Transactions of the St. Petersburg State Marine Technical University

BACKGROUND: Information control systems (ICS) play a key role in supporting effective management decision-making at all organizational levels. This is especially relevant for captains and managers who need to quickly receive, process, and distribute information during the planning and control.

AIM: To analyze the operational features of the ship ICS and develop a mathematical model for in-depth system design at the design study phase.

METHODS: The methods include analysis of international ICS design and operation practices and mathematical modeling with an option of computer experiments.

RESULTS: The authors identified three management levels, i.e. strategic, tactical, and operational, and determined information requirements on each level. The paper describes the ICS architecture and specifications, the importance of user involvement in design, and the need for staff training and cost reduction. The authors developed a mathematical model allowing to conduct computer experiments to prove the efficiency of design solutions.

CONCLUSIONS: Efficiency of ICS directly depends on the correct selection of information, user involvement in the design, and staff training. The presented model shows how theoretical approaches are used in real-life practice and may be used as a basis for further improvement of ICS for ships.

BACKGROUND: Research vessels are equipped with various winches designed to solve a wide range of problems. In this regard, there is a need for their design. The two most pressing real-world problems are:

1. Defining the electro-mechanical cable (EMC) configuration and the submerged depth of an underwater vehicle (UV) for a given EMC length;
2. Determining the EMC length required to ensure a given submerged UV depth.

The designs are based on the current profile and the underwater vehicle towing speed. For the initial stages (physical and mathematical models), we use a motion reversal-based approach known in ship theory, i.e. we consider the flow of liquid around the vessel rather than a vessel’s motion in a liquid, to solve both problems. In this case, as UVs are towed at a constant speed, the mechanical system consisting of the EMC and the UV is a distributed-parameter system. This indicates that the system has infinite degrees of freedom. The state of equilibrium of this mechanical system is unknown and we need to determine it.

AIM: To calculate a flexible electo-mechanical cable (EMC) configuration when towing an underwater vehicle in a specific current profile using numerical techniques and computer technology.

The object is a flexible EMC with a connected UV.

The subject is a mechanical system with multiple degrees of freedom. Its configuration is determined by the proposed calculation algorithm and a developed calculation program.

BACKGROUND: Today, automation of hull structure design is of great interest in the shipbuilding industry. The development and advancement of Russian automated hull design systems for transport vessels, military ships, floating structures, including floating docks, are the most promising and priority tasks. Optimization and search design of hull structures allows formalizing the problem of automated decision-making and ensures the specified structural parameters, including low weight, labor intensity of manufacture or cost depending on the problem formulation.

AIM: This works aims to formulate and solve the problem of designing floating dock hull structures based on requirements to strength and stability under overall longitudinal bending state. Based on the automated parametric design method for ship structures developed by the Department of Ship Design and Maintenance of St. Petersburg State Marine Technical University and adopted as a basis for the development of automated design systems for ship and other engineering structures, the problem under consideration is designated as the high-level problem of designing the floating dock structures.

METHODS: It is assumed that the previous lower-level stages have implemented structure design processes based on requirements to the lowest thicknesses, local strength, strength, and stability of pontoon structures during its overall bending. The Rules of the Russian Maritime Register of Shipping (RMRS) are used as a technical standard providing the requirements to overall strength and stability. The structure of the Rules in relation to the floating dock hull design is such that it is required to apply iterative search methods to solve the problem under consideration. To solve the problem, it is proposed to use mathematic programming tools.

RESULTS: In this problem, the mathematical relationship of the cross-sectional area of the girder and the variable parameters is taken as the objective function. The trajectory of variables determines the required initial thicknesses allowance of the plate structures that have the most influence on the overall strength of the dock hull. Yield strength of such plate structures may also be included in the variable parameters. The constraints of this problem are determined based on design considerations and the RMRS Rules. Equality constraints allow to solve the problem for some fixed value of the selected variable. Equality constraints may include restrictions that allow automatic adjustment of the specified plate thickness of structures adjacent to structures of girder stays or the condition determining the yield strength. Inequality constraints are determined by the relevant overall strength and stability as specified in the RMRS Rules.

CONCLUSION: The described problem is tested by examples of structural designs of a cast-in-place dock with a carrying capacity of 12,000 tons and a pontoon dock with a carrying capacity of 29,300 tons. The study shows that the proposed method can adequately solve the problem and MS Excel’s Solver tool may be used to solve it.

BACKGROUND: With the increasing complexity of gas turbine units, processing of gas turbine engine (GTE) test results have become a frequent practice. However, the methods are mostly based on mathematical GTE models and climatic reference maps rather than the principles of similarity. In this case, it is believed that that methods based on the specified parameters are outdated or their application is limited to only the simplest gas turbine engine designs. This paper shows that the similarity theory of modes can be successfully applied to solve some real-life engineering problems for state-of-the-art gas turbine units.

