https://www.elibrary.ru/title_about_new.asp?i 1605-8119 44 2 2020 1-112

RAR RUS 159-163 FSBEI HPE “Kh.M. Berbekov Kabardino-Balkarian State University” Kozlov

Nalchik, Russia

FSBEI HE “Kh.M. Berbekov Kabardino-Balkarian State University” Dolbin

Nalchik, Russia

Nanocomposites polymer/graphene stiffness Dependence on the nanofiller structure: the fractal model The dependence of the elastic modulus of the nanofiller for polymer/graphene nanocomposites on the structure of graphene aggregates has been shown. It is established that this structure is defined by the dimension of Euclidean space, in which these aggregates are formed. The indicated structure is most accurately characterized by its fractal dimension. 10.18720/MPM.4422020_1 nanocomposite graphene structure aggregation fractal dimension Euclidean space modulus of elasticity https://mpm.spbstu.ru/article/2020.76.1/ MPM244_01_kozlov.pdf

RAR RUS 164-171 ITMO Univesity Kremleva

St.Petersburg, Russia

Ioffe Institute Sharofidinov

St.Petersburg, Russia

ITMO University Smirnov A.M.

St.Petersburg, Russia

ITMO University Podlesnov

St.Petersburg, Russia

Togliatti State University Dorogov Maksim

Togliatti, Russia

Peter the Great St. Petersburg Polytechnic University Odnoblyudov

St.Petersburg, Russia

ITMO University V.E. Bougrov

St.Petersburg, Russia

F-1445-2014 7202768874 0000-0003-3738-408X ITMO University Romanov Alexey alexey.romanov@niuitmo.ru

St.Petersburg, Russia

Growth of thick gallium oxide on the various substrates by halide vapor phase epitaxy In this work, we report on the results of structural characterization of α- and β-Ga2O3 layers grown on various substrates: Al2O3, AlN/Al2O3 and AlN by halide vapor phase epitaxy. Scanning electron microscopy analysis is used to control the thickness of the Ga2O3 layers. The maximum achieved thickness is 46 µm, this is for α-Ga2O3 grown on the bulk AlN substrate. X-ray analysis is used to find the crystallographic orientation of the layers and to characterize the structure quality of the samples. Measured full-width at highmaximum of rocking curves of 15' and 56' confirms crystal quality of the grown α-Ga2O3 and β-Ga2O3 layers on AlN and AlN/Al2O3 substrates, correspondingly. Using AlN as substrate material or buffer AlN layer leads to an increase of Ga2O3 layer thickness and crystal quality in comparison to the layers grown on Al2O3 substrate. 10.18720/MPM.4422020_2 Wide-bandgap semiconductor monoclinic gallium oxide trigonal gallium oxide halide vapor phase epitaxy scanning electron microscopy X-ray analysis https://mpm.spbstu.ru/article/2020.76.2/ MPM244_02_kremleva.pdf

RAR RUS 172-185 59122315900 0000-0002-1572-2108 Kurukshetra University Kumar Rajneesh

Kurukshetra, India

H.P. University Vohra

Shimla, HP, India

Steady state response due to moving load in thermoelastic material with double porosity The present study is to focus on the steady state response due to moving load in a homogeneous, isotropic thermoelastic material with double porosity in the context of Lord-Shulman theory [1] of thermoelasticity with one relaxation time. The load is moving at a constant velocity along the one of the coordinate axis. Fourier transform has been applied to obtain normal stress, tangential stress, equilibrated stresses and temperature distribution. The resulting expressions are obtained in the physical domain by using numerical inversion technique. Numerically computed results for these quantities are depicted graphically to study the effect of porosity for normal force and thermal source. Some particular cases are also deduced from the present investigation. 10.18720/MPM.4422020_3 thermoelasticity double porosity moving load Fourier transform https://mpm.spbstu.ru/article/2020.76.3/ MPM244_03_kumar.pdf

RAR RUS 186-209 Federal Science Center Scientific Research Institute for System Analysis of Russian Academy of Sciences Betelin

Moscow, Russia

Federal Science Center Scientific Research Institute for System Analysis of Russian Academy of Sciences Galkin

Moscow, Russia

V.I.Shpilman Research and Analytical Center for the Rational Use of the Subsoil Shpilman

Tyumen, Russia

Federal Science Center Scientific Research Institute for System Analysis of Russian Academy of Sciences Smirnov

