

Home – Home – Jornals – Journal of Applied Mechanics and Technical Physics 2018 number 3
2018 year, number 3
D. Daghan^{1}, O. Donmez^{2}
^{1}Nigde Omer Halisdemir University, Nigde, Turkey, TR51350 ^{2}American University of the Middle East, Egaila, Kuwait
Keywords: Schamel equation, direct integration, solitons, ionacoustic plasma
Abstract >>
A numerical investigation of the properties of two different ionacoustic solitons has been performed by using analytical solutions of the Schamel equation. A new type of the analytical solution of the Schamel equation that describes soliton propagation with a negative phase velocity has been found for the first time. This new type of the solution has been applied to investigate the physical properties of two different plasmas and to understand the effect of nonextensivity and the effect of trapped electrons on ionacoustic waves in a superthermal plasma. It is shown that the soliton amplitude and width depend on the nonextensivity parameter, superthermality of the electron distribution, and characteristic trapping parameter.

S. D. Gilev, V. S. Prokop'ev
Lavrentyev Institute of Hydrodynamics, Siberian Branch, Russian Academy of Sciences, Novosibirsk, Russia, 630090
Keywords: magnetocumulative generator, cascade systems, generation of electromagnetic energy, magnetic cumulation, inductively coupled circuits, generatorload correlation
Abstract >>
A circuit of a multicascade magnetocumulative generator based on a dynamic variation of the coupling coefficient of inductively coupled circuit is proposed. Each cascade contains two circuits including two pairs of inductively coupled coils. One pair of coils is subjected to simultaneous straining, and one of the coils in the other pair is arranged with the backtoback connection. It is shown that the energy in the load can be gradually increased (from one cascade to another) by using additional cascades. By an example of a twocascade system, the proposed circuit is compared to the known circuits of cascade system design based on the magnetic cumulation principle (generator with a stepup transformer and dynamic transformer). Within the framework of the model that ignores the ohmic resistance of conductors, it is demonstrated that the proposed circuit allows one to obtain a greater energy in the highinductance load than the circuits with the stepup or dynamic transformer owing to a change in the sign of the magnetic flux in the secondary circuit. It is found that the increase in energy in the new circuit is independent of the coupling coefficient (at high values of this coefficient) and become greater as the number of cascades is increased.

V. A. Batishchev
Southern Federal University, RostovonDon, Russia, 344090
Keywords: free boundary, boundary layer, cooling, bifurcation, thermocapillary effect, rotatio
Abstract >>
Rotation bifurcation in a steady axisymmetric thermocapillary flow of an incompressible fluid filling a semiinfinite space bounded by the free surface with a nonuniform distribution of temperature is studied. The fluid flow is calculated on the basis of NavierStokes equations under the assumption of small diffusion coefficients. It is shown that the bifurcation triggers a rotational regime in a thin Marangoni boundary layer in the case of local cooling of the free boundary near the axis of symmetry and in the presence of an external flow; there is no rotation outside this layer. In the case of local heating of the free boundary, rotation is not observed

E. N. Cheremnykh^{1,2}
^{1}Institute of Computational Modeling Siberian Branch, Russian Academy of Sciences, Krasnoyarsk, Russia, 660036 ^{2}Siberian Federal University, Krasnoyarsk, Russia, 660036
Keywords: OberbeckBoussinesq equations, convection, numerical experiments
Abstract >>
This paper touches upon an initialboundaryvalue problem that describes the unidirectional thermogravitational motion of fluid in a plane channel in the case of solid immobile upper and lower walls with temperature distribution thereon and in the case of a heatinsulated upper wall. The motion is caused by a joint effect of the longitudinal temperature gradient and given nonstationary flow rate. The initialboundaryvalue problem is inverse relative to the pressure gradient along the channel. An exact stationary solution is obtained. A solution of the nonstationary problems in Laplace images is determined, and the results of numerical calculations are presented.

