• Advances in materials Research
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• v.5 no.4
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• pp.205-221
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• 2016

In this article, the buckling responses of functionally graded curved (spherical, cylindrical, hyperbolic and elliptical) shell panels under elevated temperature load are investigated numerically using finite element steps. The effective material properties of the functionally graded shell panel are evaluated using Voigt's micromechanical model through the power-law distribution with and without temperature dependent properties. The mathematical model is developed using the higher-order shear deformation theory in conjunction with Green-Lagrange type nonlinear strain to consider large geometrical distortion under thermal load. The efficacy of the proposed model has been checked and the effects of various geometrical and material parameters on the buckling load are analysed in details.

• Bulletin of the Society of Naval Architects of Korea
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• v.21 no.2
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• pp.19-27
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• 1984

An extension of the finite element method to the stability analysis of shells of revolution under static axisymmetric loading is presented in this paper. A systematic procedure for the formulation of the problem is based upon the principle of virtual work. This procedure results in an eigenvalue problem. For solution, the shell of revolution is discretized into a series of conical frusta. The buckling mode in the circumferential direction is assumed, this assumption makes the problem economical for the computing time. The present method is applied to a number of shells of revolution, under axial compression or lateral pressure, and comparision are made with other theoretical results. The results show good agreement each other. The effects of aspect ratio, boundary conditions and buckling modes on the buckling strength of shells of revolution are studied. Also the optimum shape of cylindrical shell under uniform axial compression is obtained from the view point of structural stability.

• Journal of Advanced Marine Engineering and Technology
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• v.23 no.5
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• pp.702-710
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• 1999

U-shaped bellows are usually used to piping system pressure sensor and controller for refriger-ator. Bellows subjected to internal pressure are designed for the purpose of absorbing deformation. Internal pressure on the convolution sidewall and end collar will be applied to an axial load tend-ing to push the collar away from the convolutions. To find out deformation behavior of bellow sub-jected to internal pressure the axisymmetric shell theory using the finite element method is adopted in this paper. U-shaped bellows can be idealized by series of conical frustum-shaped ele-ments because it is axisymmetric shell structure. The displacements of nodal points due to small increment of force are calculated by the finite element method and the calculated nodal displace-ments are added to r-z cylindrical coordinates of nodal points. The new stiffness matrix of the sys-tem using the new coordinates of nodal points is adopted to calculate the another increments of nodal displacement that is the step by step method is used in this paper. The force required to deflect bellows axially is a function of the dimensions of the bellows and the materials from which they are made. Spring constant is analyzed according to the changing geometric factors of U-shaped bellows. The FEM results were agreed with experiment. Using developed FORTRAN PROGRAM the internal pressure vs. deflection characteristics of a particu-lar bellows can be predicted by input of a few factors.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.26 no.11
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• pp.2245-2252
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• 2002

Design sensitivity analysis scheme is proposed in an elasto -plastic finite element method with explicit time integration using a direct differentiation method. The direct differentiation is concerned with large deformation, the elasto-plastic constitutive relation, shell elements with reduced integration and the contact scheme. The design sensitivities with respect to the process parameter are calculated with the direct analytical differentiation of the governing equation. The sensitivity results obtained from the present theory are compared with that obtained by the finite difference method in a class of sheet metal forming problems such as hemi-spherical stretching and cylindrical cup deep-drawing. The result shows good agreement with the finite difference method and demonstrates that the preposed sensitivity calculation scheme is a pplicable in the complicated sheet metal forming analysis and design.

• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 1998.03a
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• pp.28-31
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• 1998

Wrinkling is one of the major defects in sheet metal products and may be also attributable to the wear of the tool. The initiation and growth of the wrinkles are influenced by many factors such as stress state, mechanical properites of the sheet material, geometry of the body, and contact condition. It is difficult to analyze the wrinkling initiation and growth considering the factors because the effects of the factors are very complex and the wrinkling behavior may show wide variation for small deviation of the factors. In this study, the bifurcation theory is introduced for the finite element analysis of wrinkling initiation and growth, All the above mentioned factors are conveniently considered by finite element method. The finite element formulation is based on the incremental deformation theory and elastic-plastic material modeling. The finite element analysis is carried out using the continuum-based resultant shell elements considering the planar anisotropy of the sheet metal. The proposed method is verified by employing to column buckling problem. And then, the initiation and growth of wrinkling in deep drawing of cylindrical cup are analyzed.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.16 no.3
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• pp.2263-2271
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• 2015

