Mechanics of Confined Thin-Walled Cylinders Subjected to External Pressure

2013 ◽  
Vol 66 (1) ◽  
Author(s):  
Daniel Vasilikis ◽  
Spyros A. Karamanos
Keyword(s):  
Mechanical Response ◽  
Surrounding Medium ◽  
External Pressure ◽  
Numerical Results ◽  
Maximum Pressure ◽  
Imperfection Sensitivity ◽  
Nonlinear Finite Elements ◽  
Good Comparison ◽  
Practical Engineering ◽  
Thin Walled

Motivated by practical engineering applications, the present paper examines the mechanical response of thin-walled cylinders surrounded by a rigid or deformable medium, subjected to uniform external pressure. Emphasis is given to structural stability in terms of buckling, postbuckling, and imperfection sensitivity. The present investigation is computational and employs a two-dimensional model, where the cylinder and the surrounding medium are simulated with nonlinear finite elements. The behavior of cylinders made of elastic material is examined first, and a successful comparison of the numerical results is conducted with available closed-form analytical solutions for rigidly confined cylinders. Subsequently, the response of confined thin-walled steel cylinders is examined. The numerical results show an unstable postbuckling response beyond the point of maximum pressure and indicate severe imperfection sensitivity on the value of the maximum pressure. A good comparison with limited available test data is also shown. Furthermore, the effects of the deformability of the surrounding medium are examined. In particular, soil embedment conditions are examined, with direct reference to the case of buried thin-walled steel pipelines. Finally, based on the numerical results, a comparison is attempted between the present buckling problem and the problem of “shrink buckling.” The differences between those two problems of confined cylinder buckling are pinpointed, emphasizing the issue of imperfection sensitivity.

Buckling Design of Confined Steel Cylinders Under External Pressure

2009 ◽  
Author(s):  
Daniel Vasilikis ◽  
Spyros A. Karamanos
Keyword(s):  
Design Methodology ◽  
Surrounding Medium ◽  
Structural Response ◽  
External Pressure ◽  
Design Guidelines ◽  
Efficient Design ◽  
Imperfection Sensitivity ◽  
Initial Imperfections ◽  
Shell Buckling ◽  
Nonlinear Finite Elements

Thin-walled steel cylinders surrounded by an elastic medium, when subjected to uniform external pressure may buckle. In the present paper, using a two dimensional model with nonlinear finite elements, which accounts for both geometric and material nonlinearities, the structural response of those cylinders is investigated, towards developing relevant design guidelines. Special emphasis is given on the response of the confined cylinders in terms of initial imperfections; those are considered in the form of initial out-of-roundness of the cylinder and as an initial gap between the cylinder and the medium. Furthermore, the effects of the deformability of the surrounding medium are examined. The results indicate significant imperfection sensitivity and a strong dependency on the medium stiffness. The numerical results are employed to develop a simple and efficient design methodology, which is compatible with the recent general provisions of European design recommendations for shell buckling, and could be used for design purposes.

Buckling Design of Confined Steel Cylinders Under External Pressure

2010 ◽  
Vol 133 (1) ◽  
Author(s):  
Daniel Vasilikis ◽  
Spyros A. Karamanos
Keyword(s):  
Design Methodology ◽  
Surrounding Medium ◽  
Structural Response ◽  
External Pressure ◽  
Design Guidelines ◽  
Efficient Design ◽  
Imperfection Sensitivity ◽  
Initial Imperfections ◽  
Shell Buckling ◽  
Nonlinear Finite Elements

Thin-walled steel cylinders surrounded by an elastic medium, when subjected to uniform external pressure may buckle. In the present paper, using a two-dimensional model with nonlinear finite elements, which accounts for both geometric and material nonlinearities, the structural response of those cylinders is investigated, toward developing relevant design guidelines. Special emphasis is given on the response of the confined cylinders in terms of initial imperfections; those are considered in the form of initial out-of-roundness of the cylinder and as an initial gap between the cylinder and the medium. Furthermore, the effects of the deformability of the surrounding medium are examined. The results indicate significant imperfection sensitivity and a strong dependency on the medium stiffness. The numerical results are employed to develop a simple and efficient design methodology, which is compatible with the recent general provisions of European design recommendations for shell buckling and could be used for design purposes.

Buckling of Clad Pipes Under Bending and External Pressure

2011 ◽  
Author(s):  
Daniel Vasilikis ◽  
Spyros A. Karamanos
Keyword(s):  
Numerical Solutions ◽  
Local Buckling ◽  
External Pressure ◽  
Structural Behaviour ◽  
Nonlinear Finite Elements ◽  
Buckling Resistance ◽  
Manufacturing Procedure ◽  
Thin Walled ◽  
Bending Response ◽  
Outer Pipe

