Visnik of the Volodymyr Dahl East Ukrainian National University

Mathematical modelling of excavator productivity taking into account the parameters of the adsorbed vapour layer in the tribo-connections of an axial-piston pump

V.B. Kosolapov, A.V. Zverev — Sun, 23 Nov 2025 00:00:00 +0000

The performance of crawler hydraulic excavators largely depends on the efficiency of the hydraulic system, primarily on the volumetric capacity of the axial piston pump that supplies the working equipment. During prolonged operation, the mating surfaces of the pump tribopair (cylinder block – distribution washer, piston – cylinder) are subject to wear, which leads to an increase in internal leaks and a gradual decrease in volumetric efficiency and, as a result, machine productivity. Modern hydraulic fluids for construction equipment contain anti-wear additives based on surfactants (SAS), which are physically adsorbed on microscopic irregularities of metal surfaces and form a thin protective film.

This adsorbed film partially compensates for surface roughness, increases the actual contact area, reduces local contact stresses at the base of irregularities and thus slows down wear. However, the thickness of this film is not constant: it decreases during the operation of the excavator due to a reduction in the concentration of SAS under the influence of mechanical loads and temperature. To compensate for this phenomenon, in the practice of operating hydraulically driven machines, the working fluid is periodically replaced as planned, thus restoring the concentration of SAS to its initial level. The article proposes a refined mathematical model in which the thickness of the SAS film is described by an exponential law. At the same time, the restoration of the properties of the hydraulic fluid over a fixed time interval is taken into account by introducing the function of changing the thickness of the surfactant film into the expression for calculating the effective tribological clearance associated with the model of leakage changes in the pumping unit of an axial piston pump. On this basis, the dependence of the change in the volumetric efficiency of the pump on the operating time of the excavator and the frequency of hydraulic fluid replacement is determined.

On this basis, the dependence of the volumetric efficiency of the pump on its operating time was obtained and, ultimately, the dependence of the excavator's performance on its operating time, taking into account the frequency of replacement of the hydraulic fluid in the hydraulic drive.

The model is parameterised for a CAT 320 class hydraulic excavator with a bucket volume of 0.75 m³ (two pumps with a capacity of 215 l/min, working pressure up to 35 MPa) and can be used to justify the choice of hydraulic fluids and maintenance intervals for hydraulic drives in construction and road machinery.

Finishing processing of parts in a combined working environment under the action of oscillations. physical phenomena and dynamics of contact interaction

О.V. Romanchenko — Sun, 23 Nov 2025 00:00:00 +0000

This article analyzes finishing processes using a combined abrasive medium under the action of oscillations, combining mechanical, physical, chemical, and energetic phenomena. The study investigates the physical nature of oscillation processes, the patterns of interaction between abrasive particles and the surface of workpieces, and identifies the conditions under which maximum processing efficiency is achieved. A comparative analysis of traditional finishing methods – grinding, tumble finishing, abrasive-jet machining, and vibration machining – is presented. Their advantages, disadvantages, and application limits in modern mechanical engineering are identified.

A new finishing method is proposed: machining with a combined working medium, which combines abrasive, chemical, thermal, electrical, and mechanical action. This medium consists of abrasive granules, process solutions, and process intensifiers, which, under the action of vibrations, perform a complex, deterministic circulatory motion, creating numerous micro-impacts on the surface of the workpiece. This enables cleaning, grinding, polishing, surface layer strengthening, residual stress removal, adhesion enhancement, and surface preparation for coating application. Like traditional methods, this method enables the simultaneous processing of a large number of parts, while its integrated approach allows for achieving the required surface quality in a shorter processing time.

The mechanism of contact interaction between the abrasive medium and the part surface is revealed. It is established that the process is accompanied by impact, cavitation, adhesion, wear, wave propagation, and energy dissipation. The oscillations are divided into frequency ranges, from infrasonic to ultrasonic. The effects of free, forced, parametric, and self-oscillations on the process are examined, as well as their influence on the behavior of the working medium and the workpieces.

It is shown that the machining process is a complex vibration-impact system with distributed parameters, in which the frequency, amplitude, properties of the abrasive, part geometry, and equipment operating modes play a significant role.

