bluuebunny/crossref_metadata_2025 huggingface dataset:
Basement vibration isolation efficiency investigation
Authors: Smirnov Vladimir
Published: August 2020

The article deals with experimental investigation of insertion loss estimation for a building elastic shielding vibration isolation system. Precision mechatronics production facility is located inside it with VC-D requirements for their foundation vibration level. A road with double tram lines lays 23 m off the exterior building’s walls producing reasonable vibration background noise. In order to reduce surface wave amplitudes elastic layer of Sylomer® polyurethane pads are glued to the underground exterior walls of the building. The vibration measurements were conducted before and after the elastic shield installation and the insertion loss was estimated using these results. Moreover, simultaneous dual channel analysis of vibration transfer through the wall structure was evaluated. Measured vibration isolation efficiency reaches 14 dB in octave band 31.5 Hz in vertical and from 9 to 15 dB in horizontal direction. For higher frequencies vibration isolation efficiency reduces due to wave effects in the isolators.
Relative brightness of facades in the L-shaped urban buildings
Authors: Zemtsov Viktor , Korkina Elena , Zemtsov Vladimir
Published: August 2020

Day lighting of premises under conditions of compacted urban development is depended of brightness of the finishing material of the facades of buildings of the surrounding buildings. Measure of influence of opposing buildings on the light regime of the premises is determined by relative brightness coefficient of facade, which is the ratio of the brightness of the facade to the average brightness of the sky. Derivation of the formula for coefficient of relative brightness of the facade in L-shaped urban buildings is presented. The derivation of the formula is based on the some components. The first component is the light transmission rate component on the facade of the designed building, which takes into account the reflection of daylight from an area of the earth’s surface. The second component is a coefficient, which takes into account the increase in the light transmission rate component on the facade of the projected building. This is due to the exchange of reflected light fluxes between the facades of the buildings and the land surface, which is adjoined to the buildings. Relative brightness coefficient values are calculated depending on the building geometry and the reflective properties of the facade finishing material.
Structural solutions of wood-concrete floors using shear-resistant joints
Authors: Labudin B V , Popov E V , Sopilov V V , Nikitina T A , Karelsky A V , Bardin I N , Vakhlov D G
Published: August 2020

Currently, various composite structures made of wood, steel and concrete are used in construction. Some studies are aimed at developing the direction of wood-concrete slab-ribbed structures. Analyzing the methods of joining wood-concrete structures, it was found that the stiffness at the “edge-slab” border has a significant effect on the stress-strain state of the whole structure, and rigid joints allow using the positive properties of concrete and wood materials more rationally, taking into account structural, rheological and physical properties. To increase the shear resistance at the border of joining, a new combined joint based on the unilateral gear plate “Bulldog” and a screw nog is proposed. A numerical model has been made to calculate the joint deformation due to the action of a single shear force, which is based on the law of deformation of linearly elastic materials and the Winkler model. It describes the deformation of a nog lying on an elastically deformable base. Empirical formulae were used to take into account the nonlinearity of deformations during the long-term impact of force on the joint in conjunction with the anisotropy of wood. The dependence curves of the joint stiffness coefficient on the diameter of nog, gear plate and the restraint value of nog in the wood are constructed for dowel and combined joints. It was shown that reinforcement of the joints (up to 6-7 times) could be achieved by increasing the diameter of the nog, and combined compounds based on a gear plate allows to increase this indicator by 2…4 times. The use of screws is recommended as cross-links, the presence of concrete in the head and thread in the wood will reduce the negative effect of warping of wood during shrinkage on the operation of the proposed compounds.
Parametric oscillations of viscoelastic orthotropic plates of variable thickness
Authors: Normuminov Bakhodir , Abdikarimov Rustamkhan , Khodzhaev Dadakhan , Khafizova Zulfiya
Published: August 2020

Viscoelastic orthotropic rectangular plates of variable thickness are considered in the paper under the effect of periodic load. It is believed that under periodic load, the plates allow displacements commensurate with their thickness. Based on the Kirchhoff-Love hypothesis, a mathematical model of the problem of parametric oscillations of a viscoelastic orthotropic rectangular plate of variable thickness is constructed in a geometrically nonlinear statement. A method for solving the problem under consideration is proposed, based on the application of the Bubnov-Galerkin method with polynomial approximation of displacements and deflection, and on a numerical method based on the use of quadrature formulas. In calculations, the three-parameter Koltunov-Rzhanitsyn kernel is used as a weakly singular kernel. Based on the algorithm for solving the problem, a program was developed in the Delphi algorithmic language to solve the problem of parametric oscillations of viscoelastic orthotropic rectangular plates of variable thickness under the effect of an external periodic load. The effect of geometrical nonlinearity, viscoelastic properties of the material, physico-mechanical and geometrical parameters of a viscoelastic orthotropic plate on the areas of dynamic instability was investigated. The results obtained are in good agreement with the results of other authors.
Dynamic stability of viscoelastic rectangular plates with concentrated masses
Authors: Khodzhaev Dadakhan , Abdikarimov Rustamkhan , Normuminov Bakhodir
Published: August 2020

