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Long pipe nonlinear moment-curvature curve with bifurcation points & early post-bifurcation wrinkling

FROM:
S. Houliara and S.A. Karamanos (Department of Mechanical and Industrial Engineering, University of Thessaly, Volos 38334, Greece),

“Buckling and post-buckling of long pressurized elastic thin-walled tubes under in-plane bending”, International Journal of Non-Linear Mechanics, Vol. 41, No. 4, May 2006, pp. 491-511, doi:10.1016/j.ijnonlinmec.2005.11.002

ABSTRACT: The present paper focuses on the structural stability of long uniformly pressurized thin elastic tubular shells subjected to in-plane bending. Using a special-purpose non-linear finite element technique, bifurcation on the pre-buckling ovalization equilibrium path is detected, and the post-buckling path is traced. Furthermore, the influence of pressure (internal and/or external) as well as the effects of radius-to-thickness ratio, initial curvature and initial ovality on the bifurcation moment, curvature and the corresponding wavelength, are examined. The local character of buckling in the circumferential direction is also demonstrated, especially for thin-walled tubes. This observation motivates the development of a simplified analytical formulation for tube bifurcation, which considers the presence of pressure, initial curvature and ovality, and results in closed-form expressions of very good accuracy, for tubes with relatively small initial curvature. Finally, aspects of tube bifurcation are illustrated using a simple mechanical model, which considers the ovalized pre-buckling state and the effects of pressure.

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