卷 4, 编号 3 (2025)

BACKGROUND: Today, the finite element method (and software packages based on it, mainly foreign) is substantially the only computational method that actually allows solving parametrization problems of static deformation and vibration of complex structures. They often require much effort to prepare the inputs, advanced computing equipment, and funds to purchase the corresponding software packages. The development of an approach allowing to occasionally reduce the requirements and to relatively easily develop domestic computational software based on it seems quite relevant.

AIM: To develop approaches that allow for less labor-intensive and faster parametrization of static deformation and associated flexural, longitudinal, and torsional steady-state oscillations (vibrations) of structures, allowing modeling by systems of quasi-one-dimensional finite element models.

METHODS: The basic investigation method used in the study is a modification of the partial response method with some significant advantages in solving problems of steady-state forced vibration or static deformation of structures that allow modeling using quasi-one-dimensional finite element models. The proposed method — the discrete modification of the partial response method — consists in the recording of partial responses and recurrent partial parameters of algebraic equations to calculate the matrix entries. In this case, the conventional solution of the boundary value problem is replaced by the solution of a series of conjugation problems for pairs of partial systems, where each has its own boundary data. The number of pairs under consideration corresponds to the number of sections, for which the researcher wants to parametrize the studied process (amplitudes of linear and angular displacements, internal forces, and end reactions). The scope of problems to be solved is significantly expanded by using the method proposed by the authors to correct and/or modify the inertia and rigidity of elements of a quasi-one-dimensional finite element model and the external load acting on it. This approach allows us to build quasi-one-dimensional models for solving both one-dimensional and multidimensional problems and problems requiring to consider the additional factors that complicate the vibration pattern.

RESULTS: The paper presents several applications of the discrete modification of the partial response method in combination with the correction and modification of the parameters of quasi-one-dimensional finite element models.

CONCLUSION: The study allows us to conclude that the aim has been achieved, which is confirmed by the development of a discrete modification of the partial response method, allowing to calculate deformation parameters and steady-state vibrations for a certain class of structures.

BACKGROUND: A review of the literature shows that the study of temperature distribution and the effect of pressure is an important basis for the design of the most wear-resistant and durable valves and significantly affects the choice of materials. Studying the temperature distribution inside valves at the pressure exerted on them during engine operation is experimentally a very time-consuming and demanding task. It is required to perform such calculations with software allowing to consider certain loads based the crankshaft rotation angle of the test sample.

AIM: The object of the study was a valve of a factory-built small-sized marine engine and the same valves with a modified design and added spiral guides (screens, blades) to study the effect of temperature exerted on them depending on the crankshaft rotation. All studied valves had the homogeneous structural material.

METHODS: To conduct the study, we used the finite element method implemented in the Ansys software, where a non-stationary thermomechanical calculation of valves with different designs made of homogeneous material was performed using the small-sized marine engine Ch8.5-11 valve with the subsequent analysis of the results, their study, and comparison.

For the convenience of the solution, the study was divided into two parts. In this part, the influence of temperature during the operation of the small-sized marine engine Ch8.5/11 is studied; the future study will involve the transfer of the studied temperature fields to the pressure in the small-sized marine engine cylinder tested by the valves.

RESULTS: At this stage, the finite element method was used to build and visualize the temperature fields of valves with different designs, to calculate the heat flux density, and to analyze the value of the spiral guides installed on the valves in relation to the temperature. As the calculation was non-stationary, we selected the highest test temperature stresses exerted on the valves during operation for the small-sized marine engine study.

CONCLUSION: The simulation allowed to collect data on the temperature distribution inside valve trays of the studied 40X steel valves, which can be viewed at any time of the studied interval. The study of the heat flux in valves of different designs revealed that the heat flux increased in the valve with 3 blades (283.12 W/mm²) and the heat flux in the design with 6 blades was 281.49 W/mm².