The dynamic properties of the working medium are examined: circulation motion, elastic impact interaction of particles, pressure wave formation, contact processes, and deformation of surface layers. The influence of process solutions on the intensity of the process is demonstrated. Mathematical relationships describing changes in contact parameters, impact energy, particle velocity, and interaction force are presented.

The proposed approach expands the capabilities of finishing machining in mechanical engineering, particularly for parts with complex geometries and high surface finish requirements, and creates the basis for further development of technologies for machining with combined abrasive media under the action of vibrations.

The influence of reservoir lining material on the performance of processing of parts with a combined working media under the influence of oscillations

О.V. Romanchenko, A.G. Ivchenko — Sun, 23 Nov 2025 00:00:00 +0000

This work examines the effect of the lining material of a reservoir used for processing combined free working media under the action of oscillations on the overall productivity of the surface finishing process. The method is based on the transmission of pulses from the oscillating walls of the reservoir to the working media, which creates a stable circulating flow of the abrasive media, chemical solutions, and workpieces. The relative movement of the media elements determines the metal removal rate, and the presence of passive zones within the reservoir significantly affects the uniformity of the finish processing. While the parameters of the oscillation process have been thoroughly studied in the scientific literature, the influence of the abrasive properties of the reservoir walls remains understudied, despite the widespread use of rubber coatings in industrial equipment.

This paper presents the results of an experimental study conducted on equipment with a 25-liter reservoir. Two lining configurations were investigated: a traditional lining with a rubber surface and a surface lined with silicon carbide plates. Porcelain balls and a sodium bicarbonate solution were used as the working medium. Before the main machining operation, a cleaning step was performed using a continuous water supply. After the main operation, a repeat cleaning step was performed. After machining, the mass of metal removed from the samples was assessed in a series of ten parallel tests for each lining configuration.

The data obtained showed that changing the reservoir wall roughness did not significantly affect the circulation of the working media. The use of an abrasive silicon carbide lining significantly increased process productivity – the average metal removal rate increased by 40%. The possibility of intensifying oscillating machining by using wall materials with abrasive properties without compromising the stability of the working media was experimentally confirmed. The study demonstrates the potential of using abrasive coatings to improve the machining efficiency in equipment designed for finishing with abrasive tools without a rigid kinematic connection.

Сreation of a resource-saving technology for dyeing cotton fabric with pigments using catholite, a product of water electroactivation

M.Н. Koval, N.Н. Romanenko, H.S. Stoliarenko — Sun, 23 Nov 2025 00:00:00 +0000

The textile industry occupies one of the leading positions in the manufacturing sector both globally and in Ukraine. The increased demand for high-quality fabrics due to the rapid development of the clothing and footwear industries requires new technological solutions for their manufacture, which will lead to a reduction in the cost of finished products, a reduction in the consumption of dyes (pigments) and the environmental friendliness of dyeing and printing processes in dyeing and finishing industries. The relevance of the work is determined by the need to create resource-saving technologies for pigment printing of textile materials, which involves reducing the consumption of pigments and auxiliary substances, eliminating corrosive ingredients in printing ink that are harmful to the human body, and reducing the environmental impact. The aim of the article is to create a resource-saving technology for printing cotton calico fabric with pigment dyes by minimising the composition of pigment printing paint using a liquid product of water electroactivation – catholyte; to study printed fabric samples for the stability and intensity of the colours obtained. The paper presents the results of experimental studies conducted in the production conditions of an operating textile enterprise on the creation of a new composition of discharge pigment dye, in which the toxic and harmful 25% ammonia solution is replaced by a liquid product of water electroactivation, catholyte (pH = 10±0.5), which made it possible to reduce the consumption of printing ink components (thickener, binder and pigment) by 10% each compared to the basic technology. The article shows that the proposed composition of discharge dye with a new formula using catholyte provides a colour intensity of 97-103% (compared to 100% intensity with the basic formula), colour fastness of cotton fabric to dry and wet friction, washing with soap and ‘sweating’ at a level of 3-5 points, which indicates the promise of creating a resource-saving technology for pigment printing on cotton fabrics using catholyte.

