Introduction. Thermal effect of fire on technical means is a common and serious problem. In this regard, it seems an urgent task to study physicochemical and thermal transformations in devices based on cadmium telluride during man-made or natural fires. For a number of materials, such studies have not been conducted, and the available results are insufficient or narrowly focused. The proposed article presents new data on the defect resistance and applicability of the material depending on the thermal effect. The work objective is to study the features of degradation under the influence of extreme temperatures to create new materials with specified properties.

Materials and Methods. Cadmium telluride (CdTe) samples used in solar panels and detectors were studied. In the practical part of the work, the thermal effect on the sample of normal and extreme temperatures was evaluated, followed by the study of the material by transmission electron microscopy methods. The experiments simulated a zone of thermal impact of a fire. The computational and theoretical work consisted in improving the mathematical model of physical and chemical transformations and the evolution of defects under thermal influence up to 1092 °C. The mathematical model took into account the heat dose characteristic of uncontrolled combustion. The Maple software package was used to solve the equations.

Results. The formation of defects in a CdTe sample at significantly different levels of thermal exposure was visualized. The lower limit was about 20 °С, the upper one was more than 600 °С. Transformations in CdTe control samples under the influence of temperatures up to 1092 °С with a step of 15 °С were worked out in detail. Point defects caused by the influence of temperature were presented as a factor of destruction of the material, and consequently, failures in the operation of the device. A system of equations was solved that takes into account a set of parameters: the frequency of vibrations of atoms in the lattice, temperature, concentrations of CdTe nodes, interstitial atoms and vacancies, migration and attachment of interstitial atoms and vacancies. The concentrations of vacancies and interstitial atoms in CdTe samples depending on thickness and temperature were graphically presented. The results of scientific research allowed us to assert that CdTe-based detectors worked relatively correctly only at a heat dose of up to 400 °С. In the ranges of 400-600 °С, the defective network of the material actively evolved, preventing destruction. However, a further increase in thermal exposure led to complete degradation of the equipment, which did not allow the use of cadmium telluride in extreme conditions, even for a short time.

Discussion and Conclusion. The proposed improved model of physical and chemical transformations in CdTe-based devices in heat-affected areas will allow a more selective approach to the use of equipment. In addition, it is necessary to improve materials and increase their resistance to extreme temperatures.

Introduction. Risks of accidents and fires during transportation and pumping of oil and petroleum products is a significant problem of technosphere safety. The reasons may be leaks due to corrosion damage to pipelines, tanks and oil storage tanks. In view of the possible serious financial, environmental and social consequences of such incidents, it is important to constantly seek new, more effective approaches to preventing corrosion processes. It is obvious, for example, that at present not all chemical compounds capable of suppressing or inhibiting the destruction of metals and alloys have been thoroughly studied. The presented scientific work is partly aimed at overcoming the lack of data in this area. The objective is to investigate an insufficiently studied compound salicylidene-aniline, which can be a corrosion inhibitor similar to other nitrogen-containing compounds similar in structure and composition.

Materials and Methods. The gravimetric method was used to study the inhibitory, adsorption and complexing properties of salicylidene-aniline. The experiments were carried out with St3 steel plates. The mass of metal samples without an inhibitor and with an inhibitor was recorded before and after exposure in the test media. The effect was determined by the change in the corrosion rate. When setting up experiments, the authors were guided by GOST 9.905–82 "Unified system of corrosion and ageing protection. Corrosion test methods. General requirements". The volume of the corrosive medium was determined according to GOST 9.506–87 "Unified system of corrosion and ageing protection. Corrosion inhibitors of metals in water-petroleum media. Methods of protective ability evaluation". The corrosion criteria were taken from GOST 9.908–85 "Unified system of corrosion and ageing protection. Metals and alloys. Methods for determination of corrosion and corrosion resistance indices". The calculations were based on the valuation principle, which sets the ratio of a multiplicative metrized linear order on a set of particular criteria. An integral indicator based on mathematical and methodological approaches was used for ranking.