Thin-walled constructions such as plates and shells, with installed units, devices and assemblies, are widely used in engineering and construction. In calculations, such attached elements are considered as concentrated at points and rigidly fixed elements. The influence of concentrated masses is taken into account in the equation of motion using the Dirac delta function. Recently, more and more attention has been paid to the nonlinear and inhomogeneous properties of a structure. Dynamic stability of viscoelastic orthotropic rectangular plates with concentrated masses in a geometrically nonlinear statement is considered in the paper. Using the Bubnov-Galerkin method, based on a polynomial approximation of deflections, the problem is reduced to solving a system of ordinary nonlinear integro-differential equations. The results of the problem are obtained by the proposed numerical method based on the use of quadrature formulas. Dynamic stability of viscoelastic rectangular plates with concentrated masses under various boundary conditions was studied over a wide range of changes in physico-mechanical and geometrical parameters of the plate.
Improving the resistance of frame buildings to emergency impact through voltage regulation
Authors: Chernyh Alexander , Moskalev Mikhail
Published: August 2020

In recent decades, especially after the September 11, 2001 attacks, more and more attention has been started to pay to the problems of the progressive collapse of frame buildings. This problem is especially topical while constructing the buildings with an increased level of responsibility. This problem is mostly solved by duplicating of supporting structure elements which results in significant increasing the cost of building structures. However, there is the other approach: by using the tension resisting ties, strained in accident, the structure can be relieved. Under this study a numerical experiment has been performed using the Scad software to proof this theory. For the numerical experiment there was chosen a building with two bays each 30 meters long at 6 meter intervals of load-bearing structures. According to the results of numerical simulation more than 20% of the supporting structures’ material has been saved compared to the absence of ties. This approach can be taken to the construction of almost all frame buildings with an increased level of responsibility and allows saving material.
Qualification tests of adhesive systems, the assessment of the durability of glued wooden structures
Authors: Chernykh Aleksandr , Kazakevich Tatyana , Kiryutina Svetlana , Korolkov Dmitry , Nizhegorodtsev Denis
Published: August 2020

The question of the use of qualification tests of adhesive systems to determine their residual life is considered. The purpose of the study. Testing the hypothesis about the possibility of applying qualification tests of adhesive systems and regression equations to predict the residual life. Methods. Experimental studies of water resistance of adhesive joints, tensile strength along fibers, heat and frost resistance of adhesive joints, and resistance of adhesive joints to delamination were carried out. Results. Based on the test results, data were obtained on the water resistance of adhesive joints, the tensile strength along fibers, the heat and frost resistance of adhesive joints and the resistance of adhesive joints to delamination. The dependences of the limit on the strength of time are obtained. The residual life was calculated using the obtained equations. Discussion. Based on the studies, it was found that the qualification test data of adhesive systems can be used to determine their durability (residual life). In the future, the results of these studies can be applied for widespread implementation and for inclusion in regulatory documents.
Dynamic loading of the beam on the Pasternak base initiated by the sudden settlement of part of the base
Authors: Travush V I , Gordon V A , Kolchunov V I , Leontiev E V
Published: August 2020

The article presents a methodology for the analytical assessment of the dynamic loading of a beam based on a mathematical model of a transient dynamic process in a loaded structure resting on an elastic two-parameter Pasternak base, initiated by sudden settlement of a part of the base. Determine that the sudden formation of a defect leads to a decrease in the overall rigidity of the structure and a violation of the static balance of the beam-base system. The arising inertia forces cause a dynamic response, redistribution and growth of deformations and stresses. As a result, there may be a violation of the regular functioning of the structure, loss of bearing capacity and destruction. From the standpoint of structural mechanics, the problem boils down to an analysis of the manifestations of structural nonlinearity of a loaded elastic system. It is shown that the factor of sudden formation of a defect significantly increases internal forces compared with the quasistatic formation of the same defect. It is also shown that taking into account the Pasternak parameter reduces (compared with the one-parameter Winkler base) the level of dynamic bending moments during sudden partial destruction of the base.
Causes of defects in timber arches of the buildings covering and methods of strengthening
Authors: Naichuk A Ya
Published: August 2020