V. Sh. Shagapov^{1,2}, A. S. Chiglintseva^{2}, A. A. Rusinov^{3}, M. K. Khasanov^{4}, I. G. Khusainov^{4}
^{1}Institute of Mechanics and Machinery, Kazan, Russia, 420111 ^{2}Mavlyutov Institute of Mechanics, Ufa, Russia, 450054 ^{3}Bashkir State University, Birsk, Russia ^{4}Bashkir State University, Sterlitamak, Russia
Keywords: gas injection, filtration, snow block, selfsimilar solution, hydrate formation, volume region, Leibenson linearization
Abstract >>
The problem of injection of a hydrateforming gas (methane) into a snow block, whose pores in the initial state are saturated by the same gas. Selfsimilar solutions describing the temperature and pressure fields and the snow, hydrate, and gas distributions in the block are constructed. It is shown that three characteristic zones can be distinguished, depending on the initial thermobaric state of the snowmethane system and the rate of gas injection into the filtration region: a near zone, in which snow completely is converted into hydrate and, consequently, the hydrate layer is saturated with gas; an intermediate zone, in which gas, snow, and hydrate are in phase equilibrium; a far zone filled with gas and snow. It is shown that the length of the heated zone decreases with increasing initial snow content in the block and with decreasing injected gas pressure. It is also shown that the length of the region of hydrate formation increases with increasing permeability. It is also noted that the heating of the intermediate zone occurs more rapidly.

V. A. Balashov, E. B. Savenkov
Keldysh Institute of Applied Mathematics, Russian Academy of Sciences, Moscow, Russia, 125047
Keywords: квазигидродинамическая система уравнений, многофазная гидродинамика, диффузная граница, quasihydrodynamic system of equations, multiphase hydrodynamics, diffuse boundary
Abstract >>
A quasihydrodynamic system of equations describing flows of a heatconducting viscous compressible multiphase multicomponent fluid is constructed taking into account surface effects. The system was obtained by generalizing the methods of obtaining a singlephase quasihydrodynamic system and a multicomponent flow model taking into account the surface effects based on the concept of microforces and microstresses. The equations are derived using the ColemanNoll procedure. The results of the calculations show that the constructed model is applicable for modeling multiphase multicomponent flows with allowance for surface effects on the interfaces.

N. M. Nouri, S. Mohammadi, M. K. Neyestanaki, E. Beygi
Iran University of Science and Technology, Narmak, Tehran, Iran
Keywords: осесимметричное погруженное тело, винт в кольцевой насадке, кривизна скелетной линии профиля, спутный след, гидроупругость, разложение по собственным модам, axisymmetric underwater vehicle, ducted propeller, camber ratio, wake flow, hydroelastic, modal analysis
Abstract >>
The effects of the camber ratio on the hydrodynamic and structural behaviors of a NACAbased ducted marine propeller in the wake flow behind an underwater axisymmetric body are numerically studied by computational fluid dynamics methods, in particular, the finite element method. The results are presented in terms of the efficiency, deflection, pressure coefficient, and natural frequencies. It is shown that the wake flow strongly affects the performance of the selected propulsion system. It is shown that the distributions of the camber ratio over the blades of the propeller nonlinearly changes its resistance against cavitation occurrence and deflection, and also changes its hydrodynamic performance and vibrational behavior.

A. N. Nuriev^{1}, A. G. Egorov^{2}, O. N. Zaitseva^{2}
^{1}Nizhny Novgorod State University, Nizhny Novgorod, Russia, 603950 ^{2}Kazan Federal University, Kazan, Russia, 420008
Keywords: вторичные стационарные течения, акустические течения, режимы течения, уравнение НавьеСтокса, численное моделирование, secondary stationary flows, acoustic flows, flow regimes, NavierStokes equation, numerical simulation
Abstract >>
This paper considers methods for controlling secondary flows arising near an oscillating circular cylinder by changing two process control parameters: the dimensionless amplitude and the vibrational Reynolds number. A direct numerical modeling study is performed. It is shown that by varying the indicated parameters in a relatively small range, it is possible not only to intensify mass transfer processes, but also change the direction of the main secondary flows.