The thin cylindrical shell structure under compression should be checked with buckling stability. Initial imperfection effects on buckling strength has been investigated by many researchers. Even though there have been a number of these studies, more studies of buckling strength with various initial imperfections are still necessary. In Eurocode, there is a design parameter that is applicable only on specific imperfection by section thickness rather than on various initial imperfection. In this study, structural analyses, using geometry and material nonlinear analysis, of cylindrical buckling strength with various initial imperfection were performed and compared with Eurocode design strength and Finite Element Method (FEM) analysis results. Moreover, the modified design parameter, which gives more exact prediction result of buckling strength under bending with initial imperfection, is proposed for various initial imperfections.

• Journal of Korean Society of Steel Construction
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• v.11 no.4 s.41
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• pp.373-384
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• 1999

The shell structures with composite materials have the advantages in strength, corrosion resistance, and weight reduction. The objective of this study is to analyze anisotropic composite circular cylindrical shells with shear deformation theory. In applying numerical methods to solve differential equations of anisotropic shells, this paper use finite difference method. The accuracy of the numerical method can be improved by taking higher order of interval ${\Delta}$ to reduce error. This study compares the results of finite difference method with the results of ANSYS based on finite element method. Several numerical examples show the advantages of the stiffness increasement when the composite materials aroused. Therefore, it is expected that results of this study give various guides for change of the subtended angles, load cases, boundary conditions, and side-to-thickness ratio.

• Proceedings of the Korean Society of Marine Engineers Conference
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• 2005.11a
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• pp.212-213
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• 2005

The results of an experimental and analytical study of composite pressure hull on buckling pressure are presented for URN 300. We predicted the buckling and post buckling analysis of composite laminated cylindrical shell and panel under external compression by using ABAQUS/Standard[Ver 6.4]. To obtain nonlinear static equilibrium solutions for unstable problems, where the load-displacement response can exhibit the type of nonlinear buckling behavior, during periods of the response, the load and/or the displacement may decrease as the solution evolves, used the modified Riks method. Experiments were conducted to verify the validation of present analysis for cross-ply laminated shells. The shells considered in the study have four different lamination patterns, [${\pm}{\Theta}$/0/90]$_{14s}$,[${\pm}{\Theta}_{14}$/$0_{14}$/$90_{14}$],[${\pm}$45/0/90]$_{18s}$ and [/0/90]$_{18s}$. At the result of this study, the optimized ply orientation angle is $75^{\circ}$. The critical load from experiment is 69% of that of numerical analysis, because the fracture of matrix was generated before buckling. So URN 300 is not proper to use at the condition under high external pressure.

• Journal of the Computational Structural Engineering Institute of Korea
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• v.17 no.2
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• pp.193-201
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• 2004

The aim of this study is focused on getting an almost exact solution which is the simplicity and exactness of an axisymmetrically loaded cylindrical shell. This method replaces the finite element method which is a very powerful tool for analysis of any kind of structure which has an arbitrary shape, but is still a numerical analysis. Instead, this study uses the method of distribution of end actions which is a kind of iteration technique to implement the leading matrix method. The distribution and carry-over factors of a cylinder are calculated by the theory of a differential equation of a beam on an elastic foundation. The results are satisfactory when this method is applied to a cylinder that is subjected to a concentrated load and hydrostatic pressure when compared with the BEF analogy separately.

• Steel and Composite Structures
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• v.20 no.1
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• pp.147-166
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• 2016

The paper presents comprehensive quasi-static stability analysis results for a real funnel-flow cylindrical steel silo composed of horizontally corrugated sheets strengthened by vertical thin-walled column profiles. Linear buckling and non-linear analyses with geometric and material non-linearity were carried out with a perfect and an imperfect silo by taking into account axisymmetric and non-axisymmetric loads imposed by a bulk solid following Eurocode 1. Finite element simulations were carried out with 3 different numerical models (single column on the elastic foundation, 3D silo model with the equivalent orthotropic shell and full 3D silo model with shell elements). Initial imperfections in the form of a first eigen-mode for different wall loads and from 'in-situ' measurements with horizontal different amplitudes were taken into account. The results were compared with Eurocode 3. Some recommendations for the silo dimensioning were elaborated.