Combined effect of boron alloying and ausforming on austenite transformation in low carbon steels under continuous coolingA.A. Vasilyev, D.F. Sokolov, S.F. Sokolov, A.A. Zisman & N.G. Kolbasnikov
The combined effect of boron addition and ausforming on the structure of low carbon low alloyed steel after the transformation of austenite has been investigated in a wide range of cooling rates. It is shown that boron hinders formation of polygonal ferrite in continuous cooling regardless of austenite predeformation and suppresses appearance of acicular ferrite. A qualitative explanation of this effect is proposed in terms of the deformation induced boron segregation on boundaries of austenite...
Investigation and modeling the austenitization kinetics of steels with complex microstructure under continuous heatingA.A. Vasilyev, D.F. Sokolov, S.F. Sokolov & A.I. Rudskoy
An experimental investigation of the austenitization under continuous heating of various microstructures of 8 industrial steel grades with wide range of chemical compositions was carried out. A quantitative mathematical model describing the austenitization kinetics of the steels with complex microstructure and predicting austenite grain size in dependence on the chemical composition, volume fractions of structural components (ferrite, pearlite, bainite, martensite), ferrite grain size and heating rate, was developed. Values of the model empirical parameters were...
Employment of Eulerian, Lagrangian, and arbitrary Lagrangian-Eulerian description for crack opening problemE.A. Ivanova, D.V. Matyas & M.D. Stepanov
Numerical study of crack opening in the solid material of rock formation is presentedin this article. Initially introduced straight-line crack is widened by increasing internal pressure. The crack shape evolution resembles hydraulic fracturing and is considered as a transient process. Commercial code LS-DYNA was employed to obtain solutions by three types of descriptions, they are compared to the solution obtained in Eulerian description by a program based on the finite-volume method and written in Python...
TERAHERTZ EMITTERS BASED ON NEGATIVE-U MATERIALSFOR MEDICAL APPLICATIONSN.T. Bagraev, P.A. Golovin, V.S. Khromov, L.E. Klyachkin, A.M. Malyarenko, V.A. Mashkov, B.A. Novikov, A.P. Presnukhina, A.S. Reukov & K.B. Taranets
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.
Isomeres and isotopes of carbonAlexander I. Melker
The nuclear geometry has been developed by analogy with the fullerene geometry. On the base of this geometric approach, the structure of carbon isomers and isotopes, which can be obtained by means of nuclear synthesis, has been designed. The mechanisms of possible nuclear reaction are discussed. Carbon is an unusual element. It has four isomers of different symmetry: three-fold, six-fold and tetrahedral ones, two being stable and one halfstable. The isotopes of carbon inherit the...
Development of a composite hatch coverD. Mamchits, А. Nemov, A. Karandashev, D. Büchler, R. Vasilyev & M. Ignatiev
Two designs of a composite marine hatch cover were developed on the basis of the design of a steel one. One of the proposed designs features composite structure made by means of manual lay-up technology, and the other one is based on a truss composite structure which can be produced by rod winding process. Selection of the most rational materials and design parameters was carried out on the basis of finite element simulations and use...
Simple Wigner-Langevin equationAndrey L. Sanin
A new dynamical equation is derived by substituting the Schrödinger-LangevinKostin equation into the definition for the Wigner function, it can be called the quantumclassical Wigner-Langevin equation. The proposed equation contains partial derivatives for time and phase space variables of the Wigner function, its coefficients are spatial derivatives of potentials that take into account friction, white noise and external influence. The transition to the classical regime of motion is also discussed.
Nuclear geometry: from hydrogen to boronAlexander I. Melker
Possible ways of nuclear synthesis in the range from hydrogen to boron are studied. The geometric model of these nuclei is suggested. The basis for this model is the analogy between tetrahedral fullerene C4 and helium 2He4 . It is assumed that a nucleus of helium 2He4 has the form of a tetrahedron, where: 1) All the apices are equivalent and therefore they are protons, 2) Each neutron in a nucleus decomposes into a proton...
Migration of nonequilibrium grain boundaries in metal-graphene composites with ultrafine-grained matrixS.V. Bobylev
We propose a theoretical model describing stress-induced migration of nonequilibrium grain boundaries constrained by the presence of second phase inclusions in metal-graphene composites with the ultrafine-grained matrix. Within the framework of the model, the structure of nonequilibrium boundaries is represented as a combination of dislocation structure of equilibrium boundary and dislocations introduced from outside, trapped by the boundary during deformation. Using the disclination theory approach, a change in the energy of the system associated with...
