http://elartu.tntu.edu.ua/handle/lib/54157 Tue, 13 Oct 2026 11:17:29 GMT 2026-10-13T11:17:29Z http://elartu.tntu.edu.ua:80/retrieve/394879/Cover.jpg http://elartu.tntu.edu.ua/handle/lib/54157 http://elartu.tntu.edu.ua/handle/lib/54174 Назва: Features of the fracture of the control valve rod of a thermal power plant steam turbine Автори: Krechkovska, Halyna Короткий огляд (реферат): The reasons for the failure of the steam turbine control valve rod after 17 years of operation were analyzed. It was found that its fracture began in several places along the perimeter of the rod, followed by coalescence and subsequent spontaneous failure. Fractographic analysis showed that the crack propagated via a high-temperature fatigue fracture mechanism. Impact toughness, strength, and ductility properties determined on axial steel specimens of the control valve rod complied with regulatory requirements. However, the parameters of transverse specimens made from the rod head were lower. A decrease in all these characteristics was also observed in the high-temperature operating zone compared to the low-temperature zone, indicating more intense metal degradation. The control valve rod had 12091 operating hours and 206 shutdowns, which significantly impacted this process. Macrofractographic analysis showed that the rod fracture occurred because of multiple microcrack initiation in the nitrided layer along the perimeter in the zone of the fillet transition (stress concentrator) between the conical part and the head. Further growth of cracks into the depth of the section and their merging led to sudden fracture. Microfractographic studies confirmed the fatigue mechanism of crack initiation under low-amplitude cyclic loading. At the initial stage, characteristic fatigue grooves were observed, corresponding to the second section of the fatigue kinetic diagram. Their results showed that at a temperature of 540°C, the crack growth rate was 5·10⁻⁸ m/cycle. The rod fracture occurred due to multi-cycle fatigue, and only at the final stage did signs of low-cycle fracture appear. Tue, 26 May 2026 00:00:00 GMT http://elartu.tntu.edu.ua/handle/lib/54174 2026-05-26T00:00:00Z http://elartu.tntu.edu.ua/handle/lib/54170 Назва: Integrated frequency-based method for flight planning of stratospheric gliders with anomaly filtering Автори: Artomov, Ihor; Krytskyi, Dmytro; Artomova, Alina; Popov, Serhiy; Artomov, Artemii Короткий огляд (реферат): This paper presents, for the first time, an integrated method for flight planning of stratospheric gliders operating within swarm-based multilevel systems, which combines frequency analysis of time series of key flight performance indicators with an adapted Irwin criterion for filtering anomalous parameter deviations. The proposed approach enables the detection of long-period oscillations caused by stratospheric atmospheric processes and collective swarm dynamics, and allows for the timely identification of critical deviations that may disrupt swarm coordination, lead to additional energy losses, or cause degradation of the multilevel control system. The developed method is aimed at ensuring stability, adaptability, and energy efficiency of long-duration stratospheric soaring and can be applied to improve the effectiveness of flight planning for stratospheric gliders in multilevel autonomous systems. Existing approaches to flight planning for stratospheric vehicles are generally focused on local optimization of energy consumption or kinematic parameters and are based on the assumption of process stationarity. At the same time, most studies leave unresolved the issues of comprehensive analysis of the spectral structure of flight parameters, integration of frequency-domain methods into route evaluation procedures, and formalized detection of anomalies that may impair swarm coordination, accumulate energy losses, and degrade multilevel control systems. The objective of this study is to develop and substantiate an integrated algorithm for frequency analysis of flight planning indicators of stratospheric gliders in swarm-based multilevel systems using an adapted Irwin criterion for anomaly filtering. The proposed algorithm is intended to improve the accuracy of assessing long-period oscillations of flight parameters, enhance swarm interaction stability and energy efficiency of prolonged stratospheric soaring, and increase the reliability of multilevel autonomous control systems. The obtained results provide a scientific basis for the further development of adaptive control algorithms for swarm stratospheric gliders and may be used to improve the performance of autonomous multilevel systems in monitoring, communication, and surveillance applications. Tue, 26 May 2026 00:00:00 