Results. The effect of hydrochloric acid medium on steel samples St3 was studied. Four concentrations of the inhibitor were taken: 0 %, 0.01 %, 0.1 %, and 0.2 %. The mass of metal samples without an inhibitor and with an inhibitor was recorded before and after exposure in the test media. The effect was determined by the change in the corrosion rate. The mass index of corrosion was calculated. The surface quality during destruction and corrosion inhibition was determined in five stages: the elements to be evaluated were selected, the purpose of the evaluation was formulated, the elements of the technical condition of the object under study were found, the essence of determining the usefulness or value of the criterion was described, and the essence of optimization was explained. The studied properties were ranked with respect to the multiplicative metrized linear order on a set of particular criteria. For the calculations, the task was set — to determine the components of vector B in accordance with one of the evaluation stages. We are talking about the stage when the usefulness or value of the criterion is analyzed by points on the numerical axis indicating the state of the object "better — worse". We constructed an indicator z approximating a known or specified (learning) matrix of paired relationships between objects. The resulting indicator allowed us to assess the technical condition of the surface during the course of corrosion and when it slowed down due to the addition of salicylidene-aniline. The result was obtained for samples with a surface area from 10.1∙10^-4 m² to 11.9∙10^-4 m². During the experiment, the mass of the metal decreased by 0.2–0.8 times with the inhibitor and almost by 3.5 times without it. The mass index of corrosion was recorded from 0.15 g/m²∙h to 0.48 g/m²∙h. At the same time, the protective ability of the inhibitor was quite high: the minimum was 77.4 %, the maximum was 94.8 %. This is a convincing indicator. It is also worth mentioning such an advantage of salicylidene-aniline as a low danger. Its hazard class is III (for comparison: the hazard class of aniline is a level higher — II).

Discussion and Conclusion. The authors propose to use salicylidene-aniline as a means to increase the safe service life of oil pipelines and tanks. The potential of this composition as an effective corrosion inhibitor, highly soluble in oil and petroleum products, has been proven. Such properties of salicylidene-aniline as slow oxidation and moderate toxicity are noted.

Introduction. About a third of employees of medium and large agricultural enterprises work in hazardous and harmful conditions. It is worth clarifying that the situation in this area is constantly changing, information may become outdated. The presented scientific work is designed to solve this problem. New information should be considered and systematized to study current data. The work objective is to analyze recently published official statistics on the impact of working conditions on the health of agricultural sector workers and, in particular, women. In addition, the problems of the formation and development of occupational diseases of women employed in agriculture are considered.

Materials and Methods. The data of the Federal State Statistics Service, the Ministry of Health of the Russian Federation, as well as the works of foreign and Russian scientists who studied the peculiarities of work in agriculture were used as research materials. Official statistics data were summarized in the form of tables, visualized as diagrams. The illustrative material allowed us, in particular, to compare the indicators, to identify the most significant risks associated with the work of women in the agro-industrial complex.

Results. About 35% (that is, more than a third) of the personnel of medium and large enterprises of the agro-industrial complex are women. Many of them work in harmful and dangerous conditions. From 2015 to 2021, the corresponding minimum recorded figure was 26.4% of all women employed in agriculture, the maximum was 37%. Generalized statistical data suggested that from 2015 to 2021 the situation was not significantly improving, a downward trend was not formed. If to speak about hard work, the proportion of women performing such functions increased from 13.8 % to 17.7%, that is, by 2021 the situation noticeably worsened. We noted the progress with strenuous labor processes in agriculture. The proportion of women engaged in such jobs almost halved: from 3.5% to 1.8%. Physical overload, which functionally overstrain the organs and systems of the body, should be recognized as a particularly harmful factor for agricultural sector workers. The most problematic industry from the point of view of women's health was animal husbandry.

Discussion and Conclusion. The results of the work allow us to conclude about the unsatisfactory working conditions of women in agriculture. The situation can be improved by state control, mutual interest of employers and employees in the organization of workplaces and the compliance with labor protection requirements. A systematic approach should reduce the number of occupational diseases among women, improve the health indicators of agricultural workers.

Introduction. Ensuring high reliability and safety of operation of passenger elevator units is largely determined by the implemented maintenance conditions (MC). The frequency of performing preventive actions depends, first of all, on the level of elevator utilization. Time, power indicators and the degree of remaining life are used to evaluate it. Among the time indicators, the net machine time coefficient (NMT) and the turn-on frequency are accepted, which are random variables depending on a number of internal factors characterizing the operating conditions of the unit. The work objective is to establish the relationship between the average values of NMT, as one of the main indicators of the load of the elevator unit, and the main internal factors.

Materials and Methods. The research was carried out on the basis of processing and generalization of statistical materials of dispatching control of time indicators of a number of passenger elevator units. 11 elevators were randomly selected, differing in the number of floors, the specific number of residents using the elevator, and the speed of movement of the cab. Graphical-analytic methods were used to construct empirical dependences of NMT on the number of residents, the speed of the cab and the number of floors of the building. Along with the technical parameters of the elevator, random changes in the NMT indicators for individual periods of the day were taken into account.