The results of the survey of covering of large-span public buildings located on the territory of the Republic of Belarus, which are in exploitation from 10 to 30 years. The bearing structures of the covering were timber glued arches with spans from 48 m to 60 m. the Main defects were both through and deep cracks that appeared in the timber of the arches during exploitation. To restore the performance of timber arches with defects in the form of cracks, methods of strengthening are proposed. The effectiveness of using glued steel rods for strengthening arches with cracks was tested experimentally. For this purpose, two prototypes of semi-arches made of glued timber for a span of 26.9 m were tested: one semi-arch of a solid cross-section bxh = 100 × 670 mm; the second semi-arch with a crack on the neutral axis, reinforced with glued steel rods. As a result of tests, the ultimate load of a semi-arch with a solid cross-section is 2.4 times greater than the calculated value; and a semi – arch with a crack through the entire length is 1.8 times greater.
Atmospheric dispersion modelling of dust emissions from the dried bottom of the Aral Sea
Authors: Ravshanov Z , Abdullaev Z , Khafizov O
Published: August 2020

The problem of spreading of harmful emissions from the dried part of the Aral Sea is extremely relevant for the Central Asian region, but it is also important for other countries of the near and far abroad in view of the transboundary transport of pollutants in the atmosphere. In order to solve the problem of predicting the distribution of the concentration of air pollutants, researchers are usually use mathematical tools. Modelling the processes of transport and diffusion of pollutants in the atmosphere claims to address various factors, such as weather and climate conditions, soil erosion, physic and mechanical properties of aerosol particles, etc. Thus, this study was aimed to develop a model and computational algorithm for solving the problem. The particular attention was paid to the description of wind erosion since most emissions in the Aral Sea region occur by the removal of salt-dust particles from the soil surface. There were conducted a series of computational experiments using the developed mathematical apparatus. The obtained results presented in the paper are illustrating the influence of various factors on the process of atmospheric dispersion. Comparison of the results of computational experiments with experimental data showed sufficient agreement, which confirms the adequacy of the developed mathematical model of the process of spreading of fine aerosol particles in the atmosphere.
Ground and confined underground waters and their salt content
Authors: Ravshanov N , Daliev Sh , Abdullaev Z , Khafizov O
Published: August 2020

A article developed a mathematical model for monitoring and predicting changes in groundwater level and salt concentration, as well as for representing the process of flooding, salinization and waterlogging in the design of hydraulic structures. A qualitative analysis of the research work on this issue is presented. Since the process is represented by a nonlinear differential equation, a numerical algorithm based on finite-difference schemes was developed to solve it. Mathematical models of the processes of geofiltration of salt migration have been improved and computational algorithms have been developed. A numerical algorithm has been developed for calculating the problem of changing the groundwater level, taking into account active porosity, flow rate in two-layer formations.
Production of wooden I-beams from angular elements for low-rise housing
Authors: Byzov V E , Melekhov V I , Toropov A S
Published: August 2020

Due to the deterioration of the environmental situation, an increasing number of coniferous trees are affected by butt heart rot. For a more sustainable use of resources, one needs to use round assortments with the presence of sound rot for the manufacture of sawn products. I-beams are widely used in low-rise wooden housing construction. High installation speed without the use of heavy equipment and ease of assembly increase the speed and adaptability of building construction. A method for manufacturing I-beams from corner elements obtained as a result of cutting round timber with heart rot is proposed. The elements of the angular cross section are glued together to obtain an I-beam. The strength characteristics of an I-beam glued from angular cross-sectional elements are determined. It was established that the design characteristics of I-beams obtained by the proposed technology withstand operational loads. Values of normative and shear stresses arising upon application of loads do not exceed 50% of the permissible values. The beam deflection does not exceed 80% of the permissible deflection value. The use of round timber with core rot increases wood resources for low-rise housing.
Physical essence of the “nagel effect” for main reinforcement in an inclined crack of reinforced concrete structures
Authors: Kolchunov V , Smirnov B , Naumov N
Published: August 2020

The physical essence of the “nagel effect” for main reinforcement in an inclined crack of reinforced concrete structures for the model of deformation of reinforced concrete structures includes formation of the first block and the second block of an inclined crack. This effect is considered is constructions under the action of vertical load, with linear displacements (normal to the axis of the beam) and rotations of the fixed end. We can find the unknownτadfrom the canonical equations for structural mechanics. When we multiply the single diagrams of bending moments caused by displacements Δ1and Δ2and displacement caused by longitudal forceNs(x) and incrementΔNs. In this case, for the “nagel effect”, we take into account the presence of several forces and displacements: the force P1 for the surface for the second block; adhesion to the surface of the reinforcementτadand a special force for the effect of discontinuity (ΔT); displacements for mutual shifts of the crack edges (Δ1); movement from the width of the crack opening (Δ2=acrc); angle of rotation for the fixed ends; variable longitudinal force in the fixed ends.
Energy efficiency of multi-apartment residential houses with individual heat supply
Authors: Navaseltsau Uladzimir , Navaseltsava Dzina , Shenogin Mikhail
Published: August 2020