Сavitation treatment of mixtures of linear alkanes with hydrogen peroxide and auxiliary agents as a method for increasing the octane number of motor fuels

D.V. Serhiienko, O.B. Tselishchev, S.O. Kudryavtsev, M.G. Loriia — Sun, 23 Nov 2025 00:00:00 +0000

The paper presents the results of a study on the use of cavitation treatment of mixtures of linear alkanes with hydrogen peroxide and alcohol co-agents to increase the octane number of motor fuels. Cavitation, accompanied by the formation and collapse of vapour bubbles in a liquid, creates localised zones with extreme temperatures (10³–10⁵ K) and pressures (up to 100 MPa), in which radical reactions, isomerisation, cracking and the formation of oxygen-containing compounds occur. The introduction of H₂O₂ into the system leads to the formation of hydroxyl radicals (•OH), which are capable of initiating the activation of inert alkanes and promoting their structural transformations. Alcohols, in particular bioethanol and isopropanol, act as both high-octane components and modifiers of radical processes, increasing the selectivity of the formation of desired products. Experimental data show that cavitation treatment with hydrogen peroxide H₂O₂ provides an octane number increase of 1.3–3.5 RON, with isopropanol provides an octane number increase of 0.3–0.9 RON, and with bioethanol — up to 2.6 RON, with optimal alcohol concentrations of 1.0%, 3.5% and 6.5% by volume.

The combination of cavitation with additives reduces alcohol consumption by 14–17% for A-95 and A-98 fuel grades compared to mechanical mixing. The industrial prospects for implementation have been analysed, in particular the advantages of hydrodynamic cavitation in terms of cost and energy efficiency, as well as the existing limitations — the need to optimise process parameters, control the formation of by-products, prevent equipment erosion and refine isomerisation mechanisms. Areas for further research are proposed, including detailed parameter mapping, assessment of long-term fuel stability, and scaling of the process to an industrial level. The results confirm the technical and economic feasibility of the technology as an alternative or supplement to traditional methods of increasing the octane number.

Dynamics of failure probabilities in ship power plant equipment considering cascade effects

V.V. Vychuzhanin, О.V. Vychuzhanin — Sun, 23 Nov 2025 00:00:00 +0000

The article presents a comprehensive and scientifically substantiated approach to modeling the technical condition, degradation processes, and reliability of ship power plants (SPP) considering cascade failure effects and probabilistic dependencies between components. A hybrid diagnostic–prognostic methodology is proposed, integrating continuous-time Markov processes, Bayesian networks, gradient boosting algorithms (XGBoost), and simulation modeling within a unified analytical framework. The approach enables quantitative assessment of the dynamic evolution of reliability under complex interactions between subsystems. The interrelation between SPP components is formalized through a cascade influence coefficient matrix αᵢⱼ, which reflects how the malfunction of one unit increases the probability of failure in another. Bayesian networks are used to capture causal relationships between failures and to continuously update probabilistic assessments based on new monitoring data, while machine learning algorithms determine the most informative parameters for predictive diagnostics, such as vibration amplitude, oil temperature, and cooling system pressure. The model was trained and validated using operational data from the OREDA database and expert evaluations, demonstrating high predictive accuracy (AUC > 0.95, MAE < 4.7%). Simulation experiments identified two critical operational intervals (≈10,000 and 20,000 hours), when cascading effects lead to exponential growth of total failure probability. The cooling system and main engine were found to be the most vulnerable nodes initiating degradation chains that propagate throughout the system. The developed methodology enables integration into digital twin architectures for adaptive recalibration, anomaly detection, and risk-based maintenance optimization. The study contributes to the formation of a data-driven, cognitive basis for intelligent monitoring and predictive maintenance of maritime energy systems, enhancing their reliability, resilience, and operational efficiency under uncertainty and extended service life.

Directions for optimizing IT service management processes

I.D. Pogorielovska, S.S. Burian — Sun, 23 Nov 2025 00:00:00 +0000

Standards, methodologies and practices of technical support services are considered. The problems of the efficiency of traditional technical support channels in modern companies are analyzed, an innovative hybrid solution is proposed based on the integration of Telegram Bot with Jira Service Desk. Architectural solutions, algorithms of the system operation and features of the implementation of online interaction between users and support service specialists are highlighted. A three-stage security architecture is developed with division into Internet zones, a demilitarized zone and an internal corporate network. Algorithms of authorization, distribution of applications and processing of online sessions are proposed, taking into account the workload of specialists and a multi-criteria approach. A database is designed with a minimum set of information without confidential business data, which meets modern principles of information security and provides quick access to the necessary information. Caching mechanisms are used to reduce the load on internal systems and increase the overall productivity of the solution. The proposed online consultation mechanism transforms the traditional asynchronous request management system into a tool for real-time operational interaction, which is critically important in remote work conditions. The ability to instantly contact a specialist and solve a problem in a live dialogue mode significantly increases the efficiency of technical support and user satisfaction. The practical value of the developed system lies in the possibility of its implementation in organizations of various sizes and business profiles. The developed system is scalable, secure and provides all the necessary capabilities for the effective organization of technical support for users. This solution is especially relevant for Ukrainian companies in the context of modern realities of remote work and the need to ensure the continuity of business processes.

