The  aim  of  the  study  is  to  verify  the  operability,  reliability  and  functionality  of  a  closed-loop  hydrostatic transmission, which enhances the durability of the hydraulic drive by isolating the working fluid from atmospheric air and maintaining  excess  pressure  at  the  pump  inlet.  The  selected  research  object  is  a  closed-loop  hydrostatic  transmission configuration, where drain leakage return is carried out by an ejector pump, while a hydropneumatic accumulator serves as a closed hydraulic reservoir that maintains excess pressure. Theoretical relationships for the designed components of the hydraulic system were derived using mathematical modelling by equations of normal dimensionless hydraulic numbers and a Microsoft Excel package. Design methods of continuity and modification were applied to construct the test bench. Based on existing research, the influence of various contaminants on the system failure characteristics was determined, and the positive effect of the purity of the working fluid on the durability and reliability of the hydraulic drive was highlighted. An overview of existing open, combined open-closed and closed hydrostatic transmissions revealed their disadvantages in terms of ensuring fluid purity. A proposed hydraulic schematic formed the basis for designing and manufacturing a test stand for investigating the closed-loop hydrostatic transmission. Criteria for selecting the pneumatic-hydraulic accumulator were defined, and a methodology for calculating parameters was substantiated. A versatile design of the ejector pump, operating under various flow pressure conditions, was developed, including replaceable components for the flow section (nozzles, mixing chambers, throats and confusers). The test program and methodology involve four test algorithms: stand preparation, tests without drain leakage, tests with maximum allowable drain leakage, and tests with intermediate drain leakage volumes, resulting in a total of one hundred sixty experiments. This study allows the feasibility of applying the presented closed-loop hydrostatic transmission in various types of machinery to be assessed.

The work develops a technology that provides an increase in the operational properties of the surface layer of finished polyamide parts in order to increase wear resistance without affecting their load-bearing capacity. To study the impregnation of a polyamide-6 sample with a mixture of motor oil and hexane, full-scale experimental research was carried out following the algorithm developed using a laboratory unit. In the work, the program code for the control board was used that operates in conjunction with the PowerGraph software for processing the acquired data. During the study, a method for drying samples with the dimensions of 4x50x50 mm in a high-frequency electric field (up to 2500 Hz) was selected in order to heat and remove moisture from the polymer evenly within a short period. Darcy's law describing the process of impregnating polyamide with oil was used. In order to increase the efficiency of impregnation and reduce the viscosity of the filler, its optimal composition was determined: a mixture of M-8B engine oil and hexane at a ratio from 8:2 to 4:6, respectively. A setup based on the UZP-2500 device was developed and automated by introducing a control board and sensors to measure the strength of the anode current and temperature of a polyamide sample. In addition, a regulating device with the power of a high-frequency generator operating in the current range of 0.25–0.35 A was built into the unit. Under the processing modes (the temperature of the polyamide sample is 75°C; the hexane content in the mixture is 40%), a method for controlling the drying temperature was established by switching off the high-frequency generator for 700 ms. The research results allow a new technological process of oil filling in polyamide parts operated in friction units to a given depth at known values of the impregnation rate to be developed. These results can help to increase the wear resistance and, consequently, the service life of the surface layer of finished polyamide parts used in railway wagon trucks exposed to friction and wear.

