Nizhny Novgorod State Technical University

This study assessed the influence of the orientation of printed layers (90°, 45°, and 0°) in 12Kh18N10T alloy specimens relative to the direction of uniaxial deformation on the microstructure, physical and mechanical properties, and nondestructive testing parameters. It was found that deformation of specimens results in the intensive formation of structural defects, which significantly impact the strength properties of material (increasing the yield strength and microhardness), as well as the nondestructive testing diagnostic parameters. These results of research can be used to assess the condition of structures made of stainless chromium-nickel steels using the DMD method.

In the context of the digital transformation of industrial production, the need for intelligent maintenance and repair systems capable of ensuring reliable operation of machine-tool equipment without operator involvement is growing. This present study reviews the current state and future development of diagnostic and condition-monitoring systems for metalworking machine tools. A review of international standards and existing solutions from domestic and international vendors in vibration diagnostics has been conducted. Particular attention is paid to non-intrusive vibration diagnostics, digital twins, multiparametric analysis methods, and neural network approaches to failure prediction. The architecture of the developed system is presented. The concept of the system is developed in full compliance with Russian and international standards of vibration diagnostics. At its core, the comprehensive digital twin relies on machine learning methods. The proposed architecture is a predictive-maintenance system built on interconnected digital twin realizations: the dynamic machine passport of a unit, operational data, and a comprehensive digital twin of the machine-tool equipment. The potential of neuromorphic computing on a hardware platform is being considered as a promising element for local-condition classification and emergency protection. At the current development stage, the operating principle has been demonstrated along with the integration into the control loop. The system is now at the beginning of laboratory testing. It demonstrates capabilities for comprehensive assessment of the equipment’s technical condition based on multiparametric data, short-term vibration trend forecasting using a Long Short-Term Memory network, and state classification using a Multilayer Perceptron model. The results of the system’s testing on a turning machining center have been analyzed.

We present an electromagnetic study of a metamaterial receiver based on split-ring resonators with integrated cold-electron bolometers. We suggest a modified antenna design that allows one to significantly increase the absorbed power and the bandwidth. The trade-off between the bandwidth expansion due to miniaturization and the reduction in absorption efficiency determined by the Airy spot size of the coupling lens is investigated. To solve this issue, a simultaneous miniaturization of the size of the entire structure with an increase in the number of array elements is proposed. The design with a 37-element array demonstrates an increase in power absorption by a factor of 1.4 compared to the original 19-element single-ring array, as well as an increase in operating bandwidth from 160 to 820 GHz.

The presented work is devoted to multi-agent modeling of computer operator behavior. The use of multi-agent architecture makes it possible not only to emulate various behavioral strategies, but also to systematically study the influence of individual factors related to user behavior on the results of human-machine interaction. The tools developed on the basis of computer operator models can be used both for testing user interfaces (UX testing) and for analyzing risks associated with the human factor in mission-critical applications. The purpose of this work is to create a software prototype for simulating human-machine interaction, taking into account the operator's behavioral profile and conducting experiments aimed at studying the characteristics of various types of operators. The results obtained make it possible to formalize user profiles and offer recommendations for adapting interfaces to their features.

One approach to detecting cyber threats at a digital substation is examined by developing and investigating a basic algorithm for ensuring the information security of the process bus using fundamental laws of electrical engineering (Kirchhoff’s laws, Ohm’s law, the principle of superposition, detection of current imbalance) in combination with the patterns and operational rules of the computing networks of a digital substation that employ the seven-layer ISO/OSI model. A method is proposed for detecting cyber threats at a digital substation related to the falsification (spoofing) of current and voltage measurements, as well as unauthorized interference with the substation’s digital bus or with measurement sensors and devices for processing currents and voltages.

