Ship Propeller Shaft Research Articles

Environmentally Acceptable Lubricants for Stern Tube Application: Shear Stability and Friction Factor

Stern tube lubricants are essential in maritime operations, safeguarding ship propeller shafts from wear and corrosion while ensuring efficient propulsion. Their role in reducing friction and maintaining system integrity is critical. With growing environmental concerns, the adoption of environmentally acceptable lubricants (EALs) for stern tubes has gained importance, balancing operational performance with environmental protection. This study investigates the rheological and tribological properties of EALs formulated for ship propeller stern tube applications. The primary focus is on comparing these EALs with conventional mineral oils to assess their suitability in marine environments. EALs are increasingly favored due to their biodegradability and reduced environmental impact. Key parameters such as shear stability, friction factor, and temperature dependency were evaluated using a range of experimental methods including rotational viscometry and tribological analysis. The results indicate that the newly formulated EALs based on synthetic esters exhibit the highest viscosity index, a higher range of shear stability, and lower friction factors, compared to commercially available mineral oils, especially under varying operational conditions. These findings contribute to the ongoing efforts to promote eco-friendly lubricants in maritime industries, aligning with global environmental protection initiatives.

Process Planning for Large Container Ship Propeller Shaft Machining Based on an Improved Ant Colony Algorithm

To accommodate the production and manufacture of complex and customized marine components and to avoid the empirical nature of process planning, machining operations can be automatically sequenced and optimized using ant colony algorithms. However, traditional ant colony algorithms exhibit issues in the context of machining process planning. In this study, an improved ant colony algorithm is proposed to address these challenges. The introduction of a tiered distribution of initial pheromones mitigates the blindness of initial searches. By incorporating the number of iterations into the expectation heuristic function and introducing a ‘reward–penalty system’ for pheromones, the contradictions between convergence speed and the tendency to fall into local optima are avoided. Applying the improved ant colony algorithm to the process planning of large container ship propeller shaft machining, this study constructs a ‘distance’ model for each machining unit and develops a process constraint table. The results show significant improvements in initial search capabilities and convergence speed with the improved ant colony algorithm while also resolving the contradiction between convergence speed and optimal solutions. This verifies the feasibility and effectiveness of the improved ant colony algorithm in intelligent process planning for ships.

Propelling precision of longitudinal vibration mitigation in ship propeller shafts through advanced nonlinear intelligent semi-active control leveraging adaptive neuro-fuzzy inference system with linear quadratic regulator

This study presents a pioneering method to address longitudinal vibrations in ship propeller shafts by integrating an intelligent semi-active control system. By leveraging Adaptive Neuro-Fuzzy Inference System (ANFIS) and Linear Quadratic Regulator (LQR) techniques, the proposed system offers a novel solution to a longstanding challenge in maritime engineering. The efficacy of the semi-active control system is assessed through two complementary analyses: frequency domain analyses and Percentage Reduction Index (PRI) values. The investigation reveals substantial PRI values, ranging from 24.68% to 46.87%, indicating notable enhancements in vibration control with the adoption of semi-active technology. Furthermore, frequency domain analyses demonstrate significant advantages, with a peak reduction of 68.21% observed at 750 r/min. To rigorously evaluate the statistical significance of these improvements, paired t-tests were conducted between the semi-active control system and passive strategies. The results confirm a statistically significant difference in vibration reduction ( p < .05) between the two systems. Specifically, for Percentage Reduction Index Values, the t test yielded a p-value of .023, while for Frequency Domain Analyses, the t-statistic significantly exceeded the critical value (t ≈ 8.09, tcritical ≈ 2.571). Both data sets provide compelling evidence to reject the null hypothesis, indicating a significant difference in vibration reduction between the semi-active control system and passive strategies. The PRI values consistently demonstrate superior performance for the semi-active control system, highlighting its effectiveness in mitigating vibrations. These findings validate the effective ness of the system. These results show the practical implications of implementing semi-active control systems in maritime engineering, offering enhanced safety, fuel efficiency, and operational reliability in ship propeller shaft applications.