The aim of the experimental research is to validate the theoretical findings obtained from a mathematical model of a two-mass impact system. The research object is a physical model of a two-mass impact system, designed to prevent the transfer of the reactive component to the tool carrier. The model includes a housing, inertial mass, elastic member and impact part. In the operating position, a compressed elastic member is placed between the inertial mass and the impact part, held together by dogs. The height at which the impact part detaches from the inertial mass is determined by the position of the clamp, which separates the moving impact part and inertial mass during free fall. The study involved the fundamental principles of similarity theory, planning theory and data processing. The height at which the impact part detaches from the inertial mass and the impact part is taken as an independent factor, while the energy of a single impact serves as the response function, determined by the diameter of the cone impression delivered by the impact part onto a wooden base. Based on the analysis of physical laws, similarity criteria for the impact mechanism were established, along with dependent and independent indicators, and transfer equations from real parameters to model parameters were derived. The research findings indicate that the total area of air holes should be at least half of the cross-sectional area of the housing for a physical model. The relationship between the diameter of the cone impression on the wooden base and the impact energy was determined. The adequacy of the mathematical model describing the processes in the impact device was confirmed, with a maximum discrepancy of 18% between the results of mathematical and physical modelling of the operating process for the impact mechanism characterised by an increased energy of a single impact. Therefore, the research results validate the results obtained from the mathematical model of the impact mechanism. Further studies should focus on refining the physical model to record the rebound height of the inertial mass as a function of the parameters of the impact mechanism.

This  article  develops  a  tool  for  impact-centrifugal  processing  and  establishes  processing  modes  that increase the microhardness of the surface. An experimental study was carried out, where the tightening force, the number of working strokes, the rotation frequency of the hardener and the motion were proposed as technological parameters of impact-centrifugal processing. The experiments were carried out using flat machine-cut samples based on aluminium alloy D16T. A prototype of the rotary hardener with the standard fastening was designed and manufactured. During the experiment, it was revealed that, for the variation in average microhardness, the contribution of the rotation frequency is higher than that of the longitudinal motion. A significant influence of the tension on the surface microhardness is noted: following processing with a rotary hardener, it increases. It is shown that, to a greater extent, this increase depends on the technological tightening force and to a lesser extent on the rotation speed of the tool; it is recommended to increase these parameters. It was found that a 2-fold increase in tightening force resulted in an increase in microhardness by 70 HV 0.1, while increasing the tool rotation speed by 200 rpm led to an increase in microhardness by 42 HV 0.1. However, technological parameters must be selected taking into account the operability of the hardener. It was shown that the longitudinal motion has little influence on the increase in microhardness. The prototype of the designed tool can be used for processing at milling, boring, and grinding machines with computerised numerical control through a standardised fastening unit. This ensures sufficient technological flexibility and allows it to be used for reinforcing flat surfaces and fillet radii. The forecasted increase in the surface microhardness of the D16T sample using a rotary hardener amounts to 38.5% of the initial value in the experimental area with satisfactory productivity.

This paper investigates the cutting forces arising when using a single abrasive grain. Analytical studies were carried out using a model of a single abrasive grain in the form of a rod with a radiused apex acting on the workpiece material. The slip-line method (method of characteristics) was used to calculate the deformation intensity of a plastically edged workpiece material under the action of a single grain. Mathematical models were developed for the following factors: plastic deformation of the material, edging of the stagnated zone and its friction against the grain surface when moved upwards in the form of chippings, grain friction against the plastically deformed material, and the action of the dynamic component of plastic deformation. The significance of the dynamic component in the overall balance of forces related to plastic deformation was established by determining the ratio of dynamic stress on the break line and shear yield point. This dependence calculated for D16T and 30HGSA materials showed the feasibility of accounting for the dynamic component subsequently processed by free orthogonal cutting and rolling contact deformation using a special machine with numerical control. Further, using the same machine, drilling of probing holes was performed with video recording of the surface image prior to and following drilling. By varying the speckle images, the displacements of material particles on the sample surface were determined by the digital image correlation method, following which the radial deformations were determined by differentiating the obtained displacement values. Statistical analysis of a sample of radial deformations equidistant from the centre of the hole while varying the rotation angle by Fourier transformation with the calculation of the distribution period showed that the distribution is periodic. It is established that the periodograms constructed using experimental data have local maxima at a period value close to 180 degrees. This determines that the main calculated components of the residual stresses and the angle of their rotation be constant when selected to calculate the values of radial deformations at arbitrary points around the hole. The paper presents an approach that allows residual stresses to be determined by drilling probing holes and assessing the displacement of material particles on the sample surface due to the redistribution of residual stresses. For the analytical description of experimental data, it is proposed that an approximating periodic function be used, and the physical meaning of its coefficients is determined.