V. I. Penkovskii, N. K. Korsakova
Lavrentyev Institute of Hydrodynamics, Siberian Branch, Russian Academy of Sciences, Novosibirsk, Russia, 630090
Keywords: математическая модель, циркуляция крови, нижние конечности, гетерогенная среда, фильтрация, артерии, вены, капилляры, метод конечных элементов, mathematical model, blood circulation, lower limbs, heterogeneous medium, filtration, arteries, veins, capillaries, finite element method
Abstract >>
A mathematical model of blood circulation in human lower limbs is proposed. The model is based on the laws of motion (filtration) of a viscous fluid in a heterogeneous medium consisting of two or more interpenetrating continua. It is assumed that the blood system consists of a distribution network of comparatively large vessels (arterioles) connected to small capillaries and a similarly structured collection network of small capillaries united into larger veins. A system of parabolic differential equations is derived, for which a problem with no initial data is posed. A periodic (in time) solution of the system corresponding to harmonic oscillations defined by the cardiac rhythm is found. Analytical solutions for particular cases of problems following from the general model of blood circulation are obtained. Numerical calculations are performed, and a numerical solution is found for a onedimensional problem with parameters similar to those corresponding to real conditions of blood circulation with allowance for the crosssectional area of the muscular tissue of the lower limb.

M. K. Khasanov^{1}, M. V. Stolpovskii^{2}, I. K. Gimaltdinov^{2}
^{1}Bashkir State University, Sterlitamak, Russia, 453103 ^{2}Ufa State Oil Technical University, Ufa, Russia, 450062
Keywords: пористая среда, газовый гидрат, фильтрация, углекислый газ, porous medium, gas hydrate, filtration, carbon dioxide
Abstract >>
This paper presents the results of numerical modeling of gas hydrate formation upon injection of carbon dioxide into a finitelength reservoir saturated with methane and water. It is shown that at different stages, hydrate formation can occur on both the frontal surface and in a reservoir region of finite length. The effects of pressure on the boundaries of the reservoir and the permeability and initial water saturation of the reservoir on the hydrate formation process were studied. The dependences of the time of the complete conversion of water into gas hydrate state in the entire reservoir on the injection pressure and reservoir permeability were obtained.

A. I. Filippov, O. V. Akhmetova, A. A. Kovalskii
Bashkir State University, Sterlitamak, Russia, 453103
Keywords: волновое уравнение, волновое поле давления, фильтрация, анизотропная среда, коэффициент поглощения, волновое число, фазовая скорость, wave equation, pressure wave field, filtration, anisotropic medium, absorption coefficient, wavenumber, phase velocity
Abstract >>
Analytical frequency dependences of the absorption coefficient, wavenumber, and phase velocity were constructed for filtrationwave fields in a highly permeable interlayer bounded from above and from below by layers having high permeability in the vertical direction. It is shown that as the frequency decreases, the phase velocity of the wave decreases to values below this velocity in the porous medium, and lowfrequency deceleration occurs.

A. M. Bragov, Vl. V. Balandin, V. L. Kotov, Vl. Vl. Balandin, E. Yu. Linnik
Scientific Research Institute of Mechanics, Nizhny Novgorod, Russia, 603950
Keywords: удар, проникание, мерзлый песчаный грунт, конус, сила сопротивления внедрению, обращенный эксперимент, численный расчет, impact, penetration, frozen sandy soil, cone, force of resistance to penetration, reversed experiment, numerical calculation
Abstract >>
A reverse experiment technique is used along with the technology of measuring rods to study the impact and penetration of a steel conical shocker in frozen sandy soil. This paper presents the dependences of maximum values of the force of resistance of cones with base diameters of 10.0, 12.0, and 19.8 mm to penetration into soil on the impact velocity in the range of values 100400 m/s. The numerical solution of the problem in an axisymmetric formulation with the use of the “Dinamika2” software package is used to show the effect of waves reflected from the walls of the container on the contact force. A comparative analysis of the forces of resistance to penetration of the shocker into compacted dry, watersaturated, and frozen sandy soils is carried out.

D. A. Pozharskii
Don State Technical University, RostovonDon, Russia, 344000
Keywords: анизотропия, трансверсальноизотропное тело, контак, anisotropy, transversely isotropic body, contact
Abstract >>
Within the framework of the anisotropic theory of elasticity, a threedimensional contact problem of interaction of two massive transversely isotropic bodies, whose dimensions substantially exceed the size of the contact region. In this case, the isotropy planes of contacting elastic bodies are mutually perpendicular. Exact and numerical solutions of the problem are determined. Calculations for various transversely isotropic materials are carried out.

