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Wyszukujesz frazę "Murawski, L." wg kryterium: Autor


Tytuł:
Methodology of threat autonomous assessment and forecasting the lifetime of the marine structure
Autorzy:
Murawski, L.
Tematy:
monitoring systems
non-destructive tests
ship structures lifetime prediction
damage identification
damage localization
lifetime forecasting
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Wydawca:
Instytut Techniczny Wojsk Lotniczych
Powiązania:
https://bibliotekanauki.pl/articles/245864.pdf  Link otwiera się w nowym oknie
Opis:
Structural Health Monitoring (SHM) is a natural extension and supplement of Non-Distractive Tests (NDT). Structure assessment during periodical NDT tests is performed by highly trained human team. However, during long sea voyage, ship crew has no knowledge and possibility for detailed assessment and, what is more, has no knowledge lifetime predicting of ship structure. SHM systems should have good designed sensors types, distribution, and automatic recording unit. However, most important (and most difficult for designing) is autonomous and self-contained procedures for marine structures hazard assessment. In the paper, basic assumptions for numerical algorithms of signal processing, damage identification and localization, threat assessment and forecasting of structure lifetime are presented. SHM systems can be based on several different measurements techniques like: comparative vacuum monitoring, electromagnetic layer, Lamb waves, vibration based methods, acoustic emission, and fibre optics. Last three methods are most promising in the marine environment, according to the author experience. Global ship hull deformation should be monitored as quasi-continuous measurements. Optical Time-Domain Reflectometer method (OTDR) is planned by author for hull global deformation monitoring. Some local strain-stress concentration of hull structure and propulsion system bearings' reactions will be monitored by Fibre Bragg Grating (FBG) sensors. Both techniques (OTDR and FBG) have been shortly described in the paper.
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Kinematic of marine piston-crankshaft system
Autorzy:
Murawski, L.
Tematy:
marine propulsion system
piston-crankshaft kinematic
slow speed engines
inertia forces
propulsion system vibrations
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Wydawca:
Instytut Techniczny Wojsk Lotniczych
Powiązania:
https://bibliotekanauki.pl/articles/246452.pdf  Link otwiera się w nowym oknie
Opis:
Two-stroke, slow speed main engines are often installed on merchant ships, because of its very high efficiency. That kind of engine has an output of about 5500 kW per cylinder. The mass of piston-crankshaft system reaches over a dozen tons. That reciprocating masses are source of high level of dynamic inertia forces (mass forces). Those forces have big influence on engines working parameters and characteristics. One of them is instability of crankshaft rotational speed, which leads to dangerous torsional vibrations of propulsion system. Some inconsistency can be observed during analysis of piston-crankshaft system kinematic. In the theoretical engine books, the piston speed and acceleration has only two harmonic components, the inertia forces are depended on engine rotation speed and they doubled rotation speed. However, empirical formulas, published by engines producers, give us at least five harmonic components of mass forces. The author tries to find out the theoretical reason of existing (measured) higher harmonic orders of engines inertia forces. It is a first step for developing monitoring system of propulsion system’s torsional vibrations coupled with axial vibration, dynamic shaft line alignment and crankshaft springing. In the paper two analytical methods of piston displacement, speed and acceleration are presented. Well-known (from literature) equations are compared with more-detailed analytical procedures. The analysis was performed for one of the biggest marine MAN B&W engine, type 7K98MC. A discussion about the analysis results was included in the final part of the paper.
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
The influence of shaft line alignment accuracy on the operational reliability of marine propulsion systems
Autorzy:
Murawski, L.
Tematy:
shaft line alignment
marine propulsion systems
propulsion system's bearings damages
operating parameters of the power transmission system
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Wydawca:
Instytut Techniczny Wojsk Lotniczych
Powiązania:
https://bibliotekanauki.pl/articles/241911.pdf  Link otwiera się w nowym oknie
Opis:
The paper presents a method of identification parameters of shaft line alignment and its influence on operational reliability of marine propulsion system. The discussion about shaft line parameters (bearings' reactions, bending moment and shear forces acting on crankshaft or gear box, and stresses distribution in the shaft line) which has an influence on marine propulsion system reliability was presented. Proper shaft line alignment is often a problem for repair shipyards, for aged ships without sufficient documentation. Some data can be draw by measurements; e.g. shaft line dimensions or intermediate bearings' reactions. Other data (stern tube bearing load, real axis of shaft line) have to be determined on the base of calculations. Author proposed combined experimental-analytical method for identified and optimization (correction) some existing parameters and checking power transmission system’s foundation. Specialised software (based on Finite Element Method) has been developed for shaft line alignment calculations. Main novelties of the software are elastic supports (model of bearings – boundary conditions) of the shaft line, continuous support as a model of stern tube bearing and influence coefficients calculations. An example analysis with discussion has been performed for cargo ships with medium-speed main engine. Multi-variant computations supported by measurements of the ships’ shaft line have been carried out. Changes in shaft line alignment have been proposed in order to increase reliability of propulsion system.
