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 of the cutting force under the velocity of a single grain impacting the workpiece surface of above 50 m/s. Graphs depicting the relative grain force and the relative depth of grain penetration are given. The proposed calculation method for cutting forces using a single grain can be used to determine the total force of interaction between the single grain and the work-piece material. In order to adopt the defined processing method and the workpiece material, the number of grains in contact, the contact duration, and the cutting speed should be found. On this basis, the process performance and the quality of the workpiece surface can be calculated.

In this work, we aim to validate the efficiency of the previously created and patented laboratory test installation for simulating the high-pressure operation of a thermal barrier of high-pressure reservoirs and for determining the thermal conductivity of thermal barrier materials. Simulation of thermal barrier operation in the test installation was carried out under elevated pressures (up to 50–70 MPa). The pressure on the thermal barrier layer was created and regulated by an Instron 5989 test machine as part of the installation. Control of temperature changes and evaluation of the thermal insulation performance were performed by a calculation method based on temperature readings in the control points of the upper and lower rods of the installation. These values were obtained by contact (using thermocouples of surface temperature control) or non-contact (using thermal imaging equipment) methods. A pilot study into the performance of a thermal barrier material “tennesite” was carried out at different pressures. At pressures of 30, 40 and 50 MPa, the thickness of the tested samples comprised 4.64 mm, 4.35 mm and 4.00 mm, respectively. Variations in pressure were established to have a negligible effect on the thermal conductivity of the studied material. Thus, at pressures of 30, 40 and 50 MPa, the temperature drop in the samples comprised 198°С, 188°С and 190°С, respectively. The installation showed high efficiency in simulating the thermal protection of the studied material. Thus, at a layer thickness of 4 mm under the internal pressure of 50 MPa and the working temperature inside the equipment housing up to 300°С, the material is capable of reducing the thermal impact on the protected part of the structure by about three times (from 298.6°С to 108.4°С). The presented design can be used when investigating the behavior of various thermal barrier materials operated under elevated pressures. The results obtained confirm the efficiency of the proposed laboratory installation.

The authors demonstrate the potential of a methodological approach for monitoring the damage kinetics and evaluating the load-bearing capacity of composite structural elements based on the method of acoustic emission. This methodology was developed by specialists of the Blagonravov Mechanical Engineering Research Institute of the Russian Academy of Sciences. The methodology was implemented for a fatigue test of an aircraft panel represented by a complex hybrid structure with a lining made of layered composite and a cellular internal structure of aluminum foil with polymeric filler that has a continuous layered structure in the gripping area. Fatigue tests were carried out at 4 Hz from the zero-loading cycle with an amplitude of 145 kN. To record the accumulation of damages, R15–AST transducers by Mistral (USA) and an A-line 32D 8-channel acoustic emission system by Interunis-IT LLC were used. Comparing the weight content of location impulses with their threshold values in energy clusters characterizing the kinetics of micro-, meso-, and macro-damages of the composite material structure made it possible to determine the bearing capacity of the aircraft panel at respective stages of damage kinetics. The results of the acoustic emission diagnostics are given for the examined aircraft panel during cyclic loading, including the coordinate location of acoustic emission sources, accumulation of acoustic emission events by channels, the dynamics of partial activity changes, and weight content of location impulses at damage evolution stages of a composite material. Therefore, the acoustic emission diagnostics of the aircraft panel made it possible to identify the areas of intensive damage accumulation in the hybrid structure of the panel and control the actual bearing capacity by defining the extent of its damages at various scale and structural levels during cyclic loading. The described methodology of using acoustic emission diagnostics for monitoring the damage kinetics and actual bearing capacity of highly loaded composite elements extends the research potential of the acoustic emission method.

