Technical Mechanics
type: channel
description: From 1993 to 1997, the Institute of Technical Mechanics of the National Academy of Sciences of Ukraine and the State Space Agency of Ukraine published an interdepartmental collection of papers entitled Tekhnicheskaya Mekhanika, which in September 1997 received the status of a scientific journal entitled Tekhnicheskaya Mekhanika (in Russian) and Tekhnichna Mekhanika (in Ukrainian). In 2017, the institute was issued a new state registration certificate for the journal, in accordance with which the journal has the official English title of Technical Mechanics, may publish papers in English, and is entitled to international distribution. The journal publishes review and research articles on the following topics: 1.Applied Mechanics 2. Applied Mathematics 3. Aviation and Space Engineering 4. Automation and Computer-Integrated Technologies 5. Physics and Astronomy
publisher: текст 3
language: en-US
publication name: Technical Mechanics
items: ON-OFF SPACECRAFT RELATIVE CONTROL IN SLIDING MODE VIA REINFORCEMENT LEARNING
items: NUMERICAL ANALYSIS OF THE EFFECT OF THE DESIGN AND MANUFACTURING PARAMETERS OF STARTER LEAD-ACID BATTERIES ON THEIR DISCHARGE CHARACTERISTIC
items: MODEL OF 3-D PRINTING ZONE HEATING CONTROL
items: COMPUTER SIMULATION OF THE EFFECT OF ELLIPTICAL INCLUSION ARRANGEMENT ON THE STRAINING OF A CYLINDRICAL SHELL WITH A CIRCULAR HOLE
items: MATHEMATICAL MODELING OF ELECTRON DENSITY DETERMINATION USING A STATIONARY CYLINDRICAL LANGMUIR PROBE UNDER IONOSPHERIC CONDITIONS
items: COMMON WHEEL PROFILE FOR PASSENGER AND FREIGHT CARS TO BE OPERATED BOTH ON THE UKRAINIAN AND ON THE WEST-EUROPEAN RAILWAYS
items: DEVELOPING THE RESEARCH LINES OF VIKTOR V. PYLYPENKO, AN ACADEMICIAN OF THE NATIONAL ACADEMY OF SCIENCES OF UKRAINE
items: MODELING OF THE CHECK VALVE OPERATION IN THE RECONFIGURABLE HYDRAULIC FEED SYSTEM OF A LIQUID ROCKET ENGINE
items: SINGLE-LAYER MARCHING ALGORITHM TO CALCULATE SUPERSONIC FLOW ABOUT ROCKETS WITH THE COMPUTATIONAL REGION DIVIDED INTO SEVERAL SUBREGIONS
items: PARAMETERS OF THE ST-40M HALL-EFFECT THRUSTER IN ITS OPERATION ON XENON AND KRYPTON

ON-OFF SPACECRAFT RELATIVE CONTROL IN SLIDING MODE VIA REINFORCEMENT LEARNING
type: item
description: DOI: https://doi.org/10.15407/itm2025.04.077 The paper addresses the problem of on-off spacecraft relative control in sliding mode for autonomous on-orbit servicing operations under actuator amplitude limits, action discreteness, and parametric uncertainties. The goal is to develop and assess an approach that combines sliding-mode control with modern reinforcement-learning methods tailored for resource-constrained onboard implementation. Relative motion dynamics is formulated in an orbital coordinate frame with normalized states and discretized in time. Binary actions with pulse-width modulation, subject to constraints on the thrust level, pulse duration, and duty cycle, represent the impulsive nature of actuation. We propose a combined synthesis in which the sliding-surface parameters and switching rules are tuned via proximal policy optimization within an actor-critic architecture. The actor and critic are implemented as neural networks that approximate the policy and the value function, respectively. The actor neural network takes the state vector as input information and outputs the mean and standard deviation of the parameters of the sliding mode control law. The value function penalizes both the state error and control effort, thus enabling a trade-off among the response speed, accuracy, and propellant consumption. Two uncoupled agents are designed to control spacecraft relative orbital motion in in-plane and out-of-plane directions independently. The proximal policy optimization hyperparameters are selected to ensure a trade-off among the learning time, stability, and control performance. The reinforcement-learning agents are trained and analyzed considering four cases that differ in the thrust levels and weighting matrices. The quality functional combines state deviation and thrust use penalties, thus enabling a trade-off among the response speed, accuracy, and propellant consumption. The results confirm the potential of this approach for autonomous spacecra…
creator: V. V. SOROCHINSKII
creator: S. V. KHOROSHYLOV
creator: I. L. LEVCHUK
creator: T. M. DUBOVYK
creator: H. M. HUZ
creator: O. O. ROMANCHUK
rights: Copyright (c) 2025 Technical Mechanics
date: 2025-12-11
publication date: 2025-12-11
number: 4
starting page: 77
ending page: 92