The present paper concerns the structural behaviour of clad pipes. This is a double wall pipe, composed by two pipes that are in contact through an appropriate manufacturing procedure; a thick-walled carbon steel “outer pipe”, and a thin-walled corrosion-resistant inner pipe, referred to as “liner” pipe. To predict the bending response and the buckling curvature of the thin-walled liner, it is necessary to account for its contact with the confining thick-walled outer pipe. Because of this confinement, existing numerical solutions or analytical predictions for the bending buckling resistance of unconfined thin-walled tubes are inadequate to predict the buckling resistance of the bent liner. In the present work, the problem is solved numerically, using nonlinear finite elements to simulate the clad pipe, accounting for the interaction between the liner and the outer pipe. First, the manufacturing process of the clad pipe is simulated to determine the liner hoop prestressing. Subsequently, bending curvature is applied (with and without the presence of external pressure). Stresses and strains are monitored throughout the deformation stage with emphasis on possible detachment of the liner from the outer pipe and the formation of local buckling on the liner wall.

scholarly journals Buckling of spherical shells revisited

2016 ◽  
Vol 472 (2195) ◽  
pp. 20160577 ◽  
Author(s):  
John W. Hutchinson
Keyword(s):  
Middle Surface ◽  
External Pressure ◽  
Maximum Pressure ◽  
Imperfection Sensitivity ◽  
Spherical Shells ◽  
Mode Localization ◽  
Axisymmetric State ◽  
New Findings ◽  
Post Buckling ◽  
The 1960S

A study is presented of the post-buckling behaviour and imperfection sensitivity of complete spherical shells subject to uniform external pressure. The study builds on and extends the major contribution to spherical shell buckling by Koiter in the 1960s. Numerical results are presented for the axisymmetric large deflection behaviour of perfect spheres followed by an extensive analysis of the role axisymmetric imperfections play in reducing the buckling pressure. Several types of middle surface imperfections are considered including dimple-shaped undulations and sinusoidal-shaped equatorial undulations. Buckling occurs either as the attainment of a maximum pressure in the axisymmetric state or as a non-axisymmetric bifurcation from the axisymmetric state. Several new findings emerge: the abrupt mode localization that occurs immediately after the onset of buckling, the existence of an apparent lower limit to the buckling pressure for realistically large imperfections, and comparable reductions of the buckling pressure for dimple and sinusoidal equatorial imperfections.

Discussion of “Mechanics of Confined Thin-Walled Cylinders Subjected to External Pressure,” (Vasilikis, D., and Karamanos, S., 2014, Appl. Mech. Rev., 66(1), p. 010801)

2013 ◽  
Vol 66 (1) ◽  
Author(s):  
Arnold M. Gresnigt
Keyword(s):  
Mechanical Properties ◽  
Residual Stresses ◽  
Experimental Test ◽  
Mechanical Response ◽  
External Pressure ◽  
Strain History ◽  
Test Results ◽  
Fabrication Method ◽  
Collapse Pressure ◽  
Thin Walled

The collapse pressure of confined cylinders depends on many factors. In addition to the thorough investigations of Vasilikis and Karamanos, more factors can be candidates for further investigation, such as the effect of variations in the material mechanical properties of the liner pipe in compression and the effect of residual stresses. The mechanical response of the materials in compression depends on the type of steel and the stress-strain history, which depends on the fabrication method of the cylinder. This is illustrated with theoretical and experimental results on pipes under external pressure, as used in offshore applications. There is a need for more experimental test results for validation. More applications of confined cylinders are mentioned that are worth investigation.

Elastic buckling of thin-walled polyhedral pipe liners encased in a circular pipe under uniform external pressure

2018 ◽  
Vol 123 ◽  
pp. 214-221 ◽  
Author(s):  
Zhaochao Li ◽  
Yan Tang ◽  
Fujian Tang ◽  
Yizheng Chen ◽  
Genda Chen
Keyword(s):  
External Pressure ◽  
Circular Pipe ◽  
Elastic Buckling ◽  
Uniform External Pressure ◽  
Thin Walled

Imperfection sensitivity of unstiffened cylindrical shells under external pressure

ce/papers ◽  
2021 ◽  
Vol 4 (2-4) ◽  
pp. 1789-1796
Author(s):  
Esmaeil Azizi ◽  
Natalie Stranghöner
Keyword(s):  
Cylindrical Shells ◽  
External Pressure ◽  
Imperfection Sensitivity

Free Vibration of Thin-Walled Open Section Beams With Unconstrained Damping Treatment

1981 ◽  
Vol 48 (1) ◽  
pp. 169-173 ◽  
Author(s):  
S. Narayanan ◽  
J. P. Verma ◽  
A. K. Mallik
Keyword(s):  
Free Vibration ◽  
Cross Section ◽  
Transverse Vibration ◽  
Natural Frequencies ◽  
Vibration Characteristics ◽  
Numerical Results ◽  
Simply Supported ◽  
Clamped Beams ◽  
Thin Walled ◽  
Open Cross Section

Free-vibration characteristics of a thin-walled, open cross-section beam, with unconstrained damping layers at the flanges, are investigated. Both uncoupled transverse vibration and the coupled bending-torsion oscillations, of a beam of a top-hat section, are considered. Numerical results are presented for natural frequencies and modal loss factors of simply supported and clamped-clamped beams.

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