This paper aims to analyze the existing designs of bucket teeth in earth-moving machines with the purpose of selecting an optimal design in a scientifically grounded manner. The research objects included six design models of teeth of earth-moving machines made of alloyed manganese steel 110G13L. Teeth models were built using the KOMPAS-3D software. Lateral elastic internal stresses and elastic strains in the teeth models were determined using the COMSOL Multiphysics software. Lateral elastic internal stresses and elastic strains were calculated for the applied load of 9 kN in soft soil and 90 kN in rocky soil. Optimal teeth designs were determined for soils of various hardness. In soft soils, a ripper tooth and a combined curved tooth with an extra ripper tooth showed the optimum combination of efficiency and strength. Thus, provided that the elastic strain of a standard tooth in soft soils equals 100% and depending on the initial state, a ripper tooth and a combined curved tooth with an extra ripper tooth showed the strain values of 30–50% and 32–35%, respectively. In hard soils, a combined curved tooth with an extra ripper tooth and a regular curved tooth showed the optimum combination of efficiency and strength. Thus, provided that the elastic strain of a standard tooth in hard soil equals 100% and depending on the initial state, a combined curved tooth with an extra ripper tooth and a curved tooth showed the strain values of 18–20% and 42–45%, respectively. The feasibility of using buckets with combined teeth of optimal design in earth-moving machines was scientifically substantiated. Future research will investigate various bucket designs of earth-moving machines to find their optimal modifications for soils of various hardness.

This work is aimed at improving the performance of various handling equipment by optimizing the transportation cycle, e.g., decreasing the time of acceleration and deceleration by damping load oscillations, increasing the steady-state motion speed, and decreasing the time of pauses. The object of modeling is an overhead crane with a capacity of 15 ton, a stroke of 15 m, and three degrees of freedom. A Lagrange equation of the first kind as a non-linear heterogeneous system was used. A mathematical analysis of the damping process was carried out by energy balance modeling. As a result, the optimal amplitude and frequency of damping impulses required to change the suspension length within 5% were obtained. These impulses have a maximum frequency of three oscillations per second and are supplied in a reversed phase to load oscillations. According to calculations, energy costs for damping load oscillations are below 3–4% of the lifting motor power. It is shown how damping is implemented in manual control, and coefficients are calculated to define the amplitude of changes in the load and arm suspension length. The ranges of changes in these coefficients comprise 0.85–0.9 and 1.1–1.15 for setting the amplitude and frequency of damping impulses when using an automatic system. On this basis, a load oscillation damping system for a moving overhead crane is developed. Options are proposed for the damping system: by an operator or an automatic control system. The mathematical model of a crane is suitable for studying various types of equipment. Due its high efficiency and relatively low cost, the proposed method of damping is recommended when designing new equipment or improving the existing equipment.

The work is aimed at solving the problem of using reconfiguration and additional reactive power sources to restore power to consumers of the medium-voltage distribution network in the case of emergency disconnections of connections by bus section circuit breakers. The reconfiguration problem for a 118-node test distribution network is solved using a high-speed algorithm involving the construction of a maximum spanning tree on a network graph as the basis for determining information about the composition of branches and chords of independent circuits necessary to restore power following disconnection. To ensure acceptable voltage levels following power restoration, additional reactive power sources determined using singular Jacobian matrix analysis methods are installed in the sensor nodes of the network. For the test circuit, the modes for single disconnections of individual sectional switches, including in dead-end sections, are analysed. By optimally reconfiguring the network in the normal mode, it is possible to reduce voltage deviations from 13% to 7%. For the modes caused by disconnections of individual bus section circuit breakers that lead to unacceptable voltage deviations, the set-down locations and reactive power of additional sources are selected. In the most severe of the considered disconnection scenarios, the installation of additional sources provided a reduction in voltage deviations from 18 to 8%. Thus, the methods proposed by the authors make it possible to restore the test network mode following emergency disconnections and ensure that the voltages in the network nodes are maintained within acceptable limits, both in normal and in post-emergency modes.

