Issue № 2(30) Vestnik of Tver State Technical University. Series «Technical Science»

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• N.B. DEMKIN AND HIS CONTRIBUTION TO THE DEVELOPMENT OF TRIBOLOGY
  Authors: V.V. IZMAILOV
  Abstract: The model of discrete contact between technical surfaces, developed by Nikolai Borisovich Demkin and his scientific adviser Igor Viktorovich Kragelsky, is examined. This model made a significant contribution to the advancement of tribology. Due to its flexibility and relative simplicity, the model has become widely used in the theoretical description of various contact processes, including friction, wear, contact conductivity, contact stiffness, and joint tightness. The model's underlying assumptions are formulated, and its application to calculating the key performance characteristics of contact joints – the actual contact area and contact deformation – is demonstrated. Examples of successful model development, taking into account new capabilities of surface research tools, are presented, including applications to calculating contact characteristics, taking into account adhesive interactions, the influence of nanoroughness, and others.
  Keywords: technical surfaces, discrete contact, contact area, contact deformation, theoretical model.

• CONTRIBUTION OF THE TVER SCIENTIFIC SCHOOL OF TRIBOLOGY TO THE CREATION AND STUDY OF MAGNETIC LUBRICATING FLUIDS
  Authors: A.N. BOLOTOV
  Abstract: Magnetic lubricants are a tool for creating next-generation engineering systems – active, adaptive and highly reliable. Their application is most justified in special equipment, where decisive importance is given not to cost, but to unique functional capabilities: tightness, controllability and operation in extreme conditions. In serial mechanical engineering, their use is still constrained by economic factors, but for critical components (aerospace industry, energy, precision equipment) they already offer unparalleled solutions today. A brief review of the Tver scientific school in the field of magnetic fluids intended for lubricating machine friction units is presented. The practical use of magnetic lubricants helps reduce wear of parts, improve energy efficiency of equipment and increase its reliability. The relationship between the chemical composition, structural stability and performance properties of magnetic lubricants is revealed, which makes it possible to purposefully develop compositions with specified parameters adapted to various operating conditions of friction units. A comprehensive theoretical and experimental basis for further research in this area has been created. The main achievements are systematized and the prospects for the development of magnetic lubricants are revealed, which is important for improving performance properties in mechanical engineering and other industries.
  Keywords: magnetic lubricating fluids, tribology, magnetic nanoparticles, colloidal stability, magnetic fluid bearing, Tver scientific school.

• MODERN TRIBOLOGY: METHODOLOGICAL ASPECTS OF RESEARCH
  Authors: E.A. RATKEVICH, A.N. BOLOTOV
  Abstract: The article examines problems in tribology research methods. An integrated multiscale methodology needs to be developed. The methodology should combine experimental data at the macro- and microscopic levels. Chemical transformations on surfaces during friction should also be taken into account. All data is processed using computer modelling methods. The methodology allows for detailed investigation of friction and wear processes at all structural levels, from the atomic to the macroscopic scale. This significantly improves the accuracy of predicting the durability of materials. New opportunities are emerging for designing innovative solutions in high-tech fields. Methods such as spectroscopy, microindentation, tribometry and atomic force microscopy were evaluated, as well as the prospects and possibilities of using artificial intelligence and machine learning to describe tribological processes.
  Keywords: tribology, macroscopic analysis, microscopic analysis, atomic force microscopy, tribometry, spectroscopy, computer modelling.

• FRICTIONAL CHARACTERISTICS OF CERAMIC MATERIALS AT HIGHER TEMPERATURES
  Authors: A.F. GUSEV, V.V. IZMAILOV, M.V. NOVOSELOVA
  Abstract: The friction characteristics of a number of nitride ceramic materials paired with a steel counterbody were experimentally determined at room and elevated temperatures (up to 450 °C). These included the Amonton and Coulomb friction coefficients and the parameters of specific friction force, expressing its dependence on the normal stress in the contact. For all the friction pairs studied, the Amonton friction coefficient decreases by a factor of two or more with an increase in the normal load. The Coulomb friction coefficient was determined as the coefficient of the binomial linear regression dependence of friction force on the normal load; it is constant for a given friction pair under the given operating conditions. A close correlation was found between the corresponding frictional interaction parameters at the stress and force levels.
  Keywords: ceramic materials, friction, friction coefficient, specific friction force, temperature.

