|
|
||
|
|
|
|
Th cracks have various orientations, alpha.
From:
Yoontae Kim (Northeastern University), “Buckling of a cracked cylindrical shell reinforced with an elastic liner”, Master’s thesis, Department of Mechanical Engineering, Northeastern University, Boston, MA, August 2011
ABSTRACT: Shell structures have been widely used in engineering applications such as pipelines, aerospace and marine structures, and cooling towers. Occurring suddenly and generally inadvertently due to its nature, buckling is one of the main failure considerations in the design of these structures. Presence of defects, such as cracks, corrosion pits, blow-out holes, in shell structures may severely compromise their buckling behavior and jeopardize the structural integrity.
In this study, a numerical investigation on the buckling behavior of a cracked cylindrical shell reinforced with an elastic liner and subjected to combined axial compression was carried out. The effect of supporting liner on the buckling behavior of the cracked shell at different crack sizes and orientations were investigated. In the next step, the buckling behavior of a cracked cylindrical shell with an elastic liner subjected to the internal pressure and axial compression was studied. Different buckling modes of the cracked shell, including global, transition and locales modes are identified for different loading conditions.
The results showed that longitudinal crack has a more detrimental effect on the buckling strength of the cylindrical shell in cylinders with no elastomeric liner or with elastomeric liners with low relative stiffness. In addition, cylinders with elastomeric liners of high relative stiffness circumferential crack have a more detrimental effect on the buckling strength of the cylindrical shell.
The finite element analysis also showed that increasing the thickness of the supporting layer or increasing its stiffness, can significantly increase the critical crack size at each angle. The shells reinforced with elastic liners subjected to the internal pressure and axial compression shown that the internal pressure does not affect the overall buckling behavior of perfect cylindrical shells. For circumferential crack, the internal pressure increases the buckling load of the cylindrical shell. In contrast, for longitudinal crack, the internal pressure decreases the buckling load of the cylindrical shell. We found that the critical buckling load of the cracked cylinder with various thicknesses of the elastomeric liner can be expressed at each crack angle by a single parameter, namely stretching stiffness ratio of liner and shell layers.
Page 246 / 444