Transactions of the St. Petersburg State Marine Technical University

BACKGROUND: Import substitution issues are very topical in the domestic machine building industry. Recently, thin-walled curvilinear cross-sections have been obtained in the optimization of design and technological parameters thin-walled curvilinear cross-sections have been recently emphasized in the optimization of structural and technological parameters of power machine elements. The method of calculation of strength characteristics for a thin-walled closed profile is similar to those commonly used for the calculation of solid profiles, but for the calculation of sections with unclosed thin-walled curvilinear profiles it is limitedly applicable, due to the mismatch of the center of torsion with the center of mass of the section area.

AIM: To presents some highlights on the strain state of units and parts of various power machines and devices with curved light-gauge open profiles operating in various strain conditions.

METHODS: It describes the methodology of the proposed general algorithm for the automated calculation of the basic stiffness parameters of strained curved light-gauge open profiles with the determination of the shear center. It also reviews different options for determining these parameters for light-gauge line profiles and complex light-gauge profiles of components.

RESULTS: An experimental setup has been developed that allows to identify the planes of loading determining the shear center at their intersection. It shows experimental data on determining the shear center for a random light-gauge open profile. The data is used to develop the loading plane vs variation of the vertical cross section curves. The developed program is not only an effective tool for design and calculation, but also can be useful for scientific research related to the design of machine and equipment elements.

CONCLUSIONS: The author makes a conclusion on the high accuracy of calculations using the developed software by comparing the calculated analytical coordinates with experimental data. The developed program is not only an effective tool for design and calculation, but also can be useful for scientific research related to the design of machine and equipment elements.

Today, in submarine projects, the largest group of actuators is remotely controlled valves, which are controlled by solenoid-controlled directional valves. Comparative analysis allows to select development options and evaluate alternative uses of devices to control remotely controlled valves.

The article aims to conduct a comparative analysis of four-way solenoid-controlled directional valves used on submarines as control devices of remotely controlled valves. The comparative analysis shows that state-of-the-art directional valves have uniform design, specifications, and the operating principle, which are prerequisites for the development of a new, more compact and advanced directional valve to improve equipment layout in submarine compartments with numerous devices.

BACKGROUND: The article examines steam condensation in a power plant condenser. The steam condenser is an indispensable cold source in the thermodynamic process of a power plant and the condenser is a large, metal-intensive component that determines the overall dimensions of the power plant. A new solution used to increase performance of a round steam condenser is the proposed design of a condenser tube bundle, a screw-type tube bundle for a steam condenser. Oval heat exchange tubes of the proposed bundle are helically twisted.

METHODS: The article calculates a tube bundle for a steam condenser with different out-of-roundness and swirl parameters using a new algorithm of nodal bundle calculation. The condenser tube bundle is broken down into condensation layers as the steam moves from the periphery to the center. For each layer, the heat transfer ratio, condensation surface area, temperature factors and the condensed heat are calculated.

RESULTS: The calculation results are compared with tube bundle performance of a steam condenser with linear cooling tubes.

CONCLUSIONS: The calculation shows that the maximum effect is achieved by the helical twisting and the reshaping of the circular heat exchange tube to an out-of-round one.

BACKGROUND: The study may improve the viability, safety, and environmental friendliness of the maritime industry. The development of such technologies is in line with global digital transformation and automation trends and the strategic interests of the State. Research in this area helps develop innovative solutions applicable in various industries—from logistics to national security.

AIM: The article discusses the parameters of the motion control system of an unmanned boat, the development of an unmanned boat controlled movement simulation diagram, and how results that may be used to design a specific unmanned boat are achieved.

METHODS: The authors used linear and nonlinear functions to control the boat’s motion, developed and transformed mathematical models into structural diagrams.

RESULTS: The authors analyze parameters of the unmanned boat control system as part of the study.

CONCLUSIONS: The study resulted in the development of mathematical models of the unmanned boat motion control system used to design a specific unmanned boat.

This article examines the development of control algorithms for nuclear power plants using complex mathematical models that allow for studying the operation of a nuclear power plant in various dynamic modes, especially during start-up and cooldown. The models are based on the change in the physical state of the liquid metal coolant.

The article reviews the operating experience of nuclear power plants with liquid metal coolant and the application of complex mathematical models. Analysis of papers and online resources on the topic. Recent research has been used as a science and technology base for the development of a new generation of nuclear power plants with liquid metal coolant based on innovative solutions with increased nuclear and radiation safety, reliability, and improved weight, dimensional and operational parameters. To develop a nuclear power plant ahead of schedule and conduct comprehensive tests and research before its large-scale production, it is required to develop comprehensive mathematical models. Every experiment with a nuclear power plant is first tested on a computer model. This allows for safe and low-cost research of the reactor’s behavior in various modes, including emergency, for further development of control algorithms.

BACKGROUND: Dedicated papers often study the influence of phase fluctuations of signals received by radar stations with a synthetic aperture antenna on the azimuth resolution and accuracy of stationary moving ground objects for arbitrary aircraft trajectories without additive interference.

AIM: To determine how additive interference and phase fluctuations influence azimuth resolution and accuracy of a radar station with a synthetic aperture antenna during arbitrary movement of an aircraft and ground objects.