GMT http://elartu.tntu.edu.ua/handle/lib/54170 2026-05-26T00:00:00Z http://elartu.tntu.edu.ua/handle/lib/54172 Назва: Modal analysis of aircraft engine blisks Автори: Boiko, Ihor Короткий огляд (реферат): The article deals with the actual problem of ensuring the vibrational reliability of aircraft engine blisks by conducting modal analysis, which makes it possible to determine natural vibration frequencies and modes. The localization of vibrations, increased resonance stresses and threat of disk destruction have been subjected to analysis due to heterogeneous geometric configuration of blades caused by machining errors and operational wear. The paper presents a comparative analysis of experimental natural vibration frequencies and mathematical modeling by the finite element method (FEM) using a specialized software demonstrating high convergence of results. Particular attention is paid to evaluating the effectiveness of various technological refinements for both compressor centrifugal impellers and axial stages. These modifications include trimming the leading edge and tailoring the profile thickness into several distinct shapes. The primary objective of these adjustments is to shift the natural vibration frequencies beyond the engine's resonance operational range. The study covers the analysis of the influence of centrifugal forces, which increase the dynamic stiffness of the structure, aerodynamic loads, as well as the temperature factor, which significantly reduces frequencies due to changes in the material's elasticity moduli under high-temperature operation. To evaluate resonance conditions, Campbell diagrams are used, which make it possible to graphically determine the intersection points of natural frequencies with excitation harmonics from the engine's structural elements. The practical part is based on the analysis of the dynamic characteristics of the AI-450MS, D-36, and PZL-10W engine components to confirm the possibility of avoiding resonance zones through structural modifications. Additionally, the role of harmonic analysis is considered, which, unlike modal analysis, makes it possible to take into account the system damping and determine the amplitude-frequency characteristics of the blade under influence of specific exciting forces. Tue, 26 May 2026 00:00:00 GMT http://elartu.tntu.edu.ua/handle/lib/54172 2026-05-26T00:00:00Z http://elartu.tntu.edu.ua/handle/lib/54171 Назва: Water temperature measurement in an automated terrarium using a Pt1000 sensor Автори: Zdorenko, Valerii; Basaliuk, Maksym Короткий огляд (реферат): The article considers the application of a platinum resistance thermometer Pt1000 for accurate measurement of water temperature in an automated terrarium. A mathematical model of the resistance-temperature dependence R(T) based on the Callendar–Van Dusen equations is presented. The static and dynamic characteristics of the sensor are analyzed, and the influence of lead wire resistance and measurement channel noise is evaluated. An experiment was conducted to investigate the response of the Pt1000 sensor to a rapid temperature change in a water environment. The obtained curves demonstrate a fast initial temperature jump in the sensor contact zone with hot water, followed by a transient mixing of layers with damped oscillations and gradual establishment of thermal equilibrium. The experimental results confirm a first-order dynamic model with an effective thermal time constant τ and are consistent with analytical estimates of thermal inertia. The obtained dependencies make it possible to improve calibration accuracy and optimize digital filtering algorithms in terrarium microclimate control systems. Tue, 26 May 2026 00:00:00 GMT http://elartu.tntu.edu.ua/handle/lib/54171 2026-05-26T00:00:00Z http://elartu.tntu.edu.ua/handle/lib/54173 Назва: Technological features of cast iron treatment Автори: Kovbashyn, Vasiliy; Bochar, Igor Короткий огляд (реферат): The paper deals with the use of vibration technology, which is an effective means of reducing residual stresses in castings. Vibration can be used to achieve a stress relief sufficient to prevent further warping of castings due to the redistribution of residual stresses. In addition, it was shown that residual stresses in cast iron castings can be reduced without vibration by additional static loading with holding under load. The research resulted in obtaining the necessary data to assign vibration modes. It was established that the stress amplitude has a decisive influence on the magnitude of the reduction of residual stresses during vibration. The duration required for the complete stabilization of the stress relief process under vibratory action was determined. As a result of prolonged holding