Vol 25, No 5 (2021)

The present paper aims to describe shape changes in a microroughness model developed for the working surfaces of parts at degrees of deformation commensurate with the height of the original microprofile; to establish how the degree of microprofile upsetting affects its shape under constrained loading conditions; as well as to estimate the stress state of the microprofile by stress intensity. A numerical model describing the surface microprofile of parts was calculated using the ANSYS Workbench environment. Lead, tin, aluminum, and copper were used as microprofile materials. In addition, microprofile upsetting was computer simulated under constrained loading conditions. The valley bottom was found to rise at a 10–20% microprofile upsetting by 0.213–0.275 mm relative to the original profile height, depending on its material. The relative length of the smoothed microprofile section amounted to 0.786–0.925 mm of its original length. The base angle of the deformed microprofile reached 570 and 800 for copper and lead models, respectively. The depth of valleys ranged from 1.4 mm (23% of the original profile height) for lead models and from 1.8 mm (30% of the original profile height) for copper models. In the case of maximum microprofile upsetting, an increase in the yield strength of microrough material from 10 to 60 MPa contributed to a reduction in the base angle of the deformed microprofile, as well as relative length and the vertical rise of microprofile valleys at their highest point. No interlocking of lateral microprofile surfaces was observed. At a 50% upsetting, the stress state of the microprofile exceeded its ultimate strength by 4–8 times. The shape changes simulated for the microprofile from plastic metallic materials are described. The performed numerical simulation correlates well with the experimental results obtained for lead microprofile models. It is worth noting that the complete smoothing of the microprofile is likely to occur through the rise of valleys and the approaching of its lateral surfaces. The study results can be used for designing and manufacturing valve gate assemblies.

The present study is designed to study processes occurring during the electrical discharge machining (EDM) of tool steels, the influence of orbiting electrode motion on its accuracy, as well as to justify the application of individual orbiting trajectories and implement these data into production. To that end, a trajectory program was written in machine codes for a Mitsubishi EA-28 die-sinking electrical discharge machine using the CIMCO EDIT software package. Also, a prototype punch and ejector of the blanking die were produced and measured. The standard modes of Mitsubishi EA-28 were used to carry out machining in Blasospark GT 250 dielectric fluid to a roughness of Ra 0.6 in 9 passes. The experiments revealed the influence of electrode geometry on the machining of sharp corners, i.e., the formation of unwanted radii on the workpiece. However, this phenomenon is not observed when the corners are drilled with small diameter holes (0.4–0.6 mm). Depending on the machining process along the inner or outer trajectory, inverse electrode motion is also observed. The production part (punch of the blanking die) was machined using a new orbit adjusted to the geometry of the product. The part was found to be consistent with the requirements and the engineering drawing, thus allowing the assembled die to enter the main production. The results of the performed tests, as well as the study of domestic and foreign experience, were used to develop recommendations on the use of individual orbits in the EDM of tool steels, hard alloys, and other hard-to-machine conductive materials. The method of orbiting motion along a particular trajectory was implemented at Cheboksary Electrical Apparatus Plant (Cheboksary).

The paper determines the effect of proposed joint voltage and frequency predictive controllers for distributed generation (DG) plants on quality indicators characterizing the control process in different operating modes of power supply systems. The studies are conducted in the MatLab environment (Simulink and SimPowerSystems simulation packages) employing control engineering methods. It is proposed to design and adjust joint predictive controllers by determining the resonant frequency of oscillations for the master generator rotor. This approach provides better quality indicators of voltage and frequency control in power supply systems while maintaining the same settings for the controllers of DG plants. With an additional load in an isolated power supply system, the maximum voltage sag is found to be 1.75 times lower than for local predictive control and 3.5 times lower as compared to the use of conventional controllers. For the specified mode, predictive controllers enable a threefold reduction in the transient time between rotor rotational speeds in a synchronous generator. In the start mode of a powerful electric motor, the predictive controllers of synchronous generators in the power supply system enable a 1.5 times reduction in voltage sag, with a 1.4 times reduction in overvoltage following its start. In the case of a short-term three phase short-circuit, joint predictive controllers allow a 1.5 times decrease in transient time and a 2.3 times decrease in the overshoot of power line frequency as compared to local control. In addition, frequency oscillation in the power system is also reduced. Similar effects are observed in other operating modes of the considered power supply systems equipped with DG plants. The performed dynamic simulation confirms the effectiveness of using joint voltage and frequency predictive controllers for DG plants, which consists in a positive impact on the quality of processes involved in controlling the parameters of power supply systems in various operating modes.

