Wyniki wyszukiwania - BazTech

1

Guided waves in ship structural health monitoring – a feasibility study

Roch Emil, Zima Beata, Woloszyk Krzysztof, Garbatov Yordan

Polish Maritime Research

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2023

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nr 2

76--84

EN

Ships and offshore structures operate in a severe corrosion degradation environment and face difficulty in providing longlasting corrosion protection. The Classification Societies recommend regular thickness measurements leading to structural component replacements, to ensure structural integrity during service life. The measurements are usually performed using ultrasonic thickness gauges and such an approach requires multiple measurements of the corroded structural components. Otherwise, the collected data are insufficient to precisely assess the corrosion degradation level. This study aims to perform numerical and experimental analyses to verify the use of guided ultrasonic waves in defining the corrosion degradation level of the corroded structural components of a ship. The study incorporates the fundamental antisymmetric Lamb mode, excited by piezoelectric transducers attached at the pre-selected points on stiffened panels, representing typical structural ship components. The specimens are exposed to accelerated marine corrosion degradation, the influence of the degree of degradation on the wave time of flight being analysed. The study indicates that guided waves are a promising approach for diagnosing corroded structural components. The signals characterised by a high signal-to-noise ratio have been captured, even for relatively long distances between the transducers. This proves that the proposed approach can be suitable for monitoring more extensive areas of ship structures by employing a single measurement.

2

The effect of numerical 2D and 3D FEM element modelling on strain and stress distributions at laser weld notches in steel sandwich type panels

Niklas K., Kozak J.

Polish Maritime Research

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2018

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nr 1

121--127

EN

Like other means of transport, merchant ships face the problem of increasing requirements concerning the environment protection, which, among other issues, implies the reduction of fuel consumption by the ship. Here, the conventional approach which consists in making use of higher strength steels to decrease the mass of the ship hull can be complemented by the use of new steel structures of sandwich panel type. However, the lack of knowledge and experience concerning, among other issues, fatigue strength assessment of thin-walled sandwich structures makes their use limited. Untypical welds imply the need for individual approach to the fatigue analysis. The article presents the effect of numerical FEM modelling with the aid of two-dimensional (2D) and three-dimensional (3D) elements on the results of strain and stress distributions in the areas of toe and root notches of the analysed laser weld. The presented results of computer simulation reveal that modelling of strain and stress states in 2D (instead of full 3D) affects only the results in close vicinity of the notch, and the observed differences rapidly disappear at a distance of 0.05 mm from the bottom of the notch. The obtained results confirm the possibility of use of numerically effective 2D strain and stress state models for analysing the fatigue strength of laser weld according to local approach.

3

The errors of the numerical calculations of dynamic characteristics of cantilever beam mounted on the plate

Van Doan D., Murawski L.

Journal of KONES

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2018

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Vol. 25, No. 1

433--440

EN

The safety, comfort of the crews, stability, economics of the equipment when ship operating is the leading requirement in the field of designing and manufacturing marine structure and machinery. As a result, all parts of the ships must be tested and inspected to meet the basic safety requirements of the shipping association. The design, manufacture, testing in the maritime field in general and shipbuilding sector in particular are expensive, time consuming: such as aerodynamic experiments of the engine, collision test, ship manoeuvring, vibration test and balance of deck beams, hull beams, hatch covers, shafts ...thus experimental works are sometimes impossible. Along with the development of computer science, many numerical models and software programs have been developed to solve these difficult problems. There are many numerical modelling methods, starting with the finite difference method, the boundary element method, the finite element method, the no mesh method, the weight residue or the energy method. The Work will be limited to the analysis of the most popular numerical modelling method - finite element method using Patran and Nastran software. In the first step of our research, T-beam was analysed as a part of ship hull structure (thin-walled structure). The article goes into the analysis of the accuracy of selected numerical models for the natural vibration frequency of the T-beams mounted on the plate. After modelling, calculating the natural frequency of the T-beam using the Patran - Nastran software, the results were compared with the theoretical values. From that, we evaluate the dispersion and error of different numerical models and select the optimal numerical model. Optimal model will be used for modelling full ship hull with superstructure.

4

Okrętowe stale austenityczne : charakterystyka eksploatacyjna

Jurczak W.

