• 한국전산구조공학회:학술대회논문집
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• 한국전산구조공학회 2001년도 봄 학술발표회 논문집
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• pp.197-204
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• 2001

The purpose of this paper is to develope the evaluation technique to find proper elastic constants that characterize the material nonlinearity of structural membrane. The stress-strain curves of membrane material show strong nonlinearity. But generally the analysis is carried out under the assumption on material linear and geometrical nonlinear method. Because, it is very difficult to evaluate proper tangential stiffness. This paper use multi-step-linear approximation method taking the concept of effective stress for the evaluation of stiffness of membrane material, and then compare the results between linear and nonlinear analysis. Also. it shows better results than linear method

• Nuclear Engineering and Technology
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• 제47권7호
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• pp.859-866
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• 2015

The aim of this work is to investigate the transport mechanism of radioactive nuclides through the reverse osmosis (RO) membrane and to estimate its effectiveness for nuclide separation from radioactive liquid waste. An analytical model is developed to simulate the RO separation, and a series of experiments are set up to confirm its estimated separation behavior. The model is based on the extended Nernst-Plank equation, which handles the convective flux, diffusive flux, and electromigration flux under electroneutrality and zero electric current conditions. The distribution coefficient which arises due to ion interactions with the membrane material and the electric potential jump at the membrane interface are included as boundary conditions in solving the equation. A high Peclet approximation is adopted to simplify the calculation, but the effect of concentration polarization is included for a more accurate prediction of separation. Cobalt and cesium are specifically selected for the experiments in order to check the separation mechanism from liquid waste composed of various radioactive nuclides and nonradioactive substances, and the results are compared with the estimated cobalt and cesium rejections of the RO membrane using the model. Experimental and calculated results are shown to be in excellent agreement. The proposed model will be very useful for the prediction of separation behavior of various radioactive nuclides by the RO membrane.

• 한국소음진동공학회논문집
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• 제12권3호
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• pp.221-227
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• 2002

The longitudinal and lateral in-plane vibrations of an axially moving membrane are investigated when the membrane has translating acceleration. By extended Hamilton's principle, the governing equations are derived. The equations of motion for the in-plane vibrations are linear and coupled. These equations are discretized by using the Galerkin approximation method after they are transformed into the variational equations, j.e., the weak forms so that the admissible functions can be used for the bases of the in-plane deflections. With the discretized equations for the in-plane vibrations, the natural frequencies and the time histories of the deflections are obtained.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2001년도 춘계학술대회논문집B
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• pp.613-617
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• 2001

The longitudinal vibration of an axially moving membrane is studied when the membrane has translating acceleration. The equation for the longitudinal vibration is linear and coupled, The equation for the longitudinal vibration are discretized by using the Galerkin approximation after they are transformed into the variational equations, i.e., the weak forms so that the admissible function can be used for the bases of the longitudinal deflection. With the discretized equations for the longitudinal vibration, the time responses are investigated by using newmark method.

• 한국공간구조학회논문집
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• 제6권1호
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• pp.117-127
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• 2006

경량 연성구조시스템 중 하나인 막 구조물은 대공간 구조물에 많이 사용되어진다. 막 구조물은 축강성이 강하고 휨강성이 매우 작은 재료를 주 구조재로 사용하기 때문에 다른 구조물과 달리 구조설계에서는 형상해석, 응력-변형해석 그리고 재단도 등의 일련의 과정을 필요로 한다. 재단도의 작성에는 구조물의 크기나 곡률 그리고 재료적 강성에 따라 많은 변수가 작용하며 다른 설계과정과는 매우 다르다. 따라서 일반 구조설계용 프로그램은 막 구조물의 구조설계에 부적당하다. 본 연구에서는 막 구조물의 측지선을 이용한 재단도 작성 프로그램을 개발하고, 예제를 통해 재단도 작성결과를 비교 고찰하도록 한다.

• Journal of applied mathematics & informatics
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• 제27권1_2호
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• pp.441-452
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• 2009

In this paper, a fifth order numerical method is presented for solving singularly perturbed differential-difference equations with negative shift. In recent papers the term negative shift has been using for delay. Similar boundary value problems are associated with expected first exit time problem of the membrane, potential in models for neuron and in variational problems in control theory. In the numerical treatment for such type of boundary value problems, first we use Taylor approximation to tackle terms containing small shifts which converts it to a boundary value problem for singularly perturbed differential equation. The two point boundary value problem is transformed into general first order ordinary differential equation system. A discrete approximation of a fifth order compact difference scheme is presented for the first order system and is solved using the boundary conditions. Several numerical examples are solved and compared with exact solution. It is observed that present method approximates the exact solution very well.

• 소성∙가공
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• 제1권1호
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• pp.95-103
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• 1992

The plane strain analysis for simulating the stretch/draw forming operation with an arbitrarily-shaped tool profile is introduced. An implicit, incremental, updated Lagrangian formulation with a rigid-viscoplastic constitutive equation is employed. Contact and friction are considered through the mesh-normal, which compatibly describes arbitrary tool surfaces and FEM meshes without depending on the explicit spatial derivatives of tool surfaces. The linear line elements are used for depicting the formed sheet, based on membrane approximation. The FEM formulation is tested in the sections of automotive inner panel and two-side draw-in. Not only the excellent agreement between measured and computed strains is obtained in the stretched section, but also the numerical stability of formulation is verified in the draw-in section.

• 대한수학회지
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• 제36권2호
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• pp.299-316
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• 1999

We consider two finite difference approxiamations to a singular boundary value problem arising in the study of a nonlinear circular membrane under normal pressure. It is shown that the rates of convergence are O(h) and O($h^2$), respectively. An iterative scheme is introduced which converges to the solution of the finite difference equations. Finally the numerical experiments are given

• 한국소성가공학회:학술대회논문집
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• 한국소성가공학회 1995년도 춘계학술대회논문집
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• pp.155-161
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• 1995

Superplastic forming/diffusion bonding(SPF/DB) processes are analyzed using a rigid visco-plastic finite element method. The optimum pressure-time relationship for a target strain rate and thickness distributions were predicted using two-node line element based on membrane approximation for plane strain shapes. Material behavior during SPF/DB of the integral structures with complicated shapes are investigated. The tying condition is employed for the analysis inter-sheet contact problems. A movement of rib structure is successfully prodicted during the forming.

• 소성∙가공
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• 제5권1호
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• pp.37-46
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• 1996

Superplastic forming/diffusion bonding (SPF/DB) processes were analyzed using a rigid visco-plastic finite element method. The optimum pressure-time relationship for a target strain rate and thickness distributions were predicted by two-node line elements based on the membrane approximation for plane strain. Material behavior during SPF/DB of the integral structures having complicated shapes was investigated. The tying condition is employed for the analysis of inter-sheet contact problems. A movement of rib structure is successfully predicted during the forming.