49 Works

Rotary actuator control based on tensile force elements made of shape memory Cu-Al-Ni crystals when operated in a cyclic mode

A.I. Priadko, S.A. Pulnev, O.O. Kovalev & I.A. Ilin
An actuator design and a function scheme are developed. A control algorithm of a cyclic actuator is considered. We provide experimental results on the control algorithm and the actuator. The actuator operating range is 60°. The actuator sped is ~ 1 degree/second. The actuator operating is stable in any rotation angle in operating range.

Corrosion resistance and mechanical performance of steel reinforcement, before and after shot-blasting process

Ch. Apostolopoulos, Arg. Drakakaki, А.I. Rudskoi, G.Е. Коdzhaspirov & Alk. Apostolopoulos
As it is widely known, corrosion of steel reinforcement is one of the main causes of deterioration of the reinforced concrete structures. Corrosion phenomena combined with seismic loads aggravate the situation. For this reason, in the present paper, an effort is made to upgrade the performance of steel reinforcement against corrosion, using the shot blasting method. Precisely, two groups of specimens were prepared, one of which had previously been shot blasted. Afterwards, the specimens were...

Heating and destruction of biological tissue by high-inensity focused ultrasound

T.A. Andreeva, A.E. Berkovich, N.Y. Bykov, S.V. Kozyrev & A.Ya. Lukin
Processes of heating and destruction of the breast fat tissue under the action of focused high-intensity ultrasound generated by a 128-element transducer are considered. The simulation of a thermal problem is carried out by anumerical solution of the heat transfer equation. The acoustic pressure field in the tissue is calculated using the Rayleigh integral. A system of dimensionless scaling parameters is proposed to describe the non-stationary process of heat propagation. The influenceof the space localization...

Micromechanics, nanophysics and non-destructive testing of the strength of structural materials

V.V. Nosov, I.E. Chaplin, E.R. Gilyazetdinov, E.V. Grigoriev & I.A. Pavlenko
Non-destructive testing of the strength of structural materials is currently based on the correlation between the results of laboratory tests of the strength of standard macro samples and the strength characteristics of the material in a real object. The heterogeneity of the strength properties of different zones of the material makes this correlation ambiguous, introducing uncertainty in the test results. The solution of the problem relates to the necessity of transition to the micro- and...

SIMULATION OF INVERSE HALL-PETCH RELATION IN NANOCRYSTALLINE CERAMICS BY DISCRETE DISLOCATION DYNAMICS METHOD

S.V. Bobylev
A theoretical model of plastic deformation of nanocrystalline ceramics in the region of small grain sizes is proposed. In the framework of the model, deformation is described as the combined action of grain boundary sliding and emission of lattice dislocations from triple junctions of grain boundaries. Using the method of discrete dislocation dynamics we obtained an inverse Hall-Petch relation, which qualitatively coincides with the experimentally measured dependences of microhardness in nanocrystalline ceramics with extremely small...

ALGORITHM FOR POSITIONING OF ROTARY ACTUATORS BASED ON SHAPE MEMORY Cu-Al-Ni TENSILE FORCE ELEMENTS

A. Priadko, S. Pulnev, O. Kovalev & I. Ilin
This paper considers positioning algorithms for rotary actuators based on shape memory Cu-Al-Ni crystals. The actuator function scheme is provided. An algorithm for positioning of the actuator based on an actual rotary angle has been developed. Experimental results on the control algorithm and the actuator are presented. The functional characteristics of the actuator (rotation speed and positioning accuracy) are considered.

Axial misfit stress relaxation in core-shell nanowires with hexagonal core via nucleation of rectangular prismatic dislocation loops

S.A. Krasnitckii, A.M. Smirnov, K.D. Mynbaev, L.V. Zhigilei & M.Yu. Gutkin
A theoretical model of axial misfit stress relaxation in core-shell nanowires with hexagonal cross section of the core through the nucleation of prismatic dislocation loops is suggested. Different nucleation sites of the loops in core-shell nanowires are considered. The energy change caused by the loop nucleation is calculated. The critical condition for the onset of the loops is given and analyzed in detail. The most favorable sites in nanowires and the optimal loop shape are...

NUCLEAR GEOMETRY: SODIUM, MAGNESIUM, ALUMINUM

Alexander I. Melker
The nuclear geometry has been developed by analogy with the fullerene geometry. On the basis of this geometric approach, it was possible to design the structure of sodium, magnesium and aluminum isomers and their isotopes, which can be obtained by means of nuclear synthesis. The most stable nuclei can be classed into two groups: basic nuclei having equal number of protons and neutrons and isotopes having one or two more neutrons. The latter ensure their...

Modeling microstructure evolution during thermomechanical processing and heat treatment of steels and predicting their mechanical properties

A.A. Vasilyev, D.F. Sokolov & S.F. Sokolov
An integral computer model/program AusEvol Pro was developed to describe the evolution of steel microstructure during thermomechanical processing (hot rolling, forging), as well as subsequent heat treatment (normalization, tempering), and to evaluate the final mechanical properties (yield stress, tensile stress, elongation), hardness and impact toughness. The program implements a set of physically based models that allow quantitative description of all significant processes of steel structure formation with account of the effects of chemical composition both...