NUMERICAL ANALYSIS OF THE EFFECT OF THE DESIGN AND MANUFACTURING PARAMETERS OF STARTER LEAD-ACID BATTERIES ON THEIR DISCHARGE CHARACTERISTIC
type: item
description: DOI: https://doi.org/10.15407/itm2025.04.093 Because the battery uses chemically active substances, monitoring its operation and condition is important. Therefore, of importance is also the study of electrochemical processes that take place during its operation. This paper presents the results of a mathematical simulation of the mass exchange in an electrochemical cell of a starter battery during its discharge. The simulation is based on known equations. The elucidation of the effect of different factors on the battery’s discharge characteristics is of importance in terms of areas of its possible application. The mathematical model accounts for the design features of the electrodes, which consist of a porous active mass and a conductive grid. The solution shows the effect of the design and manufacturing parameters on the discharge curves. As can be seen from the solution, the effect of the electric current magnitude is most pronounced. Of interest are also calculated results that show how the discharge curves vary, for example, with decreasing grid conductivity. The effect of the electrode design parameters on the discharge properties is considered. Their features are elucidated, and a numerical estimate of their effect on the battery discharge indices is given. It is shown that a decrease in the porosity of the porous space due to gas bubbles that form when charging the battery and remain in pores may also markedly affect the discharge process. It is shown that the discharge curves also depend on the diameter of the cells that form the active porous mass of the electrodes. The scientific novelty lies in complementing the mathematical model with relationships that include the design parameters of the battery electrodes. The practical value of the obtained results lies in the possibility of accounting for the effect of the electrode material porosity and particle diameter on the battery performance at the battery design stage. REFERENCES 1. Dzenzersky V. A., Plaksin …
creator: V. I. YELISEYEV
creator: V. YU. SKOSAR
creator: M. O. KATRENKO
rights: Copyright (c) 2025 Technical Mechanics
date: 2025-12-11
publication date: 2025-12-11
number: 4
starting page: 93
ending page: 101

MODEL OF 3-D PRINTING ZONE HEATING CONTROL
type: item
description: DOI: https://doi.org/10.15407/itm2025.04.102 Innovative technologies of layer-by-layer product manufacturing by fast 3-D printing open up new opportunities for producing parts of a given shape. But sometimes, during the printing process with the use of specific materials, it is necessary to additionally heat or cool the part with an air flow over it. To improve the part quality, this process must be controlled, but for production safety, 3-D printing with special materials must be unmanned. Thus, it is necessary to develop an automated system for controlling the 3-printing process. This system should include several subsystems, in particular, a system for controlling the material supply through the extruder, a system for controlling the cooling (or heating) temperature of the printing zone, and a system for controlling the printing speed, which affects the part quality. The parameters of all the systems depend on the material characteristics and the printed part shape. This paper presents a mathematical model of a control object: a subsystem for 3-D printing zine air heating control, which is based on experimental data obtained in real conditions, and structural and parametric identification procedures for this subsystem. As a result of the identification, the model parameters were obtained as a function of the control action. The analysis of these relationships showed that the model of this subsystem as an automatic control object is complex with a variable structure and non-stationary parameters that change randomly over a wide range. It was found that the whole range of the control action can be divided into five sections, within which the structure of the control object model does not change and the model parameters change over relatively small ranges. Taking this into account, recommendations were formed regarding the procedure for further synthesis of the subsystem for automatic control of the air blowing temperature. In developing this printing control subsys…
creator: S. S. VASYLIV
creator: A. V. BUBLIKOV
creator: N. S. PRYADKO
creator: O. V. KARPOV
creator: L. V. MUZYKA
rights: Copyright (c) 2025 Technical Mechanics
date: 2025-12-11
publication date: 2025-12-11
number: 4
starting page: 102
ending page: 119