Рrospects for the use of drones in agriculture

H.L. Melkonov, О.V. Yepifanova — Sun, 23 Nov 2025 00:00:00 +0000

Modern agriculture is undergoing a real transformation through the introduction of new technologies. One such innovation is the use of drones, which significantly simplify farm management processes and increase the efficiency of agribusiness.

Drones, or unmanned aerial vehicles (UAVs), have become indispensable assistants in the field of agribusiness. Thanks to their use, farmers can quickly receive important information about the condition of their fields. This allows them to quickly respond to changes and make informed decisions.

The use of drones in agriculture is becoming increasingly widespread. This is happening in proportion to the increase in the number of drones and the expansion of their functions. Drones perform monitoring, take aerial photographs, create 3D maps, sow seeds, apply fertilizers and chemicals, monitor crops and farm animals, and assist in irrigation.

The use of drones in almost every sector of the economy is growing rapidly, but the use of drones in the agricultural industry is growing at a high rate. The agricultural drone market is expected to grow from $1.2 billion in 2019 to $4.8 billion by 2025, according to some estimates. In the next few years, drone use will become more prevalent on farms large and small, from reconnaissance to security. The information collected by drones on farms is often used to make better agronomic decisions and is part of a system commonly referred to as “precision farming.” In many places, drones have already become an integral part of large-scale precision farming operations. Data collected by drones that record fields helps farmers plan planting and tilling for the best yields. Some reports indicate that the use of precision farming systems can increase yields by as much as 5%, a significant increase in an industry with typically low profit margins. The use of drones in agriculture not only increases efficiency and productivity, but also makes production more sustainable and environmentally friendly. Investment in such technologies is gradually becoming the standard of modern agribusiness, especially for those farms that seek to optimize resources and reduce costs.

Drones have great potential to transform agriculture in Ukraine and around the world. As technology advances in the future, drone production is expected to become cost-effective. The value of drones can encourage young people to work in the modern agricultural sector. The next agricultural revolution will be driven by drone data. Proper use of data can increase agricultural productivity without any negative consequences for the environment and at the same time improve farmers’ livelihoods. Therefore, drones can become a part of agriculture in the future, helping farmers better manage their fields and resources in a sustainable way.

In the primary production sector, high-tech drones allow operators to automate some processes, such as planting, livestock management, or crop spraying. These potential applications of drones open up a new branch of agricultural processes, sometimes called precision farming.

Without a doubt, drones are becoming an integral part of agribusiness. They open up new opportunities for farmers, making processes more transparent and manageable. Innovation in this area continues to develop, and we can expect drones to become even more advanced and accessible in the future.

Study of oscillatory processes in electromechatronic systems

Y.S. Rudniev, J.A. Romanchenko — Sun, 23 Nov 2025 00:00:00 +0000

In the article an analysis of oscillatory processes occurring in electromechanical and electromechatronic systems is presented.

It has been shown that oscillations reflect the exchange of energy between accumulators via an active transmission channel. The oscillations reflect the exchange of energy between the storage devices via the active transmission channel. In mechanical systems, such accumulators are masses (moments of inertia), and the transmission channels are shaft lines. An electric motor is a universal converter of electromagnetic energy into mechanical energy and vice versa. It also contains two energy accumulators between which exchange is possible: the armature (rotor) winding, which contains electromagnetic energy, and the inertia on the shaft (the accumulation of mechanical energy). In the transmission channel, energy is converted from one form to another due to the presence of an excitation flow.

The authors note that in electromechanical and electromechatronic systems, electromechanical vibrations are also possible, in addition to mechanical ones. Both internal viscous friction in the shafting and losses in the machine's anchor circle damp these vibrations.

This article examines an electromechanical system that exhibits both types of oscillations. A unified structural diagram for any type of electromechanical electric drive system, as well as its mathematical model, is presented.