under load after vibration, processes may occur in the sample material that return it to the state before vibration. In other words, if the stress reduction process after vibration stops, it may be reactivated after a certain time. It has been established that for cast iron castings, in which residual stresses reach approximately 10 kg/mm², the stress amplitude during vibration should not exceed 3–4 kg/mm², otherwise there is a risk of cracks in the castings during vibration. The nature of the stress reduction during vibration is probably the same as during natural aging, only the speed of this process during vibration is much higher. After repeated vibration, observations of the samples continued for another four months. After this period, no changes in the magnitude of the stresses compared to the stresses remaining after vibration were detected. The results of this work give grounds to recommend conducting industrial tests of new methods of aging cast iron castings by vibration or static loading with the aim of their widespread introduction into industry. Tue, 26 May 2026 00:00:00 GMT http://elartu.tntu.edu.ua/handle/lib/54173 2026-05-26T00:00:00Z http://elartu.tntu.edu.ua/handle/lib/54168 Назва: Investigation of Concrete Pavement Abrasion Resistance in Agro-Industrial Facilities Using Polystyrene Waste Автори: Kupchuk, Ihor; Stadnik, Mykola; Yaropud, Vitalii Короткий огляд (реферат): Concrete floor pavements in agro-industrial facilities operate under combined abrasion, impact, moisture and organic environmental exposure, which accelerates degradation of the surface layer and increases dust formation. The study evaluates the use of polystyrene waste dissolved in toluene as a polymer impregnation for strengthening concrete pavement surfaces. Concrete specimens of class C25/30 were produced using Portland cement PC I-500, quartz sand and crushed stone aggregate with a fraction of 5–10 mm; the water–cement ratio was 0.42–0.45. After 28 days of curing at +20 ± 2 °C and 95% relative humidity, control specimens and specimens treated with polystyrene impregnation were compared by abrasion, water absorption, open porosity and surface condition. The polymer solution penetrated into the capillary-porous structure of concrete to a depth of 1–3 mm and formed a denser hydrophobic surface layer. The abrasion index decreased from 0.8–0.9 g/cm² for untreated concrete to 0.3–0.5 g/cm² for treated specimens. Water absorption decreased from 12–14% to 8–10%, while open porosity decreased from 18–20% to 14–15%. The results indicate that secondary polystyrene can be used as a low-cost strengthening impregnation for concrete floors, improving wear resistance, reducing dust formation and extending service life under agro-industrial operating conditions. Tue, 26 May 2026 00:00:00 GMT http://elartu.tntu.edu.ua/handle/lib/54168 2026-05-26T00:00:00Z http://elartu.tntu.edu.ua/handle/lib/54169 Назва: Equivalent Axisymmetric 2D Modeling of Three-Dimensional Stress State Автори: Antonchenko, Vitalii; Iasnii, Volodymyr Короткий огляд (реферат): The study addresses the urgent problem of rapid structural integrity assessment for VVER-1000 reactor pressure vessels (RPVs) under pressurized thermal shock (PTS) conditions during lifetime extension. Given the high computational complexity of three-dimensional finite element modeling, the authors propose a fast computational scheme based on 2D axisymmetric models. The paper analyzes the effect of stiffness mismatch between the simplified models and the actual geometry of nozzle zones, and proposes a combined model that merges the exact vertical profile of the nozzle with the corresponding RPV shell segment. The proposed technique enables the transformation of stresses from the 2D formulation into complete profiles across the entire wall thickness, ensuring the accuracy of stress intensity factor (SIF) calculations at the level of full-scale 3D models while significantly reducing computational time. Tue, 26 May 2026 00:00:00 GMT http://elartu.tntu.edu.ua/handle/lib/54169 2026-05-26T00:00:00Z http://elartu.tntu.edu.ua/handle/lib/54163 Назва: Comparison of tribological properties of VT6 titanium alloy surface after oxidation and nitriding Автори: Student, Mykhailo; Luk’yanenko, Alexander; Pohrelyuk, Iryna; Zadorozhna, Khrystyna; Student, Oleksandra; Trush, Vasyl; Hvozdetskyi, Volodymyr Короткий огляд (реферат): Titanium alloys offer advantages over steel due to their low specific density and high specific strength. This makes them indispensable in products for the aerospace, marine, and damping industries, among others. However, their poor frictional properties significantly limit their applications. This study proposes a way to minimize this disadvantage of