NUCLEATION AND GROWTH OF FULLERENES AND NANOTUBES HAVING FOUR-FOLD SYMMETRYAlexander I. Melker, Maria A. Krupina & Aleksandra N. Matvienko
We have studied possible ways of generating and growing the fullerenes having four-fold symmetry. Beginning with cyclobutane C4H8 and clusters C8, we obtained elementary fullerenes C8 and mini-fullerenes C16, which produce the following fullerenes from C24 to C64, perfect (basic) and imperfect, as well as nanotubes. The imperfection is connected either with extra 'interstitial' or 'vacancy' carbon dimers, both types of dimers playing the role of defects. Only the basic fullerenes C24, C32, C40, C48,...
The mechanical properties improvement of thermoplastics-based fiber metal laminatesDmitry Goncharenko, Ilya Kobykhno, Elizaveta Bobrynina & Oleg Tolochko
This study investigated the possibility of increasing the fiber metal laminates mechanical properties by improving the impregnation quality due to the addition of a different number of layers of polymer film on the prepreg-metal interface. Specimens were made based on two thermoplastic polymers (polyamide-6 and polypropylene), glass fibers (E-glass), and aluminum alloy (AlMg6) by hot pressing. The theoretical calculation was performed for the tensile strength according to the rule of mixtures. The dependences of tensile...
Deformation mechanism of bimodal metal-graphene composites with nanotwinned structureN.V. Skiba
The theoretical model is suggested which describes micromechanisms of plastic deformation in bimodal metal-graphene composite consisting of large grains embedded into nanocrystalline/ultrafine-grained metal-matrix reinforced by graphene inclusions. In the framework of the model, lattice dislocation slip and grain boundary sliding has occurred in nanocrystalline/ultrafine-grained matrix, and lattice dislocation slip and migration of twin boundaries are realized in large grains with a nanotwinned structure providing the plastic deformation of bimodal metal-graphene composite. With this assumption, the...
Modeling of carbides and copper particles precipitation during tempering of bainitic-martensitic Cr-Mo-V-Cu steelsA.A. Vasilyev, S.F. Sokolov & D.F. Sokolov
The paper represents a model for the tempering effects on quenched bainitic-martensitic steels that describes both the recovery and precipitation phenomena. The latter involves various carbides (Fe3C, V4C3, Mo2C, Cr7C3) and particles of pure Cu. Thermodynamic driving forces in the nucleation of the considered particles have been calculated using empirical formulas obtained with the Thermo-Calc software. The predicted formation kinetics for the considered carbides and Cu particles complies well with relevant experimental data.
On a configurational force driving surface growth of solidsA.B. Freidin & Y.O. Izmaylova
Surface growth of solids includes a wide variety of processes starting from additive manufacturing technologies and ending with plenty of biological problems. Model of surface growth based on the expression of the configurational force, derived from fundamental laws and entropy inequality, is offered in the present paper. A new expression for the configurational force called surface growth force, which controls growth and resorption, is used. Analysis of the applicability of the developed model was carried...
Selective laser melting of copper alloyI.A. Polozov, E.V. Borisov, V.Sh. Sufiiarov & A.A. Popovich
Additive Manufacturing (AM) of copper and its alloys is a promising way to produce parts with complex geometries without tooling. One of the AM processes is Selective Laser Melting (SLM) technology that uses a laser beam to fuse powder layers to obtain a final part. Laser processing of copper is considered to be a challenging task due to its high thermal conductivity and poor laser absorptivity. In the present work, Cu-Cr-Zr-Ti alloy powder has been...
Physical fundamentals of thermomechanical processing in ultrafine-grained metallic materials manufacturingА.I. Rudskoi, G.Е. Коdzhaspirov, J. Kliber, Ch. Apostolopoulos & D.A. Kitaeva
The processing of metallic materials through the application Thermomechanical Processing (TMP) has now become of major importance in the world research and industrial companies. A great attention is paid to study of mechanism TMP applied to different techniques and technological processes providing ultrafine-grained state of metal materials including submicro – and nanocrystalline ones. The main development in terms of obtaining bulk metallic materials received in the recent years, various schemes of TMP of metallic materials,...