The aim of this work is to study the functioning of heating and hot water systems of the discussed houses, to find the reasons for increased energy consumption. Four energy-efficient houses in the Brest region (Republic of Belarus) with apartment heat supply and a mechanical ventilation system with heat recovery were selected as the object of study. The research methodology of the heating and hot water supply systems of the houses consisted of the following stages: study of project documentation; thermal imaging inspection of building structures and instrumental studies of the operation of heating systems and hot water supply; questionnaire of residents to analyze the nature of their use of the studied systems; processing received data. The values of the operational specific consumption of thermal energy for heating were determined, which doubled the design values equal to 43 kW·h/m2. The main reasons for the excess of the operating specific consumption of thermal energy for heating and ventilation over the design value is the increased heating season compared to the design average for a month and the maintenance of elevated indoor air temperatures in apartments, on average, at +21°C, which leads to increased heat losses. The functioning of the hot water supply system of energy-efficient houses is generally satisfactory for the used design solution, but sometimes due to the specific appartments’ planning leads to an excessive consumption of water and causes dissatisfaction of residents with a long waiting time for hot water with required temperature. Studies have shown that currently, the existing tariff policy in the Republic of Belarus due to low tariffs for gas and thermal energy for the population does not contribute to the efficient use of energy-efficient solutions by the masses of the population, which leads to an excessive consumption of thermal energy in modern residential buildings.
The effect of eccentricity on the strength characteristics of glued rods made of steel cable reinforcement in solid wood
Authors: Koshcheev A A , Roshchina S I , Naichuk A Y , Vatin N I
Published: August 2020

The article is devoted to the study of the behavior of glued rods made of hot-rolled steel reinforcement and steel cables in a solid wood based on experimental tests of beam elements. The influence of eccentricity on the deformation - strength characteristics is studied with a straight-line gluing of reinforcing rods. The comparative analysis of the deformability indices of the centered and lateral gluing performed by milling with fillet groove U - shaped milling cutters was carried out. The technology of manufacturing samples, which consists of preparing wood, milling and pasting rebar into the groove, were described. The diagrams of deformation - strength characteristics of samples of various types were obtained and correlated. The conclusions were drawn about a local increase in strength in the case of using a steel cable as reinforcement and the negative effect of eccentricity on the strength of the adhesive joint during tensile tests. A visual analysis of the damage occurring during the test showed that in the manufacture of full-scale structures, glued rods should be closed with an array of wood. The conclusions were drawn about the optimal depth of milling of grooves for reinforcement, taking into account the use of adhesive compositions on epoxy resin filled with quartz sand - 1.5 depth of reinforcing bar diameter.
Local deformation and strength characteristics of S-shaped reinforcement in wood
Authors: Koshcheev A A , Roshchina S I , Aleksiievets V , Labudin B V
Published: August 2020

Reinforced wooden beam structures under the influence of critical loads are subject to brittle fracture, which is dangerous when operating beams in buildings. To solve this problem, reinforcement of wooden beams for civil and industrial buildings was invented using steel rope as a reinforcing element. The rope is located in the stretched area of the beams along the original S-shaped trajectory. Numerical studies of the deformation of the reinforcement model using the LIRA program are performed. Based on numerical studies, samples were made for testing for pulling S-shaped anchoring elements from solid wood. The analysis of deformation - strength characteristics based on the results of tests on a tensile testing machine glued curved rods. A triple increase in the ductility of the deformation of the paste in the zone of destructive loads was revealed. The main problems of this type of reinforcement are the appearance of stress concentrators in areas with a small radius of curvature of the reinforcement. As a result of the study, the optimal trajectory of the reinforcement insert was determined with the aim of obtaining higher strength and deformation characteristics - with a reduced oscillation amplitude. The possibility of using structures in the form of safety elements has been established, which allows to increase the destruction time of beam systems when exceeding the permissible load.
Strength and deformability of lightweight metal trusses with elements from cut I-beams
Authors: Popova M , Sergeev M , Lukina A , Shunqi Mei
Published: August 2020

The article is devoted to the study of the strength and deformability of light metal trusses with elements made of cut I-beams based on experimental tests. A truss design is proposed based on the idea of a waste – free technology for obtaining the maximum number of truss elements in the process of cutting the initial billet-a rolling I-beam. The manufacturing technology of the farm, research tasks and test samples are described. The developed and manufactured designs of truss models were a geometric similarity of trusses with parallel belts with a span of 24 m, a cross – section height along the shelves of the belts-2.4 m, with the length of the belt panels equal to 3 m, calculated for different loads. The analysis of the obtained results showed that the theoretical values of axial stresses in the elements of truss models differ from the values of experimental axial stresses in General by no more than 8%. According to the results of numerical studies of the stress-strain state of trusses in the elastic stage of their operation, it was established: - truss structures have sufficient stiffness and strength (the coefficient of load-bearing capacity was a value that varies for trusses of various series within the range of 1.34 – 1.7); - the stress values in the truss elements calculated during the processing of the results of numerical studies have a large similarity with the stress values calculated on the basis of experimental data.
Stress-strain state of wooden beams with external reinforcement
Authors: Lukin M V , Roshchina S I , Gribanov A S , Naychuk A Ya
Published: August 2020