MATERIALS AND METHODS: The article reviews and analyzes the influence of phase fluctuations and additive interference on the key parameters of a synthetic aperture antenna during arbitrary movement of an aircraft and ground objects.

RESULTS: The article presents relationships to assess the resolution and accuracy of azimuth determination by a radar station with a synthetic aperture antenna under the influence of phase fluctuations of the reflected signal and additive interference during arbitrary movement of an aircraft and ground objects.

CONCLUSIONS: It is shown that under the influence of additive interference, the expected value and dispersion of the object’s angular position and the output signal duration in the angular position depend on the ratio of the output performance of this noise and the reflected signal.

BACKGROUND: In Russia, wire and arc additive manufacturing and laser direct deposition technologies are actively developing and applied in various industries. Wire and arc additive manufacturing is gaining interest as a cost-effective technology that uses a standard robotic welding cell.

AIM: To study a possible application of SPRUTCAM CAM (Computer Aided Manufacturing) system to automate the control program generation for wire and arc additive manufacturing of metal products.

MATERIALS AND METHODS: The article illustrates the stages of 3D modeling, creating a digital equipment twin, building the tool’s movement path and generating a control program by making a copy of a medieval axe handle.

RESULTS: A SPRUTCAM control program was uploaded to the robotic arm controller and executed without errors. The control program allowed to make a blank axe handle. The article reviews the experiment, identifies key issues, and proposes ways to solve them.

CONCLUSIONS: The study showed that SPRUTCAM can successfully be used to automate the wire and arc additive manufacturing; however, it requires additional adjustment and optimization of parameters.

BACKGROUND: The development of metal-ceramic materials is a complex task, where phase structure control is key to achieving the required physical and mechanical properties. The study investigates the effects of substrate pre-heating temperature on the structural-phase composition and microhardness of titanium matrix composites manufactured by direct laser deposition. The main issue in the manufacturing of metal-ceramic composites is hot cracking. Substrate preheating is a promising approach to reduce thermal stresses and minimize defects such as cracks and pores. The development of defect-free metal-ceramic composite manufacturing processes is of particular importance for the aircraft and aerospace industries.

AIM: To experimentally investigate the effect of the substrate preheating module on the phase composition, microstructure and microhardness of Ti-6Al-4V/B₄C metal-ceramic composite manufactured by direct laser deposition. Based on a comprehensive analysis, to show that substrate heating may be effectively used to make metal-ceramic coatings free of cracks and pores.

MATERIALS AND METHODS: To manufacture composite materials, the direct laser deposition method is used with a substrate preheating module. To fully investigate this phenomenon, synchrotron X-ray is used along with conventional microstructure diagnostic techniques.

RESULTS: Comparative analysis of the microstructure, phase analysis and microhardness distribution did not reveal any significant changes during substrate pre-heating.

CONCLUSIONS: Experimental data allows to conclude that substrate pre-heating can be used as a version of the direct laser deposition method. Pre-heating contributes to manufacturing defect-free composites in a wide range of laser exposure modes.

BACKGROUND: Today, aluminum alloys are applied in many industries, including aerospace, shipbuilding, chemical, mechanical engineering, etc. Wire and arc manufacturing used to produce aluminum alloy products saves much time and cost. A big problem related to additive technologies is the anisotropy of properties. Tensile properties are usually higher along the deposition path (X axis) than the manufacturing path (Z axis). One way to reduce the anisotropy is to use alternative growth strategies. This study aims to establish the dependence of material properties on the layer deposition strategy.

AIM: The article investigates the effect of the layer deposition technique on production, structure and properties of thick-walled elements during wire and arc additive manufacturing from aluminum alloy ER5356.

MATERIALS AND METHODS: For this purpose, samples were manufactured with the following deposition techniques: linear oscillations normal to the manufacturing path; linear oscillations at a 45-degree angle to the manufacturing path; elliptical oscillations along the manufacturing path, and a zigzag normal to the manufacturing path. The article explores the structure and mechanical properties of samples made by wire and arc additive manufacturing with different filling techniques.

RESULTS: For developing a strategy with linear oscillations at a 45-degree angle to the manufacturing path (Strategy 2) and elliptical oscillations along the manufacturing path (Strategy 3), there were unstable areas at the start/end points of the process. The lateral surface quality of samples 2, 3 and 4 is the same; whereas sample 1 has more pronounced ripples. The least anisotropy of 4% was achieved using the first strategy. For the other three strategies, this value varied from 10.2 to 14.2%. Porosity of the samples for all four strategies did not exceed 1% of the cross-sectional area. Deteriorated mechanical properties along the Z axis are associated with brittle phases at the layer boundaries (strategies 2 and 3) and the incomplete fusion of layers (strategy 4).

CONCLUSIONS: The results show that a stable structure is produced only by techniques with linear oscillations normal to the manufacturing path and with a zigzag motion. In the other two cases, unstable areas at the edges of the sample are observed. Moreover, the quality of the side surface is similar in all four samples. In addition, it is worth noting that a required level of mechanical properties with low anisotropy was achieved only with the strategy providing for linear oscillations normal to the manufacturing path.