Engineering working operations based on parameters of product manufacturability using a computer-aided design algorithm

The study aimed to develop an algorithm for computer-aided design (CAD) of working operations. A processing route for machining components was developed based on the criteria of production manufacturability, industrial data and a digital model of the product. The process of machining a workpiece was analysed using a method of theoretical separation. The machining process of a frame workpiece was used as a model. The identified formal parameters formed a basis for developing a CAD algorithm and a model of manufacturing route associated with the mechanical processing of a work-piece applying a condition-action rule, as well as mathematical logic. The research afforded a scheme for selecting process operations, given the manufacturability parameters of a product design. The concept of CAD algorithm was developed to design a production process of engineering products with given manufacturability parameters, including industrial data. The principle of forming a route and selecting a machining process was proposed. Several criteria of production manufacturability (labour intensity, consumption of materials, production costs) were selected to evaluate mechanical processing. A CAD algorithm for designing technological operations considering the parameters of manufacturability was developed. The algorithm was tested by manufacturing a frame workpiece. The developed algorithm can be used for reducing labour costs and development time, at the same time as improving the quality of production processes. The formalisation of process design is a crucial stage in digitalisation and automation of all production processes.

Analysis of the temperature-frequency effect on dielectric losses in a grain medium

The aim of the study is to determine the influence of the thermal effect on dielectric losses in grain mass subject to bruising during drying and storage on the example of wheat across a wide external electric field frequency range. The study of the electrophysical characteristics of a dispersed medium comprising mechanically activated wheat grains takes into account the effect of the degree of breakage on the dielectric parameters of the studied medium. The studies were carried out on experimental samples having different degrees of mechanical activation of particles, which ranged in size from from 50 to 1000 μm. Variations in the dielectric loss tangent were studied using the dielectric method across a wide temperature-frequency range. Studies of variations in dielectric properties were carried out for wheat sam-ples subjected to grinding according to the mechanical activation method at temperatures varying from 20°C to 255°C with a constant heating rate of 0.7 deg / min. During the course of the experiment, the frequency of the external electric field was varied from 25 Hz to 1∙106 Hz. Dielectric constant and dielectric loss tangent calculations were carried out using data on electrical capacity and conductivity obtained using an E7-20 immittance meter and a measuring cell in the form of a flat capacitor. An analysis of variations in these dielectric characteristics was also performed. The obtained stable correlation of the dielectric loss tangent with the frequency of external electric impact and the degree of heating of the samples was most pronounced for finely dispersed samples (particle size 50 μm). Variations in dielectric characteristics are most significant when the frequency decreases to 100 Hz and below. The study of variations in the main dielectric parameters can be used to prevent self-heating and ignition of the grain mass during storage, as well as for selecting the most efficient energy-saving drying mode.

Current state of steelmaking slag processing

In the present work, the properties and composition of steelmaking slag are assessed by analysing existing processing methods, including desulfurisation and dephosphorisation. The atomic absorption and optical emission methods were used to study the chemical composition of slag samples, and metallographic analysis was used to study their microstructure. Major approaches to processing slags applied in Russia and abroad were studied. It was shown that steelmaking slags are neutralised and treated by various methods and subsequently applied in construction and road industries, while the obtained phosphorus-containing products are used in agriculture instead of superphosphate. In addition, these products reduce lime consumption and improve slag formation in steelmaking. The key factor hampering reusing electric steelmaking and converter slags for metal refining is shown to be the presence of phosphorus. The chemical composition of slag samples from the electric steelmaking production was analysed; the iron content amounted to 33.2 wt%, calcium – 19.15 wt%, phosphorus – 0.33 wt% and silicon – 5.39 wt%. Iron is present in the oxidised form (FeO, Fe2O3 and Fe3O4), silicon and calcium in the form of dicalcium silicate (2CaO ∙ SiO2 ), phosphorus in the form of calcium silicophosphate having complex composition – Ca2(SiO4)6(Ca3(PO4)2. Phosphorus is fed to the melting units with gangue minerals, agglomerate, ore and fluxes. When the slags are reused, phosphorus returns to the metal, thus contaminating the final product. Possible methods for extracting phosphorus from steelmaking slags include magnetic and electrostatic separation, gravity and flotation concentration, as well as hydrometallurgical processing.