The stress-strain state of wood-composite beams was studied numerically. Numerical studies were performed on wood-composite floor beams with a cross-section size of 100×240 mm and a length of 4.8 m. it was Experimentally proved that the deformability of wood-glued beams is reduced by 1.8…2.1 times, compared to conventional wooden beams. For wooden beams in the elastic design stage, the limiter is the calculation of the 2nd group of limit States (for stiffness), for composite beams, the calculation of the 1st group of limit States (for strength. The calculation proved that the deformability of wood composite beams is reduced by 1.8…2.1 times, compared to conventional wooden beams. The high efficiency of the finite element method calculation for evaluating the criteria of load-bearing capacity of wood-composite beams up to their destruction is proved.
Wooden beams with local wood modification
Authors: Gribanov A S , Roshchina S I , Naichuk A Ya , Melekhov V I
Published: August 2020

The purpose of this work is to study the strength of wooden beam structures with local modification of wood in the compressed zone. To achieve this goal, the physical and mechanical characteristics of modified wood were determined using modifiers based on ed-20 epoxy-diane resin, urea-formaldehyde resin, and dimethacrylic polyester. The best physical and mechanical characteristics were obtained for samples using dimethacrylic polyester: the ultimate strength was 84 MPa, the elastic modulus was 21 GPa. The increase in strength compared to solid wood was 46%, and the increase in the modulus of elasticity was 54%. Tests of beam structures with a span of 4.5 m and a cross section of 100x200 mm with local modification of wood in the compressed zone with a polymer composition based on dimethacrylic polyester were carried out. The increase in the strength of beams with local modification in the compressed zone compared to solid wood was 11% within the design loads, and the increase in stiffness by 18%. The “load-strain” relationships are constructed based on the test results. It is established that the greatest effect can be achieved when using external reinforcement systems together in a stretched zone by reducing the influence of defects and defects in beam structures and local modification of the extremely stressed compressed zone.
Numerical study of filtration process of ground and pressure waters in multilayer porous media
Authors: Daliev Sherzod , Abdullaeva Barno , Kubyasev Kurash , Abdullaev Otabek
Published: August 2020

A article discusses the process of forecasting changes in the level of ground and pressure water. A brief analysis and computational experiments of scientific papers on mathematical and numerical modeling of the object under study are given. For a comprehensive study of the problem under consideration, a mathematical model was developed that takes into account the external source, evaporation, filtration coefficients, active porosity, filtration rate and two-way boundary conditions. An effective numerical algorithm has been developed for predicting changes in the ground water level using a combination of finite-difference schemes and run-through methods. It has been studied that changes in the level of ground and pressure water, filtration permeability, water loss coefficient and filtration rate associated with the water level can have a serious impact on the environmental process.
Mathematical modeling of a waterjet jet for structural material cutting
Authors: Shpilev Vasiliy , Reshetnikov Mikhaile , Borodulina Svetlana , Zakharchenko Mikhail , Ivashchenko Yuri
Published: August 2020

When modeling a jet during hydroabrasive processing of structural materials, we will represent it as a heterogeneous environment. And accordingly, the hydroabrasive flow will be considered as a heterogeneous flow. The equations describing the formation of a heterogeneous flow are based on the equation of conservation of momentum of the total movement and allow for the interaction of the background flow and particles of the abrasive. A mathematical model of a heterogeneous flow, reveals the mechanism of formation of a waterjet jet. Based on the mathematical model, the hydrodynamic forces and surface stresses acting between the abrasive and the liquid can be taken into account. It also takes into account speed, concentration, mass, density of the fluid and abrasive. Knowing these parameters, it is possible to use the mathematical model of a heterogeneous flow to find the optimal conditions for the formation of a waterjet flow and the processing of structural materials.
Man-made soils and mining wastes as raw materials for building composites
Authors: Zakrevskaya Lubov , Gavrilenko Andrei , Andreeva Ksenia , Lubin Petr , Kapush Ilya , Udin Igor
Published: August 2020

The crucial task up to date is to find effective solutions to expand the raw material base of the construction industry by involving local natural and man-made raw materials instead of traditional expensive energy-intensive materials. An inexhaustible source of raw materials can be mining waste, such as dolomite and lime. Currently, they are large-tonnage industrial deposits that limit the area of development. The problems of strengthening man-made cohesive soils for the manufacture of wall materials, and their use as natural bases is also front and center. The optimal compositions of soil-concrete mixtures based on waste carbonate deposits are selected. The goal of this work was to design a composition of a complex binder for strengthening clay soil. The second goal of the work was to obtain masonry soil-concrete products. For this purpose, waste from the dolomite production of the Melekhovsky deposit was used. To solve the problems, authors carried out such tests as chemical analysis, mineralogical analysis, X-ray phase analysis, raster electron microscopy, compressive strength test, frost resistance test, and water resistance test. Comparing the obtained results, it is now becoming apparent that the compositions of GD-4 and GD-5 at close density values have high strength characteristics at design age. The content of dolomite waste above 30% leads to an increase in strength, the best results are achieved with a dolomite content of 34.6-45.3%, in this range also with increasing binder content, water absorption and density increase, and therefore porosity decreases. The phosphates that make up the composite increase its water resistance.
A composite ceramic material for an abrasive tool
Authors: Bolotov A N , Novikov V V , Novikova O O
Published: August 2020

