• 대한기계학회논문집
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• 제19권6호
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• pp.1439-1450
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• 1995

Bellows is a familiar component in piping systems as it provides a relatively simple means of absorbing thermal expansion and providing system flexibility. In routine piping flexibility analysis by finite element methods, bellows is usually considered to be straight pipe runs modified by an appropriate flexibility factor; maximum stresses are evaluated using a corresponding stress concentration factor. The aim of this study is to develop a bellows finite element, which similarly includes more complex shell type deformation patterns. This element also does not require flexibility or stress factors, but evaluates more detailed deformation and stress patterns. The proposed bellows element is a 3-D, 2-noded line element, with three degrees of freedom per node and no bending. It is formulated by including additional 'internal' degrees of freedom to account for the deformation of the bellows corrugation; specifically a quarter toroidal section of the bellows, loaded by axial force, is considered and the shell type deformation of this is include by way of an approximating trigonometric series. The stiffness of each half bellows section may be found by minimising the potential energy of the section for a chosen deformation shape function. An experiment on the flexibility is performed to verify the reliability for bellows finite element.

• Progress in Superconductivity
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• 제3권2호
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• pp.183-187
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• 2002

In this paper we analyzed the electromagnetic behavior of high $-T_{c}$ superconductor under the quench state using finite element method. Poisson equation was used in finite element analysis as a governing equation and was solved using algebra equation using Gallerkin method. We first investigate d the electromagnetic behavior of U-type superconductor. Finally we applied our analysis techniques to 5.5 kVA meander-line superconducting fault current limiters (SFCL) which are currently developed by many power-system researcher in the world. Meshes of 14,600 elements were used in analysis of this SFCL. Analysis results show that the distribution of current density was concentrated to inner curvature in meander-line type-superconductors and maximum current density 14.61 $A/\m^2$ and also maximum Joule heat was 6,420 W/㎥. We concluded that this meander line-type SFCL was not pertinet fur uniform electromagnetic field distribution.n.

• Journal of electromagnetic engineering and science
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• 제3권2호
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• pp.126-132
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• 2003

In this paper, a coupled-line type waveguide bandpass filter is newly proposed. The proposed bandpass filter configuration consists of magnetically coupled waveguide cavities. In order to show the background of the proposed waveguide bandpass filter, the general coupled line TEM bandpass filter theory, which means the coupled line filter with arbitrary coupled line length and impedance level, will be briefly introduced. Calculations for the even- and odd-mode wave impedance of a coupled line waveguide structure are achieved based on the normalized impedance concept for a broad-side coupled waveguides by using vector finite element method(VFEM) calculation. Measured result of an implemented coupled-line type waveguide filter is presented.

• Structural Engineering and Mechanics
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• 제6권6호
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• pp.633-641
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• 1998

Finite element solutions are presented for the optimal design of symmetrically laminated rectangular plates with various types of internal line supports. These plates are subject to a combination of simply supported, clamped and free boundary conditions. The design objective is the maximisation of the biaxial buckling load. This is achieved by determining the fibre orientations optimally with the effects of bending-twisting coupling taken into account. The finite element method coupled with an optimisation routine is employed in analysing and optimising the laminated plate designs. The effect of internal line support type and boundary conditions on the optimal ply angles and the buckling load are numerically studied. The laminate behavior with respect to fibre orientation changes significantly in the presence of internal line supports as compared to that of a laminate where there is no internal supporting. This change in behavior has significant implications for design optimisation as the optimal values of design variables with or without internal supporting differ substantially.

• 한국정밀공학회:학술대회논문집
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• 한국정밀공학회 1995년도 춘계학술대회 논문집
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• pp.620-625
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• 1995

Finite element analysis tool was developed to analyze the casting process. Generally, casting processes consists of mold filling and solifification. In order to investigate the effects of process variables and to predict the defects, both filling and solidiffication process were simulated simultaneously. At filling process, especiallywe consider thermal coupling to investigate thermal history of material during the filling stage. And thermal condition at the final stage of filling is used as the initial conditions in a solidification process for the exact simulation of the actual casting processes. At mold filling process, Lagrangian-type finite element method with automatic remashing scheme was used to find the material flow. To avoid numerical instability in low viscous fluid, a perturbation method with artificial viscosity is adopted. At solififfication process, enthalpy-based finite element method was used to solve the heat transfer problem with phase change. And elastic stress analysis has been performed to predict the thermal residual stress. Through the FE analysis, solidiffication time, position of solidus line, liquidus line and thermal residual stress are studied. Finite element tools developed in this study will be used process design of casting process and maybe basic structure for total CAE system of castigs which will be constructed afterward.