The research aims to lower tooling costs by reducing the time allotted to designing coatings on domestic cemented carbide metal-cutting tools by using the atomic force approach. The object of the study is coatings on cemented carbides of the tungsten carbide group such as titanium carbide (TiC), titanium nitride (TiN), and titanium (Ti) coatings or a nitride-based titanium, chromium and aluminum (Ti,Cr,Al)N composite coating. To select the most rational coatings, the article employed the method of calculating the functionals of interatomic systems using the density functional description of single atoms. The simplest measure to reduce the cost of designing metal-cutting instruments for manufacturing parts made of difficult-to-machine materials is to develop coatings for this tool type. The article considers various atomic arrangements in the coating material in relation to the WCo8 cemented carbide (VK8, tungsten carbide-cobalt alloy containing 8% cobalt). The calculated values of the interaction energy of the coating material atoms with one another and with the cemented carbide material ranged from 3.04 to 3.5 J/m2. Moreover, the research has established a correlation between the calculation results and the performance parameter of metal-cutting tools considering fracture toughness K1c (MPa ∙ √m). The main result of the study is that the employed computational method made it possible to determine the adhesion value for the atoms of the above-mentioned coating materials with tungsten carbide and cobalt atoms packed in different scale configurations. This enables the classification of coatings from the perspective of ensuring maximum performance properties of the tooling material. The present article assumes that the higher the adhesion value, the better the performance properties. The hypothesis has been confirmed experimentally as well as by the values of fracture toughness K1c. Thus, the most rational coating options have been selected for specified operating conditions of a metal-cutting tool, which permits reduction of tool design costs and makes it possible to predict the performance properties of tools at the design stage.

The aim of the study is to define the correlations describing the flow parameters during super-cavitating flow past an obstacle, often found in various elements of thermal power systems and units, as well as to offer a simple and reliable method for analysing experimental datasets for the flows in such systems. Full-scale modelling of cavitation processes was carried out using a circulating hydrodynamic set-up. The process of super-cavitation flow past cones with base diameters of

15.45 and 21.75 mm and opening angles of 154° and 127°, respectively, in a working section having a diameter of 30 mm, was investigated. The obtained experimental data comprises a four-dimensional array that describes the dependence of the cavity length arising behind the obstacle and the pressure inside the cavity on the flow rate and temperature. Due to the complexity of processing and visual representation, this array was divided into two three-dimensional arrays. The approximation of the obtained data was carried out by locally estimated scatterplot smoothing (LOESS). The results demonstrated that the transition from vapour–gas to vapour cavitation is independent of the geometric dimensions of the obstacle. In addition, the dependence corresponding to the transition process to vapour cavitation was obtained by processing the experimental data. An empirical equation describing such a transition is proposed. Therefore, the method of smoothing a locally estimated scatter plot (local polynomial regression) illustrates the correlation between the processed data. The proposed empirical equation allows the critical length of the cavity to be determined that corresponds to the transition from vapour–gas to vapour cavitation and can be used for the design and operation of thermal power equipment.