Navigating Tranquillity with H∞ Controller to Mitigate Ship Propeller Shaft Vibration

Navigating Tranquillity with H∞ Controller to Mitigate Ship Propeller Shaft Vibration

РАЗРАБОТКА БЛОКА ОБРАБОТКИ ИНФОРМАЦИИ ДЛЯ ПРОГРАММНО-АППАРАТНОГО КОМПЛЕКСА СИСТЕМЫ МОНИТОРИНГА КРУТИЛЬНЫХ КОЛЕБАНИЙ СУДОВОГО ВАЛОПРОВОДА

The article considers torsional vibrations in combination with other technical factors, which remain a cause of damages and breakdowns of the ship's propeller shafts, intermediate shafts and crankshafts. Torsional vibrations inevitably occur in the ship plants. It can be explained by the uneven torque of the engine and the torque on the propeller (exposure of the propeller, uneven movement of the water flow, stormy weather, etc.), which leads to alternating twisting of the shaft. To reduce torsional vibrations, dampers are used, which require periodic performance testing by using the torsiography procedure. In contrast to the existing monitoring systems of the technical condition of the damper, it is planned to install an information processing unit for the software and hardware complex for monitoring torsional vibrations of the ship's shaft line and the parameters associated with them (vibration and temperature changes of the flexible elements of the connecting couplings). The unit under development will allow to constantly monitor the level of torsional vibrations and, if they increase, to signal the ship's mechanic to switch to another operational mode of the main engine, which will increase the reliability and automation of the ship power plants, the safety of navigation, and reduce the economic costs of ship operating

Failure criticality evaluation of ship propeller shaft system based on Fuzzy FMECA method

The propeller shaft system is the key system for power transmission on board. The components of the system are complex, the working environment is bad, the failure modes are numerous, and the failure consequences are serious. FMECA (Failure Modes, Effects and Criticality Analysis) is difficult to accurately and quantitatively carry out criticality assessment. Therefore, in view of the complex navigation environment, the fuzzy FMECA method is used to evaluate the failure mode criticality of propeller shaft system. On the basis of FMECA, the factor set with maintainability and testability is established, and the factor level set, fuzzy evaluation matrix and factor weight set are determined, and the consistency judgment is made. Finally, the fuzzy comprehensive evaluation is carried out to obtain the accurate and quantifiable failure mode criticality ranking. Compared with the traditional FMECA method, fuzzy FMECA can consider the limited maintenance conditions and test conditions on board, accurately quantify the criticality degree, and take into account more expert opinions, so as to improve the authenticity, accuracy and repeatability of criticality assessment. Therefore, the fuzzy FMECA method can better evaluate the criticality degree of propeller shaft system, and the results can effectively guide the improvement of propeller shaft design and maintenance work.

Residual life estimation of structural beam using experimental and numerical modal analysis methods

A structural beam is a common element in many mechanical structures such as ship propeller shaft, crane boom, and air craft wings. In the present paper experimental and numerical modal analysis are carried out for estimating the damage detection, geometric location of the damage, severity of damage and residual life of structural beam to prevent unexpected failures of the mechanical structures. Experimental and numerical modal analysis results for healthy and cracked beam are compared for validation of numerical methodology used in the present paper. Experimental modal analysis is performed on both healthy and cracked beam with the help of impact hammer, acceleration sensor and FFT analyzer associated with EDM (Engineering Data Management) software. Modal tests are conducted using impact method on selected locations of the entire healthy and cracked beam to find the first three natural frequencies, which are used to detect the presence of damage and geometric location of the damage. Three parametric studies are carried out to know the effect of crack depth, crack location and crack orientation on the natural frequencies of the cracked beam. Finally, residual life of a healthy and cracked beam was estimated using Basiquin’s equation and finite element analysis software called ANSYS 18.1.