Autobusy : technika, eksploatacja, systemy transportowe

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2017

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R. 18, nr 12

928--932, CD

PL

W artykule przedstawiono wyniki badań mechaniczno-elektrochemicznych stali 1.3964 i 1.4301 zastosowanych do konstrukcji współczesnego niszczyciela min. Eksploatacja w środowisku morskim i obciążenia eksploatacyjne, wynikające z pracy kadłuba na fali, powodują powstawanie, w określonych warunkach, korozji naprężeniowej o charakterze elektrochemicznym. Naprężenia w elementach konstrukcji okrętowych i wartość potencjału elektrochemicznego to podstawowe parametry charakteryzujące podatność tych materiałów na korozję, początkowo wżerową, a później międzykrystaliczną. Zastosowanie metody lokalnego pomiaru potencjału elektrochemicznego (Patent PL 216723) podczas eksploatacji i wyznaczenie towarzyszącego mu lokalnego odkształcenia (naprężenia) stanowi podstawę diagnostyki korozyjnej, której zainicjowanie poprzedzone jest pękaniem warstewki tlenkowej, sygnalizowanej obniżeniem wartości potencjału elektrochemicznego. Stal 1.3964 zastosowana na nośne elementy konstrukcyjne kadłuba i nadbudówki posiada wyższe właściwości mechaniczne i lepszą odporność na korozję od stali 1.4301.

EN

The article presents the results of mechanical and electrochemical tests of steel 1.3964 and 1.4301 used for the construction of a modern mine destroyer. Exploitation in the marine environment and the operating loads resulting from the ship’s body movement on the wave cause, under certain conditions, electrochemical stress corrosion. Stresses in shipbuilding components and the value of electrochemical potential are the basic parameters characterizing the susceptibility of these materials to corrosion, initially pitting and later the intercrystalline one. The use of local electrochemical potential measurement method (Patent PL 216723) during operation as well as determination of the accompanying local deformation (stress) form the basis for corrosion diagnostics, which initiation is preceded by the oxide film’s cracking signalized by the reduction of the electrochemical potential. Steel 1.3964 used for the body’s and superstructure’s structural components has higher mechanical and corrosion resistance than steel 1.4301.

5

Model niszczenia zmęczeniowego spawanego złączy prostopadłych płyt

Kozak J., Górski Z.

Przegląd Spawalnictwa

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2011

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R. 83, nr 4

49-53

PL

Występujące w konstrukcjach statków pęknięcia zmęczeniowe powstają w miejscach szczególnie wrażliwych na obciążenia zmienne, tj. miejscach koncentracji naprężeń, do których należą złącza spawane. W przypadku zmęczeniowego pękania spawanych konstrukcji złożonych, do których należą konstrukcje kadłubów statku, proces pękania można podzielić na dwa stadia: propagacji pęknięcia w kierunku grubości oraz rozwoju pęknięcia na jego szerokości. Dodatkowo, niektóre z pęknięć zmęczeniowych rozwijają się w sposób niewidoczny i nie mogą być zauważone przez inspektora nadzoru, ze względu na warunki, w jakich odbywa się inspekcja (statek stojący w doku, oględziny w miejscach podatnych na pękania z reguły trudno dostępne, zanieczyszczone, znajdujące się w zamkniętych, nieoświetlonych przestrzeniach). W celu wyjaśnienia mechanizmu powstawania i rozwoju zmęczeniowego niszczenia w złożonych konstrukcjach spawanych przeprowadzono badania zmęczeniowe modelu spawanego złącza prostopadłych płyt poszycia w modelu węzła konstrukcyjnego statku - decydującym o wytrzymałości kadłuba. Badany model stanowił replikę węzła obłowego (miejsca połączenia burty z dnem) statku, wykonaną w skali zbliżonej do rzeczywistej i poddany był sinusoidalnemu wahadłowemu obciążeniu zmiennemu, które odpowiadało obciążeniu występującemu w konstrukcji rzeczywistej, wywołanemu siłami bezwładności od przyśpieszeń konstrukcji poddanej kołysaniu poprzecznemu. Na podstawie analizy wyników zaproponowano dwustopniowy model niszczenia zmęczeniowego węzła obłowego statku, wg którego opracowano analityczną metodę (wykorzystującą metodologię naprężeń nominalnych lub mechaniki pękania) określania trwałości zmęczeniowej złożonych węzłów konstrukcji okrętowych.

