RAS Institute of Applied Mechanics

Moscow, Russia

RAS Institute of Applied Mechanics

Moscow, Russia
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Myagkov N.N.,RAS Institute of Applied Mechanics
Journal of Experimental and Theoretical Physics | Year: 2017

The problem of aluminum projectile fragmentation upon high-velocity impact on a thin aluminum shield is considered. A distinctive feature of this description is that the fragmentation has been numerically simulated using the complete system of equations of deformed solid mechanics by a method of smoothed particle hydrodynamics in three-dimensional setting. The transition from damage to fragmentation is analyzed and scaling relations are derived in terms of the impact velocity (V), ratio of shield thickness to projectile diameter (h/D), and ultimate strength (σp) in the criterion of projectile and shield fracture. Analysis shows that the critical impact velocity Vc (separating the damage and fragmentation regions) is a power function of σp and h/D. In the supercritical region (V > Vc), the weight-average fragment mass asymptotically tends to a power function of the impact velocity with exponent independent of h/D and σp. Mean cumulative fragment mass distributions at the critical point are scale-invariant with respect to parameters h/D and σp. Average masses of the largest fragments are also scale-invariant at V > Vc, but only with respect to variable parameter σp. © 2017, Pleiades Publishing, Inc.

Vorotilin V.P.,RAS Institute of Applied Mechanics
Journal of Experimental and Theoretical Physics | Year: 2017

A generalization of the theory of chemical transformation processes under turbulent mixing of reactants and arbitrary values of the rate of molecular reactions is presented that was previously developed for the variant of an instantaneous reaction [13]. The use of the features of instantaneous reactions when considering the general case, namely, the introduction of the concept of effective reaction for the reactant volumes and writing a closing conservation equation for these volumes, became possible due to the partition of the whole amount of reactants into “active” and “passive” classes; the reactants of the first class are not mixed and react by the mechanism of instantaneous reactions, while the reactants of the second class approach each other only through molecular diffusion, and therefore their contribution to the reaction process can be neglected. The physical mechanism of reaction for the limit regime of an ideal mixing reactor (IMR) is revealed and described. Although formally the reaction rate in this regime depends on the concentration of passive fractions of the reactants, according to the theory presented, the true (hidden) mechanism of the reaction is associated only with the reaction of the active fractions of the reactants with vanishingly small concentration in the volume of the reactor. It is shown that the rate constant of fast chemical reactions can be evaluated when the mixing intensity of reactants is much less than that needed to reach the mixing conditions in an IMR. © 2017, Pleiades Publishing, Inc.

Lurie S.,RAS Institute of Applied Mechanics | Minhat M.,National University of Malaysia
Composites Part B: Engineering | Year: 2014

A self-consistent Eshelby method based on the three-phase model is developed to examine the behavior of bristled fiber composite material where the fibers are radially coated with micro/nanostructures such as microwhiskers, nanowires or carbon nanotubes (fuzzy fiber). The effective mechanical properties are determined by taking into account the additional bristled interphase layer that is formed between fiber and matrix due to the presence of these micro/nanofibers. The features of the proposed method are emphasized and comparative study with other methods is conducted. In addition, several parameters of the micro/nanofibers such as length, density, diameter and material affecting the effective properties of composites are examined. In general, the presence of bristled fibers can significantly improve the shear and transverse characteristics of composite materials. © 2014 Elsevier Ltd. All rights reserved.

Gus'Kov O.B.,RAS Institute of Applied Mechanics
Doklady Physics | Year: 2014

The problem of drag of an arbitrary-size solid sphere with its motion in a uniform monodispersed viscous suspension is considered in the Stokes approximation. The expression for the effective suspension viscosity is derived in the first approximation over the volume concentration of the viscous suspension. The coefficient before the concentration is found in the form of an explicit analytical function, which depends on the ratio of sizes of the dispersed particles and the body. The found coefficient coincides with Einstein's result at the limit of "point" dispersed particles, the size of which is negligibly small compared with the size of the moving sphere, but can substantially differ from it in the case of finite-size particles. © 2014 Pleiades Publishing, Ltd.

Suyetin M.V.,RAS Institute of Applied Mechanics | Vakhrushev A.V.,RAS Institute of Applied Mechanics
Journal of Physical Chemistry C | Year: 2011

The storage of hydrogen in the condensed state in high-pressure vessels is dangerous, and it is impossible to store a large amount of hydrogen using adsorbents in normal ambient conditions. In order to overcome these problems, we designed a nanocapsule and investigated it with the help of the molecular dynamics simulation. The nanocapsule combines the advantages of a high-pressure vessel and adsorbents, namely a large hydrogen mass content and safe keeping. The nanocapsule is a system of combined nanotubes. Its outlet is closed by a positively charged endohedral complex K@C60 1+. The outlet opening and closing by the K@C60 1+ ion are induced by the action of an electric field. The processes taking place during the hydrogen adsorption, storage, and desorption from the nanocapsule are analyzed, and the value of the electric field intensity required for transferring the K@C 60 1+ ion into the nanocapsule is determined. The nanocapsule discussed can retain more than 6 wt % of hydrogen under normal conditions and meets the requirements of industrial use. © 2011 American Chemical Society.