In this paper, we aim to investigate the performance of solar panels depending on the climate conditions of their location and the chemical and electrophysical characteristics of deposited dust. In particular, we study the effect of surface contamination of solar panels on their efficiency and determine the period of dust deposition that is critical in terms of power generation reduction. Experiments were conducted in April 2022 in the Republic of Tajikistan and the Chelyabinsk region of the Russian Federation. Both domestic and foreign publications on the impact of surface contamination on solar cell efficiency were reviewed. Comparative field experiments were carried out to investigate the performance of solar panels depending on environmental variables. It was found that the level of dust deposition in the Chelyabinsk region reached about 12–19 mg/m3, which is significantly lower than that in Tajikistan. However, due to its fine disperse structure, this dust is harder to remove. In Tajikistan, the capacity of the solar panel covered with dust de-creased by 46.64% relative to its nominal value in the first decade of April (the onset of dust storms). In the large industrial city of Chelyabinsk, the power output of the panels under study decreased by an average of 7.1% during this period. These findings confirm the importance of solar panel protection for maintaining the nominal values of solar power generation in the given regions. When no special protection devices are used, cleaning frequency for maintaining the re-quired efficiency of solar panels should be, on average, not less than once a week for both regions. A device is proposed for preventing dusting of the solar panel surface based on electron-ion technology. In addition, holographic films can be used to protect solar panels not only from dust contamination, but also from IR radiation. These protection approaches are the subject of future research.

In this study, we analyze the results of calculating the resistance of substation earthing equipment taking operational factors into account. The resistance of a substation earthing system was estimated using both calculation (methods of equipment operating factors, generalized parameters and induced potentials) and instrumental (ammeter-voltmeter) methods. During operation, the resistance of the studied earthing system was found to increase in comparison with the rated values, thus reducing its overall efficiency. The resistance of substation earthing equipment measured experimentally by the ammeter-voltmeter method showed the relative error of the considered calculation methods to reach 48, 46.7 and 28.6%, respectively. With the purpose of increasing the calculation accuracy of earthing equipment resistance by the method of induced potentials, it was proposed to use an operating factor. Thus, during the substation operation period of 10, 10–20 and over 20 years, the resistance of the earthing system increases by 1.02–1.1 times due to corrosion. It was shown that the installation procedure and maintenance checks (conducted at least every six years) increase the resistance of earthing systems by 1.02 and 1.05 times, respectively. Lightning discharges and short-circuit currents affect the corrosion rate of earthing systems, thereby increasing their resistance by 1.01–1.03 and 1.03–1.05 times, respectively. Therefore, the operating factor value may range from 1.115 to 1.274. The use of the operating factor in calculating the resistance of an earthing system by the induced potentials method increased the overall calculation accuracy, with the relative error not exceeding 3%. This corresponds to the normative and technical requirements stipulated by the Federal Grid Company of the Unified Energy System of Russia.

The study aims to propose new regression models using available weather data by analyzing the data published on the development of regression models for evaluating the flux of total solar radiation. Following an analysis of literature sources, primary stages in developing regression models and approaches to their implementation are described. Models are developed and compared for accuracy based on weather data (maximum and minimal temperature, air humidity, overall and lower cloudiness) in Irkutsk over 2007–2019. For calibration and validation of the models, open databases of ground measurements of weather stations were used. Ten known and seven new regression models were calibrated and validated, including three models based on the support vector method. The new models based on air temperature and humidity, atmospheric pressure, as well as overall and lower cloudiness, showed the highest accuracy in evaluating the total solar radiation with daily breakdown. The maximum mean absolute error in evaluating daily total solar radiation over 2016–2019 comprised 627.52 W·h/m2·day for the analyzed known models, 504.7 W·h/m2·day for the newly proposed regression models, and 463.2 W·h/m2·day for the regression models based on the support vector method. The conducted analysis of the mean bias error revealed models having the highest accuracy in evaluating monthly and annual sums of total solar radiation were determined. These include a known regression model using air humidity data and a regression model based on the support vector method.

The authors develop a system of optimal planning of power consumption in the Republic of Altai local grid system based on a large proportion of renewable and alternative generating power sources. The studies were carried out using the linear programming method for power consumption patterns used by generating consumers. Power consumption charts by seasons and hourly retrospective rows of weather data by wind current velocity and solar insolation over 2021 were used as source data. Wind turbines, solar photovoltaic facilities, hydro-power plants, and energy accumulators were considered as local power consumption facilities to calculate electricity generation. The article provides calculation results for electricity generation in winter, since this is when a higher power deficiency is observed. It was shown that power consumers in the region under study can independently install additional generating power sources in the form of wind turbines, solar photovoltaic facilities, hydro-power plants, and energy accumulators due to electricity deficiency. Their combined generation mitigates the unpredictability of power generation by renewable sources. The authors propose a method that allows generating consumers to minimize their material and financial expenses and reduce the carbon footprint. The significance of the study consists in the substantiation of a hybrid power supply system with a high proportion of renewable and alternative power sources, which is implemented in the Republic of Altai and can be reproduced in other local energy systems with similar weather conditions.