Modular designs for the underwater portions of an above-water and a deep-sea unmanned vehicle power-supply system are proposed. This system is based on transistor dc/dc converters with series half-bridge resonant inverters. The features of the underwater portion, which contains several modules connected in series across their input circuits, are identified. A control option for the modules of the underwater portion is proposed and validated, ensuring stable and reliable operation of the power-supply system across a wide range of loads. Simulation results for processes in the power-supply system’s underwater portion under steady-state and transient conditions are presented.

The paper investigates the vibrations and acoustic noise caused by a magnetic field generated by an asynchronous electric motor with a square-cage rotor dependent on its eccentricity. A finite element model of the AIR180M4U3 motor has been developed taking into account the relationships of electromagnetic, structural, mechanical, and acoustic processes at static eccentricity. The dependences of the noise level, the stator vibration amplitude, and von Mises stress on the eccentricity of the rotor have been obtained.

This article presents the results of a study on the possibility of using a single-speed multiphase model with free surface allowance for simulating boiling and condensation processes. The simulation is based on the VOF method, which allows the position of the interphase boundary to be tracked. To increase the stability of the iterative procedure for numerically solving volume fraction transfer equations using a finite volume discretization method on arbitrary unstructured grids, the basic VOF method is been modified by writing these equations in a semi-divergent form. The models of Tanasawa, Lee, and Rohsenow are considered models of interphase mass transfer, in which the evaporated or condensed mass linearly depends on the difference between the local temperature and the saturation temperature with accuracy in empirical parameters. This paper calibrates these empirical parameters for each mass transfer model. The results of our study of the influence of the values of the empirical parameters of models on the intensity of boiling and evaporation, as well as on the dynamics of the interphase boundary, are presented. This research is based on Stefan’s problem of the movement of the interphase boundary due to the evaporation of a liquid and the problem of condensation of vapor bubbles water columns. As a result of a series of numerical experiments, it is shown that the average error in the position of the interfacial boundary for the Tanasawa and Lee models does not exceed 3–6%. For the Rohsenow model, the result is somewhat worse, since the interfacial boundary moves faster than it should move according to calculations based on analytical formulas. To investigate the possibility of condensation modeling, the results of a numerical solution of the problem of an emerging condensing vapor bubble are considered. A numerical assessment of its position in space and the shape and dynamics of changes in its diameter over time is carried out using the VOF method, taking into account the free surface. It is shown herein that the Tanasawa model has the highest accuracy for modeling the condensation process using a VOF method taking into account the free surface, while the Rohsenow model is most unstable and prone to deformation of the bubble shape. At the same time, the dynamics of bubble ascent are modeled by all three models. The results obtained confirm the fundamental possibility of using a VOF method to simulate the processes of boiling and condensation and taking into account the dynamics of the free surface. At the same time, the problem of the studied models of phase transitions is revealed, which consists of the need for individual selection of optimal values of empirical parameters for each specific task.

Relevance. Distribution networks account for the largest share of Russia's power grid. The most common fault type in these networks is a single-phase ground fault. Selective identification of the faulty cable line can prevent its escalation into a three-phase fault, improving power supply reliability.Purpose. A multiparameter method of ground fault protection uses several electrical quantities to determine the network mode. This method makes the protection selective and more sensitive. Different electrical quantities are of different value for the mode recognition task. The goal of the research is to study the parameters of current and voltage that are used for relay protection. Investigation of the ability to recognize network mode based on this parameters.Methods. We obtained statistics by using simulation modeling of the cable network in the Matlab software package in the Simulink expansion package in all possible modes. And then we used discrete Fourier transform of the full period to obtain filtred harmonics and quadrature components of the values of zero-sequence currents and voltages.Results. The article describes the block and functional diagrams of measuring elements that uses the dependencies of electrical quantities are proposed. The article determines the areas formed by electrical quantities on the graph in different modes such as internal and external steady-state single-phase ground faults and arc intermittent single-phase ground faults. The graph consists of the dependence of two electrical quantities. It was also revealed that the areas of different modes have mutual intersections.Conclusions. The results of the study are suitable for the implementation of multiparameter protection.