This paper investigates the cutting forces arising when using a single abrasive grain. Analytical studies were carried out using a model of a single abrasive grain in the form of a rod with a radiused apex acting on the workpiece material. The slip-line method (method of characteristics) was used to calculate the deformation intensity of a plastically edged workpiece material under the action of a single grain. Mathematical models were developed for the following factors: plastic deformation of the material, edging of the stagnated zone and its friction against the grain surface when moved upwards in the form of chippings, grain friction against the plastically deformed material, and the action of the dynamic component of plastic deformation. The significance of the dynamic component in the overall balance of forces related to plastic deformation was established by determining the ratio of dynamic stress on the break line and shear yield point. This dependence calculated for D16T and 30HGSA materials showed the feasibility of accounting for the dynamic component system based on a small hydropower station located in the Todzhinsky district of the Republic of Tyva. For an adequate assessment of the operational reliability of hydropower units, a logical and probabilistic method based on the kinetic theory of fault tree was used. The method allows the failures of the used equipment, as well as unplanned shutdowns of units due to a shortage of water resources in the Great Yenisey (low water, overdrying, and frozen frost), to be taken into account. The development of a generation system based on a small hydroelectric power plant for the settlements in the Todzhinsky district of the Republic of Tyva offers a load of up to 2,500 kW, which helps to reduce the cost of purchasing, delivering, and storing diesel fuel, while diesel generators can be used as backup power sources. 3 scenarios of structuring a small hydroelectric power plant were considered that involved various numbers and total capacity of hydrogenating units: 5x500 kW, 4x630 kW, and 3x800 kW. Therefore, by using the multi-criteria optimization method, the optimal structure of the generating system based on a small hydroelectric power plant having three hydroelectric units (each characterized by a capacity of 800 kW) was selected from the three proposed options, taking into account the reliability and uncertainty of the initial information.

The work aims to develop a simple and effective method for identifying the parameters of photovoltaic converter (PV-cell) models for their wide practical application. An exponential model having one diode and five parameters is adopted as the basic model of the photovoltaic converter to facilitate its easy integration into MatLab/Simulink simulation software. To identify the parameters of models of photovoltaic converters, an original method based on finding the minimum of the root-mean-square error between model and experimental volt-ampere characteristics was used. The effectiveness of the method was confirmed by determining the parameters of different models of photovoltaic modules based on various technologies: thin-film Shell ST40, monocrystalline Shell SP70, and polycrystalline Kyocera KC200GT. A developed technique for constructing mathematical models of photovoltaic converters in order to reproduce their electrical characteristics is presented. The solution is easily implemented in Excel spreadsheet software with the “Search for Solution” add-on installed. The proposed universal method for identifying the parameters of photoconverter models can be used to build models of a wide range of photovoltaic modules and solar cells. The model current-voltage characteristics of the considered photovoltaic modules are shown to be in good agreement with experimental characteristics across a wide range of temperature and insolation conditions corresponding to their actual operation. Higher accuracy is achieved when using the proposed identification method to determine the electrical parameters of mathematical models of photovoltaic converters than when using other well-known analytical and numerical methods. The result is a simple and effective method for constructing mathematical models of photovoltaic converters, which does not require the use of programming or the development of specialized numerical algorithms, allowing it to be used to solve many technical problems related to the design and operation of photovoltaic systems.

In this work, digital models for determining the electromagnetic influences of multi-wire traction networks on pipelines are developed. When developing models, an approach based on multiphase behaviour simulation of electric power systems was used. This approach adequately addresses all the influencing factors, which include modules and phases  of  currents  flowing  through  the  overhead  contact  wire  suspension,  6–10–25  kV  power  transmission  lines  laid on the supports of the overhead line, and lines of rails. In addition, it is possible to take into account similar parameters for stresses at the nodal points of a multi-wire system. Among the key factors are the railway clearance when laying pipes parallel to the railway track, railway clearance trajectory in the presence of non-parallel sections, and the electrical characteristics of the soil along the clearance route. The research results demonstrated that a 25 kV electromagnetically unbalanced traction network exerts significant influence on a pipeline running in parallel. It was shown that the maximum induced voltages at specific points along the pipe fall within the range of 300–700 V, which significantly exceeds the permissible level of 60 V. It was revealed that currents exceeding 20 A flowing through the pipe can have an adverse effect on anticorrosive protection devices. To mitigate electromagnetic impacts on the pipeline, the following measures are recommended: reducing the length of pipeline and railway clearance sections, increasing the gap between the traction network and the pipe, and installing an additional grounding source. The pipe can be connected to the supplementary grounding source through filters tuned to a frequency of 50 Hz, which involve capacitor units to prevent malfunctions during the operation of pipeline protection devices. Thus, the developed digital models allow the induced voltages generated by multi-wire traction networks and the currents flowing through the pipes to be adequately determined. These models offer an informed choice of measures that ensure the safety of pipeline maintenance.