In this paper, effects of low and high ambient temperatures on the operation of a photoelectric unit are investigated. The research methodology consisted in determination of the energy efficiency of a photoelectric unit across a wide range of ambient temperatures, providing graphical interpretations and describing the procedure of field observations. Regularities in determining the average statistical indicators of energy efficiency rise and drop in a photoelectric unit were applied for a particular range of ambient temperatures. These studies were undertaken during the winter of 2021 in the Materials Science Laboratory of V.P. Larionov Institute of Physical-Technical Problems of the North, Siberian Branch of the Russian Academy of Sciences, using a fixed climate chamber. Reference parameters were obtained for changes in the photoelectric unit generating capacity (within -60ºC to +60ºC), which can be applied in modeling operational processes and engineering calculations of operating conditions of solar power plants. It was found that, at the same illumination and ambient temperature values, a photoelectric panel generates the maximum energy at -60ºC and minimal energy at +60 ºC, with the specific power drop for this temperature range being 19%. A significant drop in the specific power of the photoelectric unit was achieved at +30 ºC and higher due to the increased internal resistance of the unit. For temperatures below -40ºC, the specific power of the analyzed unit increased insignificantly due to the decreased internal resistance of the unit. The obtained values of the generating capacity of a photoelectric unit within a wide range of ambient temperatures can be used in developing a procedure for evaluating the effects of ambient temperature and its various ranges on the operation of photoelectric units, as well as for a more accurate determination of the solar generation energy potential under certain climate conditions. In future studies, field observations are planned to identify the nature of the effect of two and more climatic factors on the operation of a photoelectric unit.

This work investigates possible options for replacing the main separator of steam power boilers to ensure their maximal service life. Separators of drum-type boilers are reviewed in terms of their advantages and disadvantages. An analysis of two steels – WB36 and 16GNMA – is carried out by comparing their performance characteristics, chemical composition, and welding procedures. Possible technical solutions for replacing overaged drum boilers are analyzed from the technical and economic perspectives. Three options were selected for replacing the separator: a similar drum made of imported grade WB36 steel; an alternative option with a small drum and a bank of off-mounted cyclones; a drumless option based on a multi-stage evaporation cycle and a bank of cyclones. The materials currently used in separators, i.e., 16GNM and 16GNMA, are compared with imported WB36 steel. It was found that each option had its own advantages and disadvantages, which should be analyzed according to the following parameters: weight and dimensions; assumed need in lifting equipment; hydraulic losses; assumed changes in automatic boiler equipment; relative costs associated with designing, analysis, and risk management. Therefore, the presented recommendations for selecting a drum replacement option are essential for extending the service life and ensuring the reliable and safe operation of boiler equipment.

The aim was to develop a procedure for obtaining an electrode paste of needle coke in case of thermophysical action in the extruder circuit to produce graphitized carbon electrodes with the required structure and properties for thermal furnaces. To study the properties and composition of electrode pastes and electrodes, X-ray powder diffraction, electron microscopy, infrared spectroscopy, and calorimetry analysis were used. To evaluate the electrode behavior upon its heating in a melt, mathematical and statistical analysis was used. The data were processed using standard MS Office programs. Experiments with graphitized carbon materials were conducted in a calorimetric laboratory at the Scientific Center for Problems of Processing Mineral and Man-Made Resources, Department of Metallurgy, Saint Petersburg Mining University (Russia), using a developed proprietary prototype of the extruder. The conditions and technological parameters for processing electrode pastes were defined and substantiated (rate of extrusion and electrode paste flow, pressure, and heating rate within the defined temperature range to achieve stable structural indicators of electrodes). According to XRD data, the proposed method of thermophysical processing of an electrode paste via a special extruder within 550–620°C and a die pressure of 60–80 MPa provides an evenly directed structure of needle coke with an average needle thickness of 12–20 nm and a length of needle phases of 5–10 mm. The behavior of electrode samples was examined in the furnace melt within 1500–1700°C. The obtained stable levels of the thermal-expansion coefficient (0.3·10-6 °C-1) and specific electrical resistance (4.5–6.0 μmOhm·m) were manifested in reduced electrode sublimation, low losses of overall weight at the electrode end, decreased oxidation, and reduced damage on its side. The proposed electrode structure ensures stable heat and electrical conductivity, as well as high heat capacity, which levels are equivalent to those of imported electrodes and electrode pastes.