A differential equation for the motor rotor motion with a stepwise increase in the control input signal was obtained. The values of the first derivatives at the initial instant were found. The damping coefficients and oscillation frequencies were determined.

An electromechanical system was modeled in MATLAB/Simulink using a structural diagram with a constant electromagnetic motor torque and specified parameters. The logarithmic damping decrement was determined in the absence of mechanical damping and in the presence of shaft line losses.

The reaction of the electromechanical system to the sudden appearance of a control action at the input is presented, as well as the reaction in the absence of mechanical damping and when the anchor is powered from a current source, from which it is evident that in the absence of internal viscous friction in the shaft line, mechanical vibrations are still damped due to internal viscous friction in the engine itself.

Dielectric environment in high-voltage equipment

N.M. Filimonenko, K.V. Filimonenko — Sun, 23 Nov 2025 00:00:00 +0000

The article is devoted to the analysis of modern alternatives to SF6 in high-voltage equipment of power systems, with a focus on their electrical performance, safety, and environmental efficiency.

For a long time, SF6 has remained the primary dielectric medium in high-voltage power system equipment. However, considering its extremely long atmospheric lifetime and high global warming potential, governments have focused efforts on reducing emissions of this gas. In response, the industry has begun implementing SF6-free technologies in traditional applications, including switchgear, circuit breakers, and high-voltage lines or busbars.

SF6 is an inert and non-toxic gas that is of great importance for electrical switchgear used for the distribution and transmission of electricity worldwide. This equipment is placed at network nodes to interrupt short-circuit currents as soon as they occur. SF6 is a voltage-insulating gas that has three times better insulating properties than air, better than any other gas. It therefore allows the design of small, enclosed and gas-tight switchgear with a small footprint, which has recognized advantages in harsh environmental conditions and with limited space, such as in wind towers. SF6 currently has no cost-effective and energy-efficient alternative for switchgear above 52 kV, i.e. for use in the transmission network, where it is used due to its excellent current-interrupting capabilities.

Among the SF6-free solutions, gas mixtures based on fluorinated compounds with low climate impact stand out, particularly fluoro-nitrile (3M™ Novec™ 4710) and fluoro-ketone (3M™ Novec™ 5110). The use of these mixtures in gas-insulated equipment allows for a reduction of greenhouse gas emissions by more than 99% compared to SF6, while maintaining high electrical and operational performance. The article presents the key components of alternative gas mixtures and provides updated data on their performance, safety, and environmental effectiveness in modern power systems.

Іntelligent methods for predicting failures of power electrotechnical equipment based on multilevel digital twins

O.V. Tsvietkov — Sun, 23 Nov 2025 00:00:00 +0000

The article explores the use of intelligent approaches to predicting failures of power electrical equipment through the implementation of multilayer digital twins that integrate physical modeling, machine learning technologies, and big data analytics in order to enhance the reliability of power grid operation. The study aims to develop and experimentally validate a comprehensive digital model that synthesizes physics-informed mathematical equations with deep learning algorithms to achieve higher accuracy in residual life prediction and minimize the occurrence of technical failures in transformer equipment and asynchronous electric motors. The methodological framework of the research is based on the formation of a multilayer architecture of a digital twin, which includes: a sensor layer for data aggregation, a physical modeling layer of electromagnetic, thermal, and mechanical phenomena, an analytical layer employing machine learning algorithms, and a decision-making layer incorporating elements of fuzzy logic. The scientific results obtained showed that the use of a hybrid model can reduce the root mean square error (RMSE) to 0.031, reduce the mean absolute percentage error (MAPE) to 2.8%, and increase the F1-score to 0.93, which significantly exceeds the performance of classical diagnostic methods. It has been established that the completeness of sensor information and the frequency of model updates exert a decisive influence on predictive accuracy, while the system’s ability to automatically adapt to load variations has been experimentally confirmed. The developed architecture has shown strong resilience to data deficiency and a high level of generalization (CV < 0.06). The applied significance of the study lies in reducing emergency downtime by 30–40%, optimizing maintenance costs, and transforming the management of equipment condition toward a risk-oriented strategy. Future research directions include the standardization of digital twin technologies, the advancement of explainable AI methods, and the implementation of basic cybersecurity systems for next-generation industrial digital platforms.