COMPUTER SIMULATION OF THE EFFECT OF ELLIPTICAL INCLUSION ARRANGEMENT ON THE STRAINING OF A CYLINDRICAL SHELL WITH A CIRCULAR HOLE
type: item
description: DOI: https://doi.org/10.15407/itm2025.04.052 Thin-walled plate-shell structural elements find wide application in many sectors of engineering and the national economy, particularly in the aerospace and the oil and gas industry, power engineering, mechanical engineering, construction, etc. The integrity and homogeneity of structures can be compromised by the presence of inhomogeneities. Such structures often have various manufacturing defects or design inhomogeneities: holes, cutouts, recesses, inclusions, microcracks, and other similar formations, which act as local stress concentrators. Under real-world operating conditions, an increased stress concentration in the zones of local stress concentrators significantly affects the strength and durability of structural elements, thus making a search for ways to reduce stress concentration a key issue in solid mechanics. When designing up-to-date equipment, optimizing material consumption and extending the service life of components using novel materials and technologies is a priority, which determines their competitiveness in various industries. This study involves a computer simulation and a finite element analysis of the stress and strain fields of thin-walled cylindrical shells with a small circular through hole and several elliptical inclusions of a different material symmetrically arranged around it. For definiteness, it is assumed that the inclusions are homogeneous and located in the plane of the shell. This paper analyzes the effect of the geometry, the mechanical properties, the number, and the arrangement of the inclusions on the stress and strain fields of the shells in the vicinity of the holes under the action of a uniaxial uniform tensile load applied to the shell ends. The distributions of the stress and strain intensities in the zones of local stress concentration are obtained. The obtained numerical results are compared with the results for shells without inclusions and with known similar results for pla…
creator: E. L. HART
creator: O. D. SHEBANOV
rights: Copyright (c) 2025 Technical Mechanics
date: 2025-12-11
publication date: 2025-12-11
number: 4
starting page: 52
ending page: 66

MATHEMATICAL MODELING OF ELECTRON DENSITY DETERMINATION USING A STATIONARY CYLINDRICAL LANGMUIR PROBE UNDER IONOSPHERIC CONDITIONS
type: item
description: DOI: https://doi.org/10.15407/itm2025.04.067 The goal of this article is to theoretically substantiate the applicability of the classical formula of the single cylindrical probe theory to determining the electron density based on measurements of the currents of a floating probe system in ionospheric conditions. Probe measurements in the ionosphere are modeled using a cylindrical probe and the body of a very small satellite placed transversely in the incident supersonic flow of a collisionless plasma. The ionospheric plasma is considered to be Maxwellian and consists of electrons and singly charged atomic ions of oxygen and hydrogen. A mathematical model of current collection by the floating probe system “probe – plasma – satellite body” was developed based on classical relationships for the electron and ion currents to a thin cylinder placed transversally in the incident flow. To model the collection of the hydrogen ion current by the satellite body, the results of numerical calculations of the ion current to the cylinder using the two-dimensional Vlasov-Poisson model were approximated. The probe bias potential was determined such that, under ionospheric conditions, the electron region of the floating probe system's current-voltage characteristic is closest to that of a single probe. The determination of the electron density using the classical calculation formula of the single-probe theory was simulated for probe current measurements in the low voltage portion of the electron region of the current-voltage characteristic of the floating probe system. The limiting methodological error in determining the electron density under ionospheric conditions within the framework of the probe system model considered was estimated. The effect of probe current measurement errors on the determination of the electron density using the calculation formula of the single-probe theory was studied. The obtained results may be used in the preparation and interpretation of ionospheric pla…
creator: D. N. LAZUCHENKOV
creator: N. M. LAZUCHENKOV
rights: Copyright (c) 2025 Technical Mechanics
date: 2025-12-11
publication date: 2025-12-11
number: 4
starting page: 67
ending page: 76

COMMON WHEEL PROFILE FOR PASSENGER AND FREIGHT CARS TO BE OPERATED BOTH ON THE UKRAINIAN AND ON THE WEST-EUROPEAN RAILWAYS
type: item
description: DOI: https://doi.org/10.15407/itm2025.04.120 One of the most important problems in the current development of the Ukrainian railway transport is to speed up the integration of Ukraine into the European railway service. For cars to operate on the Ukrainian and West-European railways, it is necessary to use gauge-changeable wheelsets, which can automatically change from one gauge to another, and provide wheel-rail contact pair compatibility on the railways of both standards: with R65 rails of cant 1/20 in Ukraine and UIC rails of cant 1/40 in West Europe. To solve this problem, the Institute of Technical Mechanics of the National Academy of Sciences of Ukraine and the State Space Agency of Ukraine developed wheel profiles for passenger and freight cars: ITM-73EP and ITM-73EC, respectively. The goal of this work was to study the possibility of using one of these profiles as a common wheel profile for passenger and freight cars with prospective trucks to be operated both on the Ukrainian and on the European railways. The study was concerned with passenger cars with 68-7041 trucks and freight cars with 18-7020 (an axle load of 23.5 tf) and 18-9817 (an axle load of 25 tf) trucks. The use of wheels with both profiles was compared in terms of car dynamic stability at service speeds on tangents of the Ukrainian and European railways and wheel-track interaction indices in curves (with account for different degrees of rail side wear). The results of the calculations made it possible to identify the profile expedient to be used as a common one for passenger and freight cars. According to predictive estimates, the use of wheels with this profile will speed up passing between tracks with different gauges and provide a high ride quality and improved indices of wheel-track interaction on both railways. REFERENCES 1. Gauge-changeable wheelsets. URL: https://www.railway.supply/uk/rozsuvni-zaliznichni-kolisni-pari/ (Last accessed on October 10, 2025). (in Ukrainian). 2. Ukrainian Nati…
creator: T. F. MOKRII
creator: L. H. LAPINA
creator: S. S. PASICHNYK
rights: Copyright (c) 2025 Technical Mechanics
date: 2025-12-11
publication date: 2025-12-11
number: 4
starting page: 120
ending page: 130