O. I. Stoyanovskii^{1}, A. N. Maznichevskii^{2}, A. A. Pikarevskii^{1}, E. S. Vasyukova^{2}
^{1}Lavrentyev Institute of Hydrodynamics, Siberian Branch, Russian Academy of Sciences, Novosibirsk, Russia, 630090 ^{2}Limited Liability Company "Laboratory of Special Metallurgy", Chelyabinsk, Russia, 454047
Keywords: износостойкость, дисперсионнотвердеющие стали, аустенизация, карбиды, микроструктура, ускоренный абразивный износ, wear resistance, precipitation hardening steels, austenization, carbides, microstructure, accelerated abrasive wear
Abstract >>
A method of thermal treatment of DI37VI steel exhibiting precipitation hardening is developed with due allowance for the steel microstructure and determining the chemical composition of carbides and the matrix after each operation. In the case of lowtemperature tempering, the mechanical properties of steel are found to be little different from its properties obtained by means of multiple hightemperature tempering (aging); in the latter case, however, the wear resistance of steel in the case of cutting of steel bars is 1.5 times higher. It is demonstrated that the wear resistance of steel is significantly affected by the chemical composition of carbides and the matrix.

G. V. Kozlov, I. V. Dolbin
KabardinoBalkarian State University, Nalchik, Russia, 360004
Keywords: нанокомпозит, полиуретан, углеродные нанотрубки, фрактальная структура, степень усиления, перколяция, nanocomposite, polyurethane, carbon nanotubes, fractal structure, degree of reinforcement, percolation
Abstract >>
A percolation model of nanocomposite reinforcement is under study. It is shown that the degree of reinforcement of polyurethane  carbon nanotube nanocomposites depends on the structure of nanofillers, which are annular formations. This structure is most accurately characterized by its fractal dimension. It is established that the creation of a structure with negative percolation indices allows for a significant increase in the degree of reinforcement of considered nanocomposites at low nanofiller concentrations.

A. M. Lepikhin^{1}, V. V. Moskvichev^{1,2}, A. P. Chernyaev^{2}
^{1}Institute of computational Technologies, Siberian Branch, Russian Academy of Sciences, Krasnoyarsk, Russia, 660049 ^{2}Nauka Special Design and Technological Bureau, Krasnoyarsk, Russia, 660036
Keywords: металлокомпозитный бак, испытания на прочность, повреждения, акустикоэмиссионный контроль, metalcomposite tank, strength tests, damage, acousticemission control
Abstract >>
This paper presents the results of experimental studies of damage accumulation in a metalcomposite highpressure tank in pneumatic strength tests. The deformation and fracture of the composite structure, accompanied by matrix cracking and fiber rupture, are analyzed. It is shown that the cracks and fractures generate acousticemission signals of various types. The results of acousticemission control were used to develop a criterion for ranking tanks based on the strength characteristics of the pressure composite shell.

V. N. Paimushin^{1,2}, V. A. Firsov^{1}, V. M. Shishkin^{3}
^{1}Kazan National Research Technical University named after A. N. Tupolev, Kazan, Russia, 420111 ^{2}Kazan Federal University, Kazan, Russia, 420008 ^{3}Vyatka State University, Kirov, Russia, 610000
Keywords: вязкоупругий материал, ядро наследственности, конечный элемент, метод прямого поиска, целевая функция, viscoelastic material, hereditary kernel, finite element, direct search method, object function
Abstract >>
A technique for identification of hereditary properties under conditions of shorttime creep of Plexiglas is developed. The technique is based on experimental determination of shifting of the center of decaying flexural oscillations of vertically fixed test samples after their preliminary curing in a static bent state. Mathematically, the technique is based on using the finite element method and integral equations of the theory of hereditary viscoelasticity with the KoltunovRzhanitsyn hereditary kernel. An object function is constructed for identification of rheological parameters of this kernel. The minimum of this function is found by the direct search method, which does not require the function gradient to be known. The hereditary kernel of Plexiglas averaged on the basis of data for several test samples is obtained as a function of time.

P. A. Drokin
Institute of Experimental Physics, Sarov, 607190
Keywords: тонкое кольцо, разрушение взрывом, скорость границы области пластического течения, число фрагментов, thin ring, explosion, speed of the boundary of the plastic flow region, number of fragments
Abstract >>
A model of the explosive fragmentation of a thin ring was developed which take into account the statistical dispersion of the destructive relative deformation along the length of the ring. A formula is proposed for calculating the speed of motion of the boundary of the region near the plastic rupture in which the plastic flow of the ring material is stopped. Methods of numerical and analytical calculation of the average number of fragments of the ring were developed. The calculation results were compared with known experimental data.