The paper describes the features of the electrochemical formation of a modern abrasive tool material. The technology for obtaining the material consists in obtaining a composite diamond-bearing ceramic layer on the surface of diamond-aluminum sintered blanks by microarc oxidation. It was established that the degree of diamond metallization with copper and the relative density of a sintered blank affects oxidation the most. It was impossible to obtain a composite ceramic material by microarc oxidation with diamonds coated with nanodispersed copper with a metallization degree of over 100%. The relative density of sintered blanks should be 80–90% to form a composite material with optimal physicomechanical and tribotechnical properties. Diamond concentration did not affect the creation of stable spark discharges that form aluminum oxide. The optimal alkali concentration in the electrolyte to reach the maximum thickness of the diamond-bearing composite material was about 2 g/l. Comparative tests showed that the wear resistance of a diamond-bearing composite material with a ceramic matrix based on aluminum oxide was notably higher than traditional analogues under similar friction conditions. Finally, the paper determines the scope of the obtained diamond-bearing ceramic material as a tool for precision processing of superhard materials in precision engineering, instrumentation engineering, and the medical industry.
Diagrams of concrete behavior over time
Authors: Varlamov A , Kostyuchenko Y , Rimshin V , Kurbatov V
Published: August 2020

The article presents a new vision of building diagrams of the work of materials in time. The main starting point is the law of conservation of energy of a closed system. The material is represented by an initial graph of the energy acceleration distribution. The external influence is represented as a rectangular form of energy acceleration distribution. At every moment of time, the external acceleration of energy exceeds the acceleration of the material’s energy. The obtained dependence of the material diagram is analyzed. Graphs of various forms of energy acceleration are obtained. Their summation shows the true diagram of the work of the material. Defining the characteristic points of the concrete behavior diagram, a true diagram of concrete behavior over time is constructed. By changing these characteristic points, we track the changing behavior of concrete over time.
Modification of bitumen for road construction
Authors: Provatorova Galina , Vikhrev Alexander
Published: August 2020

To increase reliability and durability of road surfaces, asphalt concrete based on modified bitumens is actively used. Experts’ research shows that in modified bitumen extracted from road surfaces after 10 years of operation there are no significant changes in viscosity. The purpose of this study is to improve the properties of bitumen and asphalt concrete based on it by modifying road bitumen with carbon nanotubes. Bitumen was modified with carbon nano-tubes obtained by deposition from the gas phase in the laboratory of Vladimir State University. The selection of the optimal amount of the introduced modifier was performed, modified bitu-men was prepared, its properties were determined, and a comparative analysis of the properties of asphalt concrete made on modified and non-modified bitumen was carried out. Due to the introduction of carbon nanotubes into the heated bitumen, the strength and elasticity of the resulting asphalt concrete are significantly increased. The test results showed an improvement in all quality indicators of asphalt concrete by 7-9%, which allows us to say that the resulting composite has increased strength characteristics.
Influence of presteaming period and curing temperature on the plasticized concrete strength
Authors: Leshkanov Andrei , Dobshits Lev , Anisimov Sergey
Published: August 2020

Heat-moisture treatment (HMT) is the main way to speed up the strength of reinforced concrete products. But this technology is the cause of high energy and resource costs. The use of traditional plasticizing additives in concrete is difficult in terms of early strength reduction. The modern industry of chemical additives allows regulating superplasticizers (SP) molecular structure. The use of such modifiers in concrete leads to early strength increase. The combination of HMT and SP using in concrete hardening makes the optimization of steaming parameters possible. HMT variable modes of concrete modified with polycarboxylate SP were investigated for early strength. The stripping concrete strength with an increase in SP dosage from 0.4 % to 2.0 % by cement mass decreases as follows: at the maximum curing temperature of 40 °C – on 32.8 %; at the temperature of 60 °C – on 27.2 %, at the temperature of 80 °C – on 23.8 %. The concrete compressive strength after HMT without the presteaming period is lower by only 5.4-14.3 % in comparison with concrete steamed with one for 1-2 hours. The research was carried out on concrete using sand with a low size modulus of 1.70. The authors show the superplasticizer effectiveness in terms of reducing the water-cement ratio and joint action with HMT. Mathematical models of the early concrete strength were obtained depending on curing temperature, presteaming period duration, and the SP dosage. The obtained results can be used in the reinforced concrete products production, subject to additional research.
Effect of superplasticizer and silica fume on the properties of self-compacting mortars
Authors: Smirnov A O , Dobshits L M , Anisimov S N
Published: August 2020

