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The effect of the introduction of B4C on the adhesive and cohesive properties of self-fluxing coatings

https://doi.org/10.58224/2618-7183-2024-7-6-5
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Аннотация
Wear and tear of technical equipment elements is a serious problem that negatively affects the productivity of production processes. The work analyzed the strength of cohesive and adhesive bonds of wear-resistant coatings obtained by detonation gas-dynamic spraying method based on a self-fluxing alloy, depending on the introduction of B4C particles into the composite composition. The chemical composition of the cohesive bonds of the resulting coatings and the effect of boron-containing elements on their strength were analyzed. The method of transverse scratching of transverse sections of thick coatings is a qualitative assessment of adhesive and cohesive properties and helps to determine the mechanisms of their destruction. The purpose of the work is to study the effect of the introduction of B4C particles on the adhesive and cohesive properties of coatings obtained by detonation gas-dynamic spraying based on self-fluxing NiCrBSi alloy. Methods for studying coating samples obtained by detonation gas-thermal method: scanning electron microscopy, energy dispersive analysis, optical metallographic microscopy, scratch testing. Previously, wear-resistant coatings based on self-fluxing NiCrBSi-B4C alloy have proven their effectiveness as protective coatings for centrifugal beet cutter knives. This study substantiates the feasibility of obtaining a composite based on such coatings with the introduction of boron carbide to improve its strength characteristics.
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Protection of construction sites from unmanned aerial vehicles using mesh fences

https://doi.org/10.58224/2618-7183-2024-7-6-6
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Аннотация
Introduction. During a special military operation, unmanned aerial vehicles (UAVs) are actively used by the enemy to attack industrial and energy facilities of the Russian Federation. One of the most effective ways to protect objects from UAVs is the use of enclosing structures using trapping nets. They make it possible to prevent the UAV from contacting the enclosing structures of a building or structure and minimize the consequences of an explosive charge explosion. Research methods. Calculation methods based on the formulas of M.A. Sadovsky were used to determine the permissible distances from the UAV-trapping grids to the enclosing structures of the object. The deflection of the grids was determined by the calculation method by solving a partial differential equation describing the transverse vibrations of the membrane.
Objective: To determine the possibility of using mesh structures to prevent damage to industrial, energy and civil facilities by damaging explosive explosion factors carried by UAVs. Tasks. Selection and justification of calculation methods for assessing the degree of damage by an explosive charge to the protected object and the magnitude of the deflection of the grids during an attack of the UAV; calculation of the permissible distance from the trapping mesh structures to the enclosing structures of a building or structure; assessment of the deflection of the grids under the dynamic influence of the UAV. Results. Calculations performed within the framework of the study made it possible to determine the permissible distances from the trapping mesh structures to a building or structure with different explosive masses; the deflection values of the grids under the dynamic influence of UAVS on them. Conclusions. The calculations of the distance from the trapping mesh structures to the protected objects made it possible to identify the effectiveness of this method of ensuring security in the event of a UAV attack. The materials of grids and structures of supporting elements used in construction make it possible to implement physical (passive) protection against UAVS in practice.
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The high-tech and effective method of strengthening reinforced concrete structures with CFRP materials with preliminary modification of the cross-section shape

https://doi.org/10.58224/2618-7183-2024-7-6-7
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Аннотация
It is known that the effectiveness of reinforcement with CFRP composite materials of reinforced concrete structures of round or oval sections is significantly higher than rectangular or square ones due to the uneven distribution of internal limiting pressure in the latter. This study is devoted to the study of the effectiveness of a new method of strengthenet based on a preliminary change in the shape of reinforced concrete and concrete columns of square section. The sharp corners of the columns create a concentrating internal limiting stress in the CFRP composite cage, while the amplification system collapses prematurely, and the amplification efficiency is greatly reduced. To comprehensively solve this problem, the authors have manufactured, strengthened and tested a number of reinforced concrete columns with different variants of CFRP composite reinforcement. For the purity of the experiment, reference racks were also made, not reinforced, and reinforced with CFRP composite clips without rounding. All prototypes were made of the same materials, as well as strengthened and tested using the same techniques. The paper describes the features of traditional and modern methods of composite strengthenet of reinforced concrete columns, analyzes the main disadvantages of existing strengthenet methods and, based on this, presents a new strengthenet method that allows more efficient use of composite materials in the transverse direction. The new strengthenet method is described in detail, the main schemes and procedure for performing strengthenet work are presented. The final stage of the work is the main results of an experimental study, where the characteristics of reference samples were compared with similar structures strengthened in the transverse direction with CFRP composite materials. The experimental results show that the proposed amplification method is highly effective. For the best effect, it is proposed that the material used for rounding has higher strength and less deformability compared to concrete columns.
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Heat transfer from a cylindrical heater to a medium with variable thermophysical characteristics and heat source power