Nano- and microparticle aggregation: unique optical vectors for control

Alexandra G. Bezrukova & Olga L. Vlasova
The multiparameter analysis of simultaneous optical data for systems of nano- and/or micro-particles (3D disperse systems, dispersions, colloids, ensembles with the average diameter less than 10 micrometers) can be presented as the system characteristics characterized by N-dimensional unique vectors of optical parameters that can elucidate changes in the state of system particles. The application of ND unique optical vector approach is shown for several biomedical dispersions at the processes of aggregation. This approach can serve...

Natural isomers of fullerenes from C4 to C20

Alexander I. Melker & Aleksandra N. Matvienko
We have systematized possible ways of forming the isomers of mini-fullerenes, namely elementary fullerenes: tetrahedron C4, triangular prism C6, cube C8, pentagonal prism C10, hexagonal prism C12, as well as their derivatives, which were obtained by joining elementary fullerenes. Combined with the graph analysis, this approach allows obtain a clear knowledge of their structure. Among them there are barrel-shaped fullerenes: C12, C16, C20; tetrahedral ones C12 and C16; bi-shamrocks C14 and C18, bipyramids C14 and...

Element-free numerical modeling with discrete gradient and its application to crystal defects

A.A. Zisman
The gradient operation has been extended to discrete data in terms of nodal coordinates. On this ground, the nodal strains and related stresses are expressed directly in terms of nodal displacements and the stress divergence in terms of nodal stresses. To make use of truly discrete modeling in computational solid mechanics, the stress balance equation is formulated. For a case study, the latter is applied to an edge dislocation where atom positions of a dislocated...

Crystallographic texture of industrial automotive steels and effect of tertiary cementite dissolution on its development

Alexander A. Vasilyev, N.Y. Zolotorevsky, Dmitry F. Sokolov & S.A. Philippov
X-ray investigation of crystallographic texture and its correlation with r m value (Lankford coefficient) was performed on a representative set of industrial automotive steels of different grades. Though the majority of steels had the structure of polygonal ferrite with small fractions of pearlite in the hot rolled condition, steels with a more complex structure were also included in the study. For this set of steels, a linear dependency has been shown to hold between r...

Experimental study and modeling of changing mechanical properties in tempering of bainitic-martensitic steels

A.A. Vasilyev , D.F. Sokolov & S.F. Sokolov
Dependences of mechanical properties (yield stress, tensile stress, relative elongation) and impact toughness on the tempering time at various temperatures have been investigated for 10 industrial bainitic-martensitic steels with a wide range of chemical compositions (C(0.04-0.27), Mn(0.33-1.57), Si(0.22-1.09), Cr(0.02-1.14), Ni(0.01-3.74), Cu(0.02-1.03), Mo(0.01-0.43), Nb(0.002-0.044), V(0.003-0.200), Ti(0.001-0.045), B(≤0.003) (mass.%)). Based on the obtained experimental results, a quantitative model is developed to predict the mechanical properties of the considered steels after tempering. The modeling results comply well with...

Epoxy-polyester coatings with additives of PTFE particles and nanoparticles of SiO2

G.V. Vaganov, V.V. Vaganov, A.Yu. Kolesnikova, E.A. Serikova & E.M. Ivan'kova
Hydrophobic and super-hydrophobic coatings based on epoxy-polyester powder compositions modified with polytetrafluoroethylene (PTFE) particles and nanoparticles silicon dioxide were obtained. The degree of hydrophobicity of the coatings depended on the concentration of PTFE particles. Coatings containing optimal amounts of PTFE exhibited superhydrophobic properties with a high contact angle of wetting with water up to 161° and a low roll angle <3°, while maintaining a high level of physical and mechanical properties of the coatings. The...

Combined effect of boron alloying and ausforming on austenite transformation in low carbon steels under continuous cooling

A.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...

Development of numerical methods and virtual tests for cyclic durability by finite element method

A. Papirovskiy, S. Alekseev, A. Tarasov & A. Borovkov
This paper deals with the issue of fatigue failure of materials. The process of generation of fatigue properties for the steel 08PS is described and obtained in the laboratory. The technique of conducting virtual tests for cyclic durability for vehicles is proposed. Virtual tests for cyclic durability by using the finite element method on the example of an off-road car body are performed.

Employment of Eulerian, Lagrangian, and arbitrary Lagrangian-Eulerian description for crack opening problem

E.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...

Investigation and modeling the austenitization kinetics of steels with complex microstructure under continuous heating

A.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...

TERAHERTZ EMITTERS BASED ON NEGATIVE-U MATERIALSFOR MEDICAL APPLICATIONS

N.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.

Nuclear geometry: from hydrogen to boron

Alexander 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...

Isomeres and isotopes of carbon

Alexander 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 cover

D. 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 equation

Andrey 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.

NUCLEATION AND GROWTH OF FULLERENES AND NANOTUBES HAVING FOUR-FOLD SYMMETRY

Alexander 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,...

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Affiliations

  • Peter the Great St. Petersburg Polytechnic University
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  • Institute of Problems of Mechanical Engineering
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