Determining the standard of fitting between ship’s stern tube and propeller

The stern tube is fitted with a ship’s propeller shaft with a degree of technical redundancy, to protect the shaft against corrosion by seawater and wear with a bearing shaft, during work. Currently, the calculation and selection of this assembly is still done by experience, without a clear scientific basis. This paper, which presents the calculation of the required technical redundancy for the joint between the stern tube and the ship propeller shaft, based on the load acting on the joint, from which the corresponding standard fitting is selected, ensuring the this technical redundancy.

The Possibilities of Improving the Fatigue Durability of the Ship Propeller Shaft by Burnishing Process

Heavily loaded structural elements operating in a corrosive environment are usually quickly destroyed. An example of such an element is a ship propeller operating in a seawater environment. This research presents a fatigue resistance test performed on elements operating in seawater. Different processing parameters applied on the samples in particular were compared with the specimens whose surface had been burnished differently and they were compared to specimens with a grinded surface. The research shows that the structural elements whose surface has been burnished can have up to 30% higher fatigue strength in a seawater environment than the elements whose surface has been grinded. During burnishing, an important feature of the process is the degree of cold rolling of the material. The resistance of the component to fatigue loads increases only to a certain level with increasing the degree of the cold rolling. Further increasing the degree of cold rolling reduces the fatigue strength. Introducing additional stresses in the components (e.g., assembly stresses) reduces the fatigue strength of this component in operation and these additional stresses should be accounted for while planning the degree of the cold rolling value. A device that allows for simultaneous turning and shaft burnishing with high slenderness is presented in the appendix of this article. This device can be connected to the computerized numerical control system and executed automatic process according to the machining program; this solution reduces the number of operations and cost in the process.

To assess the operational life of ship's propeller shafts

To assess the operational life of ship's propeller shafts

Crack Identification and Localization In Structural Beams Using Numerical and Experimental Modal Analysis- A Review

This article presents a critical review of recent research done on crack identification and localization in structural beams using numerical and experimental modal analysis. Crack identification and localization in beams are very crucial in various engineering applications such as ship propeller shafts, aircraft wings, gantry cranes, and Turbo machinery blades. It is necessary to identify the damage in time; otherwise, there may be serious consequences like a catastrophic failure of the engineering structures. Experimental modal analysis is used to study the vibration characteristics of structures like natural frequency, damping and mode shapes. The modal parameters like natural frequency and mode shapes of undamaged and damaged beams are different. Based on this reason, structural damage can be detected, especially in beams. From the review of various research papers, it is identified that a lot of the research done on beams with open transverse crack. Crack location is identified by tracking variation in natural frequencies of a healthy and cracked beam

ВЛИЯНИЕ НЕОДНОРОДНОСТИ РАСПРЕДЕЛЕНИЯ КОЭФФИЦИЕНТА ЖЕСТКОСТИ ДЕЙДВУДНЫХ ПОДШИПНИКОВ НА СОБСТВЕННУЮ ЧАСТОТУ ПОПЕРЕЧНЫХ КОЛЕБАНИЙ ВАЛОПРОВОДА СУДНА

One of the most significant factors affecting the natural frequency of transverse vibrations of shaft-slide bearing systems is the stiffness coefficient of the slide bearing. The need to consider the influence of heterogeneity of stiffness coefficient of the bearing on its natural frequency is caused by the fact that when the bearing is worn, the modulus of longitudinal elasticity of the material changes, and since the bearing wears unevenly, the non-uniform distribution of the stiffness coefficient occurs. The problem of determining the natural frequency of transverse vibrations of a ship propeller shaft based on the foundation with a variable stiffness coefficient along the length has been studied. The differential equation of the propeller shaft vibrations written taking into account the stiffness coefficient variable along the shaft length is considered. It has been noted that, in the general case, this equation is a fourth-order partial differential equation and cannot be integrated in quadratures for an arbitrary stiffness distribution function along the shaft length. A numerical-analytical method for determining the natural frequency of a system based on approximation of the stiffness distribution function by a piecewise-linear function is proposed. The method is applied to calculate the natural frequencies of the pipeline section taking into account the functions describing the change in the stiffness coefficient. The proposed method allows to consider the section of the shafting enclosed in the stern bearing, subject to the non-uniform distribution of the stiffness coefficient of the bearing, and is the basis for improving the accuracy of finding the true natural frequency of transverse vibrations of the shafting.