Asymptotics of a thermal wave in one-dimensional harmonic crystalA.M. Krivtsov, E.A. Podolskaya & V.Yu. Shubina
An asymptotic representation is obtained at large times for the thermal wavefront propagating in a one-dimensional harmonic crystal. The propagation of thermal waves from a localized thermal perturbation and the transition zone between regions with different temperatures is considered. An explicit solution is given for a number of the simplest forms of the initial temperature distribution. It is shown that during the wave evolution, the wavefront smoothes, e.g., for a power-law dependence its degree increases...
Growth of thick gallium oxide on the various substrates by halide vapor phase epitaxyA.V. Kremleva, Sh.Sh. Sharofidinov, A.M. Smirnov, E. Podlesnov, M.V. Dorogov, M.A. Odnoblyudov, V.E. Bougrov & A.E. Romanov
EXPERIMENTAL STUDY AND MODELING OF PRE-DEFORMATION EFFECT ON AUSTENITE TO FERRITE TRANSFORMATIONA.A. Vasilyev, D.F. Sokolov, S.F. Sokolov & A.A. Zisman
Transformation kinetics of undeformed and deformed austenite during continuous cooling has been investigated on several industrial steels. Dimensions of both prior austenite grains and ferrite grains in ferrite-pearlite structures obtained for various states of parent austenite and cooling rates were determined. Based on the obtained experimental data a physically motivated model is formulated for the ferritic transformation with allowance for the effects of deformation and concurrent recovery of austenite. Under consideration is the deformation influence...
3D finite element, connected with orthogonal finite functions, in modeling and investigation of elastic homogeneous and heterogeneous materialV.L. Leontiev & I.V. Efremenkov
A novel 2D finite element (FE) associated with orthogonal finite functions (OFF, orthogonal splines) was developed for the ANSYS software and was tested early. The expansion of this method is presented here. The novel 3D FE, connected with 3D OFF is proposed for modeling and investigation of the stress-strain state of homogeneous and heterogeneous elastic bodies. The accuracy of the solutions obtained with this 3D FE is as high as for the classic ANSYS 3D...
Natural isomers of fullerenes from C30 to C40Alexander I. Melker, Aleksandra N. Matvienko & Maria A. Krupina
We have systematized possible ways of forming the isomers of midi-fullerenes, namely C30, C32, C34 C36, C38 and C40. Similar to the isomers of midi-fullerenes from C20 to C28, there are three the most natural mechanisms of their formation: 1) Embedding carbon dimers into initial fullerenes; 2) Fusion of carbon cupolas having the same symmetry; and 3) Fusion of fullerenes having compatible symmetry. The energies of the fullerenes calculated through the use of molecular mechanics...
Natural isomers of fullerenes from C20 to C28Alexander I. Melker & Aleksandra N. Matvienko
We have systematized possible ways of forming the isomers of midi-fullerenes, namely C22, C24, C26 and C28. There are three the most natural mechanisms of their obtaining: embedding carbon dimers into initial fullerenes; fusion of carbon cupolas having the same symmetry; fusion of fullerenes having compatible symmetry. The minimum energy fullerenes are obtained through the use of the first mechanism. It is worth noting that these fullerenes conserve the topological three-fold symmetry. At the same...
ASYMPTOTICAL REGIMES OF THE HYDROFRACTURING PLANAR 3D MODELE.V. Shel
In the proposed paper the Planar 3D model of hydraulic fracturing was investigated. All of the hydraulic fracturing equations were substituted into the mass conservation law and scaled. Nontrivial dimensionless parameters of the problem were found. Asymptotic regimes of the equation, the Radial or the Pseudo3D model, correspond to the infinitely small or the infinitely large dimensionless parameters. Thus, the limiting conditions of these models were found in the terms of the dimensionless parameters.
Laser-driven metal alteration for glucose detection sensorA. Kondrateva, V. Babyuk, D. Strekalovskaya, L. Filatov, P. Gabdullin, O. Kvashenkina, Y. Prokopenko, A. Gruzdev, K. Petruhno & A. Kuznetsov
In this work, an experimental comparison of the laser-driven alteration of nickel, copper, and steel surface efficiency was carried out. The selection of the material most suitable for non-enzymatic measurement of the glucose amount in the medium was carried with respect to surface modification efficiency. The electrooxidative activity of the fabricated structures with a modified surface was investigated with respect to the glucose addition to a 0.1 M solution NaOH by potentiostatic method. The modified...
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Peter the Great St. Petersburg Polytechnic University49
Institute of Problems of Mechanical Engineering7
University of Patras2
St Petersburg University2
Institute of Macromolecular Compounds1
University of Virginia1
Saint Petersburg Mining University1
Saint Petersburg State University1