Self-compacting concrete is a highly flowing concrete that compact under self-weight without any vibration effort. The mortar phase of self-compacting concrete determines its rheological, strength characteristics, and durability. This paper discusses the effect of superplasticizer and silica fume on the properties of self-compacting mortars. Mini-slump flow diameter tests were conducted to determine the rheological properties of mortar mixtures, and compressive strength, density, water absorption, porosity experiments to assess the hardened properties of mortar specimens. Analysis of regression models shows that the use of superplasticizer reduces the water demand of mortar mixtures by up to 40 %, and the addition of silica fume leads to the densification of cement stone structure and reduces the porosity of concrete to 24 %. The maximum compressive strength at 2 days can be achieved with a superplasticizer content of 0.8-1.0 % and 0-5 % silica fume by binder weight, and at 28 days – with 1.0-1.2 % superplasticizer and 10-15 % silica fume content. According to X-ray phase analysis in a cement stone containing superplasticizer and silica fume, the degree of cement hydration increases and reduces the amount of portlandite, which leads to an increase in the strength and durability of the concrete.
The role of colmatation in liquid corrosion of hydrophobized concrete
Authors: Fedosov S V , Rumyantseva V E , Konovalova V S , Evsyakov A S
Published: August 2020

To reduce water absorption of cement concretes resort to hydrophobization by introducing special additives in the manufacturing process of the product. In the study of liquid corrosion of hydrophobized cement concretes of the W4, W6 and W8 waterproofness grades in media of various degrees of aggressiveness, the terms for achieving a state close to the equilibrium concentration of calcium cations in the solution were established. Based on the experimental data on the liquid corrosion of cement concretes of various grades in terms of water resistance, the optimum amount of hydrophobizing calcium stearate additive was determined, which is sufficient to prevent corrosion damage in concrete, depending on the degree of aggressiveness of the medium. Tests of strength characteristics of hydrophobized cement concretes of the W4, W6 and W8 waterproof grades were carried out. It is established that when alkali and alkaline-earth stearates are introduced into concrete as hydrophobic additives, its strength is significantly increased compared to non-hydrophobized concrete samples. Some special cases of changes in the mass conductivity coefficient during colmatation of hydrophobized cement concretes of the W4, W6 and W8 waterproof grades are considered and graphically illustrated. Profiles of changes in the rate of colmatation and the thickness of the colmatant layer for cement concretes with and without hydrophobizing additives are presented. The profiles show that over time there is a weakening of the mass flow, which is obviously associated with an increase in the colmatant layer. The rate of colmatation is also reduced due to the fact that the layer of colmatant partially or completely clogged the pores and prevents further penetration of the aggressive medium deep into the concrete.
Effect of laser radiation parameters on surface modification of critical engineering part
Authors: Abrakhin S I , Arakelian S M , Bukharov D N , Abrakhina S I , Evstyunin G A
Published: August 2020

In this work, computational experiments were carried out using the MatLab Laser ToolBox package to determine the power range of a radiation source for realizing nanomodification of the C45 grade steel surface without melting. The dependences of the sample maximum temperature are determined depending on the power of the laser radiation source, beam diameter, and scanning speed. It has been found that for a steel plate, a power of more than 3.7 kW in the case of a slowly moving source (10 mm/s) and more than 4.9 kW in the case of a fast-moving source (20 mm/s) are required for melting. Moreover, an increase in power of a slow source by 0.2-0.3 W is accompanied by an increase in the maximum temperature by 200 K at the beginning and will increase towards the end of the heating process, which goes into melting stage.
Examination of engine cylinder-piston group damages
Authors: Bazhenov Yu , Kirillov A , Bazhenov M
Published: August 2020

Results of investigations of engine cylinder-piston group (CPG) damages and causes of their occurrence are given. The object of the study is the KIA Ceed engine, which came for examination due to a significant decrease in power, increased consumption of motor oil, violation of the dynamics of the car. The analysis of the technical condition of the disassembled engine showed that the parts of the crank mechanism and the cylinder head have no operational damages. Serious damages were detected only in the cylinder-piston group of the engine: abrasive wear of the working surfaces of cylinders, pistons and compression rings, coking of oil removal rings, deposits on the surfaces of all pistons of the engine. According to the results of the studies, the cause of loss of efficiency by the engine is the destruction of the ceramic catalyst, the products of which in the form of ground powdered substance enter the cylinders together with the exhaust gases. This occurs at the moment of simultaneous opening of exhaust valves of two cylinders having different exhaust gas pressure. A small amount thereof, together with the catalyst breakage products, penetrates the lower pressure cylinder through the manifold. A study of the substance of deposits on the pistons of the engine and the destruction products of the elements of the ceramic catalyst (cordierite Al4Mg2O16Si5), carried out on the powder diffractometer BRUKER AXS, showed the identity of their diffraction composition. This indicates that damage to the parts of the CPG and loss of performance by the engine is caused by destruction of the ceramic catalyst.
Dielectric study of syntactic foams based on polydimethylsiloxane and hollow glass microspheres at X-band microwave frequency
Authors: Mastalygina E E , Chukhlanov V Yu
Published: August 2020