АВТОМАТИЗАЦИЯ МЕТОДИКИ РАСЧЕТА СОБСТВЕННОЙ ЧАСТОТЫ ПОПЕРЕЧНЫХ КОЛЕБАНИЙ ГРЕБНОГО ВАЛА

Improving the designing quality of engineering systems and accuracy of their calculations is the basis for increasing the technical and economic indicators of modern engineering. Using automated calculations during the design phase raises labour productivity and product quality. There have been discussed the stages of software implementation of engineering calculations of the natural frequency of transverse vibrations of the ship propeller shafts. The problem of determining the first natural frequency of transverse vibrations of the shaft depending on the method of its fixing has been solved. A computational scheme has been build, which presents a uniform cross-section beam based on a point elastic support with a concentrated mass at its end. Differential equations for oscillations have been derived; the method of finding the natural frequencies has been described. For proper calculating natural frequency there has been developed a sequence and its software implementation in Maple environment with application of computer algebra package. The effect of the method of fixing on natural frequency of shaft transverse vibrations has been estimated. The problem of finding natural frequency of transverse vibrations on the extended elastic stern shaft bearing has been considered. The algorithm presented in the paper serves as a basis for formalizing and automating the stage of calculating transverse vibrations and is also applicable for calculating the natural frequencies of various elements, including the shaft and the sliding bearing.

A Method to Assess Transverse Vibration Energy of Ship Propeller Shaft for Diagnostic Purposes

Abstract The article discusses a key problem of ship propulsion system vibration diagnostics, which concerns assessing this part of mechanical energy transmitted from the main engine to the ship propeller which is dissipated due to propeller shaft vibration. A simplified calculation model is proposed which allows the total energy of the generated torsional vibration to be assessed from the shaft deflection amplitude measured at the mind-span point between the supports. To verify the developed model, pilot tests were performed on the laboratory rotational mechanical system test rig. In those tests, cyclic bending moment was applied to a unified (cylindrical) material sample, which modelled, at an appropriate scale, structural and functional properties of a real propeller shaft.

Numerical modeling and experimental analysis on coupled torsional-longitudinal vibrations of a ship's propeller shaft

A simplified lumped-mass model was established using ordinary differential equations, focusing on the coupled torsional-longitudinal vibrations of a ship's propeller shaft. The numerical simulation based on the presented algorithm was then developed and the dynamic behavior was investigated. A theoretical solution setup with simple model was solved to demonstrate the accuracy of the proposed lumped-mass model. Based on this model, the coupled natural frequencies and the maximum acceleration of each direction were determined. Experimental tests were conducted to validate the applicability of the numerical model, over a range of rotational speeds and loading conditions. It is found that the natural frequencies are unaffected while the maximum acceleration are increased with the rotational speed as well as the loading. Natural frequencies representing other directions are induced by the coupling effect, and enhance the dynamical response. The ultimate response in the direction without excitation is enlarged because of the coupling effect. An appropriate coupling stiffness coefficient value has been proposed based on the discussion on modeling and experimental results.

Усовершенствование технологии автоматической наплавки под флюсом при ремонте судовых гребных валов

During the operation of surfaces in ship propeller shafts they are worn out intensively. To prolong their life there are used at shipyards an automatic surfacing under flux (ASF) which, besides high efficiency is characterized with a considerable share of a basic metal participation in surfacing worsening properties of a deposited layer.
 The aim of the paper consists in the technology improvement of ship propeller shafts restoration with the aid of ASF and SBM decrease on the basis of complex mechanization and energization of a technological process.
 The process energization consists in the transfer character control of electrode metal through an arc by geometry and properties of driven rollers at the expense high-frequency extra-axial oscillations of an electrode (EOE) created by a special mechanical generator. The developed ASF technology ensures pad quality meeting requirements of the Register.