AIM: To consider application of similarity theory methods to process test results and analyze the operation of state-of-the-art gas turbine units and to propose advanced dimensionless groups.

METHODS: To analyze the possible use of the reduced gas turbine unit (GTU) parameters, we calculated the corresponding variable modes using a thermodynamic GTU model with a free power turbine developed and verified based on field tests at various outside air temperatures.

RESULTS: Calculations of variable modes based on a mathematical GTU model were used to analyze the applicability of existing standard reduced GTU parameters and the corresponding dimensionless groups. The authors propose an advanced dimensionless group (a power parameter) and show its possible engineering applications.

CONCLUSIONS: Variant calculations based on a mathematical GTU model show that it is possible to present the outcomes of tests in arbitrary conditions in a convenient representable form based on the power parameter, even if the conventional similarity of modes is not achieved. The power parameter allows for continuous testing of the rated GTU power in any actual operating mode for continuous monitoring of its status.

BACKGROUND: The development of antifriction materials for stern tube bearings and their manufacturing to replace imported ones will ensure the sustainable development of national shipbuilding and allow to achieve the goals set by the Government of the Russian Federation to implement the shipbuilding development strategy. For example, the ambitious 120 MW Leader icebreaker (Icebreaker 9 Ice Class) project designed to develop the Northern Sea Route requires high performance antifriction liners. In the context of sanctions, it is required to both replace imported materials and surpass their mechanical properties. In this regard, the problem of developing new antifriction composites with improved mechanical properties is relevant.

AIM: To determine the applicability of graphite-reinforced polysulfone as an antifriction material for marine stern tube bearings.

MATERIALS AND METHODS: For the experiment, we used a composite and casting matrices to make test pieces. Caprolon was selected as the comparable material. The study was conducted on a tribometer using the disk and bar contact principle. We recorded the friction time, shaft (disk) rotation frequency, shaft force on the test piece, tribometer power consumption during the process, and crater wear width. The tests allowed to determine wear segment depth, friction torque, dynamic friction coefficient, and linear and weight wear.

RESULTS: The tribological evaluation of graphite-reinforced polysulfone allowed to develop a mathematical linear wear model of PSF+10%C. Tests were conducted both for the PSF+10%C composite and caprolon taken as a reference; they allowed to determine the relative wear resistance of the composite in the range of 0.08–0.33 for the given experimental conditions.

CONCLUSION: The resulting material PSF+10%C has poorer wear parameters, friction coefficient, and relative wear resistance coefficient compared to caprolon. The study does not allow us to recommend the composite for use in stern tube bearings. However, the resulting mathematical wear model may be used in other scientific and technology applications.

BACKGROUND: Every metal machining operation has difficulties associated with heat localized in the cutting area, leading to various problems such as tool wear, increased roughness, etc. Today, it is important to look for environmentally friendly and cost-effective solutions by technologies that reduce or eliminate the use of cooling lubricants. Surface texturing has proven to be a promising method for improving the tribological properties of the tool face. Microtextures can have various geometry and shape and are usually created either on the approach surface or the face of the cutting tool. Texture quality largely depends on the processes. The basic methods for improving tribological properties are chip capturing, contact length reduction, and improved lubricity, which ultimately helps to reduce cutting force, tool wear, and roughness of the workpiece. It is known that, in drilling, the cutting action occurs inside the hole, and it is always difficult to minimize the effect of friction at the interface of the tool and the workpiece as cutting fluids can hardly enter the processing area due to the upward movement of the chips sliding along the groove surface. This problem can be solved by functionalizing the drilling tool surface using microtextures.

AIM: In this paper, a drilling tool with microtextures on the groove and edge created by laser machining is used to reduce sliding friction.

METHODS: We assessed the influence of geometry (radius, height, and location) of microtextures on wear during sliding friction by laboratory and field tests.

CONCLUSIONS: The textured tool was found to be more effective than the non-textured one. The study showed that the main methods allowing to improve the performance of drilling tools with microtextured surfaces are the contact length reduction, the wear debris capturing, and lubrication micro-layering in the cutting mode. The study will be useful for further development of this subject.

BACKGROUND: Joining dissimilar materials is a complex but important task for industry as dissimilar materials are necessary in complex structures. This paper presents the results of microstructure optimization of a laser welded dissimilar Al-Cu-Li joint with different Cu/Li ratios.

AIM: The aim was to study the structure of a laser welded dissimilar Al-Cu-Li joint and to develop methods to improve this structure based on heat treatment.