Pyroelectrometallurgical processing of bismuth-containing oxides

In this work, we substantiate and develop a general pyroelectrometallurgical technology for processing bismuth dross and oxides (the intermediate products of lead bullion refining by the Betterton-Kroll process) to obtain crude bismuth. The research focuses on bismuth dross (3–5% Bi; 80–85% Pb) remelted at 500–600°С in the presence of NaNO3 and NaOH, as well as the obtained alkaline melt (bismuth oxides, 1–5% Bi; 60–70% Pb). The conducted experiments allowed us to determine optimal parameters of the main steps of processing bismuth oxide, as well as the characteristics of obtained products. Reduction smelting of bismuth oxides at 1150°C (with the addition of sodium carbonate, quartz and fine coke in the amount of 66, 25 and 5% of bismuth oxides mass, respectively) is proposed, leading to bismuth lead formation. Its decoppering is carried out at 350–600°C with 2.0% sulfur (by its weight), added to the melt. We propose to carry out the alkaline treatment of the decoppered Pb-Bi alloy at 500oC in contact with sodium hydroxide, sodium nitrate and sodium chloride, taken in amounts up to 10.2, 8.3 and 1.4% by weight of bismuth lead, respectively. Subsequent electrolysis comprises electrolytic processing of purified Pb-Bi alloy ingots at 550oC. The electrolyte consists of a melt with the following composition, %: NaCl – 7, KCl – 35, PbCl2 – 18 and ZnCl2 – 40. As a result, two end products were obtained by the proposed bismuth oxide processing. The anodic product at the second stage of electrolysis, crude bismuth (yielded 1.1% by the weight of oxides) contains 93.62% Bi and 4.14% Pb, extraction from oxides amounts to 19.0% Bi and 0.1% Pb. About 1.2% Bi and 9.1% Pb of their initial content in the oxides are transferred to the cathodic product containing 0.033% Bi and 97.83% Pb (the yield equalled 5.1% of the oxides).

Study of a segmented ventilation system of the brake disc and determination of the aerodynamic and heat exchange characteristics of the airflow

This study aims determine a relationship between the aerodynamic and heat exchange characteristics of the air flow in a segmented ventilation system of the brake disc with improved heat dissipation in the boundary layer of the air flow. Classical equations of heat and mass transfer in the boundary layer of the air flow cooling the brake disc ventilation chamber were used. The cooling performance of the system was assessed using the method of similarity. The obtained theoretical findings were confirmed by CFD-modelling. Mathematical models were developed for vented discs with both continuous grooves and slotted grooves. A criterion for assessing the performance of brake disc ventilation systems was proposed, consisting in turbulization of the air flow inside the device under study. According to the obtained analytical dependencies, a 20-fold acceleration of the air flow decreases the turbulization parameter by 1.24 times. An increase in the temperature difference in the boundary layer by 8 times leads to an increase in the turbulization parame-ter by 86.2 times. Using the criterion proposed for assessing the work performance, the aerodynamic and heat exchange characteristics of the system under study were calculated. As a result, a relationship between the design parameters of the segmented ventilation system and improved heat dissipation in the boundary layer of the cooling air flow is proposed. The conducted CFD modelling confirmed the aerodynamic characteristics of the system under study obtained theoretical-ly. This mathematical model together with the turbulization parameter can be used when both developing modern vented brake discs and assessing the existing cooling systems of friction units in order to minimize the possibility of reduced heat exchange processes.

Effect of the sector radius of a workpiece-deforming tool on the stress-strain state in the contact zone with a cylindrical surface

This paper aims to determine the effect of the sector radius of a workpiece-deforming tool on the stress-strain state in the center of elastoplastic deformation and residual stresses in the hardened zone of the surface layer of cylindrical workpieces. A mathematical model of local loading was constructed using the finite element method and AN-SYS software. This model was used to determine the values of temporary and residual stresses and deformations, as well as the depth of plastic zone, depending on the sector radius of the working tool. The simulation results showed that, under the same loading of a cylindrical surface, working tools with different sector radii create different maximum tempo-rary and residual stresses. An assessment of the stress state was carried out for situations when the surface layer of a product is treated by workpiece-deforming tools with a different shape of the working edge. It was shown that, compared to a flat tool, a decrease in the radius of the working sector from 125 to 25 mm leads to an increase in the maximum temporary and residual stresses by 1.2–1.5 times, while the plastic zone depth increases by 1.5–2.4 times. The use of a working tool with a flat surface for hardening a cylindrical workpiece ensures minimal temporary residual stresses, com-pared to those produced by a working tool with a curved surface. A decrease in the radius of the working sector leads to an increase in temporary residual stresses by 2–7%. The plastic zone depth ranges from 1.65 to 2.55 mm when chang-ing the sector radius of the working tool.

Determination of average relative capital investment of 30–125 MW combined-cycle plants commissioned at Russian thermal power plants in 2015–2020. Comparative analysis with data obtained in 2010–2014

The present work examines average relative capital investment and fuel consumption for electric and thermal energy supply of the combined-cycle plants having 30–125 MW gas turbines commissioned at Russian thermal power plants in 2015–2020. In this work, we used general calculation methods of average relative capital investments and fuel consumption for the electrical and thermal energy supply using power equipment of thermal power plants. To assess the scope of commissioning gas turbines incorporated into the combined-cycle plants, they were classified into three groups by electrical power: 30–59 MW, 60–99 MW and 100–125 MW. The scope of commissioning gas turbines incorporated into the Russian combined-cycle plants in 2015–2020 was analysed. The average relative capital invest-ment in combined-cycle plants having 30–125 MW gas turbines, as well as the average specific fuel consumption for the electrical and thermal energy supply, were calculated. The calculations were carried out for each part of combined-cycle plants integrated into thermal power plants with a breakdown by seven Unified Energy Systems of Russia. The quantita-tive commissioning of gas turbines is compared for the periods from 2010 to the economic crisis of 2014 and after 2014 to the present: a ~2.5-fold decrease is demonstrated. A preliminary evaluation of the increase in average relative capital investment in combined-cycle plants having gas turbines of the same electric power was performed.