• 한국정밀공학회지
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• 제13권3호
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• pp.110-122
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• 1996

Finite element analysis tool was developed to analyze the casting process. Generally, casting process consists of mold filling and solidification. Both filling and solidication process were simulated simultaneously to investigate the effects of process variables and to predict the defect. At filling process, thermal coupling was especially considered to investigate thermal history of material during the filling stage. And thermal condition at the final stage of filling is used as the initial conditions in a solidification process for the exact simullation of the actual casting processes. At mold filling process, Lagragian-type finite element method with automatic remeshing scheme was used to find the material flow. A perturbation method with artificial viscosity is adopted to avoid numerical instability in low viscous fluid. At solidification process, enthalpy-based finite element method was used to solove the heat transfer problem with phase change. And elastic stress analysis has been performed to predict the thermal residual stress. Through the FE analysis, solidification time, position of solidus line, liquidus line and thermal residual stress are found. Through the study, the importance of combined analysis has been emphasized. Finite element tools developed in this study will be used process design of casting process and may be basic structure for total CAE system of castings which will be constructed afterward.

• 한국소성가공학회:학술대회논문집
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• 한국소성가공학회 1996년도 추계학술대회논문집
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• pp.20-28
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• 1996

An Eulerian finite element method for the analysis of steady state rolling/extrusion of sintered powder metals is presented. Initial guess of the porosity distribution in an Eulerian mesh is obtained from the velocity and scaled pressure field computed by the Consistent Penalty finite element formulations-the standard one and the consistent penalty type one-are invoked for the analysis of strain hardening, dilatant viscoplastic deformation of porous metals. Comparisons of the predicted distributions of porosity to those by a Lagrangian finite element method and by experiments reported in the articles prove the effectiveness and validity of the proposed method.

• 한국전산구조공학회:학술대회논문집
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• 한국전산구조공학회 1996년도 봄 학술발표회 논문집
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• pp.62-69
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• 1996

In this study, an equivalent domain integral (EDI) method is presented to estimate the track-till integral parameter, J-value, for two dimensional cracked elastic bodies which may quantify the severity of the crack-tit) stress fields. The conventional J-integral method based on line integral has been converted to equivalent area or domain integrals by using the divergence theorem. It is noted that the EDI method is very attractive because all the quantities necessary for computation of the domain integrals are readily available in a finite element analysis. The details and its implementation are extened to both h-version finite element model with 8-node isoparametric element and p-version finite element model with high order hierarchic element using Legendre type shape fuctions. The variations with respect to the different path of domain integrals from the crack-tip front and the choice of 5-function have been tested by several examples.

• 한국공간구조학회논문집
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• 제12권4호
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• pp.57-69
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• 2012

This study investigated the behaviors of the gabled hyperbolic paraboloid shell structure subjected to differential settlement and the horizontal displacement due to the elongation of tie rod/beam on supports. Two types of shell structure with different roof slopes are used in study; conventional type which has perimeter beams around the shell panel, and simple type which removes the edge beams along the slab edge line. The effect of the removal of edge beam under vertical or horizontal displacement on supports, and the roof slope was compared using the finite element analysis.

• 한국강구조학회 논문집
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• 제16권2호통권69호
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• pp.257-265
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• 2004

line-type 유한요소법을 이용하여 불균등 단부 모멘트를 받는 보의 비탄성 좌굴 거동에 대하여 연구하였다. 잔류응력은 단순형과 다항식형 모델을 채택하였으며 잔류응력으로 인해 발생하는 단면의 불균등 항복을 고려하였다. 본 연구에서 얻어진 비탄성 횡-비틀림 좌굴에 대한 결과는 강구조편람의 허용응력법에 의한 설계 경우와 비교하였다. 결과적으로, 강구조편람에 의한 설계는 중지간 보에서 중간 브레이싱이 있는 경우나 없는 경우 모두 과설계가 됨을 알 수 있었다.