EN

Occurring in the ship construction fatigue cracks arise in the areas of design are particularly susceptible to changing loads such as acute stress concentration area, which includes the welded joints. For fatigue fracture of welded construction of complex structures which include the hulls of the ship, the process of cracking can be divided into two stages: propagation through the element thickness stage and the stage of crack propagation in the width direction of the element. In addition, some of the fatigue cracks are not visible in the developing process, and as such can not be seen by an observer (inspector), given the conditions in which the inspection (the ship standing in the dock, just out of service, places susceptible to cracking as a rule are hard-contaminated, in a closed, unlit spaces). In order to clarify the mechanism of formation and propagation of fatigue damage in the composite structures was carried out fatigue tests of welded perpendicular plate of the hull of the ship design of node model - determines the strength of the hull on a global scale. The test model was a replica of the bidge corner (ship's side with the bottom side joint) of the ship, made in a scale similar to the actual and subjected to a sinusoidal changing load, which corresponded to the load occurring in the actual structure induced by forces of inertia from the acceleration of the structures subjected to transverse swing. Based on the analysis results, it is proposed two-stage model of the fatigue ship bilge node damage on which analytical method (a combination of deformation methods and the methods based on fracture mechanics) to determine the fatigue life time of complex nodes in the ship structures was proposed.

6

Multi-objective optimization of high speed vehicle-passenger catamaran by genetic algorithm. Part II. Computational simulations

Sekulski Z.

Polish Maritime Research

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2011

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nr 3

3-30

EN

Real ship structural design problems are usually characterized by presence of many conflicting objectives. Simultaneously, a complete definition of the optimum structural design requires a formulation of size-topology-shape-material optimization task unifying the optimization problems of the four areas and giving an effective solution of the problem. So far, a significant progress towards the solution of the problem has not been obtained. An objective of the present paper was to develop an evolutionary algorithm for multiobjective optimization of structural elements of large spatial sections of ships. Selected elements of the multi-criteria optimization theory have been presented in detail. Methods for solution of the multi-criteria optimization problems have been discussed with the focus on the evolutionary optimization algorithms. In the paper an evolutionary algorithm where selection takes place based on the aggregated objective function combined with domination attributes as well as distance to the asymptotic solution, is proposed and applied to solve the problem of optimizing structural elements with respect to their weight and surface area on a high speed vehicle-passenger catamaran structure, with several design variables, such as plate thickness, scantlings of longitudinal stiffeners and transverse frames, and spacing between longitudinal and transversal members, taken into account. Details of the computational models were at the level typical for conceptual design. Scantlings were analyzed by using selected rules of a classification society. The results of numerical experiments with the use of the developed algorithm, are presented. They show that the proposed genetic algorithm can be an efficient tool for multi-objective optimization of ship structures. The paper is published in three parts: Part I: Theoretical background on evolutionary multi-objective optimization, Part II: Computational investigations, and Part III: Analysis of the results.

7

Multi-objective optimization of high speed vehicle-passenger catamaran by genetic algorithm. Part I. Theoretical background on evolutionary multi objective optimization

Sekulski Z.

Polish Maritime Research

|

2011

|

nr 2

3-18

EN

Real ship structural design problems are usually characterized by presence of many conflicting objectives. Simultaneously, a complete definition of the optimal structural design requires a formulation of size-topology-shape-material optimization task unifying the optimization problems from these four areas and giving an effective solution of this problem. So far, a significant progress towards the solution of this problem has not been obtained. An objective of the present paper was to develop an evolutionary algorithm for multi-objective optimization of the structural elements of the large spatial sections of ships. Selected elements of the multi-criteria optimization theory have been presented in details. Methods for solution of the multi-criteria optimization problems have been discussed with the focus on the evolutionary optimization algorithms. In the paper an evolutionary algorithm where selection takes place based on the aggregated objective function combined with domination attributes as well as distance to the asymptotic solution is proposed and applied to solve the problem of optimizing structural elements with respect to their weight and surface area on a high speed vehicle-passenger catamaran structure with several design variables, such as plate thickness, scantlings of longitudinal stiffeners and transverse frames, and spacing between longitudinals and transversal members. Details of the computational models were at the level typical for conceptual design. Scantlings were analyzed using the selected rules of a classification society. The results of numerical experiments with the use of the developed algorithm are presented. They show that the proposed genetic algorithm can be an efficient multi-objective optimization tool for ship structures optimization. The paper will be published in three parts: Part I: Theoretical background on evolutionary multi-objective optimization, Part II: Computational investigations, and Part III: Analysis of the results.