METHODS: We used scanning electron microscopy, synchrotron radiation diffraction, and tensile testing. Synchrotron radiation (SR) diffraction allowed to detect lithium-containing phases, where they cannot be fully detected using less bright radiation sources due to their volume fraction and scattering.

RESULTS: The study shows that welding promotes creation of a mechanically unfavorable microstructure; dendritic grains of aluminum surrounded by an eutectic network of intermetallic compounds T₁Al₂CuLi, T₂Al₆CuLi₃, and T₃Al₅CuLi₃. In this state, the weld seam had low mechanical properties; tensile strength σ_В was 252 MPa, yield strength σ_0.2 was 184 MPa, and linear strain δ was 2.9%. Thermal quenching at 530 °C allowed to almost completely dissolve the eutectic network, which was confirmed by scanning electron microscopy. Artificial aging at 170 °C for 16 hours allowed for the recrystallization of the strengthening phases. As a result, the welded joint tensile strength σ_В increased to 344 MPa, yield strength σ_0.2 increased to 230 MPa and the linear strain δ increased to 4.8%.

CONCLUSION: The study allowed to identify the structure of laser welded dissimilar Al-Cu-Li joints and showed that this structure can be improved by heat treatment, ensuring a significant increase in both the strength properties and ductility of the joint.

BACKGROUND: A state-of-the-art aircraft gas turbine engine is an advanced technology consisting of a compressor, combustion chamber, turbine, nozzle, and other components. It includes the axial compressor with multistage rotor and stator blades important for the reliable operation of the gas turbine engine. All these components are subject to static, dynamic, and cyclic loads causing fatigue cracking, thermally induced stress, and mechanical damage. To increase the service life of gas turbine engines and reduce maintenance costs, technologies are used to restore worn or damaged moving blade surfaces.

AIM: To restore worn surfaces of moving blades of DR-59L high-pressure turbine by laser cladding.

MATERIALS AND METHODS: Prior to repairing the blades, we tested a range of laser cladding parameters on a check test piece to determine a defect-free structure. Stellite-21 cobalt alloy powder was used as a filler. To evaluate the structure and mechanical properties of the claded test pieces, we conducted metallographic studies and mechanical tests.

RESULTS: By modeling the blade airfoil restoration process, we determined the operational conditions of the laser cladding process. No defects were detected during the capillary test of the restored surfaces. The uniaxial tensile test of the restored blade airfoil showed increased tensile strength and elongation.

CONCLUSIONS: Laser cladding technology allowed to restore the worn surfaces of moving blades of DR-59L high-pressure turbine; thereby increasing the service life of the engine unit.

At the recommendation of the Editorial Board of Transactions of the St. Petersburg State Marine Technical University journal and in accordance with the guidelines of the Association of Scientific Editors and Publishers, the Journal’s Editorial Board conducted a comparative analysis of the two articles. The analysis revealed an almost complete similarity of the following publications:

• Balyakin AB, Nosova EA, Oleynik MA, Zlobin EP. The Effect of Laser Radiation Power and Heat Treatment on The Properties of Heat-Resistant Nickel Alloy Samples. Transactions of the St. Petersburg State Marine Technical University. 2024;4(12):15–29. EDN XMROEV
• Balyakin AB. Process of Direct Laser Growth of Heat-Resistant Alloy: Influence of Power and Heat Treatment on Microstructure and Mechanical Characteristics. Bulletin of the Siberian State Industrial University. 2023; 4(46): 64–78. doi: 10.57070/2304-4497-2023-4(46)-64-78 EDN STILTW

The Introduction, Research Methods and Principles, Primary Results, Discussion, and Conclusion sections are identical.

However, the list of references differs, and only a few of the same sources are present.

The article entitled The Effect of Laser Radiation Power and Heat Treatment on The Properties of Heat-Resistant Nickel Alloy Samples published in the Transactions of the St. Petersburg State Marine Technical University journal is a semantic copy of the article entitled Process of Direct Laser Growth of Heat-Resistant Alloy: Influence of Power and Heat Treatment on Microstructure and Mechanical Characteristics published in the Bulletin of the Siberian State Industrial University journal.

Notably, the manuscript was first submitted to the Bulletin of the Siberian State Industrial University journal before being submitted to the Transactions of the St. Petersburg State Marine Technical University journal. Due to the detection of duplicate articles in two scientific editions on May 4, 2025, the Editorial Board of the Transactions of the St. Petersburg State Marine Technical University journal decided to withdraw the article cited as Balyakin AB, Nosova EA, Oleynik MA, Zlobin EP. The Effect of Laser Radiation Power and Heat Treatment on The Properties of Heat-Resistant Nickel Alloy Samples. Transactions of the St. Petersburg State Marine Technical University. 2024;4(12):15–29. EDN XMROEV.