Wyniki wyszukiwania - Biblioteka Nauki

1

Numerical calculations of behaviour of ship double-bottom structure during grouning

100%

Niklas K.

Polish Maritime Research

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2008

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nr Special Issue

EN

The idea of the CORET project consists in adding, to the existing construction, special polymer-concrete coatings intended for the increasing of ship’s capability against losing structural tightness during collision or grounding. In order to correctly design the protective barriers, to perform relevant numerical simulations is necessary. The elaborating of numerical models of ship structure behaviour during collision is very complicated and requires auxiliary simulations (on submodels) to be performed. This paper is devoted to elaborating a numerical model of a fragment of ship double-bottom structure. On the basis of experimental tests it was possible to verify and calibrate the numerical model which may be used in further design work aimed at the increasing of crashworthiness of structure during collisio

2

Strength analysis of a large-size supporting structure for an offshore wind turbine

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Niklas K.

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tom S 1

156--165

EN

The offshore wind power industry is the branch of electric energy production from renewable sources which is most intensively developed in EU countries. At present, there is a tendency to install larger-power wind turbines at larger distances from the seashore, on relatively deep waters. Consequently, technological solutions for new supporting structures intended for deeper water regions are undergoing rapid development now. Various design types are proposed and analysed, starting from gravitational supports (GBS), through monopiles and 3D frame structures (jackets, tripods), and ending with floating and submerged supports anchored to the seabed by flexible connectors, including TLP type solutions. The article presents the results of examination of an untypical large-size gravitational support intended for waters with the depth of up to 40 m. Firstly, a general concept of the new design is presented, while the next basic part of the article describes the support design in detail and provides its strength analysis. The examined support has the form of a large steel container consisting of conical segments. The strength analysis was conducted using the finite element method (FEM), in accordance with the standard DNVGL-ST-0126. Modifications introduced to the most heavily loaded structural node of the support, which was the set of base bottom trusses, is also included. The results of the performed analysis prove that the presented concept of supporting structure for a 7MW turbine meets fundamental strength criteria. The nonlinear buckling analysis was performed to evaluate the critical force acting on the support, which turned out to be 1.44 times as large as the maximum load of the wind turbine. Potentially important issues for further analyses have been identified as those resulting from the asymmetry of basic loads acting on the support.

3

Search for optimum geometry of selected steel sandwich panel joints

100%

Niklas K.

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tom 15

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nr 2

EN

Application of steel sandwich panels to ship structures requires many problems to be solved. Joints between the panels as well as those between the panels and other structures is one of the more difficultproblemsassociatedwiththestructuresinquestion.Thispaperpresents the searching for process of optimum geometry of a panel-to-panel joint of longitudinal arrangement, performed by means of the ANSYS software. A configurationwas searched for of parameters which can ensure as-low-as possible values of geometrical stress concentration coefficients at acceptable mass and deformations of the structure.Analysis of the obtained results made it possible to propose the optimum geometry of the considered joint

4

Search for optimum geometry of selected steel sandwich panel joints

100%

Niklas K.

Polish Maritime Research

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2008

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tom nr 2

26-31

EN

Application of steel sandwich panels to ship structures requires many problems to be solved. Joints between the panels as well as those between the panels and other structures is one of the more difficult problems associated with the structures in question. This paper presents the searching for process of optimum geometry of a panel-to-panel joint of longitudinal arrangement, performed by means of the ANSYS software. A configuration was searched for of parameters which can ensure as-low-as possible values of geometrical stress concentration coefficients at acceptable mass and deformations of the structure. Analysis of the obtained results made it possible to propose the optimum geometry of the considered joint.

5

Determination of seakeeping performance for a case study vessel by the strip theory method

63%

Niklas K. , Karczewski A.

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tom 27

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nr 4

6

Określanie rozkładu odkształceń i naprężeń w złączach spawanych stalowych paneli typu sandwicz metodą MES

63%

Kozak J. , Niklas K.

Przegląd Spawalnictwa

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2011

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tom R. 83, nr 4

33-38

PL

Rozwój technologii spawania laserowego umożliwił masową produkcję konstrukcji cienkościennych, w tym również stalowych paneli sandwicz. Technologia wykonywania spoin łączących poszycia paneli z usztywnieniami daje możliwość uzyskania łączenia o szczególnej geometrii i właściwościach materiałowych. Złącza spawane wiązką laserową, w porównaniu ze złączami innego typu, charakteryzują się specyficznym sposobem zachowania pod obciążeniem zmiennym, a w konsekwencji - odmiennym sposobem niszczenia zmęczeniowego. Podstawą analizy zmęczeniowej złącza spawanego było określenie koncentracji naprężeń w karbach. W tym celu zbudowano model numeryczny MES wiązką laserową. W artykule przedstawione zostały kluczowe aspekty modelu numerycznego i wyniki dotyczące wpływu sposobu modelowania na odkształcenia i naprężenia w karbach. Dla karbu w grani spoiny wyniki teoretyczne porównano z danymi eksperymentalnymi rozkładów odkształceń otrzymanymi techniką laserowej ekstensometrii siatkowej.

EN

A development of laser welding technology has enabled mass production of thin-walled structures, including steel sandwich panels. The technology of welding plates with stiffeners results of the joints a specific geometry and material properties. Laser welds in comparison with other types of joints, are characterized by a specific way of behavior under cyclic load, and as a consequence a different way of fatigue damage. The basis of fatigue analysis of laser welded joint was determination of stress concentrations in the notches. For this purpose, a model of numerical FEM laser welded joint was built. The article presents the main aspects of the numerical model and the results concerning the influence of the way of modeling on the deformation and stresses in the notches. For the weld root notch, numerical results with experimental data of strain distributions obtained by the laser extension grid technique are compared.

7

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

63%

Niklas K. , Kozak J.

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2018

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tom 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.