The rapid development of shipping in the Arctic region has increased the demand for special ice-class vessels, leading to the search for new and improved methods for modeling ship movement in ice conditions. Developing a mathematical model of ship-ice interaction is a complex task due to the challenges in simulating ice properties and there is no single universally accepted approach to ice modeling. However, numerous methods are available that can solve specific problems with sufficient accuracy. Despite their effectiveness, known numerical modeling methods for ship-ice interaction have significant limitations related to high computational costs and limited accuracy, highlighting the need for further improvement. The search for optimal combinations of different numerical methods and improving computational efficiency has become a key research area to improve the safety and cost efficiency of Arctic shipping. To conduct a comprehensive analysis of and systematize existing numerical modeling methods for ship-ice interaction and identify promising areas for their improvement to improve the efficiency of Arctic shipping. The review includes a comparative analysis of the advantages and disadvantages of each method (DEM, FEM, CEM, SPH, PD, and LBM) and an assessment of their applicability for solving specific ship-ice interaction modeling problems. The following aspects of method application were examined: computational efficiency, simulation accuracy, and optimal applications. The authors systematized the main numerical modeling methods for ship-ice interaction; identified common characteristics of all studied methods; determined key areas for improving existing approaches; developed recommendations for determining ice resistance, and made a list of software packages to implement modeling methods. The study highlights the need for further research in optimizing computational processes and improving the accuracy of ship-ice interaction modeling. This review provides recommendations for selecting a method to model ship movement in ice. However, all existing methods have their limitations, necessitating further development, including the development of combined approaches and the improvement of computational processes.

BACKGROUND: The parameters of powder flow delivered to the direct laser deposition area affect the interaction of the powder, laser, and melt pool, directly determining the bead shape and the quality of the deposited material. Controlling the spatial distribution of powder flow in the processing area is key for improving the process performance and repeatability.

AIM: To develop a semi-analytic approach to find powder particle trajectories in the problem of direct laser deposition using a discrete jet nozzle.

METHODS: The carrier gas flowfield in an unobstructed half-space filled with a protective gas is approximated by an analytical solution of the Euler equation. Powder trajectories are determined by numerical integration of the equation of motion based on the Stokes’ law.

RESULTS: Powder trajectories are determined by the distribution of the carrier gas velocity at the tube outlet by applying the exact solution of the Euler equation for specific parameters of powder particles and carrier gas used in additive manufacturing.

CONCLUSION: The paper presents an elementary semi-analytic model of powder delivery in the problem of direct laser deposition allowing to obtain the spatial distribution of powder particles in the processing area.

BACKGROUND: The efficiency of a contemporary gas turbine engines can be improved by increasing the operating temperature inside the engine, resulting in extreme thermal stress on materials. The temperature of combustion products inside aircraft engines can reach temperatures exceeding the melting points of the alloys used, limiting their applications. To protect working parts, thermal control coatings and cooling systems with punch holes are used. Laser perforation is a promising method that provides high precision and cost-effectiveness of hole punching processes for combustion liners with thermal control coatings. The development and improvement of such technologies is relevant for the aerospace industry and general mechanical engineering, where a balance between quality, performance, and cost is required.

AIM: To develop an efficient laser perforation solution for combustion liners with thermal control coating, providing an optimal combination of precision, surface quality, and performance. The paper analyzes and compares existing punching methods to support the choice of the best possible technology.

METHODS: The paper provides a technical analysis of existing perforation solutions for aerospace and general industrial applications. Punching options for combustion liners are considered based on data from open sources. The experimental part included the use of a serial five-axis laser processing machine SLP520 with a fiber laser.

RESULTS: Analysis showed that laser perforation outperforms alternative methods in terms of accuracy and processing speed. Optimal laser radiation parameters ensure the lowest thermal effect on the thermal control coating and high repeatability. Experiments showed that a long-focus lens ensures fixed diameter and shape of the holes and a boron nitride protective paste helps prevent splashes around the holes.

CONCLUSION: Laser perforation is an effective punching solution for cooling holes in combustion liners with thermal control coating. The proposed technology provides high precision, quality, and repeatability, making it preferable for aerospace applications. Further research may be aimed at studying the effect of protective paste on the thickness of the modified layer.