Results. Empirical dependences of the NMT on the main internal factors — the density of occupation, the number of floors of the building and the speed of the cab movement were established. Mathematical models provided results adequate to experimental values. The error when comparing the calculated data with the actual data did not exceed 10 % in most cases.

Discussion and Conclusion. The value of the empirical dependencies obtained consists in the ability to assess the workload of units during the current period of operation without additional multi-day measurements. Empirical formulas can be used as basic relations in simulation modeling at any stage of the life cycle.

Introduction. Non-destructive methods are most often used to assess the condition of the metal structure. Dangerous stress is determined by the value of the yield strength. This approach has weaknesses. This is, firstly, the probabilistic nature of the methodology (the minimum value of the indicator obtained during laboratory tests is entered into the regulatory and technical documentation). Secondly, the limitations on the number of samples should be overcome. Thirdly, the different duration of operation causes a significant difference in the mechanical characteristics of the metal, which to a certain extent complicates the long-term prediction of the condition of the structure. The presented work is designed to solve these problems within the framework of the study of new and long-operated facilities in the Rostov region. The scientific research objective is to analyze fatigue changes and determine possible degradation of the metal.

Materials and Methods. The mechanical characteristics of the material under study were reliably described by the Weibull distribution law through the shear parameter (the minimum possible value of the characteristic) and the shape parameter (magnitude dispersion). For scientific research, the indentation method based on a modified Rockwell hardness estimation method was used as part of the work. A conical indenter was embedded in the surface, then the reaction of the metal was analyzed. To implement the method, an analog-to-digital converter and a laptop were used. For correlation analysis, intermediate characteristics were taken: depth, maximum and minimum velocities, maximum and minimum acceleration of cone insertion. A correlation was established with the mechanical characteristics determined by standard tensile and hardness tests of the metal.

Results. Objects with zero and long-term operation were studied. The measurements were carried out in a warehouse, production site, stadium, bridge, Palace of Sports and on a power line support. From the group of new and used structures, one was selected for a detailed fixation of the values of yield strength. So, before the start of operation, the condition of three metal trusses of the warehouse was analyzed. It was established that the lowest value of the yield strength here was 240 MPa, the maximum was 345 MPa. On the power transmission line poles, which have been in operation for 43 years, the lowest recorded value of the yield strength was 235 MPa, the highest was 384 MPa. For each of the six structures, the minimum and average distribution of the metal yield strength values was given, and the coefficients of variation of this indicator were given. The recorded values were summarized in the form of a table. The average values for all new and used designs were calculated. Graphically presented data illustrate the growth of the coefficients of variation of the yield strength with increasing service life.

Discussion and Conclusion. A comparative analysis of the obtained values of the yield strength of building structures of approximately the same strength class suggests that the influence of operating time can both increase and decrease the studied indicator. At the same time, long-term operation is a factor that increases the average value of the coefficient of variation. To monitor the strength capabilities of the structure, it is advisable to use a non-destructive method, selectively monitoring the mechanical characteristics of the elements before and during operation.

Introduction. Publications on sintered metal powder parts consider interparticle bonding in hot-deformed materials and features of low-alloy structural steels, as well as the use of carbon-containing materials. The authors of the presented article have previously investigated sintering in relation to structural changes in the material, described changes in physical and mechanical properties, reduction of oxides, recrystallization, etc. This paper shows the relationship of mechanical properties of powder steels with the parameters of intracrystalline bonding. The kinetics of its development during sintering is demonstrated for the first time. The study objective is to find out how sintering affects the interparticle bonding and structure of powder alloys with iron and carbon. The task is to study the technological modes of sintering samples from alloyed and pure iron powder to achieve the best mechanical characteristics.

Materials and Methods. The powders of the Höganäs company were sintered at a temperature of 900-1150 ºС for 0.5–2.5 hours. The protective gas medium (dissociated ammonia) made it possible to prevent oxidative and other sintering reactions. For static cold pressing, a hydraulic press 2PG-125 with a maximum force of 1250 kN was used.

Results. For the first time, the presence of intracrystalline bonding mechanisms with different intensity during sintering has been experimentally established. The dependences of the increment of the relative area of the contact surface on the duration of the isothermal exposure were constructed. With an increase in the sintering temperature to 1150 ºС and a holding time of more than 80 minutes, the contact surface area gradually increased. It was shown that the samples from the powder grades under consideration formed an intracrystalline bonding on the entire contact surface at 1150 ºС. Therefore, this technology can be recommended for practical use. The addition of graphite to the charge slows down the growth of the contact surface. At the same time, the molds from pure powder ABC100.30 and from Distaloy HP-1 powder showed differences. In the first case, with the addition of graphite to the charge, the contact surface developed more intensively than in the second one. The obtained results were recorded in the photo and visualized in the form of graphs.