DEVELOPING THE RESEARCH LINES OF VIKTOR V. PYLYPENKO, AN ACADEMICIAN OF THE NATIONAL ACADEMY OF SCIENCES OF UKRAINE
type: item
description: DOI: https://doi.org/10.15407/itm2025.04.003 This paper presents the results of studies along the principal research lines of Viktor V. Pylypenko, an Academician of the National Academy of Sciences of Ukraine, obtained by his pupils over the recent years. The following lines are considered: the development of a theory of cavitation oscillations in liquid-propellant rocket engine (LPRE) pumps, the study of low-frequency dynamics in liquid-propellant rocket propulsion systems (LPRPSs), the analysis and assurance of liquid-propellant launch vehicle pogo stability, the mathematical simulation of dynamic processes in solid-propellant rocket engines, the development of pneumatic vibration protection modules, and the improvement of drilling technology by using cavitation hydrovibrator. A hydrodynamic model of cavitating LPRE pumps was developed further: it was verified using theoretical and experimental transfer matrices of cavitating pumps, and two new coefficients were introduced: the time of disturbance transfer delay due to the presence of cavities and the cavitation resistance distribution coefficient; from the results of dynamic tests of 26 pumps, the cavity elasticity was determined for pumps with extended ranges of their geometric parameters and operating conditions; a pump choking mechanism was developed, and it was shown that the pump choking characteristic is a specific nonlinearity involving a critical cavity flow; a mechanism of hard excitation of cavitation self-oscillations was proposed, and they were mathematically simulated. A theory of LPRPS low-frequency dynamics was developed further: procedures were developed for determining the effect of a nonsimultaneous engine startup and external and internal factors on LPRE startup thrust spread; a mathematical simulation was conducted to study sustainer engine startup and shutdown transients in the common feed system of the sustainer engine and the liquid-propellant thrust system of the Cyclone-4M launch vehicle’…
creator: S. I. DOLGOPOLOV
creator: O. D. NIKOLAYEV
creator: N. V. KHORIAK
rights: Copyright (c) 2025 Technical Mechanics
date: 2025-12-11
publication date: 2025-12-11
number: 4
starting page: 3
ending page: 18

MODELING OF THE CHECK VALVE OPERATION IN THE RECONFIGURABLE HYDRAULIC FEED SYSTEM OF A LIQUID ROCKET ENGINE
type: item
description: DOI: https://doi.org/10.15407/itm2025.04.019 Among the various automation units used in pneumatic–hydraulic systems of rocket hardware, check valves are widely employed. They are most commonly used in the filling lines of different tanks and in the pressurization lines of launch vehicle propellant tanks, where they prevent reverse flow and the ingress of vapors into the pressurization system. In liquid rocket engines (LREs), check valves are installed in drainage lines and in inert gas purging circuits. Particular attention is given to the use of check valves in reconfigurable hydraulic systems, in which the flow direction changes during the LRE operation. The goal of this study is to develop a mathematical model of dynamic processes in a check valve, verify it using CFD simulations of the pressure distribution over the valve poppet surface, and apply it to the analysis of transient processes in a reconfigurable hydraulic system. To determine the flow force acting on the valve poppet, this paper proposes an approach in the lumped-parameter approximation based on the flow rate balance of the working fluid in the valve flow passage. The model considers the radial inflow at the valve inlet, which depends on the poppet travel, and the peripheral flow through the narrow clearance between the valve body and the poppet. To implement this approach, it is sufficient to know the valve geometry and the discharge coefficients, which are assumed to be constant. For a reconfigurable propellant feed system containing check valves, a mathematical model of low-frequency dynamic processes was developed, and transient processes during the LRE startup were simulated. During the startup, the propellant feed of the LRE gas generator is automatically switched by the check valves from the start tank supply to the pump supply. Transient processes were simulated for the flow force acting on the check valve poppet determined using CFD simulation and the lumped-parameter approximation. A satis…
creator: O. S. CHERNIAVSKYI
creator: S. I. DOLGOPOLOV
creator: S. A. SHEVCHENKO
rights: Copyright (c) 2025 Technical Mechanics
date: 2025-12-11
publication date: 2025-12-11
number: 4
starting page: 19
ending page: 30

