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Buckle analysis of stiffened panel in AIRBUS 340 500/600
2002 (English)Independent thesis Advanced level (professional degree), 20 credits / 30 HE creditsStudent thesis
Abstract [en]

SAAB develops and manufactures a fuselage sub-assembly in a large commercial aircraft. This sub-assembly includes a structural part called fwd vertical panel. The aim with this master thesis is to decide at what load level the vertical panel becomes unstable for compression loading and to investigate the global behaviour of the panel. Loads from the surrounding structure in a global linear FE-model has been used. The calculations are somewhat conservative due to the complexity of the geometry and loading conditions. A non-linear FE-analysis has already been made on a separate beam included in the sub-assembly, one of the single most important stiffeners of the vertical panel. The results from that analysis is used as verification. A FE-model was created in I-DEAS from an existing geometry model. The mesh was created in the midsurface of the flat vertical panel. The vertical panel was modelled with 8-node parabolic shell elements. The vertical panel consists of several stiffeners with complex geometry. In order to reduce work effort and time, offset-beam elements where used instead of shell elements. This assumption was justified by the fact that only the panel behaviour was to be studied and that beam elements were judged to present a stiffness that well represents the true beam stiffness. Two different load cases were investigated. These load cases subject the panel to a combination of compression, shear and bending. The loads are at ultimate load level. The calculations where performed in ABAQUS. Buckle analyses were performed to study the eigenmodes of the structure. These calculations can give good results on stiff structures, but can be uncertain for a structure like this. Therefore also a static analysis using Riks method with large deformation theory and non-linear material was performed. No imperfections had to be introduced in ABAQUS because of the natural imperfections in the FE-model. The results from the static analysis were considered as reliable. The structure behaves as expected, with a global buckle along the single load path beam supporting the long edge of the panel. A recommendation when using I-DEAS to create a FE-model, is to use shell elements instead of beam element when modelling stiffeners and beams. This simplifies the calculations when large deformations and non-linear materials is taken into account.

Place, publisher, year, edition, pages
Keyword [en]
Technology, Buckle analysis
Keyword [sv]
URN: urn:nbn:se:ltu:diva-50047ISRN: LTU-EX--02/332--SELocal ID: 756684b9-e8c5-4025-9c4d-650df7b4a11eOAI: diva2:1023400
Subject / course
Student thesis, at least 30 credits
Educational program
Mechanical Engineering, master's level
Validerat; 20101217 (root)Available from: 2016-10-04 Created: 2016-10-04Bibliographically approved

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