titanium alloys by modifying their surface layers using an advanced thermochemical treatment (TCT) in a gas environment with controlled oxygen and nitrogen contents. Surface layers of VT6 titanium alloy were modified at 750°C with limited oxygen access and a controlled nitrogen flow. This TCT mode limited the thickness of TiO2 or TiN uniform layers formed on the surface of the alloy to 1–2 µm. Immediately beneath them, layers of solid-solution-hardened material with a gradient of oxygen or nitrogen content formed. Their microhardness gradually decreased, reaching the level of untreated titanium at a depth of 29–30 µm. To confirm the effectiveness of TCT, a friction test method was used under conditions of oscillatory sliding of steel and ceramic balls (as counterbodies) on a hardened surface. Wear profiles revealed small indentations from spherical counterbodies into the surface-hardened layers (from 3 to 1 µm under dry friction and boundary lubrication conditions, respectively). Hard particles of titanium dioxide or nitride altered the wear track profile on the surface of the TCT samples from relatively uniform to textured due to the selective removal of small chips. Despite the higher microhardness, the nitrided layer turned out to be 40-50% worse than the oxidized layer in terms of wear resistance, and this did not depend on the friction conditions (counterbody material, friction conditions, or the type of lubricant used). This was explained by the charging of the surface layers of the samples with superhard TiN fragments that entered the friction zone. Under dry friction, the friction coefficient between the steel ball and the surface- hardened VT6 alloy remained stable, but increased when using a ceramic ball. Under boundary lubrication, the friction coefficient remained constant by removing wear debris from the friction zone. Overall, the tests showed that controlled surface oxidation of the VT6 titanium alloy provides superior wear resistance compared to nitriding. Tue, 26 May 2026 00:00:00 GMT http://elartu.tntu.edu.ua/handle/lib/54163 2026-05-26T00:00:00Z http://elartu.tntu.edu.ua/handle/lib/54165 Назва: Boundary Element Method in Structural Mechanics for Periodic Structure Vibration Protection Автори: Kutsenko, Anastaciia; Bondar, Mariia; Kutsenko, Oleksii Короткий огляд (реферат): This paper investigates the adaptation of the direct boundary element method (BEM) for analyzing stationary vibrations in load-bearing structural components, specifically beams and plates, under intense dynamic loads. The study addresses the challenge of designing high-efficiency mitigation systems for engineered facilities with regular configurations, including cross-bar systems, multi-span floors, and pile foundations. A novel numerical scheme is proposed and substantiated to model bending wave propagation with high precision in periodically fixed elements. Fundamental solutions for one-dimensional and two-dimensional systems are derived using the Fourier integral transform combined with contour integration techniques. The computational advantages of the developed approach over the conventional finite element method (FEM) are demonstrated, focusing on dimensionality reduction and modeling accuracy in infinite domains, which is essential for foundation-soil interaction problems. The proposed methodology effectively identifies stop-bands-frequency ranges where wave propagation is suppressed. The findings establish a theoretical framework for designing innovative structural components capable of blocking undesirable oscillations, thereby ensuring structural safety and vibration isolation in residential and industrial environments. Tue, 26 May 2026 00:00:00 GMT http://elartu.tntu.edu.ua/handle/lib/54165 2026-05-26T00:00:00Z http://elartu.tntu.edu.ua/handle/lib/54164 Назва: Experimental study of the cavitation impregnation process of textile materials Автори: Yerii, Andrii; Syniuk, Oleh Короткий огляд (реферат): The paper investigates the efficiency of the cavitation method for impregnating textile materials and compares it with the conventional immersion method. The relevance of the study is determined by the need to improve the efficiency of textile impregnation processes using special substances while preserving the structural and mechanical properties of the materials. Particular attention is paid to the influence of ultrasonic cavitation on the intensification of mass transfer processes within the porous-capillary structure of textile materials. The research employed an experimental comparative method involving the determination of the weight characteristics of samples before impregnation, after impregnation, and after excess liquid drainage. The process efficiency was evaluated using