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Software for the dynamic analysis of machines placed on elastic pads
Autorzy:
Murawski, L.
Tematy:
marine engine
elastic foundation of power plant
rigid finite element
elastic pads
rubber couplings
non-linear characteristics of rubber machine elements
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Wydawca:
Instytut Techniczny Wojsk Lotniczych
Powiązania:
https://bibliotekanauki.pl/articles/243603.pdf  Link otwiera się w nowym oknie
Opis:
Software DYNMACH has been designed for the dynamic analysis (vibrations) of machines placed on elastic foundation pads assuming non-linear foundation characteristics. Floating platforms of marine engines are designed for noise and vibration isolation between ship hull and engine. Excessive loadings acting on ship hull can be also eliminated by elastic foundation. Analysis of that kind of marine machines is the main target of presented software. It has been assumed that the machines are modeled as rigid bodies while the foundation is treated as a set of elements of non-linear elastic-damping characteristics. Software DYNMACH is the implementation of the Rigid Finite Element Method. A machine can be modeled as a single rigid finite element composed of an arbitrary number of elementary rigid bodies. The following rigid body types are available in the library of the program: a plate, a brick, and a full cylinder. Elastic elements used for foundation modeling can have non-linear stiffness and damping characteristics. These characteristics can be assumed as functions of the foundation displacement or the expected excitation frequency. A built system can be loaded by an arbitrary number of static forces. These static forces are used for a preliminary calculation of strains and the centre of equilibrium, as well as for determination of the stiffness and damping coefficients of the non-linear elastic damping elements in the equilibrium position. Program DYNMACH can calculate the frequencies and modes of natural vibration of the loaded system, as well as calculates of system responses to dynamic excitations. Assuming only small vibration amplitudes the dynamic behaviour of the system can be considered as linear, however, this linear behaviour is imposed on the non-linear equilibrium conditions obtained from the solution of the coupled static problem. Database of different types of rubber machines couplings has been build-in the DYNMACH software.
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Comparative analysis of the calculation methods of the marine propeller’s blade thickness
Autorzy:
Murawski, L.
Tematy:
marine propeller
strength
vibration
solid structure in fluid
FEM modelling methodology
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Wydawca:
Instytut Techniczny Wojsk Lotniczych
Powiązania:
https://bibliotekanauki.pl/articles/244269.pdf  Link otwiera się w nowym oknie
Opis:
Strength of the propellers with the skewback greater than 25º has to be numerically analysed according to marine classification societies. The finite element method (FEM) is advised for that kind of calculations. Classical and typical propellers (skewback < 25º) may be designed on the base of empirical equations given by the societies. The minimal thickness of the propeller blade is determined by the equations. Each classification society has their own empirical formula. Sometimes, well-designed propeller for one society has not enough strength according to the other society. What is more, propellers designed according to the empirical formulas might be not optimal. Comparative analysis of the marine propeller’s blade strength has been described in the article. Calculations of the propeller’s blade thickness have been done by two international classification societies’ empirical formulas (ABS and DNV). The results have been compared with Finite Element Method calculations (NASTRAN program). The methodology of propeller static strength vibration analyses is presented. Numerical calculation methodology is based on solidstate mechanics with loadings determined by fluid mechanics calculations. Steady state and transient fluid flow of the propeller’s working conditions were taken into account. In order to determine the optimal modelling method of the propeller several different numerical models were compared, including free model of whole propeller and single blade with boundary conditions placed in the foot. The propeller optimization was the main target of the analyses. Propeller blade thickness might be reduced after FEM method analysis - the propeller mass saving can be achieved.
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Stiffness characteristics of main bearings foundation of marine engine
Autorzy:
Murawski, L.
Tematy:
dynamic stiffness of main engine bearings
shaft line alignment
crankshaft springing
marine propulsion system numerical analysis
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Wydawca:
Instytut Techniczny Wojsk Lotniczych
Powiązania:
https://bibliotekanauki.pl/articles/247486.pdf  Link otwiera się w nowym oknie
Opis:
During shaftline alignment and crankshaft springing analyses, knowledge of stiffness of radial bearings is essential. Dynamic stiffness's characteristics of marine main body are difficult to estimate because of lack of available documentation and complicated shape of the body. In the literature, there is a lack of the detailed data on the stiffness of the crankshaft foundation in the frame of marine main engine. Those parameters are crucial for the shaft line alignment analysis as well as for the analysis of interactions between the shaft line and the crankshaft. Especially for the high power engines, the correct model of the boundary conditions plays a key role during the analysis. The paper presents the methodology of the characteristics determination of the marine engine’s body as well as the example of computations for a MAN B&W K98MC type engine mounted on a ~3000 TEU container ship. The model of main engine body is relatively big – it contains over 800 thousand degree of freedom. The elasticity of ship hull has been estimated and taken into account during analysis. It has been found, that static stiffness parameters recommended by the producer for the shaft line alignment are evaluated correctly, however they represent only the flexibility of the engine’s body, not taking into account the flexibility of the ship’s hull. What is more, the dynamic magnification of vibration amplitudes is not taken into account.