https://doi.org/10.58224/2618-7183-2024-7-6-8
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Аннотация
The formulation and solution of the problem of non-stationary thermal conductivity in a composite material with variable thermophysical characteristics are considered. Density, heat capacity, thermal conductivity, as well as the power of the heat source due to the hydration reactions of the binder components change during the concrete hardening process. The heat transfer problem is formulated for the general case when there are no calculation formulas for thermophysical transfer coefficients. The “microprocess method” was used to calculate the dynamics of the temperature field. According to this method, the space from the outer surface of the heater is modeled by a system of successively located “rings”. When moving from the previous “ring” to the next one, the charge in the transfer coefficients and the power of the volumetric heat source were taken into account. At the same time, the initial and boundary conditions were corrected. The boundary value problems are formulated in the form of a differential equation of non-stationary heat transfer with an arbitrary initial distribution of transfer potentials, Dirichlet boundary conditions, and a heat source in the form Po=f(Fo).The obtained solutions are analyzed for some particular cases. Prospects for further theoretical and experimental research are determined.
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Development of a method to identify the need for capital repairs and renovation of administrative buildings

https://doi.org/10.58224/2618-7183-2024-7-6-9
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Аннотация
Identification of needs for production resources during repairs, restoration and reconstruction strongly relies on administrative and engineering solutions. The scope of problems, addressed by these projects, encompasses limited production and non-production resources, as well as unpredictable external risks, or ambiguous initial information about construction facilities. Today all available decision-making principles, underlying the long-term planning of capital repairs and reconstruction of civil buildings, disregard a great number of production-related and administrative factors. Advanced design software and applications, developed on the basis of various mathematical principles, used to describe construction technologies and processes, facilitate decision making by specialists responsible for the implementation of such projects. In this case, principal factors include optimal labour costs and guaranteed quality. The article outlines basic decision-making principles underlying a program of capital repairs or reconstruction of civil buildings in operation. These principles are based on computing the potential of administrative and engineering solutions. Scientific research, conducted in the process of drafting this article, encompasses the analysis of various production-related factors characteristic of production processes, including capital repairs and reconstruction. These factors are represented as a system of linguistic data flow that specifies term sets and membership functions for each condition. Most significant factors are the technical condition of permanent buildings and structures, the attitude of consumers to the subject of the study, and its operation period starting upon completion of earlier repair or reconstruction, as well as the serviceability of internal and external engineering systems. As a result of scientific research, the authors developed and tested a new method used to identify the need for construction and installation work performed within the framework of capital repairs or renovation. The novel method includes specific requirements that apply to the scope of work and the sequence of its implementation.
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The impact of the visual design of public spaces In the Arabic city

https://doi.org/10.58224/2618-7183-2024-7-6-10
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Аннотация
A good design of public urban spaces considers all the visual and aesthetic determinants dedicated to its formation. In a design of public urban spaces in European cities, it is a studying perception of form in the townscape. In addition, most design focuses on the details of constituent elements to suit the overall consideration to aesthetic form. It has a lack of design study in the Arab cities, where all the considerations are not fully applied. The design neglects the study of the visual dimensions and the cultural identity of the Arab city. Therefore, this research is to fill the knowledge gaps and deficiencies about the formation of the urban spaces in Arab cities. The Methodology of this research is descriptive and analytic. It discusses the design determinants of visual and aesthetic composition of public spaces in the Arab cities. It is also a study on the determinants of visual reading of its components by analyzing their forms and their relationship with the surrounding elements (building masses, street furniture elements) and by using the space syntax assessment technique to identify the foundations and visual access to a graphic and aesthetic design reflecting the Arabic identity.
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Construction and climatic certification of an area as a prerequisite for development of energy-efficient buildings and their external wall constructions

https://doi.org/10.58224/2618-7183-2024-7-5-1
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Аннотация
Construction and climatic certification and, therefore, the orientation of buildings and building envelopes are important aspects of design and construction, especially in the conditions of specific climatic zones of the Republic of Kazakhstan. The main points that should be taken into account when determining climatic conditions, including in certification: the study of climatic conditions at the construction site, such as solar radiation, temperature, humidity, wind and other meteorological factors. This permits to select the appropriate building structures, materials and technologies. Based on climatic data, an energy saving strategy is developed to ensure an optimal level of comfort in buildings with minimal costs for heating and air conditioning, as well as to minimize overheating in the summer and provide optimal solar lighting, take into account the prevailing wind directions to minimize the negative impact of strong winds on structures and improve ventilation. The developed methodology of construction and climatic certification and factors of the natural and climatic environment, entered into the passports of the construction object, is the basis for the creation of design documentation of the Architecture section to ensure optimal conditions for the design, construction and operation of buildings and structures.
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Design of steel fiber-reinforced concrete for slip forming