A new criterion of asymptotic stability for Hopfield neural networks with time-varying delay

The objective of this paper is to analyze the stability of Hopfield neural networks with time-varying delay. For the system to operate in a steady state, it is important to guarantee the stability of Hopfield neural networks with time-varying delay. The Lyapunov-Krasovsky functional method is the main method for investigating the stability of time-delayed systems. On the basis of this method, the stability of Hopfield neural networks with time-varying delay is ana-lysed. It is known that due to such factors as communication time, limited switching speed of various active devices, time delays often arise in various technical systems, which significantly degrade the performance of the system, which can in turn lead to a complete loss of stability. In this regard, a Lyapunov-Krasovsky type delay-product functional was con-structed in the paper, which allows more information about the time delay and reduces the conservatism of the method. Then a generalized integral inequality based on the free matrix was used. A new criterion for asymptotic stability of Hop-field neural networks with time-varying delay, which has less conservatism, was formulated. The effectiveness of the proposed method is illustrated. Thus an asymptotic stability criterion for Hopfield neural networks with time-varying delay was formulated and justified. The expanded Lyapunov-Krasovsky functional is constructed on the basis of delay and quadratic multiplicative functional, and the derivative of the functional is defined by a matrix integral inequality with free weights. The effectiveness of the method is illustrated by a model example.

Power management of variable capacitors in electrical grid systems according to the criterion of mini-mum energy loss

The aim is to manage the transmitted reactive power in electrical grids using variable capacitor batteries according to the criterion of minimum energy loss under different annual reactive load schedules and different numbers of variable capacitor sections. The main theoretical relations were obtained by the methods of mathematical modelling and integral calculus using the theory of optimal control. The influence of the power and number of sections in a capacitor battery on energy losses in the grid was estimated using computational experiments. Dependencies for energy losses in a capacitor battery, as well as for reducing energy losses in the grid, were obtained. These expressions are valid for linearized load schedules. It is shown that the dependences of energy losses in a capacitor battery and the reduction of losses in the grid on the section power have inflection points and pass through a maximum. The presence of inflection points is associated with a change in the number of capacitor sections operating throughout the year. The presence of a maximum is explained by the fact that, with an increase in the power of the capacitor battery, its operating time decreases under the complete number of variable sections. It is established that the batteries of static capacitors with two variable sections can reduce energy losses when transmitting reactive power by over 90%. For three- and four-section static capacitors, the loss reduction is close to 100%. The reduction in energy losses increases when approaching maximal levels of annual reactive load. Energy losses in electrical grid systems can be reduced by capacitor batteries with no more than three or four variable sections. In most cases, this can be achieved by two-section capacitor batteries.

Thermodynamic modelling of roasting of molybdenum sulphide concentrate with calcium hydroxide

This work aims to determine the conditions for the CaMoO4, CaSO4, Ca(ReO4)2 formation during oxidation of MoS2 and ReS2 in the presence of Ca(ОН)2. The concentrate from the Yuzhno-Shameyskoye deposit in the Sverdlovsk region, having 37% wt. Мо and 0.005% wt. Re, was selected as a feedstock for thermodynamic modelling of sweet roasting in the presence of Ca(OH)2. To determine the optimal amount of calcium-containing additives, the thermodynamic modelling was carried out using the following mass ratios: molybdenum concentrate: Ca(OH)2 = 1:0.8, 1:1, 1:1.2 and 1:1.5 in the temperature range of 100–800°С, with a step of 100°С, system pressure of 0.1 MPa in the air (molar ratio: molybdenum concentrate + Ca(OH)2: air = 1:5). The content of all sample components in moles was entered into the HSC 6.1 software package. The main reactions associated with the sweet roasting of molybdenum concentrate in the presence of calcium hydroxide were shown. It was established that the main phases formed as a result of roasting comprise CaSO4, CaSO3, MoO3, CaMoO4, CaMoO3 and CaReO4. The effect of temperature on the formation of the main gaseous products was studied under different mass ratios of molybdenum concentrate and Ca(OH)2. It was found that up to 600°C, with molybdenum concentrate to Ca(OH)2 ratio of 1:1, the concentrations of released sulphurous anhydride are lower than the maximum permissible concentrations. The calculated thermodynamic data was used for modelling the roasting process of molybdenum concentrate with calcium hydroxide. An optimal ratio necessary for the successful process operation was established: molybdenum concentrate: Ca(OH)2 = 1:1 by weight. Thermodynamic modelling showed that, in the temperature range of 100–600°С when using Ca(OH)2, no rhenium and molybdenum loss is observed, the release of sulfur is less than 10 mg/m3.