Yankovskii A.P.,RAS Institute of Applied Mechanics
Applied Physics | Year: 2011

The model of thermal conductivity of spatially reinforced fibrous medium with a disperse reinforcement bonding agent is offered at the general anisotropy of materials a component of a composition. Comparison of calculated values of effective coefficients of thermal conductivity is lead is unidirectional and is cross the reinforced composites with experimental data. The satisfactory concord of calculated and experimental values of these magnitudes is shown.

Petukhov V.G.,RAS Institute of Applied Mechanics
Cosmic Research | Year: 2012

The problem of local optimization of interplanetary low-thrust trajectories is considered with the use of the maximum principle and continuation numerical methods. Two types of problems are analyzed: problems with limited power and problems with limited thrust. The latter problem is generalized by introducing the dependence of thrust and specific impulse on available electric power. In order to reduce the problem of optimal control to a boundary value problem, the Pontryagin maximum principle is used, and then, using the continuation method, this boundary value problem is reduced to the Cauchy problem. Variants of the continuation method for optimizing low-thrust trajectories are presented in the paper, including a new method of continuation for the limited thrust problem, which does not require any choice of the initial approximation for boundary values of conjugate variables. © 2012 Pleiades Publishing, Ltd.

Krobka N.I.,RAS Institute of Applied Mechanics
17th Saint Petersburg International Conference on Integrated Navigation Systems, ICINS 2010 - Proceedings | Year: 2010

Accurate equations of errors (EE) of strapdown inertial orientation systems (SIOS) and strapdown inertial navigation systems (SINS) are discussed. The differences between accurate dynamic and kinematic EE and approximated dynamic and kinematic EE (the equations in variations) are commented. Examples of the effects which can not be seen on the base of approximated EE are presented. Usually, the EE are used in two tasks: 1) for the forecast of accuracy of system taking into account the models of errors of gyros and accelerometers, the errors of gravitational field modeling and errors of initial conditions; 2) for working out the requirements for admissible levels of errors and noises of sensitive elements and methodical errors of algorithms at demanded accuracy of system. In the report a new class of algorithms of SINS in which for the purpose of correction the output parameters in parallel with regular algorithms the EE are integrated is proposed. The limitation of accuracy of SIOS and SINS by quantum noises of gyros based on Sagnac effect (SEG) of three generations - laser gyros (LG), fiber-optical gyros (FOG), and atom interferometers (AI) on de Broglie waves (AIWB) is discussed. On the basis of analytical solutions of dynamic EE of SINS, corresponding to some types of corrected SINS and trajectories of movement, the contribution of SIOS error to resultant SINS error is analyzed. This contribution depends on trajectory of movement because it is proportional to the overload. For movements with overload equals to unit and with arbitrary rotation the limit of achievable SINS accuracy, i.e. limited by ineradicable quantum noises of gyros (Gaussian white noises), is following: 1) (55-75) m/h in case of SINS on LG with level of noise (3-4) × 10-4 deg/h1/2; 2) 10 m/h in case of SINS on FOG with level of noise 5 × 10-5 deg/h1/2; 3) less than 1 m/h in case of SINS on AIWB with level of noise 3 × 10-6 deg/h1/2.

Gus'Kov O.B.,RAS Institute of Applied Mechanics
Doklady Physics | Year: 2012

The article considers the problem on the virtual mass of a spherical solid moving with a specified acceleration in a monodispersed suspension of spherical particles for an arbitrary ratio between the sizes of particles and the solid. Within the framework of the dynamics of multiphase media, the problem on the virtual mass of solids of various shapes moving through a dispersed medium arises. In the general case, this problem is not investigated even for the solids of the simplest geometrical shapes. The known theoretical studies and others are devoted to investigation of the dynamics of spherical particles in streams of monodispersed media, when the size of a moving particle is identical to that of suspension particles. The superscripts belong to the particles, and, to distinguish them from an exponent, they are enclosed in parentheses.

Kudryavtsev A.G.,RAS Institute of Applied Mechanics
Physics Letters, Section A: General, Atomic and Solid State Physics | Year: 2013

The Fokker-Planck equation associated with the two-dimensional stationary Schrödinger equation has the conservation law form that yields a pair of potential equations. The special form of Darboux transformation of the potential equations system is considered. As the potential variable is a nonlocal variable for the Schrödinger equation that provides the nonlocal Darboux transformation for the Schrödinger equation. This nonlocal transformation is applied for obtaining of the exactly solvable two-dimensional stationary Schrödinger equations. The examples of exactly solvable two-dimensional stationary Schrödinger operators with smooth potentials decaying at infinity are obtained. © 2013 Elsevier B.V.

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