BACKGROUND: Various types of coatings are used for corrosion and wear protection of structural materials and thermal insulation. Coatings that are used in high-temperature conditions, e.g. aircraft and industrial gas turbine engines, have the most complex structure. They are used to isolate the turbine components from the hot gas flow, increasing the durability and energy efficiency of engines [1]. Thermal barrier coatings have three main requirements, including low thermal conductivity, stability at high temperatures, and high durability, and they are fairly difficult to remove.

AIM: To solve the problem of removing thermal barrier coating from moving blades of gas turbine engines subjected to intensive wear in tough operating conditions. Laser cleaning technology is proposed as the most effective cleaning method. It is an advanced technology that allows finding solutions to reduce production costs and increase the performance and quality of processes [2]. The paper discusses the importance of preserving the basic blade material during thermal barrier coating removal for its subsequent use (new coating). The aim is to remove the thermal barrier coating without damaging the basic metal and to determine the optimal conditions for such works.

METHODS: To achieve the aim, the blade made of CS70-VI alloy was cut into several parts along the length of the airfoil; one part was selected as a check test piece that was not cleaned. The remaining test pieces were tested during laboratory experiments aimed at studying the influence of input laser cleaning parameters on the removal of the thermal barrier coating. All samples were then subjected to metallographic tests to determine the material structure, microhardness, and thickness of the thermal barrier coating.

RESULTS: The paper presents metallographic analysis of microhardness and thickness of thermal barrier coating after testing confirming the effectiveness of laser cleaning to ensure the durability and reliability of moving blades for gas turbine engines.

CONCLUSION: The study involved a literature review of papers related to laser cleaning. Next, we selected the variation ranges of the main processing parameters and conducted a series of experiments followed by the metallographic analysis of test pieces. Metallographic analysis allowed to determine the conditions ensuring complete removal of the thermal barrier coating and the relationship between the thickness of the thermal barrier coating and the radiation power.

BACKGROUND: Marine electronic and electrical equipment may not be supplied to ships unless it meets the impulse noise immunity requirements. Tests of equipment designed without due regard of such requirements record its failures. It is important to be able to predict the effects of noise at the equipment design stage.

AIM: To provide mathematical models and circuit simulations of test impulse noise generators to verify the impulse noise immunity of circuits during their development.

METHODS: The study is based on the electromagnetic compatibility standards of the Russian Maritime Register of Shipping and IEC 61000-4 standards of the International Electrotechnical Commission. The study uses mathematical descriptions of pulse waveforms and electrical engineering software used to simulate circuits.

RESULTS: The study provides formulas describing standard impulse noise, detailed diagrams of test generators used in simulation software, examples of models, and errors of simulated noise parameters.

CONCLUSION: The proposed models and simulations allow predicting the effect of noise at the equipment design stage prior to noise immunity tests and reduce the time and cost of equipment modification.

BACKGROUND: There’s a need to develop computer modeling tools that allow assessing the effect of electromagnetic interference on equipment units at the design stage.

AIM: To determine the possibility of using frequency domain computational methods to simulate transient processes, when an electrostatic discharge affects equipment units.

METHODS: The paper proposes to use surface integral equations in the frequency domain to model standardized effects of electrostatic discharges on equipment units. For this, the fast Fourier transform is applied to the standardized discharge current and the effect of a lumped harmonic current source for a frequency sequence is modeled using frequency domain methods. The effect-to-interference conversion factor is determined for each frequency. The time dependences of the voltages and currents induced by electrostatic discharge are determined by the inverse fast Fourier transform applied to the product of the discharge current spectrum and the corresponding conversion factor.

RESULTS: The results obtained by the proposed frequency domain methods match the results of time domain methods with a reasonable degree of accuracy for practical calculations. In this case, the effect of each frequency component is analyzed independently, allowing for a high degree of parallelization of calculations; whereas calculations using time domain methods require completed calculations for previous time points. Requirements to the size of mesh elements are determined by the wavelength at the maximum frequency used.

CONCLUSION: The paper demonstrates the fundamental possibility of using frequency domain methods to model pulsed electromagnetic effects, including the effect of electrostatic discharge. Frequency dependences of the conversion factors and the spectral density of interference provide additional information on the relationship between interference levels and the geometry of equipment units and possible ways to reduce them.