• 산업기술연구
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• 제18권
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• pp.131-138
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• 1998

Numerical modeling for electromagnetic exploration methods are essential to understand behaviours of electromagnetic fields in complex subsurfaces. In this study, a finite element method was adopted as a numerical scheme for the 2.5-dimensional forward problem. And a finite element equation considering linear conductivity variation was proposed when 2.5-dimensional differential equation to couple eletric and magnetic field was implemented. Model parameters were investigated for near-field with large source effects and far-field with responses dominantly by homogeneous half-space. Numerical responses by this study were compared with analytic solutions in homogeneous half-space and compared with other three dimensional numerical results.

• 한국지반공학회:학술대회논문집
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• 한국지반공학회 2001년도 봄 학술발표회 논문집
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• pp.577-584
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• 2001

For construction and design of tunnels, groundwater flow models are used to find the influence of groundwater to the stability of tunnels considering the geological condition around the tunnels and the materials used in tunnel linings. For the analysis of tunnel flow, some commercial programs, e.g. MODFLOW, SEEP/W etc., are used. These programs have limitations that MODFLOW could not define curved surface smoothly in three dimensional flow media and SEEP/W is the 2-dimensional flow model. In this paper, the ability of a finite element program developed for analyzing 3-dimensional groundwater flow is examined. Confined steady state groundwater flow solution in non-homogeneous media is obtained using isoparametric element with eight trilinear hexahedron nodes and is compared with the result of MODFLOW. It was found that the solution yielded a good result with the three dimensional flow studied.

• 소성∙가공
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• 제4권1호
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• pp.39-47
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• 1995

The compression molding of SMC (sheet molding compund) at room temperature was analyzed based on rigid-viscoplastic approach by three dimensional finite element program. The developed program was tested by solving the three dimensional compression of wedge type specimens of aluminum alloys at various processing conditions. The simulation results were compared well to the experimental results available in the literature. based on this comparison the program was proved to be valid and was further applied in solving compression molding of SMC, which is a thermosetting material reinforced with chopped fiber glass. To investigate the effects of friction conditions and mold closing speeds for compression molding of SMC charge at room temperature, compressions of the cylindrical and rectangular shaped SMC were analyzed for various friction conditions and mold closing speeds. The calculated load values were compared to the experimental results for the compression molding of cylindrical specimen.

• 한국정밀공학회:학술대회논문집
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• 한국정밀공학회 1993년도 추계학술대회 논문집
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• pp.482-487
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• 1993

A prediction method for determining the welding residual stress by artificial neural network is proposed. A three-dimensional transient thermomechanical analysis has been performed for the CO $_{2}$ Arc Welding using the finite element method. The validity of the above results is demonstrated by experimental elastic stress relief method which is called Holl Drilling Method. The first part of numarical analysis performs a three-dimensional transient heat transfer anslysis, and the second part then uses results of the first part and performs a three-dimensional transient thermo-clasto-plastic analysis to compute transient and residual stresses in the weld. Data from the finite element method were used to train a backpropagation neural network to predict residual stress. Architecturally, the finite element method were used to train a backpropagation voltage and the current, a hidden layer to accommodate failure mechanism mapping, and an output layer for residual stress. The trained network was then applied to the prediction of residual stress in the four specimens. The results of predicted residual stress have been very encouraging.

• Wind and Structures
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• 제1권2호
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• pp.127-144
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• 1998

In this paper, the wake structures behind a square cylinder at the Reynolds number of 22,000 are simulated using the large eddy simulation, and the main features of the wake structure associated with unsteady vortex-shedding are investigated. The Smagorinsky model is used for parametrization of the subgrid scales. The finite element method with isoparametric linear elements is employed in the computations. Unsteady computations are performed using the explicit method with streamline upwind scheme for the advection term. The time integration incorporates a subcycling strategy. No-slip condition is enforced on the wall surface. A comparative study between two-and three-dimensional computations puts a stress on the three-dimensional effects in turbulent flow simulations. Simulated three-dimensional wake structures are compared with numerical and experimental results reported by other researchers. The results include time-averaged, phase-averaged flow fields and numerically visualized vortex-shedding pattern using streaklines. The results show that dynamics of the vortex-shedding phenomenon are numerically well reproduced using the present method of finite element implementation of large eddy simulation.

• Nuclear Engineering and Technology
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• 제54권12호
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• pp.4522-4533
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• 2022

For severe accident assessment of reactor pressure vessel (RPV), it is important to develop an accurate model that can predict transient thermo-mechanical behavior of the RPV lower head under the given condition. The present study revisits the lower head failure with two- and three-dimensional finite element models. In particular, we aim to give clear insight regarding the effect of the three-dimensionality present in the distribution of the thickness and thermal load of the lower head. For a rigorous validation of the result, both the OLHF-1 and the OLHF-2 tests are considered in this study. The result suggests that the three-dimensional effect is not negligible as far as the failure location is concerned. The non-uniformity of the thickness distribution is found to affect the failure location and time. The thermal load, which may not be axisymmetric in general, has the most significant effect on the failure assessment. We also observe that the creep property can affect the global deformation of the lower head, depending on the applied mechanical load.

• 대한전기학회:학술대회논문집
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• 대한전기학회 1987년도 전기.전자공학 학술대회 논문집(II)
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• pp.1288-1291
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• 1987

An finite element code has been developed to calculate current flowing through an 8-node trilinear cubic element from the calculated potentials on the eight node. This code was implemented to the three-dimensional thoracic model for impedance cardiography to find the total currents in the z-direction flowing through the layers which are parallel to x-y plane. The accuracy of the total current was estimated from its variation among the layers. It was found that the accuracy of the total currents in the layers was less than 0.6%.

• 한국전산구조공학회:학술대회논문집
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• 한국전산구조공학회 1993년도 봄 학술발표회논문집
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• pp.117-124
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• 1993

The Neumann Expansion method has been used for evaluating the response variability of three dimensional truss structure resulting from the spatial variability of material properties with the aid of the finite element method, and in conjunction with the direct Monte Carlo simulation methods. The spatial variabilites are modeled as three-dimensional stochastic field. Yamazaki 〔1〕 has extended the Neumann Expansion method to the plane-strain problem to obtain the response variability of 2 dimensional stochastic systems. This paper presents the extension of the Neumann Expansion method to 3 dimensional stochastic systems. The results by the NEM are compared with those by the deterministic finite element analysis and by the direct Monte Carlo simulation method

• 대한기계학회:학술대회논문집
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• 대한기계학회 2004년도 추계학술대회
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• pp.124-129
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• 2004

Finite element alternating method have been suggested and used for assessing the integrity of cracked structures. In the paper, in order to analyze arbitrarily shaped three dimensional cracks, the finite element alternating method is extended. The cracks are modeled as a distribution of displacement discontinuities by the displacement discontinuity method and the symmetric Galerkin boundary element method. Applied the proposed method to three dimensional crack included in the elbow, the efficiency and applicability of the method were demonstrated.

• Structural Engineering and Mechanics
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• 제22권5호
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• pp.575-597
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• 2006

Enhanced three-dimensional finite elements for geometrically nonlinear analysis of cable-supported structures are presented. The cable element, derived by using the concept of an equivalent modulus of elasticity and assuming the deflection curve of a cable as catenary function, is proposed to model the cables. The stability functions for a frame member are modified to obtain a numerically stable solution. Various numerical examples are solved to illustrate the versatility and efficiency of the proposed finite element model. It is shown that the finite elements proposed in this study can be very useful for geometrically nonlinear analysis as well as free vibration analysis of three-dimensional cable-supported structures.