• APPLICATION OF SURFACE PROFILE CHARACTERISTICS TO MODELING CONTACT INTERACTION OF COMPOSITE MATERIALS
  Authors: O.O. NOVIKOVA, V.V. NOVIKOV, A.N. BOLOTOV
  Abstract: The validity of the classical approach to solving contact problems for two-component composite surfaces based on the control of the microgeometry of the surface profile is shown. A homogeneous half-space of matrix material is considered as a composite surface, with spherical segments of the same radius located in it with a given volume density, simulating inclusions of a globular filler material. The profile of the composite half-space is an equivalent surface with a power-law distribution of the vertices of the micro-dimensions, similar to the reference curve of the material distribution of the real part. An engineering model for estimating the frictional characteristics of a triboassembly with composite materials has been tested in relation to the contact of a diamond-containing ceramic material and a ceramic homogeneous half-space. This model can be used to determine the friction characteristics of composite materials with globular fillers.
  Keywords: microgeometry of the surface, contact problem, friction characteristics, composite materials, friction, wear.

• SPECIFIC AND INTEGRAL CHARACTERISTICS OF FRICTIONAL INTERACTION IN CONTACT OF ENGINEERING SURFACES
  Authors: V.V. IZMAILOV, M.V. NOVOSELOVA
  Abstract: On the base of single and multiple contacts between engineering surfaces as examples, the correspondence between well-known tribological linear relationships describing their frictional interaction was analyzed, namely: the relationship between the specific friction force and the actual contact pressure and the relationship between the friction force and the external normal load (Coulomb's friction law). It is shown that the linear relationship between the specific friction force and the actual contact pressure generally corresponds to a nonlinear relationship between the friction force and the external normal load. The cause of this nonlinearity is the dependence of the real contact area on the normal contact load. However, over a limited range of normal contact load variation, this nonlinearity is weak, especially for multiple contacts. Therefore, the relationship between the friction force and the normal load can be adequately described by a binomial linear equation expressing Coulomb's friction law. The validity of this assertion is verified experimentally using four metal friction pairs.
  Keywords: engineering surfaces, real contact area, friction force, specific friction force, Coulomb's friction law.

• CAPABILITIES OF ATOMIC FORCE MICROSCOPY IN SOLVING SCLEROMETRY PROBLEMS
  Authors: D.A. BARCHUKOV, E.V. BARABANOVA, L.E. AFANASIEVA, I.A. SMOLYAKOVA
  Abstract: The results of microhardness studies using indentation and scratching with a tetrahedral diamond pyramid using a domestic PMT-3 microhardness tester are presented. Scratching of the steel surface was performed with the indenter oriented edge-first and face-first. An atomic force microscope was used to record and analyze the experimental results. The possibilities and prospects of using atomic force microscopy methods in solving sclerometry problems are shown.
  Keywords: microhardness, sclerometry, testing, diagnostics, atomic force microscopy.

• JUSTIFICATION OF THE RATE OF EGG HITTING IN AN INCUBATION SYSTEM INSTALLED IN DEPLETED PEAT DEPOSITS
  Authors: А.L. YABLONEV, A.A. ANDRIANOVA
  Abstract: Reclamation of exhausted peat deposits by flooding and subsequent stocking is the most effective method of farming. Growing valuable fish species by incubating fry requires the use of a special incubation system. The hydraulic calculation of its main element, the incubation nest, is impossible without the ability to determine the speed of the egg's flight in the nest, as a faster speed of flow will cause the egg to be washed away, while a slower speed will result in a lack of oxygen. The article proposes a mathematical model that allows for determining the speed of an egg's flight, and describes the experimental studies that demonstrated the adequacy of the developed model.
  Keywords: depleted peat deposit, flooding, stocking, incubation system, incubator nest, hovering speed, critical Reynolds number.