The study addresses the conformity of actual electricity consumption to the calculated value in electric distribution networks in which municipal consumers predominate in several cities of the Chelyabinsk region. To study the conformity between the specific electrical load established by regulatory documents and the actual value per apartment according to power consumption data in several cities of the Chelyabinsk region, the average annual power consumption by municipal consumers with a specific number of apartments was analyzed over a period of 2021–2022. The correspondence analysis of the average annual electricity consumption by municipal consumers in the studied facilities was carried out using the conventional method for calculating the electrical load over the given period following the guidelines outlined in SP 256.1325800.2016. The discrepancy between the actual electrical load on the apartment and its normative value established by the acting normative documents ranged from minus 48 to 300% with respect to electricity consumption. For the considered 16 objects located in the cities of the Chelyabinsk region, the discrepancy between the actual electrical load and the established normative values was compared. For 6 apartments, this discrepancy ranged from minus 58 to 155%. To improve the accuracy of forecasting electricity consumption and calculating electrical loads in electric distribution networks with a predominance of municipal consumers, methods using a new factor were recommended. This factor involves a generalized uncertainty coefficient Ai, whose values are determined for the considered period. When using the developed methods, relative deviations in the forecast calculations are less than or equal to 10%.

The aim is to determine the optimal parameters for the preparation and dosing of active seeding (finely dispersed aluminium hydroxide) to control the decomposition of aluminate liquor in the Bayer process. Laboratory tests were carried out on a temperature-controlled rotating water bath (Intronics, Australia). The granulometric analysis of the obtained aluminium hydroxide was carried out using the VideoTest image analysis system and a Carl Zeiss Axioskop-40 microscope (Germany) supplemented with Image Analysis software. Finely dispersed aluminium hydroxide (active seed) was obtained by mixing an alkaline aluminate solution and recycled water in various ratios. The filling order of solutions was determined – first, recycled water, followed by cooled alkaline aluminate solution. Optimal conditions for the preparation of active seeding were established: the solution was held for 48–72 hours at 50°C at an aluminate solution to recycle water ratio of 60% and 40%, respectively. The dosing of the obtained active seeding into the head decomposers was examined. It was demonstrated that using active seeding in continuous decomposition mode stabilises the particle-size distribution of the production-grade aluminium hydroxide. The presence of active seeding allowed the initial decomposition temperature to be reduced from 62°C to 58°C without altering the particle-size distribution of aluminium hydroxide. In addition, the study confirmed the positive effect of active seeding on increasing the degree of decomposition of the aluminate liquor up to 1.5%. Therefore, based on the research results, it was established that the use of the new method for preparing and dosing active seeding into the main decomposers leads to the intensification of the decomposition process in alumina production.

This study focuses on documenting the historical stages of aluminium and alumina production prior to the transition to a modern industry structure, involving the Hall-Héroult electrometallurgical process, and their technical significance for the contemporary metallurgical complex. It highlights the significance of these stages in the development of scientific knowledge related to alumina, aluminium, and their production technology when using chemical methods for obtaining metallic aluminium. The analysis includes aspects, such as classification, technical evaluation of the processes, and the raw material base. It is shown that the formation of scientific knowledge regarding alumina and aluminium is mainly associated with the practical need for using alum and, to some extent, clay minerals. Since the commencement of deliberate research into methods for aluminium production in its elemental state and virtually until the 1890s, aluminium was primarily produced using the metallothermal methods pioneered by Henri St. Clair Deville and his colleagues due to the high thermodynamic stability of aluminium compounds and the absence of affordable energy sources. It was found that from 1854 to 1890, the production of aluminium by chemical method was associated with the use of sodium aluminium chloride (NaCl·AlCl3), natural cryolite, or synthesised fluoride salts. Available technical reagents (aluminium sulphate, ammonia alum, and aluminium hydroxide), along with natural raw materials (cryolite, bauxite, and clay), were used as source materials in this period. The extraction and processing of bauxite were primarily associated with the production of alum and aluminium sulphate consumed by light industry. Although the demand for pure aluminium oxide was limited during the metallothermic production of aluminium, the driving force behind the advancement of modern technologies for alumina production was the demand for chemical products. This demand led to the development of technology for processing bauxite, which forms the foundation of the metallurgical complex in aluminium production using the Hall-Héroult electrometallurgical method.