The dielectric characteristics of syntactic foams based on polydimethylsiloxane binder and hollow glass microspheres at the X-band microwave frequency were studied. Experimental studies were carried out to determine and calculate dielectric constant, dielectric loss tangent in the range from 8 to 12 GHz, as well as radio transparency of the obtained materials. According to the results, an increase in the binder content over 15-20 vol.% led to a significant loss of radio transparency. The treatment by hydrophobizing organosilicon liquid was shown as an effective method for decreasing the dielectric loss tangent and increasing the radio transparency at the microwave radio frequency range. The developed materials proved the temperature stability and fire resistance. The expected applications of syntactic foams based on the developed materials include the various fields of structural and industrial engineering, in particular, producing the protective constructions for stationary radar stations and radio telescopes.
Method for determination of thermophysical properties of polymer composite materials
Authors: Sharshin Vladimir , Sukhorukov Denis , Sukhorukova Elena
Published: August 2020

The paper presents the results of studies of thermophysical properties: heat capacity, thermal conductivity, thermal diffusivity and heat storage ability of polymeric polymer composite materials. A method is proposed for determining these properties, based on the well-known method for determining thermophysical properties by eliminating variables. The experimental values of the thermophysical properties of polymer composite materials with the addition of powder particles of various fractions of aluminium, iron, carbon and copper are obtained. The effectiveness of the proposed method is shown by comparing the known values of the specific heat and thermal conductivity of polyurethane with experimental.
Cyclic strength of polyester acrylate composites
Authors: Erofeev Vladimir , Fomin Nikolay , Ivlev Viktor , Yudin Vyacheslav , Myshkin Anton
Published: August 2020

The results of a study of the cyclic strength of polyester-racrylate composites are presented. The mechanical properties of the samples were determined on a Shimadzu Autograph AG-X Series universal testing machine. Test process management and pre-processing of data obtained on this machine are performed using the TRAPEZIUM X * 1 software. The measurements were carried out with a constant velocity of movement of the active capture of 3 mm / min. The compression force was directed along the long axis of the sample. The cyclic mechanical impact on the sample was carried out according to the following scheme: “loading to a certain maximum stress σmax in a given cycle → complete unloading at the same speed → five times repeating the cycle with a given load σmax → repeating the five times cycling procedure with a stepwise change in maximum load σmax until the sample is destroyed. It is shown that a characteristic feature of the load – strain curves during cycling is the presence of hysteresis, which is especially significant in the first cycle. The first compressive loading of the sample leads to significant changes in the structure of PEA. In the second and subsequent cycles, the difference between the loading and unloading curves of the sample is noticeably smaller and depends little on the cycle number. Then the state of the sample is stabilized, and subsequent cycling affects it much weaker. It is characteristic that the maximum difference between the losses in the first and subsequent cycles is observed at the minimum initial voltage. At maximum loads, the unloading curve is steeper than the loading curve, and at low loads, vice versa. Hysteresis losses increase with increasing maximum load in the cycle, which corresponds to an increase in the contribution of the plastic component to the total deformation of the sample. The E (σ) dependences obtained during loading in the first cycle practically coincide with the loss curves. In subsequent cycles, a slight quantitative change in these curves is observed without changing their general nature. The dependences obtained by unloading the samples are fundamentally different from the dependences obtained by loading. In this case, the discrepancy between the E (σ) curves during loading and unloading in the composite is slightly weaker than in pure PEA.
Creep and relaxation of polyester acrylate composites
Authors: Erofeev Vladimir , Fomin Nikolay , Ivlev Viktor , Yudin Vyacheslav , Myshkin Anton
Published: August 2020

It is shown that creep and relaxation are the most important properties for structural materials. This research presents the results of a study of filled polyester acrylate composites’ creep and relaxation. The comparison of mechanical indicators with similar for unfilled materials is shown in this work. Investigation of mechanical properties of the samples was carried out on a universal testing machine Shimadzu Autograph AG-X Series at room temperature. It was revealed that the intensity of stress and creep relaxation in the composite is much weaker than in pure resin. It was found that composites are characterized by a logarithmic time dependence of stress relaxation and creep. Logarithmic dependences for the studied parameters are of the same nature. Changes in indicators are mainly due to the properties of the binder.