• THE METHOD OF DETERMINING THE LOADING LEVEL OF A BALL MILL
  Authors: V.S. BOCHKOV, K.V. BOCHKOVA, A.G. BABENKO
  Abstract: Improving the energy efficiency of ball mills, which are the main power-consuming units at mineral processing plants, is an urgent scientific and technical task. The key limiting factor is the lack of reliable systems for operational monitoring of the drum filling degree, leading to suboptimal operating modes (underloading or overloading) and significant economic losses. The article proposes a fundamentally new approach to determining the load level, based on the analysis of the spatial distribution of vibration signals over the drum surface – the "geometric method". During laboratory studies on a Bond mill, vibration parameters (vibration velocity S, vibration displacement D) were recorded for various loading combinations (balls, sand, water) and sensor positions relative to the impact source. Using time-domain, statistical, and frequency analysis methods, it was established that the dependence of the statistical characteristics of the signal (mean, median, max, std) on the angle between the sensor and the impactor is approximated in most cases by a second-order polynomial. A significant influence of the load type on the signal amplitude was revealed: the presence of bulk material (sand) leads to a multiple damping of oscillations due to energy dissipation through friction. The results confirm the fundamental possibility of creating a direct vibration-based load monitoring system independent of indirect process parameters. Recommendations for further research to develop an industrial methodology are formulated.
  Keywords: ball mill, load level, condition monitoring, vibration analysis, vibration velocity, vibration displacement, statistical signal processing, frequency analysis, geometric method, process optimization.

• RESOURCE MANAGEMENT IN COMPUTING SYSTEMS FOR OPTIMIZING THE PERFORMANCE OF FUNCTIONALLY RELATED SOFTWARE APPLICATION COMPONENTS
  Authors: M.A. GLEBSKY, I.A. EGEREVA
  Abstract: The article addresses the problem of optimal allocation of computational resources -specifically RAM and CPU time – among virtual containers within complex distributed applications. It analyzes key challenges in managing systems composed of numerous interconnected components, including dependency conflicts, competition for network ports, and unbalanced resource consumption. The study demonstrates that traditional resource allocation approaches, which focus on maximizing aggregate performance, prove ineffective under conditions of strong functional interdependence among containers, as they tend to create system bottlenecks. To address this issue, a mathematical model for resource allocation is proposed that incorporates minimum throughput requirements for each component. This approach aims to ensure balanced loading across all system elements and thereby enhance overall system efficiency.
  Keywords: virtualization, virtual containers, Docker.

• A SYSTEMATIC APPROACH TO LONG-TERM FORECASTING OF REFRIGERATION COMPRESSORS USING KEY CONTRADICTION ANALYSIS
  Authors: S.L. GOROBCHENKO, S.A. MESHKOV, N.N. WERNER, S.A. VOINASH, V.A. SOKOLOVA
  Abstract: This article proposes a method for long-term forecasting of technical systems development based on a systems analysis of a key internal contradiction. The refrigeration compressor system is chosen as the object of study. The method is based on identifying and tracking the development of the fundamental contradiction between two mutually exclusive requirements of the supersystem – ensuring productivity (quantitative) and creating pressure (qualitative). The evolution of compressors is traced, from piston to rotary, screw, centrifugal, and axial, identifying the main driving force behind their development – increased productivity, achieved primarily by increasing the rotational speed of the working parts. The analysis revealed that the mechanical principle of compression (volumetric and dynamic) is close to exhausting its capabilities, running up against physical and design limitations. A transition to fundamentally different, non-mechanical compression methods, such as magnetohydrodynamic and thermoelectric cooling, is justified as a promising direction following axial compressors. This corresponds to the general trend of working fluid transition from the macro- to the micro-level. It is concluded that forecasting based on the analysis of the key contradiction and supra-system requirements allows us to identify key development paths and create reliable long-term forecasts.
  Keywords: systems approach, long-term forecasting, technical system, refrigeration compressor, key contradiction, laws of technical system evolution, supra-system requirements, performance, compression principle, piston compressor, screw compressor, centrifugal compressor, axial compressor, magnetohydrodynamic method, thermoelectric cooling, technological evolution.