Vol 192, No 4 (2024)

The research includes the development and analysis of a mathematical model of the micropolar lubricant flow in the working gap of a modified design of an infinite radial sliding bearing, taking into account compressibility and the effect of pressure on the rheological properties of the lubricant. Considering the lubricant compressibility, the authors took into account the dependence of the viscosity and density of the lubricant on high pressure. Under typical conditions of radial bearings, significant loads can cause changes in the properties of the lubricant, which affects its ability to form a stable lubricating film. Therefore, the introduction of compressibility parameters into the model allows more accurately predicting the behavior of the lubricant and the effectiveness of lubrication in various operating modes. The new model has been developed by the well-known equations of the flow of a micropolar lubricant, the continuity and the state equation. A comparative analysis of the numerical result of theoretical models and experimental research is carried out. Thus, the research represents a significant contribution to the field of radial bearings sphere. The obtained results can be used for further improvement of bearing designs, which allows increasing their reliability and durability of mechanical engineering.

Despite the high technical level of hoisting equipment purchased abroad, a catastrophic failure of the slewing bearings of these cranes occurs after 3-5 years of service instead of the regulated 15 years. The most characteristic are: wear of 6-polyamide cassettes, cages of gear teeth and turntable; rolling elements falling out of the turntable; squeezing out the sealing tape. To identify the hidden cause of premature failure of the slewing rings of «Liebherr» cranes, the authors carried out the experiment during loading and unloading operations, which shows the tendency of warming up the elements of the slewing support, considering the cyclic nature of the crane operation. It has been established that this process is linear both for cassettes (polyamide 6 material), in which the rolling elements are located, and for the rolling elements themselves (bearing steel). For 5 loading cycles, the rolling elements warm up to a 40 mm depth to a temperature of about 40-45° C. The proposed working hypothesis allows identifing the hidden cause of premature failure of the slewing support of «Liebherr» cranes operating in central Russia. A change in the stress-strain state of the cassette is established, leading to an increase in wear of the cassettes and rolling elements, since stresses arise between the end of the roller surface and the cassette in the direction of the contact plane.

The article presents a theoretical study of kinematic pairs known as «rolling pairs» used in many areas of mechanical engineering, in particular, mechanisms. The research concerns such bodies (links) as geometric tori, which are well-known bodies of rotation. From the geometric kinematics, new representations of the mechanical motions of a torus in a «torus-torus» connection are described without the reasons that cause this motion. Two options for connecting two tori are analyzed: the axes of the tori are parallel and perpendicular. By analogy, the analysis of kinematic pairs of this type expands the elements of kinematic pairs theory and allows developing their new variants in many mechanisms used in various fields of mechanical engineering.

The article examines the issues of system management of quality assurance costs at Russian defense enterprises. The relevance of the work is determined by the increased requirements for saving resources that are currently imposed on enterprises of the military-industrial complex. The purpose of the work is to develop recommendations for building a quality cost management system at Russian defense enterprises based on a process approach. This work is based on the results of research by Russian and foreign scientists in the field of quality cost management, reflected in scientific articles, monographs, textbooks. In addition, publications of practitioners in the field of quality management in industry journals and on specialized Internet portals were used. The author offers a generalized model of the system of formation of costs for ensuring the quality of products. When managing quality costs, it is proposed to initially start from the prices of the designed products. On their basis, the optimal (taking into account existing conditions) production cost of products is calculated. Cost data is used as a guideline for R&D. Special attention is paid to the formation of responsibility centers in the quality cost management system.

The efficient and sustainable functioning of energy systems is a critical element for supplying of electricity necessary to maintain the vital functions of modern society. Therefore, the integration of meteorological data into the management of electrical grids is becoming increasingly important.

Meteorological data, such as information on weather conditions, temperature, wind and precipitation, play an essential role in the operational and strategic management of power systems. Their use allows optimizing the operation of generating and distribution stations, using the maximum capacity of lines, as well as improve the planning of repair work and infrastructure upgrades. On the basis of the weather conditions, operators of electric power grids can make more informed decisions regarding the distribution and management of energy resources.

The research is aimed at determining the role of meteorological data in the management strategies of modern energy systems.

The article analyzes the limiting modes of overhead power transmission lines in terms of heating and voltage losses. The equations linking the wire temperature, voltage loss, load power, cooling conditions and line parameters are obtained. Depending on the length, three characteristic regions can be distinguished in which the limiting modes are determined either only by heating, or only by voltage loss, or both. A combined limit mode is considered separately, in which the wire temperature and voltage loss simultaneously assume the maximum permissible values. New refined criteria for assessing the admissibility of the line mode have been obtained. As an example, the AC-240 line with a 220 kV voltage of varying length is considered, for which a number of dependencies characterizing the areas of existence and conditions for the occurrence of limit modes are constructed.

The article examines the development of a system for monitoring the volumetric supply of liquid in pumping units. The relevance of the research is due to the growing requirements for automation of control of pumping systems. The key element of the system is the observer, which allows evaluating the main parameters of the installation, such as the pump rotation speed and the moment of resistance. The electric drive of the pump uses an asynchronous motor with a squirrel-cage rotor, the rotation speed of which is controlled. The pressure in the discharge pipeline is created by a centrifugal pump. The observer is based on a model of an asynchronous motor in a fixed coordinate system, and the Luenberger observer is used to estimate the rotation speed and torque of the pump. To identify the volume flow, a centrifugal pump model is used, parameterized by a second-degree polynomial. The authors present simulation results showing the high accuracy of the developed observer, with an error of no more than 3% in steady state. The results demonstrate the effectiveness of the proposed approach for constructing a monitoring system for pumping units.

The research presents the results of testing the Mandelstam–Brillouin scattering parameters for several types of optical fibers doped with erbium and cerium ions. The obtained Brillouin reflectograms of different types are shown. The frequency characteristics of Brillouin scattering are drawn. Estimates of the initial values of the Brillouin frequency shift and the behavior of the reflectograms of the back reflected signal level for the studied fiber varieties are presented. A comparative analysis of the obtained parameters of various types of erbium optical fibers is carried out.

Diagnostic systems implemented at many industrial facilities are designed to detect defects in a timely manner, thereby prevent sudden failures with subsequent equipment downtime, accompanied by economic losses. Most diagnostic systems are based on making a decision about the serviceability or malfunction of an object based on comparing diagnostic parameters with threshold values. The problem with this approach is that going beyond the set limits is fixed after the equipment has lost maintainability or requires complex expensive repairs. Therefore, the goal is early and reliable detection of defects in electromechanical equipment. The goal is achieved by developing an algorithm for detecting the beginning of a deviation in a time series consisting of sequentially recorded diagnostic parameters. The algorithm is based on the consistent application of singular spectrum analysis and allows not only timely detecting of deviations, but also assessing the probability of a decision error. Data processing algorithm is investigated on data sets generated in accordance with the specified laws of change. Moreover, the possibility of timely and reliable detection of defects has been demonstrated on a real set of diagnostic data. The implementation of the algorithm in the management of equipment condition will contribute to improving the safety and efficiency of production facilities.

The article provides a theoretical limit assessment of the stability of a digital thermocompensated quartz oscillator with a temperature sensor based on two auxiliary quartz oscillators. The results are 7,5 ppb (for a restless environment) and 0,75 ppb (for a calm environment). Technical solutions are considered for obtaining a linear one-to-one dependence of the difference frequency value on temperature and increasing the steepness of this dependence. The proposed solutions allow obtaining a temperature measurement resolution of up to 0,001 ºС.