8

Multi-objective optimization of high speed vehicle-passenger catamaran by genetic algorithm. Part II. Analysis of the results

Sekulski Z.

Polish Maritime Research

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2011

|

nr 4

3-13

EN

Real ship structural design problems are usually characterized by presence of many conflicting objectives. Simultaneously, a complete definition of the optimum structural design requires a formulation of size-topology-shape-material optimization task unifying the optimization problems from the four areas and giving an effective solution of the problem. Any significant progress towards solving the problem has not been obtained so far. An objective of the present paper was to develop an evolutionary algorithm for multiobjective optimization of the structural elements of large spatial sections of ships. Selected elements of the multi-criteria optimization theory have been presented in detail. Methods for solution of the multi-criteria optimization problems have been discussed with the focus on the evolutionary optimization algorithms. In the paper an evolutionary algorithm where selection takes place based on the aggregated objective function combined with domination attributes as well as distance to the asymptotic solution, is proposed and applied to solve the problem of optimizing structural elements with respect to their weight and surface area for a high - speed vehicle-passenger catamaran structure, with taking into account several design variables such as plate thickness, scantlings of longitudinal stiffeners and transverse frames, and spacing between longitudinal and transversal members. Details of the computational models were kept at the level typical for conceptual design stage. Scantlings were analyzed by using the selected classification society rules. The results of numerical experiments with the use of the developed algorithm are presented. They show that the proposed genetic algorithm may be considered an efficient tool for multi-objective optimization of ship structures. The paper has been published in the three parts: Part I: Theoretical background on evolutionary multiobjective optimization, Part II: Computational simulations, and Part III: Analysis of the results.

9

Spawane konstrukcje okrętowe ze stopów aluminium

Al Obeidi A. H.

Przegląd Spawalnictwa

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2009

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R. 81, nr 2

29-31

PL

Po drugiej wojnie światowej stopy aluminium wprowadzono na skalę masową do konstrukcji okrętowych. W artykule omówiono przyczyny i celowość stosowania tego stopu w konstrukcjach jednostek pływających oraz technologię wykonywania wielkogabarytowych struktur okrętowych.

EN

It was after the World War II when aluminium found its way to the shipbuilding industry on a large scale. The article shows the reason and purpose of application of such alloys in seagoing vessel structures as well as the technology of manufacturing large size ship components.

10

Structural weight minimization of high speed vehicle-passenger catamaran by genetic algorithm

Sekulski Z.

Polish Maritime Research

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2009

|

nr 2

11-23

EN

Reduction of hull structural weight is the most important aim in the design of many ship types. But the ability of designers to produce optimal designs of ship structures is severely limited by the calculation techniques available for this task. Complete definition of the optimal structural design requires formulation of size-topology-shape-material optimization task unifying optimization problems from four areas and effective solution of the problem. So far a significant progress towards solution of this problem has not been achieved. In other hand in recent years attempts have been made to apply genetic algorithm (GA) optimization techniques to design of ship structures. An objective of the paper was to create a computer code and investigate a possibility of simultaneous optimization of both topology and scantlings of structural elements of large spacial sections of ships using GA. In the paper GA is applied to solve the problem of structural weight minimisation of a high speed vehicle-passenger catamaran with several design variables as dimensions of the plate thickness, longitudinal stiffeners and transverse frames and spacing between longitudinals and transversal members. Results of numerical experiments obtained using the code are presented. They shows that GA can be an efficient optimization tool for simultaneous design of topology and sizing high speed craft structures.

11

An algorithm for preliminary estimating hull structure mass and mass centre height of inland navigation ships

Michalski J. P.

Polish Maritime Research

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2005

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nr 1

8-12

EN

The paper presents an algorithm for preliminary calculation of mass and mass centre height of hull structure of inland navigation ships. It was elaborated basing on requirements of the Rules for the Classification and Construction of Inland Navigation Ships of Polish Register of Shipping, with application of a simplified method of estimating mass of hull plating stiffeners. The algorithm deals with the dimensioning of scantlings of structural members of classical ships intended for shipping dry cargo, and dry and liquid bulk cargoes; however it does not cover ships of entirely different structural arrangement such as roll-on-roll-offships fitted with heavy decks, as the dimensioning of their scantlings is based on different models.