the impregnation coefficient, percentage weight gain, liquid retention index, and impregnation rate. Experimental studies were carried out using an ultrasonic cavitation unit operating at a frequency of 40 kHz. The results of the study showed that the cavitation method increases the impregnation coefficient by an average of 6.9% compared to the conventional immersion method. An increase in the penetration rate of impregnating substances into the material structure and an improvement in the material’s ability to retain the working liquid were also observed. Experimental results confirmed that, under rationally selected ultrasonic treatment conditions, no significant damage to the fiber structure of the textile material occurs. The scientific novelty of the work lies in the development of a comprehensive approach to the quantitative evaluation of the efficiency of cavitation impregnation of textile materials using integral indicators of impregnation and liquid retention. In addition, the regularities of the influence of ultrasonic cavitation on the intensification of mass transfer processes in the structure of textile materials were established. The practical significance of the obtained results lies in the possibility of applying cavitation impregnation to hard-to-impregnate textile materials, particularly in the production of flame-resistant products, protective workwear, and technical textiles. The proposed approach makes it possible to reduce the duration of the technological process and improve impregnation efficiency without deteriorating the operational characteristics of the material. Tue, 26 May 2026 00:00:00 GMT http://elartu.tntu.edu.ua/handle/lib/54164 2026-05-26T00:00:00Z http://elartu.tntu.edu.ua/handle/lib/54166 Назва: Publishing page Tue, 26 May 2026 00:00:00 GMT http://elartu.tntu.edu.ua/handle/lib/54166 2026-05-26T00:00:00Z http://elartu.tntu.edu.ua/handle/lib/54167 Назва: Content Tue, 26 May 2026 00:00:00 GMT http://elartu.tntu.edu.ua/handle/lib/54167 2026-05-26T00:00:00Z http://elartu.tntu.edu.ua/handle/lib/54162 Назва: Comparative analysis of mathematical models and estimation of errors in computer modeling of the gas consumption process Автори: Shymchuk, Grigorii; Lytvynenko, Iaroslav Короткий огляд (реферат): The paper considers approaches to mathematical modeling of the gas consumption process based on three models: a model based on a cyclic random process and the classical ARIMA and SARIMA models. The gas consumption process is characterized by the presence of a trend, seasonality, cyclicity, and random disturbances, which necessitates the use of adequate mathematical models for its description and simulation. The paper presents a mathematical model of the gas consumption process in the form of an additive mixture of trend, cyclic, and random components. A comparative analysis of the ARIMA and SARIMA models, which are based on differencing operators and take seasonal features into account, is also provided. The models are compared in terms of adequacy, ability to capture cyclicity and seasonality, interpretability of parameters, and suitability for computer simulation and forecasting. To assess the accuracy of computer simulation of gas consumption process realizations, absolute and relative errors are used. It is shown that the SARIMA model is an effective baseline model for series with stable seasonality, whereas the model based on a cyclic random process is more suitable for describing gas consumption with a pronounced cyclic structure and is better suited for computer simulation tasks. Tue, 26 May 2026 00:00:00 GMT http://elartu.tntu.edu.ua/handle/lib/54162 2026-05-26T00:00:00Z http://elartu.tntu.edu.ua/handle/lib/54158 Назва: Title Tue, 26 May 2026 00:00:00 GMT http://elartu.tntu.edu.ua/handle/lib/54158 2026-05-26T00:00:00Z http://elartu.tntu.edu.ua/handle/lib/54159 Назва: Strategies for LLM-Driven User Interface Generation in Smart Systems: A Comparative Analysis with Decision Guidance Автори: Lypak, Taras; Lypak, Halyna; Kramar, Taras; Duda, Oleksij Короткий огляд (реферат): Large language models (LLM) provide opportunities to generate user interfaces directly from natural- language intent, but the emerging generative-UI literature remains focused primarily on web and chat contexts rather than smart systems. Smart-system interfaces are characterized by stricter demands, necessitating grounding in concrete device registries, validation against real-world action consequences, and explainability to non- developer users. This paper identifies and compares six distinct strategies currently used for LLM-driven UI generation (direct structured-output prompting, template-augmented generation, retrieval-augmented generation, model-driven hybrid