https://doi.org/10.58224/2618-7183-2024-7-5-2
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Аннотация
Introduction. Slip forming is one of the effective and promising methods of concrete mix casting. Development of slip forming technologies largely depends on accumulated experience and tools, one of which is the composition design methodology. The use of special types of concrete, such as fiber-reinforced concrete, requires additional knowledge and the creation of special technological tools. The purpose of the study: to develop a methodology for designing steel fiber-reinforced concrete composition for slip forming. Methods and materials. Known methods for designing concrete and steel fiber-reinforced concrete compositions are used. A methodology for designing steel fiber-reinforced concrete composition for slip forming has been developed, consisting of two stages: designing the matrix composition to ensure a given ultimate extensibility of the mixture; designing steel fiber-reinforced concrete based on a pre-obtained matrix composition. Cement CEM I 42.5N, medium-sized sand, crushed stone with particles size 5-10 mm and 36 mm length steel milling fiber are used. Results and discussion. According to the proposed methodology, the composition of steel fiber-reinforced concrete with specified properties was designed (ultimate extensibility not less than 100 mm/m; cone slump 1...4 cm; compressive strength not less than 40 MPa; flexural strength not less than 6.5 MPa). The results of laboratory tests of the obtained composition are presented. In terms of strength, workability and ultimate extensibility, the composition meets the technical specifications. Conclusions. The proposed methodology of designing the composition of steel fiber-reinforced concrete for slip forming has been successfully tested in laboratory and can be recommended for use in production.
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Mechanical characteristics of polymer composites based on epoxy resins with silicon carbide

https://doi.org/10.58224/2618-7183-2024-7-5-3
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Аннотация
This study examines the impact of the type of base matrix (epoxy resin) and the addition of silicon carbide powder on the mechanical properties of polymer composite materials. To determine the compressive strength and elastic modulus of the polymer composites, samples were prepared using ED-20 epoxy-diane resin, cured with polyethylene polyamine. In order to eliminate the dependency of the results on specific commercial brands of resins, tests were conducted on polymers from different manufacturers. Mechanical tests were performed on samples of pure resin as well as on those containing reinforcing SiC particles. The chosen research methodology allowed for the determination of the relationship between the strength of the final polymer composites and the presence of silicon carbide powder. Polymer samples in the form of 20 mm cubic specimens were fabricated in custom-made formwork molds. Compressive strength tests were carried out using a REM-100-A-1 universal testing machine, and deformations were additionally measured using a non-contact video extensometer to calculate the elastic modulus. The study revealed a positive effect from the addition of 5 wt.% SiC to the epoxy-diane resins on the specified mechanical properties. The average increase in strength was 168%, while the elastic modulus increased by 26%. The introduction of the reinforcing additive also enabled a more consistent relationship between the loads and deformations of the samples based on epoxy resins from various domestic manufacturers, significantly enhancing their applicability in construction and other industries.
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Cauchy problem for modeling of unsteady mass transfer processes in an unbounded plate by the integral laplace transform method

https://doi.org/10.58224/2618-7183-2024-7-5-4
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Аннотация
The article outlines the formulation and solution of the problem of physical and mathematical modeling of non-stationary processes of mass transfer of chemical components of the structure of reinforced concrete enclosing structures under the influence of factors (chemical, biological) of the operating environment. The theory of operational calculus (integral transformations) is used as a mathematical apparatus for jointly solving Cauchy and Laplace problems. To solve the problem and study the processes considered in the article, a dimensionless plate with a dimensionless concentration of aggressive components on its surface was chosen as an idealized model of the enclosing structure. Carbon dioxide, dissolved in the liquid and penetrating with it into the material of the structure through pores and microcracks, was chosen as an aggressive component acting on the enclosing structure. The final solutions of the considered boundary value problems are presented for the case of constant values of the kinetic coefficients of external and internal mass transfer. The results presented in this work can be used in the development of software for predicting the strength characteristics of enclosing structures operating in aggressive environments. Thanks to the obtained solutions to the problems of non-stationary mass transfer processes, using the example of the consequences of carbon dioxide corrosion, it is possible to consider the time period of the life cycle of buildings and structures, the timing of repair work with greater accuracy.
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