Estimating efficiency of forecasting technical conditions of ship propulsion systems

The article considers an approach to assessing the effectiveness of the most common methods of predicting the technical conditions and failure with reference to the ship shafting. There have been analyzed the main factors in operation of the ship shaft line, which cause the change in its technical state. It has been found that a special feature of some loads acting on the propeller shaft is their stochastic or changing nature over time, which hampers predicting the technical state of the shafting and its units. The features of stochastic and extrapolation forecasting methods have been analyzed. The possibility of using statistical methods in conditions of mass standard production of shafting units with a relatively short regulated service life is estimated. An extrapolation method is proposed for predicting the maximum permissible clearance of stern tube bearings. The case of accumulating samples of measuring results of the propeller shaft sagging in the given time intervals is considered, the approximating functions are constructed. The criteria for the reliability of the results of extrapolation methods for predicting the wear of stern tube bearings are determined. There have been developed the proposals for adapting the causal method as an alternative to the extrapolation method. A schematic diagram of a system for the ship shafting failure predicting has been developed using the registration and analysis of vibration parameters, which serves as the basis for constructing a regression model of damage accumulation. The proposed forecasting system allows studying the actual operating conditions of the shafting, defining the actual external loads and the regularities of their occurrence, measuring deformations and stresses, and determining quantitative indicators of the reliability of the shafting during normal operation and special operating modes, for example, with vibration resonance. The theoretical basis of the algorithm for calculating and registering loads affecting the service life of shafts is proposed.

Dynamic strain measurement of propeller shaft vibrations

The paper proposes an approach to the registration of vibrations parameters to increase the reliability and predict the durability of technical systems with a continuously rotating shaft. For systems with stochastic loads, such as a ship’s shaft line, the actual measurement of shaft stresses and deformations is an actual way to prevent failures and non-destructive testing under operating conditions. The adaptation of the dynamic strain measurement method made it possible to develop a software and hardware complex for recording and analysing transverse, torsional and longitudinal vibrations of shafts. The design of a hardware complex consisting of a measuring mobile and stator modules connected by a wireless network that allows dynamic strain measurement is proposed. The connection diagram and the main metrological and technical characteristics of the modules are given. To test the operability of the hardware complex, an experimental installation was built that allows carrying out investigation of the shaft line vibrations in real operation conditions. Experimental data are presented, the analysis of which allows us to predict the durability of the system.

Control of mobile equipment for the processing of marine shaft lines

The purpose of the research is to develop solutions for mobile equipment control in the processing of marine shaft lines; to solve the issues of geometric accuracy of processing; to create a corrective program to address the issues of accuracy of the geometric parameters processing; to give reasons for the application of linear electrohydraulic step drive (LEHSD) in mobile equipment control. The analysis of schemes and mathematical dependencies for calculating the trajectory of the tool movement of a mobile machine when processing shaft lines is carried out; the choice of the optimal zone for finishing the shaft line, taking into account the beats. The object of the study is a ship shaft line. The paper presents an original scheme of rotation of the shaft line section, as well as schemes for changing the position of the shaft line during processing; justifies the possibility of using a linear electrohydraulic step drive (LEHSD) with a corrective program for processing taking into account automatic measurements and a specified error.

Possibility of applying X-ray methods to control the surface quality of a shaft line after finishing

The purpose of the paper is to analyze the application limits of X-ray methods of non-destructive testing of loaded parts; to compare the results of microstresses and deformations of the details’ surface layer by methods and by the method of X-ray diffraction analysis for various modes of processing the detail surface layer. The studies are carried out on a “Dron” diffractometer. The technique and algorithm of X-ray structural studies, namely, “sin2v|/”-method are represented. Residual macro σφ and micro stresses, as well as the sizes of the areas of coherent scattering (D) on the samples surfaces processed in various modes, and their distribution in the near-surface layer are designated. Phase analysis is conducted and the presence of residual austenite. The research object is the operating surface of the 46-19-186 gear tooth after various treatments: after HFC hardening; after HFC hardening, grinding and blasting in depressions; after HFC hardening and fine-finish cutting. The X-ray structural analysis (XRD) technique is presented to determine the residual macro-σφ and microstresses, the sizes of the coherent scattering regions (D) on the surfaces of the samples processed in different modes. The outcomes of X-ray structural analysis are compared with the outcomes of metallographic studiesmaking. It was determined that the stress relaxation during the manufacture of the sample is no more than 10%, and the total instrumental error of the X-ray spectral analysis method is about 1%.

Practical confirmation of mechanical balancers effectiveness to reduce vibration of marine main diesel engines

The article discusses compensators of unbalanced moments from inertial forces of the second and variable components of the overturning moment of the main order and the elastic moment at the resonance of torsional vibrations of the shaft line of modern marine low-speed diesel engines. The efficiency of the diesel engine’s operation is analyzed based on the vibration measurements on ships and some problems caused by these devices.