A. O. Vatulyan^{1,2}, V. V. Dudarev^{1,2}, R. M. Mnukhin^{1}
^{1}Southern Federal University, RostovonDon, Russia, 344090 ^{2}Southern Mathematical Institute, Vladikavkaz, Russia, 362027
Keywords: пьезоэлектрический диск, неоднородные предварительные напряжения, колебания, акустический метод, обратная коэффициентная задача, собственные частоты, piezoelectric disk, inhomogeneous prestresses, vibrations, acoustic method, inverse coefficient problem, natural frequencies
Abstract >>
The problem of steady radial vibrations of a thin electroelastic hollow disk in a preliminary inhomogeneous plane stressstrain state is solved. Vibrations are caused by a potential difference at the electrodes placed on the end surfaces of the disk. Equations of vibrations and boundary conditions are formulated. The preliminary stress state corresponding to the solution of the Lame problem was investigated. The direct problem of determining the displacement function is solved numerically by the shooting method. The inverse problem of determining the prestress parameter from the change in the natural frequency of the disk is formulated and solved. The accuracy of determining the prestressed state for initial put data specified with an error is analyzed.

I. A. Volkov^{1}, L. A. Igumnov^{2}, D. A. Kazakov^{2}, D. N. Shishulin^{3}, I. S. Tarasov^{1}
^{1}Volga State University of Water Transport, Nizhny Novgorod, Russia, 603950 ^{2}Scientific Research Institute of Mechanics, Nizhny Novgorod, Russia, 603022 ^{3}Nizhny Novgorod State Technical University, Nizhny Novgorod, Russia, 603950
Keywords: нестационарная ползучесть, математическое моделирование, сложное нагружение, поверхность ползучести, материальные параметры, численный и натурный эксперименты, nonstationary creep, mathematical simulation, complex loading, creep surface, material parameters, numerical and fullscale experiments
Abstract >>
A mathematical model describing the nonstationary creep of metals under complex loading is proposed. The results of numerical simulation of creep of St.304 steel in complex regimes of block multiaxial cyclic deformation are given. The numerical calculation results obtained are compared with the data of fullscale experiments. Creep is simulated in complex deformation processes accompanied by the rotation of main regions of stress, strain, and creep strain tensors.

A. M. Orishich^{1}, A. G. Malikov^{1}, E. V. Karpov^{1,2}, N. A. Pavlov^{1}, I. S. Mesenzova^{1}
^{1}Khristianovich Institute of Theoretical and Applied Mechanics, Siberian Branch, Russian Academy of Sciences, Novosibirsk, Russia, 630090 ^{2}Lavrentyev Institute of Hydrodynamics, Siberian Branch, Russian Academy of Sciences, Novosibirsk, Russia, 630090
Keywords: лазерная сварка, алюминиеволитиевый сплав, закалка, искусственное старение, прочность, пластичность, микроструктура, фазовый состав, laser welding, AlLi alloy, hardening, artificial aging, strength, plasticity, microstructure, phase composition
Abstract >>
Laserassisted welding of the 1420 alloy of the AlMgLi system is experimentally studied for the purpose of its optimization. Various regimes of thermal treatment of nondetachable joints obtained by means of laser welding are considered. Thermal treatment modes that allow significant enhancement of the welded joint density as compared to the asreceived alloy are chosen. The ultimate normalized elongation of samples after aging is found to decrease by a factor of 3.

A. G. Kolpakov^{1}, S. I. Rakin^{2}
^{1}Siberian State University of Telecommunications and Information Sciences, Novosibirsk, Russia, 630102 ^{2}Siberian State Transport University, Novosibirsk, Russia, 630049
Keywords: упругость, концентрация напряжений, сварной шов, ячеечная задача, elasticity, stress concentration, weld seam, cell problem
Abstract >>
It is shown that a weld seam formed during explosion welding at a microlevel (at a wavelength of the order of several hundred micrometers) has a wavy geometry. Stress concentration caused by local geometry of the seam is calculated for various shapes and amplitudes of the weld seam wave and combinations of joined materials.