This paper investigates the extraction of silver by percolation leaching of a pelletized sample of aged tailings with organic binder Alcotac® CB6. Laboratory studies of percolation leaching were conducted using a column with a height of 0.5 m and an internal diameter of 56 mm. Pelletization was performed in a drum-type pelletizer with the consumption of Alcotac® CB6 (BASF, Germany) of 800 g/t and the pellet moisture content of 8–10% and size of 8–10 mm. The sample composition was analyzed taking into account the data obtained by optical tests, electron microscopy, X-ray diffraction, local X-ray spectrometry, X-ray fluorescence analysis, and inductively coupled plasma mass spectrometry. The research object was aged tailings of the Zhezkazgan processing plant (Ulytau region, the Republic of Kazakhstan), where copper is mostly represented by oxidized minerals (78.47%) and sulfide minerals (21.53%). The results of physical and chemical analyses conducted to determine the material composition of samples are presented, along with observations over percolation leaching of copper and silver from Zhezkazgan aged tailings. The copper leaching studies included two stages using a sulfuric acid solution as a solvent. The subsequent stage was silver dissolution by cyanide leaching. Copper extraction into the solution comprised 88.55% with a sulfuric acid consumption of 80.0 kg/t; silver extraction comprised 75.31% with a sodium cyanide consumption of 0.55 kg/t. The conducted studies showed the efficiency of using Alcotac® CB6 for percolation leaching of pre-pelletized aged tailings. During leaching, the pelletized material exhibits sufficient porosity and permeability, thus providing access of cyanic solutions to the surface of precious metals.

The aim of the study was to examine the chemistry, kinetics and mechanism of oxidizing roasting of a typical sample of sulfide copper-cobalt ore. The research object was sulfide copper-cobalt ore with the following main minerals: pyrite, pyrrhotite, chalcopyrite, sphalerite, tremolite, silicon dioxide, talc, siderite and calcite. The methodology involved high-temperature X-ray phase analysis (100–900°C), thermogravimetry, differential scanning calorimetry and mass spectrometry of the released gas (30–1100°C, heating rate – 5–20°C·min-1, air flow rate – 30 cm3·min-1). The chemistry, kinetics and mechanism of oxidizing roasting of sulfide copper-cobalt ore with a particle size of <0.1 mm were studied. It was found that the process can be represented as a set of seven elementary reactions: five exothermic reactions (at 398–445, 394–488, 440–498, 433–549 and 451–562°C), corresponding to the intense combustion of iron, copper and zinc sulfides, and two endothermic reactions (at 651–664 and 743–927°C), associated with the decomposition of residual copper and iron sulfates. Kinetic analysis (Kissinger and Augis-Bennett methods, identification of the reaction model by reference function and iterative optimization) of differential scanning calorimetry data in connection with the above reactions showed that the limiting stage of the latter is nucleation and crystal growth. The values of activation energy, pre-exponential factor and Avrami parameter ranged between 140–459 kJ·mol-1, 1.41·104–3.49·1031 with-1 and 1.0–1.7, respectively. It was established that crystallization of the products of elementary reactions is accompanied by an increase in the number of nuclei; new phase nuclei can be formed both on the surface and in the bulk of ore particles. The crystal growth is one-dimensional and is controlled by a chemical reaction at the interphase boundary or by diffusion of reagents. The results obtained can be applied in the practice of oxidizing roasting of sulfide ores and concentrates.