Analysis of damage and failure of ship propulsion shafts

The paper highlights the problem of a ship shaft line failure, which entails significant economic losses, because most vessels of the Russian fleet are equipped with a shaft line. A large number of domestic and foreign works are devoted to studying the causes of damage and failures of ship shafting. The complexity of collecting, systematizing and analyzing statistical data on breakdowns and damages of shafting lies in the fact that the data refer to different periods of time, different periods of operation and types of ships, and are also contained in various sources. There has been considered the approach to systematization of modern statistical data on damages and failures of ship shafting elements collected on the basis of defect-technological lists of the Astrakhan shipyards and from other sources. Information on breakdowns of ships, their elements and ship shaft lines within 2010 - 2019 provided by the Russian River Register of Shipping is given. The analysis of accidents on ships of the class of the Russian Maritime Register of Shipping. The places of occurrence and the nature of the propeller shaft cracks have been established, which makes it possible to assess the nature and magnitude of the destructive loads, as well as the real safety margins. The general classification of the location of the propeller shaft cracks in the order of the frequency of their occurrence is given. There have been shown the results of the analysis of defect-technological lists, which make it possible to establish the causes of ship shafting failures, which led to emergency repair, and the most common defects identified during the scheduled dock repair of ships. The influence of the diameter of propeller shafts on the nature and size of defects, as well as the frequency of their manifestation, is estimated. Based on the results of the analysis, certain measures have been proposed to reduce the number of accidents in shafting of projected vessels, and the most promising directions for improving the already developed structures of shafting in operation are outlined. The results of the analysis are in addition to the ongoing research and development work to improve the reliability of ship power systems.

Research on the centre distance separability of parallel shaft line gear pair

For gear pairs with centre-distance separability, transmission ratios are not affected by centre distance error. Based on space curve meshing theory, the centre distance separability of a line gear pair was studied. A novel line gear pair called the separable and pure rolling parallel shaft line gear pair (SPRPSLG) was proposed, which has centre-distance separability characteristics and pure rolling transmission. The basic design theory of the SPRPSLG pair was established. A design method of the SPRPSLG pair with an eccentric arc tooth profile was given. An SPRPSLG pair example was designed and manufactured using the form milling method. Kinematic experiments and meshing efficiency experiments were conducted. Gear contact spot testing and gear contact simulation analysis were carried out. The SPRPSLG pair was shown to have centre distance separability, which provides a further theoretical basis for the popularization and application of line gears.

Use of electromechanical analogies in the construction and calculation of a simulation model of the process of torsional oscillations of the shaft line of an internal combustion engine

The purpose of the article is to substantiate the possibility of using electromechanical analogies in the construction and calculation of parameters of the simulation model of the process of torsional oscillations of the internal combustion engine shaft, which will allow to move from mechanical models of shafts to their electrical counterparts. Results of the research. The article clarifies the relationship between phenomena occurring in mechanical and electrical systems, mechanical and electrical analogues are established, namely force is considered as electromotive force or voltage, velocity as current, moment of inertia as inductance, spring flexibility as capacitance, coefficient friction as electrical resistance, and the kinematic scheme of the shaft line is presented in the form of a diagram of a reactive bipolar, the parameters of which are determined during analytical calculations of the kinematic scheme of the elastic system. The concept of dynamic stiffness is introduced, which is similar to the concept of reactive resistance of a bipolar. The initial data for the calculation of a linear system in which it is assumed that the pliability of the shock absorber is zero. Conclusions. According to the results of the analogies, the parameters of the simulation model were obtained. The calculation of the elastic system using the method of electromechanical analogies allowed to build a simulation model of the shaft line of an internal combustion engine.

Analysis of influence of elastic properties of deadwood bearings on shaft line operability

The paper considers the ship shafting and its design. Depending on the constructive features, operating conditions, effects of continuous, dynamic, variable and random loads the operation of the shaft line is accompanied by wear of the shafting structure and auxiliary parts. The formulas for calculating the maximum permissible clearances during operation in stern bearings of propeller shafts are given, according to the norms and technical and operational requirements. A graph of the maximum permissible clearances in metal stern bearings is presented. There has been carried out a dynamic design of the shaft line in order to define the influence of rigid characteristics of the stern bearings on eigen frequency of transverse vibrations. It is noted that the service life of the shaft line depends on the material of bushings or liners of the bearings (bakout, babbit, textolite, caprolon, bronze, polyurethanes, rubber) and their wear degree. The design scheme of the ship shaft line on elastic supports with a coefficient of rigidity is presented. To assess the influence of the elastic properties of deadwood bearings, the method of initial parameters was used. According to the researchers’ opinion, the greater the wear, the lower their stiffness coefficient. At a certain wear degree of deadwood bearings, there occurs resonance at the lowest operating frequencies. It has been proved that the greater the deflection at the attachment point of the propeller, the lower the eigen frequency of transverse vibrations of the shaft line. It has been pointed out that the calculations should include the separation of the shaft line from the deadwood bearing, since it contributes to a decrease in eigen frequency and causes a resonance during transverse vibrations.