is proposed on the basis of numerical calculations performed.

Model of Elastoplastic Deformation of Materials, Based on the Gauge Theory of Defects with Allowance for Energy Dissipation

Mathematical models of plasticity and creep for the case of small deformations are proposed on the basis of the gauge theory of defects with allowance for energy dissipation. It is assumed that plasticity is related to the motion of dislocations, which occurs without changes in volume. In the creep model, the motion of dislocations can proceed with changes in volume, and the “extra” volume is entrained (brought) by point defects. With the help of Godunovs generalized thermodynamic approach, it is shown that the proposed plasticity model is hyperbolic according to Friedrichs.

On the mechanism of self-oscillations of a supersonic radial jet exhausting into an ambient space

Results of an experimental study and numerical simulation of self-oscillations of a supersonic radial jet exhausting from a plane radial nozzle into an ambient space are reported. It is demonstrated that flexural oscillations develop in the jet, leading to its destruction. Feedback ensured by acoustic waves in the gas surrounding the supersonic jet is found to play a key role in the emergence of self-oscillations.

Effect of gas flow swirling on coating deposition by the cold gas-dynamic spray method

The effect of gas flow swirling on the process of coating deposition onto a target by the cold gas-dynamic spray method is studied experimentally and numerically. Flow swirling is found to change the gas flow field and to reduce the gas flow rate under typical conditions of cold gas-dynamic spray. In a non-swirled flow, the shape of the deposited spot is similar to a sharp cone. In contrast, the deposited spot in a swirled flow is shaped as a crater without particles at the center of this crater. It is found that this effect is caused by centrifugal forces acting on particles in a swirled gas flow.

Lifting of dust particles behind a reflected shock wave sliding above a particle layer

The paper presents results of mathematical simulation of particle lifting behind a shock wave reflected from the face wall and sliding above the particle layer. It is shown that particle lifting occurs in a vortex initiated in the gas when the shock wave is reflected from the wall.

Mechanism of self-oscillations in a supersonic jet impact onto an obstacle 1. Obstacle with a spike

Results of numerical simulations and experimental investigations of self-oscillations arising in the case of impingement of an overexpanded or underexpanded jet onto an obstacle with a spike are reported. The mechanisms of the emergence and maintaining of self-oscillations for overexpanded and underexpanded jets are elucidated. It is demonstrated that self-oscillations are caused by disturbances in a supersonic jet, which induce mass transfer between the supersonic flow and the region between the shock wave and the obstacle. The feedback is ensured by acoustic waves generated by the radial jet on the obstacle. These waves propagate in the gas surrounding the jet, impinge onto the nozzle exit, and initiate disturbances of the supersonic jet parameters. In the overexpanded jet, these disturbances penetrate into the jet core, where they are amplified in oblique shock waves.

Method of molecular dynamics in mechanics of deformable solids

The basic principles of the method of molecular dynamics are analyzed. Symplectic difference schemes for the numerical solution of molecular dynamics equations are considered. Stability is studied, and the errors in the energy conservation law, which are induced by using these schemes, are estimated. Equations of mechanics of continuous media are derived by means of averaging over the volume of an atomic system. Expressions for the stress tensor are obtained by using the virial principle and the method of averaging over the volume. The principles of construction of EAM and MEAM potentials of atomic interaction in crystals are analyzed. Two problems of fracture of copper-molybdenum composites are solved by the method of molecular dynamics.

Numerical simulation of titanium dissolution in the aluminum melt and synthesis of an intermetallic compound

Titanium dissolution in the aluminum melt and synthesis of an intermetallic compound at constant temperature and pressure are numerically simulated by the molecular dynamics method. Owing to titanium dissolution, the TiAl3 intermetallic compound is formed near the interface between the titanium crystal and aluminum melt. Based on the theory of weak solutions, a mathematical model of titanium dissolution in the aluminum melt is constructed. Dependences of the diffusion coefficient, equilibrium concentration of titanium, and dissolution rate on temperature are obtained.

Supersonic Gas Flows in Radial Nozzles

Results of experimental investigations and numerical simulations of supersonic gas flows in radial nozzles with different nozzle widths are presented. It is demonstrated that different types of the flow are formed in the nozzle with a fixed nozzle radius and different nozzle widths: supersonic flows with oblique shock waves inducing boundary layer separation are formed in wide nozzles, and flows with a normal pseudoshock separating the supersonic and subsonic flow domains are formed in narrow nozzles (micronozzles). The pseudoshock structure is studied, and the total pressure loss in the case of the gas flow in a micronozzle is determined.