Moscow, Russia

Digital core simulator - a promising method for developming hard-to-recover oil reserves technology Territory of Russia, which occupies 12.8% of the Earth's territory, contains 12-13% of the forecast resources, and about 12% of the discovered oil reserves. Russia's proven oil reserves amount to approximately 13.9 billion tons of oil as of January 1, 2017 (~101 billion barrels). Oil recovery factor for proved reserves is ~17%. The increase of oil recovery factor represents a huge stockpile for raising the level of oil production in the country at low costs. Creation of improved core-simulator designed for indigenous supercomputers, with the opportunity to take advantage of various methods of speeding up the numerical simulations process is one of the most burning issues in the development of strategic reserves of hydrocarbons in our country. The paper gives a coverage of results of computer simulations of different strategies relevant to enhancing oil recovery from host rock formations. 10.18720/MPM.4422020_4 oil deposit oil reserves oil recovery factor numerical simulations coresimulator micro-scale https://mpm.spbstu.ru/article/2020.76.4/ MPM244_04_betelin.pdf

RAR RUS 210-220 St.Petersburg State University Smirnov

St.Petersburg, Russia

Lobachevsky State University of Nizhni Novgorod Konstantinov

Nizhny Novgorod, Russia

Evaluation of critical stresses for quasi-brittle materials at various loading rates Engineering practice shows that the design of modern structures and technical components requires adapting existing methods for testing materials to dynamic load conditions. This work discusses the experimental and theoretical basis for determining and predicting critical stresses in quasi-brittle materials (such as concrete, rock, organic glass, etc.) over a wide range of loading rates provided by different test methods and equipment. Standard tests for compression, splitting and bending are presented. The incubation time approach is used as a unified approach for determining the dynamic strength of the materials. It is shown that critical stresses in the materials under a wide range of high-speed loads can be estimated based on two strength parameters. 10.18720/MPM.4422020_5 quasi-brittle materials dynamic tests strain rate dependence dynamic strength structural-temporal approach incubation time https://mpm.spbstu.ru/article/2020.76.5/ MPM244_05_smirnov.pdf

RAR RUS 221-228 Tampere University Vatanshenas

Tampere, Finland

Seismic Isolation and Vibration Control Products Development Department, Bridgestone Corporation Mori

Japan

Tampere University Farhadi

Tampere, Finland

Tampere University Länsivaara

Tampere, Finland

Stress-strain hysteresis shape estimation of different soils using deformation-history integral (DHI) model Different soils show different nonlinear stress-strain patterns. Hence, it is difficult to come up with a general model to predict these shapes. This study investigated the suitability of the DHI model which was not originally formulated for geomaterials. This model was applied to different loading cycles of various types of soils and the model’s variables were optimized using nonlinear generalized reduced gradient (GRG) method. Up to five hysteresis springs were considered in the study. The computed error criteria indicated that the DHI model approximated the nonlinear hysteresis shapes appropriately and using three hysteresis springs presented the best estimation for almost all cases. In addition, this model approximated the initial loading cycles better than the final ones. 10.18720/MPM.4422020_6 cyclic direct simple shear (CDSS) test DHI model dynamic loading nonlinear plasticity optimization soil modeling https://mpm.spbstu.ru/article/2020.76.6/ MPM244_06_vatanshenas.pdf

RAR RUS 229-237 Institute for Problem in Mechanics RAS (IPMech RAS) Shpenev

Moscow, Russia

Temperature effect on the process of wear of a fibrous composite under high load conditions A model of the fibrous composite material friction and wear process is constructed taking into account the heating of the friction surface. The inhomogeneous temperature expansion of the composite components and the resulting fiber/matrix slippage near the friction surface and the friction surface profile change is considered. The influence of temperature on the distribution of stresses in the fiber and matrix and on the roughness of the friction surface of the composite is determined. 10.18720/MPM.4422020_7 composite mechanics composite wear composite friction tribology https://mpm.spbstu.ru/article/2020.76.7/ MPM244_07_shpenev.pdf