The paper aims to develop a site selection procedure for solar-diesel hybrid systems using a multi-criteria performance analysis of site options. The site selection process using this multi-criteria approach was carried out on the example of Kungurtug rural settlement (Tyva Republic). The area surrounding this settlement was analyzed, revealing four possible sites for a solar-diesel system. For evaluating the performance of these site options, the following criteria were adopted: ease of installation and maintenance of the solar-diesel hybrid system; surface topography and soil quality; convenience of the photovoltaic cell layout; environmental impact of the solar-diesel hybrid system; opportunities for further expansion of the system; orientation potential of the photovoltaic cell. In order to assess the significance of the concordance coefficient, the distribution quantile was determined, amounting to 16.2. For 5 degrees of freedom and a significance level of 0.05, the table value of the concordance coefficient amounted to 16.2. Since the distribution quantile is greater than the table value, the concordance coefficient can be considered significant (95% confidence level), indicating agreement between expert opinions. Experts ranked the site options to obtain relative performance estimates for the criteria; numeric indicators were converted into the relative estimates using linear transformation formulas. The multi-criteria performance estimates of the possible options were calculated for arithmetic mean and harmonic convolutions. After comparing the site options for the solar-diesel system, the second variant characterized by the highest criterion scores was selected for Kungurtug settlement. As a result, a site selection procedure for the elements of solar-diesel hybrid systems was developed using the theory of multi-criteria optimization and the method of expert evaluations, allowing a set of technical, economic, climatic, and environmental criteria to be taken into account.

The work aims to develop digital control and management systems of copper electrolytic refining processes when addressing energy efficiency issues. Thermal imaging scanners can be used to monitor the process state of an electrolytic cell. In this regard, the experience in the automation and control systems of OJSC Novgorod Metallurgical Plant was considered. Mathematical research methods and a stochastic model developed in the MatLab software were used. This model was applied at the Lao Cai copper-smelting plant (Vietnam). The proposed algorithm is based on the temperature variation in electrolyte depending on the heating of cathode and anode sections during short circuits due to dendritic growth, as well as process disturbance time. The algorithm was developed using the Visual BasicScript programming languages. The temperature rise in short circuit areas was recorded using a thermal imaging scanner immediately after the colour change of the cathode surface. It was shown that the duration of a short circuit depends on the amount of sludge deposited in an electrolytic cell. The sludge formed following the destruction of intergrown dendrites contains precious metals. The developed measures, along with those of digitisation, are necessary for effective management, taking into account the functional and kinetic characteristics of the copper refining process. The proposed solutions and control algorithms will allow remote access systems with augmented reality elements when creating a digital twin. This will reduce the specific power consumption by 20 –25% while decreasing the number of electrode short circuits. Controlling the composition and level of electrolyte and sludge will reduce material losses and maintain the concentration of noble metals in the electrolyte. To improve the control quality of automation during the electrolytic production of cathode copper, a number of technical measures were proposed that provide additional points of control to expand the process database. Furthermore, the proportion of manual periodic measurements of process parameters is reduced.

The paper determines the indicators of the developed process flow for the complex processing of red sludge via the formate method: recovery of components; yield and composition of products when processing a sample of formate solution obtained from red mud leaching. The conducted experiments used red mud generated in the production of alumina at the Urals Aluminium Smelter. The samples of formate solution obtained in the course of red mud leaching were analyzed using an Optima 8000 ICP-OES Spectrometer, a Sartorius MA-30 Moisture Analyzer to measure moisture content, as well as an ARL 9800 XRF Spectrometer to ascertain the mass fraction of elements in metal and nonmetal specimens found in one of three states (solid, liquid, or powder). These experiments were performed while continuously measuring and monitoring pH values by means of a pH meter having a thermal compensation function. The performed experiments involved the total recovery of valuable elements from formate solutions produced during red mud leaching. A concentrate containing Al, Sc, and rare earth elements (REEs) was processed to produce scandium oxide and rare earth metal concentrate (after dissolving aluminum in an alkali). Rare earth metals and scandium were shown to concentrate in the solid phase; scandium was then selectively leached with a sodium bicarbonate solution to form water-soluble carbonate complexes [Sc(CO3)4]5- having carbonate ions СО32- and НСО3-. When using the proposed technology, the overall recovery of scandium and REEs amounts to 98–99%, whereas that of aluminum, calcium formate, and sodium formate from the produced solution reaches 99%. The processing of formate solution yields the following end products: scandium oxide (99 wt% Sc2O3) and REE concentrate (content of 56.1%). The paper demonstrates the possibility in pri nciple to process solutions obtained from the flow-through leaching of red mud via the formate method.

This year we celebrate the 100th birth anniversary of Professor Anatoly Ivanovich Orlov, an outstanding metallurgist scientist, the founder of the Department of Automation of Production Processes, one of the first to receive this honorary title at Irkutsk Polytechnic Institute, now Irkutsk National Research Technical University.