pipelines, constrained generation, and multi-agent decomposition) using criteria tailored to smart-system contexts: output consistency, safety and accuracy validation, explainability, latency, implementation complexity, generalisability, and failure handling. The comparison is then adapted to three representative domains: smart-home consumer IoT, smart industrial supervisory control, and smart cultural heritage (virtual and AR museums, AI-assisted reconstruction interfaces, and smart exhibit displays). For each domain, a primary strategy is recommended, modifications required to meet specific domain constraints are demonstrated, and an adapted reference architecture is presented. A decision matrix and a selection flowchart are developed to guide the selection of an LLM-based UI generation strategy for specific smart-system deployments. The paper closes by outlining several open challenges, including the verification of accuracy-critical generated interfaces and the integration of static generation with runtime adaptation. Tue, 26 May 2026 00:00:00 GMT http://elartu.tntu.edu.ua/handle/lib/54159 2026-05-26T00:00:00Z http://elartu.tntu.edu.ua/handle/lib/54161 Назва: Assessment of the Mutual Influence of Prefabricated Steel Silo Foundations Under Staged Loading Автори: Pidgurskyi, Mykola; Pidgurskyi, Ivan; Bykiv, Denys; Zakharevych, Ivan Короткий огляд (реферат): A three-dimensional numerical model of a cast-in-situ raft foundation interacting with elastic subsoil was developed using the Finite Element Method (FEM) in the LIRA-FEM software environment, incorporating the GRUNT module for subsoil modelling. The analysis considered both isolated and two-row grouped configurations under three sequential loading stages. Key parameters, including vertical displacements and tilt, were assessed to determine the impact of mutual interaction. The results indicate that adjacent structures significantly intensify subsoil deformations. In particular, the maximum settlement increased from 115.2 mm for an isolated structure to 177.25 mm under grouped conditions, representing a 1.54-fold increase. The corresponding structural tilt reached 0.0024, exceeding the allowable limit of 0.002, while the settlement surpassed the normative maximum permissible of 150 mm. The findings demonstrate that neglecting the mutual geotechnical influence of closely spaced storage facilities may lead to exceeding ultimate limit states. Therefore, comprehensive spatial numerical modelling is essential for the safe and reliable design of modern agricultural infrastructure. Tue, 26 May 2026 00:00:00 GMT http://elartu.tntu.edu.ua/handle/lib/54161 2026-05-26T00:00:00Z http://elartu.tntu.edu.ua/handle/lib/54160 Назва: An extensible software architecture for modeling complex object-oriented multicomponent systems Автори: Petryk, Mykhaylo; Mykhalyk, Dmytro; Zaiarnyi, Mykola; Tsebriy, Oleksiy; Shynkaryk, Mykola Короткий огляд (реферат): This article presents a modular, object-oriented architecture for the PBM (Porous Media Modeling) library, a Java-based system designed to model consolidation filtering kinetics in hierarchical porous media with two- and three-level porosity structures. Developing extensible software architectures for scientific computing remains a persistent challenge, particularly for complex, multi-component systems with multi-level relationships. Current software modeling tools are tightly coupled with specific object-oriented domains and the mathematical models of physical processes, such as consolidation filtering in porous media. Consequently, these tools must satisfy strict engineering requirements regarding architectural stability, feature expansion, and the seamless integration of new numerical schemes and physical models. The proposed architecture consists of four decoupled modules: Process, Direct, GUI, and Extra. These modules are interconnected through well-defined interfaces and governed by the Factory, Strategy, and Template Method design patterns. Specifically, the Process, Direct, and Extra modules encapsulate simulation parameters and implement diverse methods for computer modeling and parameter identification. These components control the spatiotemporal distributions of key process variables across various macro- and micro-porous scales. Concurrently, the GUI module provides polymorphic visualization via the drawable interface. Ultimately, we demonstrate that this architectural design enables the seamless integration of new mathematical models, numerical schemes for high- performance computing, and analytical methods without modifying the existing codebase, thereby satisfying the open-closed principle. Tue, 26 May 2026 00:00:00 GMT http://elartu.tntu.edu.ua/handle/lib/54160 2026-05-26T00:00:00Z