Failure and Fracture Analysis of Austenitic Stainless Steel Marine Propeller Shaft

A fractured in-service ship-propeller shaft (50.8 mm, i.e., 2-inches nominal diameter) was examined to determine the causes of failure and to recommend preventive measures to minimize the risk of recurrence. The findings of the failure analysis investigation suggest strongly that the shaft failed due to rotating bending fatigue initiated from the surface and close to the keyway area. The origin is located on a surface flaw (recess or dent) of approximately 100 μm depth, which could have probably being caused either during installation, operation, or maintenance. In addition, scoring lines formed due to friction-related processes and found on the journal surface were considered as stress raisers acting as potential sites for fatigue crack initiation. Careful review of the shaft service conditions and the implementation of suitable inspection procedures adapted to the vessel planned maintenance are recommended as necessary corrective actions for failure prevention.

Sampling and onboard analytical methods for determining subnanomolar concentrations of zinc in seawater

AbstractZinc (Zn) is an essential micronutrient for bacteria and phytoplankton in the ocean. However, seawater samples for Zn measurements are highly prone to contamination due to the ubiquity of Zn in laboratories and research vessels. To identify a potential Zn contamination problem during a research cruise to the subarctic North Pacific, we compared three operational sampling approaches for trace Zn in seawater. Acid‐cleaned Niskin‐X samplers were: (1) deployed on a conductivity–temperature‐depth carousel multisampling system (CTD‐CMS) launched at the vessel's starboard side, (2) attached to a Kevlar wire lowered at the vessel's stern, and (3) attached to a Ti wire lowered from a starboard position. Zn contamination in the case of Kevlar wire hydrocasts was problematic for samples from ≤400 m because Zn is used as a sacrificial anode for the ship's propeller shaft and for the pipes of the seawater cooling system. In deep waters, consistent Zn concentrations were found using the three different sampling methods. Based on the clean seawater sampling with CTD‐CMS and the onboard analytical method, vertical profiles of dissolved Zn were then obtained. These profiles were compared with those of Si in the subarctic North Pacific. Both Zn and Si concentrations showed a clear west–east gradient in shallow waters.

Welding of large support bracket components (Type V) of ship propeller shafts

We present the practical aspects of qualification of a welding procedure for the large-size structure of brackets of screw shafts made of cast steel and performance of a real welding operation. The issue of qualification of welding procedures, conducting assembly-welding works coupled with their monitoring and local heat treatment of welded joints as well as some aspects of non-destructive testing of welds are discussed. The whole work was supervised by Lloyd's Register of Shipping.

Assessment of possible application of waterlubricated sintered brass slide bearing for marine propeller shaft

ABSTRACT Water-lubricated bearings have been applied to support ship screw shafts for over a hundered years. Development of plastic materials has caused that novel sliding polymers appeared available on the market and being approved by classification institutions, possible to be applied in shipbuilding. However in the subject - matter literature there is no reference to application of bearings fitted with metal or ceramic bushes in shipbuilding. Nevertheless they have important merits such as low resistance to motion, long service life or stability of form. But some doubts are evoked by their large value of shape elasticity module which can lead to local stress concentration at the bush edges in the case of non-axiality of bush and shaft axes. Hence this work has been aimed at the testing of a bearing made of bronze-graphite silter. In the work is presented a comparison of measurement results of resistance to motion , hydrodynamic pressure distributions in lubricating film as well as shaft axis trajectories of the bearing, with those made for a typical elastic polymer bearing. The measurement results have showed high quality of the tested material. In the opinion of these authors it could be applicable to bearing ship propeller shafts.