Discussion and Conclusion. According to the results of mechanical tests, it is possible to estimate the proportion of the contact section of the molding with intracrystalline bonding. Its feature is the structural correspondence of the interparticle surface of the splice and the intergrain boundary. The value of this boundary is determined by comparing the relative area of the contact section with the intracrystalline bonding and the relative area of the contact surface. The possibilities of improving the quality of bonding of powder steels by increasing the temperature and time of their exposure during sintering are determined.

Introduction. The work focuses on solving quality problems of castings made of Al-Si-Mg alloy (AK9). The paper draws attention to the absence of a unified theory of alloy modification and the need to find solutions that ensure good product quality. The reasons for bad quality due to the weak justification of the choice of the manufacturer of the initial charge material — ingots are considered. Ingots from two suppliers are compared in terms of the structural-phase state. The paper shows how it causes defects in castings. The inefficiency of traditional methods of suppressing the formation of brittle plates of the iron-containing phase in the alloy of the Al-Si-Mg system due to the presence of Mn in the chemical composition of the alloy is noted. If the specified flaw is inherited from the source material, the generally accepted approach does not work. The article formulates the recommendations for solving this problem. The introduction of the proposed approach into production practice can open the way to solving an important applied task — to improve the wording of tasks for tenders. The relevance of the study is due to the widespread use of alloys of the Al-Si-Mg (AK9) system in modern mechanical engineering, including in aerospace structures. The work objective is to study the influence of the structural-phase state of the source material on the qualitative characteristics of finished castings from the Al-Si-Mg alloy system.

Materials and Methods. Eight casts were analyzed, in which ingots from two manufacturers were used. Radiography revealed a correlation between the fracture structure of castings, structure and quality indicators. Scanning electron microscopy was used to analyze the microstructure and chemical composition of the phases. When setting quality requirements, the authors proceeded from the existing industry and state standards. The conditions of heat treatment of samples were taken from the same documents. The spectrograms were visualized as graphs showing the intensity of the element peak in the Auger spectrum and the energy of the electrons resulting from the Auger effect.

Results. The results of radiography gave grounds to assert that the products provided by supplier No. 1 had significant advantages in terms of quality. If we focused on the industry standard, the exclusion of the 2nd supplier's ingots from the process ensured the production of products without casting defects at the level of 73 %. Otherwise, this figure did not exceed 57 %. The rejection indicators were discontinuities, clusters of flaws, high porosity. After melting 5-8, which involved the materials of the 2nd manufacturer, the fractures of the samples after rupture were investigated. Locations with smooth, viscous and mixed relief are highlighted. An increase of up to ×500 made it possible to establish insignificant areas with a viscous relief, which was characteristic of brittle fracture by the cleavage mechanism. The absence of inclusions and liquations was established. The microstructure of the sections from discontinuous samples was considered. It turned out that it corresponded to the modified and heat-treated state of the AK9ch alloy without signs of burnout. Individual dark needle-like phases and single pores were noted. The conditions of dispersed Si precipitations, Al₃₂Si₁₀Fe₅Mn and Al₃₇Si₅Fe₅Mn chipping, as well as the separation of the Al₃₆Si₃Fe₆Mn₃ phase in skeletal form were described. The advantages of the microstructure of ingots samples from manufacturer No. 1 were listed. It corresponded to the modified state of the AK9ch alloy. The branches of dendrites and the sizes of silicon inclusions were smaller. Needle-like phases of Al_xSi_yFe_zMn_q were not detected.

Discussion and Conclusion. Light areas in the castings fractures were formed by a brittle fracture mechanism, which is due to the presence of Al_xSi_yFe_zMn_q phase plates in the alloy structure. If iron-containing phases are inherited from the source material, then traditional methods of suppressing formation do not lead to the creation of compact equiaxed polyhedra. To improve the quality of castings, it is recommended to use ingots with a pre-modified structure, without including phase plates of variable composition Al_xSi_yFe_zMn_q. The results obtained can be used, among other things, to justify the requirements for the material during tenders, which will enable the enterprises of the machine-building industry to improve the quality of products and reduce the cost of marriage. As a result, this will increase their competitiveness in the Russian and world markets.