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Vibrations resonance estimation in marine structures
Autorzy:
Murawski, L.
Tematy:
vibration
dynamic analysis
marine structures
propulsion system
crankshaft
resonance
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Wydawca:
Instytut Techniczny Wojsk Lotniczych
Powiązania:
https://bibliotekanauki.pl/articles/247863.pdf  Link otwiera się w nowym oknie
Opis:
Dynamic analyses of marine structures are one of the most important during design process as well as during exploitation. Typically, two parts of vibrations calculations are performed. Firstly, natural vibrations frequencies and modes are determined. Forced vibrations analysis is the second step of calculations. Natural vibrations give us information about possibility (e.g. at which main engine speed) of dangerous vibrations amplitudes (resonances threat). Exact values of vibrations amplitudes are results of forced vibrations analysis. Confidence level (error value) of forced vibration calculations is much lower in comparison to uncertainty of natural vibration analysis. What is more, form engineering practice point of view, natural vibrations frequencies estimation (resonance avoidance) is the most important during dynamic analysis of marine structures with propulsion systems. In the paper some examples of dynamic characteristics estimation and their changing methods (possibility) was presented. Utility of relatively simple models, with low degree of freedom number, was discussed. Modelling methods depending on the analysis target of marine slow-speed crankshafts was presented. Advantages and disadvantages of subcritical and supercritical design of marine propulsion system were discussed. An example of propulsion system natural torsional vibrations simplified analysis was presented. Location of the main torsional resonance is one of the most important decisions during design process of the marine propulsion system. Methods of fast and easy estimation as well as changing possibility of natural vibrations frequencies of marine structures is the main objective of presented paper.
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Identification of shaft line alignment with insufficient data availability
Autorzy:
Murawski, L.
Tematy:
shaft line alignment
bearings reaction
crankshaft external forces
shaft line stresses
aged ships
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Wydawca:
Politechnika Gdańska. Wydział Inżynierii Mechanicznej i Okrętownictwa
Powiązania:
https://bibliotekanauki.pl/articles/258630.pdf  Link otwiera się w nowym oknie
Opis:
The paper presents a method of identification parameters of shaft line alignment in case of the lack of producers’ data. Proper shaft line alignment is often a problem for repair shipyards, for aged ships without sufficient documentation. Author proposed combined experimental-analytical method for identified some existing parameters and checking (and eventually correcting) power transmission system’s foundation. Specialised software has been developed for shaft line alignment calculations with influence coefficients. An example analysis has been performed for cargo ships with medium-speed main engine and second one with slow-speed propulsion system. Multivariant computations supported by measurements of the ships’ shaft line have been carried out.
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Forces exciting vibrations of ships hull and superstructure
Autorzy:
Murawski, L.
Tematy:
hull vibration
superstructure vibration
main engine vibrations
excitation forces
pressure pulses
propulsion system's reactions
crankshaft-propeller phasing
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Wydawca:
Politechnika Gdańska. Wydział Inżynierii Mechanicznej i Okrętownictwa
Powiązania:
https://bibliotekanauki.pl/articles/259533.pdf  Link otwiera się w nowym oknie
Opis:
The paper presents identification of main excitation forces ofvibrations of ship hull and its superstructure, as well as investigation of influence of the analyzed excitation on ship vibration level. The following excitation forces were analyzed: dynamic pressure on the transom deck, propeller-generated hydrodynamic forces, as well as internal and external engine-generated forces. Rigidity and attenuation characteristics of lubricating oil film were taken into account in the analysis of the excitations transmitted by the propulsion system bearings (stern tube bearing, intermediate bearing, engine s main and thrust bearings). The dynamic characteristics of ship's power transmission system were also taken into account.Results of the analyzes were verified by comparing results of the computations and measurements.
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Ship structure dynamic analysis - effects of made assumptions on computation results
Autorzy:
Murawski, L.
Tematy:
drgania kadłuba statku
drgania nadbudówki statku
drgania swobodne
hull vibration
superstructure vibration
natural vibration
excitation forces
errors of finite element method
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Wydawca:
Politechnika Gdańska. Wydział Inżynierii Mechanicznej i Okrętownictwa
Powiązania:
https://bibliotekanauki.pl/articles/259656.pdf  Link otwiera się w nowym oknie
Opis:
The paper presents identification of main errors which may occur during dynamic analysis of ship's hull and superstructure. The investigation was realized on the basis of calculations of natural and forced vibrations. The analysis was performed for cargo ships with typical propulsion system. Multi-variant computations of ship vibration were carried out with the use of previously identified excitation forces. A computation method for excited vibrations of ship hull and superstructure was developed.
Dostawca treści:
Biblioteka Nauki
Artykuł

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