This study explores the possibility of producing a sodium silicate solution (liquid glass) using industrial raw materials for subsequent use in metallurgical practice. The object of the study was industrial waste from the production of aluminium fluoride, i.e., silica gel, which comprises a fine powder of silicon dioxide with a moisture content of over 55 wt %. Silica gel was purified using a low-concentration solution of sulfuric acid. The synthesis of liquid glass was carried out using the HEL Auto-Mate Reactor System. The silicon content in the solution was determined by X-ray fluorescence method using the Shimadzu EDX-7000P analyzer. To determine the alkali content in the resulting product, a titrimetric analysis method was used. The preliminary purification process allowed silica gel with an amorphous silica content of over 98 wt % to be obtained. The optimal parameters of the liquid glass production were defined: temperature – 100°C, process time – 4.5 hours, mixing speed – 300 rpm, and the concentration of the initial alkaline solution – from 10 to 17.5 wt %. The resulting liquid glass solution had a mass content of silicon dioxide from 16.65 to 23.77 wt % and a silicate module from 2.72 to 3.16, which meets the requirements of marketable products for various industries. Based on the experimental results, optimal parameters for the production of liquid glass using industrial raw materials, i.e., silica gel, are proposed. Liquid glass with the defined characteristics can be further used as a binder in metallurgical processes.

This work assesses the possibility of hydrometallurgical processing of ash and slag waste in order to extract rare and rare earth elements. The ash and slag waste from the Chita CHPP-2 combined heat and power plant was used as a research object. Inductively coupled plasma atomic emission spectroscopy (ICP-AES) was used to determine the elemental chemical composition of coal combustion products. To preconcentrate rare and rare earth elements, magnetic separators were used to isolate the -0.5+0.3 mm and -0.3+0.1 mm grain size fractions of ash and slag waste. The leaching of rare and rare earth elements from the studied samples was investigated using sulfuric, hydrochloric, and nitric acids, as well as an aqua regia solution, in combination with simultaneous ultrasonic exposure. It was determined that electromagnetic separation of the -0.5+0.3 mm and -0.3+0.1 mm grain size fractions of ash and slag waste significantly concentrates rare and rare earth elements in the magnetic fraction, including titanium (up to 25%), zircon (up to 33%), yttrium (up to 50%), lanthanum (up to 150%), and cerium (up to 5%). It was determined that an increase in the duration of ultrasonic treatment during the leaching of metals from ash and slag waste with sulfuric acid resulted in a uniform 7.25-fold increase in gallium content (from 0.008 to 0.058 g/dm3). Additionally, when decomposed with aqua regia, a 3-fold concentration of the same element was observed (from 0.008 to 0.024 g/cm3), while ultrasonic treatment offered only a slight increase in concentration. When leaching with sulfuric acid (the duration of ultrasonic exposure is 5 minutes), a 4-fold increase in the rubidium content was observed (from 0.108 to 0.457 mg/dm3). Therefore, the most effective method for extracting rare and rare earth elements from the ash and slag waste of Chita CHPP-2 involves acid leaching combined with electromagnetic separation and ultrasonic pulp leaching.