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 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.

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 Analysis of Afterburner Liner of an Aero Gas Turbine Engine

2009 ◽  
Author(s):  
Sri Shanti Potluri ◽  
Surendra Kumar Patel
Keyword(s):  
Design Methodology ◽  
External Pressure ◽  
Dominant Mode ◽  
Efficient Design ◽  
Fighter Aircraft ◽  
Turbine Engine ◽  
Aero Engine ◽  
Loading System ◽  
Low Stiffness ◽  
Main Components

The afterburner in an aero-engine is employed for augmentation of the basic thrust of the engine to improve the fighter aircraft take-off, climb and combat performance. The liner forms one of the main components of the afterburner system. Buckling is a dominant mode of failure for the afterburner structure due to its inherent slender geometry and external pressure loading system in addition to low stiffness due to high temperature. This paper deals with design aspects involved in the afterburner structure — the augmenter liner where combustion takes place during reheat. The liner therefore experiences high thermal loads, variable differential pressure and severe loads as encountered during an engine flameout condition. This paper describes the approach adopted for the design of an afterburner liner for buckling strength which assures safety and producibility by fulfillment of design and fabrication constraints. The design methodology is validated through flame out test on full-scale component. Further in pursuit of weight efficient design, the liner configuration with corrugations is attempted.

The Influence of Stochastic Imperfection Field on the Bearing Capacity of Hyperbolic Cooling Towers

2011 ◽  
Vol 374-377 ◽  
pp. 2297-2300
Author(s):  
Hai Zhao ◽  
Ya Zhou Xu ◽  
Guo Liang Bai
Keyword(s):  
Bearing Capacity ◽  
Large Scale ◽  
Initial Imperfection ◽  
Orthogonal Basis ◽  
Imperfection Sensitivity ◽  
Stochastic Field ◽  
Buckling Mode ◽  
Material Inhomogeneity ◽  
Initial Imperfections ◽  
Distribution Form

The uncontrollable factors such as construction errors, material inhomogeneity, etc. will inevitably lead to a certain initial imperfections. It is generally known that the stochastic initial imperfection of the structure is an important factor for affecting structural stability and bearing capacity. Since these imperfections are random in nature, this paper proposes the method mainly based on the standard orthogonal basis to expand the stochastic field, taking into account the decomposition of the stochastic initial imperfections related to structures, which is projected in the buckling mode orthogonal basis. In the end, the article by the stability analysis example shows that this method can use less random variables effectively describing the original stochastic imperfection field, and efficiently search for the most unfavorable initial imperfection distribution form in order to ensure the imperfection sensitivity structures have a higher reliability, so it can be applied to large-scale engineering structure stochastic imperfection analysis.

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

Novel games can come from novice game makers

2017 ◽  
Vol 25 (4) ◽  
pp. 250-252
Author(s):  
Mark Chen
Keyword(s):  
Game Design ◽  
Design Methodology ◽  
Interactive Media ◽  
Design Guidelines ◽  
Content Type

Purpose This paper aims to describe how a novice to game design pushed theory about what makes a good game. Design/methodology/approach The game in question was developed in Twine for an introductory undergraduate course in interactive media. Findings It featured very little player agency, which ironically served to give players a richer experience. Originality/value That a novice could create something deeply personal that butted against conventional game design guidelines highlights the importance of opening game design up to as broad an audience as possible.

Periodic controller for guaranteed simultaneous stabilization of two plants with robust zero error tracking

2018 ◽  
Vol 233 (5) ◽  
pp. 480-490
Author(s):  
Arindam Chakraborty ◽  
Jayati Dey
Keyword(s):  
Design Methodology ◽  
Linear Time ◽  
Pole Placement ◽  
Control Input ◽  
Efficient Design ◽  
Simultaneous Stabilization ◽  
Bounded Control ◽  
Linear Time Invariant ◽  
Time Invariant ◽  
Time Periodic

The guaranteed simultaneous stabilization of two linear time-invariant plants is achieved by continuous-time periodic controller with high controller frequency. Simultaneous stabilization is accomplished by means of pole-placement along with robust zero error tracking to either of two plants. The present work also proposes an efficient design methodology for the same. The periodic controller designed and synthesized for realizable bounded control input with the proposed methodology is always possible to implement with guaranteed simultaneous stabilization for two plants. Simulation and experimental results establish the veracity of the claim.

Clamped torispherical shells under external pressure — some new results

1988 ◽  
Vol 23 (1) ◽  
pp. 9-24 ◽  
Author(s):  
J Blachut ◽  
G D Galletly
Keyword(s):  
Failure Mode ◽  
External Pressure ◽  
Spherical Cap ◽  
Geometric Imperfections ◽  
Collapse Pressure ◽  
Modes Of Failure ◽  
Shell Buckling ◽  
Bifurcation Buckling ◽  
Initial Geometric Imperfections ◽  
The One

Perfect clamped torispherical shells subjected to external pressure are analysed in the paper using the BOSOR 5 shell buckling program. Various values of the knuckle radius-to-diameter ratio ( r/D) and the spherical cap radius-to-thickness ratio ( Rs/ t) were studied, as well as four values of σyp, the yield point of the material. Buckling/collapse pressures, modes of failure and the development of plastic zones in the shell wall were determined. A simple diagram is presented which enables the failure mode in these shells to be predicted. The collapse pressures, pc, were also plotted against the parameter Λs (√( pyp/ pcr)). When the controlling failure mode was axisymmetric yielding in the knuckle, the collapse pressure curves depended on the value of σyp, which is unusual. However, when the controlling failure mode was bifurcation buckling (at the crown/knuckle junction), the collapse pressure curves for the various values of σyp all merged, i.e., they were independent of σyp. This latter situation is the one which normally occurs with the buckling of cylindrical and hemispherical shells. A limited investigation was also made into the effects of axisymmetric initial geometric imperfections on the strength of externally-pressurised torispherical shells. When the failure mode was axisymmetric yielding in the knuckle, initial imperfections of moderate size did not affect the collapse pressures. In the cases where bifurcation buckling at the crown/knuckle junction occurred, small initial geometric imperfections at the apex did not affect the buckling pressure, but axisymmetric imperfections at the buckle location did influence it. With the other failure mode (i.e., axisymmetric yielding collapse at the crown of the shell), initial geometric imperfections caused a reduction in the torisphere's strength.

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