Wyniki wyszukiwania - BazTech

1

Maximum load carrying capacity estimation of the ship and offshore structures by progressive collapse approach

Ölmez H., Bayraktarkatal E.

Polish Maritime Research

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2016

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nr 3

28--38

EN

The aim of the paper is to represent step by step progressive collapse analysis for maximum load carrying capacity estimation of a hull girder by using variant of Smith Method, named HULT by authors, with different element separation including single plates, stiffeners, hard corners and stiffened panels. The structural elements that form the ships and offshore structures are exposed to large vertical bending moments and especially compression or tension forces in the longitudinal axis in case of hogging and sagging under bad sea conditions. In recent years, it becomes very important and valuable to practically, fast and nearly correct estimation of the maximum vertical bending moment just before breaks in two (collapse) under the worst conditions. The optimum (accuracy, time, practicality) estimation of these values depend on how accurate the stress-strain relation of the structural elements are established. In this first part of study, the ultimate strength behaviour of the stiffened panels in decks, bottoms and sides is estimated by developed semi-analytical method with updated orthotropic panel calculation approach under uniaxial (only longitudinal axis) compression loads. The second part of calculation is focused on the progressive collapse analysis of hull girders under longitudinal uniaxial compression with Smith Method but with different element discretization in contrast to the conventional beam-column elements. Also some benchmark studies of such methods on ultimate limit state assessment of stiffened panels and nine benchmark hull girders of ships are conducted, using some candidate methods such as IACS Common Structural Rules (CSR), FEA with Ansys v13 and HULT prepared by authors. The results from the tests, FEM analysis and different computational approaches are compared to determine performance of the method.

2

Simplified procedure for the free vibration analysis of rectangular plate structures with holes and stiffeners

Cho D. S., Vladimir N., Choi T. M.

Polish Maritime Research

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2015

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nr 2

71--78

EN

Thin and thick plates, plates with holes, stiffened panels and stiffened panels with holes are primary structural members in almost all fields of engineering: civil, mechanical, aerospace, naval, ocean etc. In this paper, a simple and efficient procedure for the free vibration analysis of such elements is presented. It is based on the assumed mode method and can handle different plate thickness, various shapes and sizes of holes, different framing sizes and types as well as different combinations of boundary conditions. Natural frequencies and modes are determined by solving an eigenvalue problem of a multi-degree-of-freedom system matrix equation derived by using Lagrange’s equations. Mindlin theory is applied for a plate and Timoshenko beam theory for stiffeners. The applicability of the method in the design procedure is illustrated with several numerical examples obtained by the in-house developed code VAPS. Very good agreement with standard commercial finite element software is achieved.

3

A study on superplastic forming of multiple sheet with integral stiffeners

Lee H.-S., Yoon J.-H., Yoo J.-T., Choi J.-U.

Inżynieria Materiałowa

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2014

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Vol. 35, nr 2

166--170

EN

Blow molding process is one of the common manufacturing processes in plastic and glass industry. The advantages include low cost of the tool and ability to mold complex part. In metallic system, a similar process like superplastic forming has been widely used in aerospace industry, since it is possible to fabricate very thin part and hence lightweight structure. The present study demonstrates superplastic blow forming process with IN718 and titanium and aerospace components with a complex shape which were successfully manufactured. These metals have been used for high temperature application like lightweight propulsion systems. It is interesting to notice high value of strain rate sensitivity obtained for titanium alloy, while this for IN718 was relatively low at the forming temperature. The result shows that the developed technology to design high temperature superplastic forming by the finite element method can be applied for nearly net shape forming 2-sheet, 3-sheet and 4-sheet stiffened panels for lightweight component of aerospace structure.

PL

Proces formowania przez nadmuchiwanie jest jednym z najpowszechniejszych procesów w przemyśle tworzyw sztucznych i szkła. Zalety tego procesu polegają na niskich kosztach narzędzi oraz zdolnościach do formowania złożonych części. W systemach metalicznych, podobny proces – formowanie nadplastyczne jest szeroko stosowane w przemyśle lotniczym, ponieważ umożliwia otrzymywanie bardzo cienkich grubości materiału a więc struktur lekkiej konstrukcji. Przedstawione studium demonstruje nadplastyczne formowanie przez nadmuchiwanie z wykorzystaniem IN178, tytanu oraz otrzymanie w ten sposób lotniczych komponentów o złożonym kształcie. Te metale są wykorzystane w aplikacjach wysokotemperaturowych takich jak lekkie systemy napędowe. Należy zwrócić uwagę na dużą wrażliwość na szybkość odkształcenia stopów tytanu, podczas gdy dla IN718 jest ona relatywnie niska w temperaturze formowania. Wyniki te pokazują, że rozwinięta technologia procesu projektowania wysokotemperaturowego formowania nadplastycznego za pomocą MES może być stosowana w postaci 2, 3, 4 arkuszowych paneli usztywniających dla lekkich komponentów przemysłu lotniczego.