RAR RUS 238-249 Karunya University Selvamani

India

Vibration of a hydrostatic stressed piezoelectric layer embedded on gravitating half space with sliding interface boundary In this paper, an analytical model is developed to study the influence of initial hydrostatic stress and piezo elasticity on elastic waves in a piezoelectric layer embedded on a gravitating half space with slip interface. The piezo electric layer considered for this study is hexagonal (6mm) material. The problem is described using equations of linear elasticity with initial hydrostatic stress and piezo elastic inclusions. Displacement functions in terms of velocity potential are introduced to separate the motion's equations and electric conduction equations. The frequency equations are obtained by stress free and electrically shorted boundary conditions at the gravitating half space. The numerical computation is carried out for the PZT-4A material. The obtained results are presented graphically to show the effect of piezo elastic coupling and hydrostatic stress on the elastic waves. 10.18720/MPM.4422020_8 elastic waves piezoelectric layers hydrostatic stress slip interface NEMS https://mpm.spbstu.ru/article/2020.76.8/ MPM244_08_selvamani.pdf

RAR RUS 250-255 Peter the Great St. Petersburg Polytechnic University Arutyunyan A.R.

St.Petersburg, Russia

Saint Petersburg State University Arutyunyan R.A. R.A.

St.Petersburg, Russia

Damage and fracture of viscous-plastic compressible materials Experimental creep curves and long-term strength curves for viscoelastic compressible materials have been obtained at room temperature for a wide range of stresses. The residual density change (loosening) of the material is considered as the main damage factor. A modified creep equation for the loosening medium is proposed, which can describe the second and third regions of the creep curve. Based on proposed equation the criterion of long-term strength is formulated. It is shown that in the region of relatively high stresses and under the assumption of incompressibility of the material, this criterion coincides with the known Hoff law of viscous fracture. 10.18720/MPM.4422020_9 polymer materials poly methyl methacrylate pores cracks crazing loosening damage creep density changes creep curve fracture long-term strength criterion https://mpm.spbstu.ru/article/2020.76.9/ MPM244_09_arutyunyan.pdf

RAR RUS 256-263 Peter the Great St. Petersburg Polytechnic University Arutyunyan A.R.

St.Petersburg, Russia

Influence of aging on fatigue and creep properties of polyurethane Polymers and polymer-based materials are intensive implemented in many areas of engineering practice. These applications frequently have a very high performance demand, which makes their long-term characteristics of paramount importance. These materials were subject to degradation due to environmental factors, including light, temperature, stress, and others. Because of aging process, the physical and mechanical properties of these materials are significantly changed. This paper is devoted to the experimental investigations of this problem. The research program includes experiments on alternating of fatigue, creep, longterm climatic and deformation aging of polyurethane specimens. Results have shown the effect of considerable hardening and embrittlement during the aging process. 10.18720/MPM.4422020_10 polymer materials polyurethane degradation climatic aging deformation aging fatigue creep effective time parameter https://mpm.spbstu.ru/article/2020.76.10/ MPM244_10_arutyunyan.pdf

RAR RUS 264-270 Almazov National Medical Research Centre Reukov

St.Petersburg, Russia

Peter the Great St. Petersburg Polytechnic University Taranets

St.Petersburg, Russia

0000-0001-8286-3472 Ioffe Institute Bagraev N.T.

St.Petersburg, Russia

Peter the Great St. Petersburg Polytechnic University Golovin

St.Petersburg, Russia

Ioffe Institute Khromov

St.Petersburg, Russia

0000-0001-7577-1262 Ioffe Institute Klyachkin L.E.

St.Petersburg, Russia

0000-0002-4667-7004 Ioffe Institute Malyarenko A.M.

St.Petersburg, Russia

Peter the Great St. Petersburg Polytechnic University Mashkov

St.Petersburg, Russia

Dipole Structures LLC Novikov

St.Petersburg, Russia

Almazov National Medical Research Centre Presnukhina

St.Petersburg, Russia

Terahertz emitters based on negative-U materials for medical applications The characteristics of terahertz (THz) irradiation generated by a silicon nanosandwich structure under the conditions of a stabilized drain-source current are demonstrated. The frequency of irradiation arising from the quantum Faraday effect is determined by the parameters of microcavities embedded in the edge channels of a silicon nanosandwich structure confined by the negative-U centers. The obtained characteristics of a compact THz irradiation source determine the basis for highly effective medical applications. 10.18720/MPM.4422020_11 silicon nanosandwich structure negative-U centers terahertz irradiation IR Fourier spectrometer https://mpm.spbstu.ru/article/2020.76.11/ MPM244_11_bagraev.pdf