SINGLE-LAYER MARCHING ALGORITHM TO CALCULATE SUPERSONIC FLOW ABOUT ROCKETS WITH THE COMPUTATIONAL REGION DIVIDED INTO SEVERAL SUBREGIONS
type: item
description: DOI: https://doi.org/10.15407/itm2025.04.031 This paper presents a single-layer marching algorithm to calculate supersonic flow about rockets that may be equipped with wings, stabilizers, rudders, and superstructures. In this algorithm, the rocket along its axis is divided into sections of two types: sections along the rocket structure without additional elements (type 1 sections), which are calculated using a standard one-zone algorithm, and sections along the rocket structure with additional elements, which are calculated using a multizone algorithm. To calculate supersonic flow about additional elements of arbitrary shape (wings, stabilizers, rudders, and superstructures) installed on the rocket body, use is made of a Cartesian system of coordinates with the computational region divided into several computational subregions (CSRs), whose outer boundaries are the rocket structure surface, the surfaces of the additional elements, and the bow shock front. In each specific case, the method of division of the computational region into several CSRs is determined by the shape of the additional elements installed on the rocket structure along the type 2 section under consideration. Five methods are proposed to divide the computational region into CSRs using Cartesian, cylindrical, or polar coordinates for constructing computational meshes in different CSRs, which is a reasonably universal approach to calculating supersonic flow about rockets with variously shaped additional elements. Based on the above algorithm, the development of software is underway, whose use will greatly reduce the time taken for numerical calculations of supersonic flow about rockets with variously shaped wings, stabilizers, rudders, and superstructures to a design accuracy. The advantage of the software under development is the promptness of parametric calculations, which allows one to greatly reduce the time taken for rocket pre-characterization at the tryout stage of the design parameters of roc…
creator: V. P. HALYNSKYI
rights: Copyright (c) 2025 Technical Mechanics
date: 2025-12-11
publication date: 2025-12-11
number: 4
starting page: 31
ending page: 42

PARAMETERS OF THE ST-40M HALL-EFFECT THRUSTER IN ITS OPERATION ON XENON AND KRYPTON
type: item
description: DOI: https://doi.org/10.15407/itm2025.04.043 This article presents the results of an experimental study of the parameters of the ST-40M Hall-effect thruster developed by SETS (Space Electric Propulsion Systems) in its operation on xenon and krypton. Electric propulsion systems based on Hall-effect thrusters have found wide application due to their high performance and relative simplicity of design and operation compared to other types of propulsion systems. Traditionally, xenon is used as propellant in Hall-effect thrusters. It is an inert gas with a low ionization energy and a high atomic mass, which makes it possible to achieve a high performance of the electric propulsion system while maintaining operational simplicity. However, the high cost of xenon significantly affects the overall expenses during the testing and operation of the thruster and the propulsion system. Therefore, research is underway on the use of alternative propellants that could reduce operating costs while maintaining the thruster performance at an acceptable level. The most promising alternative to xenon is considered to be krypton. It has a lower cost and ensures operational simplicity, but its higher ionization energy negatively affects the thruster efficiency. The goal of this work was to compare the main parameters of the thruster operating on xenon and krypton under identical conditions. Experimental tests were carried out in a vacuum chamber at discharge voltages ranging from 250 to 500 V and propellant mass flow rates from 1 to 1.78 mg/s for xenon and from 1 to 1.6 mg/s for krypton. A comparative analysis of the thruster parameters in its operation on xenon and krypton at a mass flow rate of 1 mg/s showed that the use of krypton leads to a deterioration in thruster performance. The anode thrust and specific impulse decreased by 25 %–37 %, while the anode efficiency dropped by 15 %–24 %. REFERENCES 1. Frongello B., Hoskins W., Cassagy R., Kalkowska L., Maliga R. Spacecraft electric prop…
creator: S. YU. ASMOLOVSKYI
creator: D. K. VORONOVSKYI
creator: S. M. KULAHIN
creator: V. V. MASLOV
creator: V. O. PERERVA
creator: A. O. TROIAN
creator: B. V. YURKOV
rights: Copyright (c) 2025 Technical Mechanics
date: 2025-12-11
publication date: 2025-12-11
number: 4
starting page: 43
ending page: 51