ALGORITHM FOR POSITIONING OF ROTARY ACTUATORS BASED ON SHAPE MEMORY Cu-Al-Ni TENSILE FORCE ELEMENTSA. 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.
SIMULATION OF INVERSE HALL-PETCH RELATION IN NANOCRYSTALLINE CERAMICS BY DISCRETE DISLOCATION DYNAMICS METHODS.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...
Corrosion resistance and mechanical performance of steel reinforcement, before and after shot-blasting processCh. 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...
Micromechanics, nanophysics and non-destructive testing of the strength of structural materialsV.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...
Rotary actuator control based on tensile force elements made of shape memory Cu-Al-Ni crystals when operated in a cyclic modeA.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.
Heating and destruction of biological tissue by high-inensity focused ultrasoundT.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...
Experimental study and modeling of changing mechanical properties in tempering of bainitic-martensitic steelsA.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...
Axial misfit stress relaxation in core-shell nanowires with hexagonal core via nucleation of rectangular prismatic dislocation loopsS.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...
Crystallographic texture of industrial automotive steels and effect of tertiary cementite dissolution on its developmentAlexander 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...
Epoxy-polyester coatings with additives of PTFE particles and nanoparticles of SiO2G.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...
NUCLEAR GEOMETRY: SODIUM, MAGNESIUM, ALUMINUMAlexander 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 propertiesA.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...
Natural isomers of fullerenes from C4 to C20Alexander 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...
Nano- and microparticle aggregation: unique optical vectors for controlAlexandra 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...
Element-free numerical modeling with discrete gradient and its application to crystal defectsA.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...
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...
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...
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...
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.
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
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...
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...
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,...
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