• 한국정밀공학회지
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• 제15권7호
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• pp.129-138
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• 1998

The objective of this study is to demonstrate the ability of a computer simulation of microstructural evolution in hot forging of C-Mn steels. The development of microstructure is strongly dependent on process variables and metallurgical factors that affect time history of thermodynamical variables such as temperature, strain. and strain rate during deformation. Then finite element method is applied for the prediction of microstructural evolution, and it should be coupled with heat transfer analysis to consider the change of thermodynamical properties during forming process. In this study, Yada's recrystallization model and rigid-thermoviscoplastic finite element method are employed in order to analyze microstructural evolution during hot forging process. To show the validity and effectiveness of the proposed method, experiments are accomplished and the results of experiments are compared with those of simulations.

• 한국생산제조학회지
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• 제20권3호
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• pp.329-334
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• 2011

The characteristic of sheet metal process is the few loss of material during process, the short processing time and the excellent price and strength. The static implicit finite element method is applied effectively to analyze stamping processes from using AutoForm software. The simulation analysis can be applied to the membrane elements and shell elements. Membrane elements can be applied to good efficiency, but lower than the accuracy of shell elements. Therefore, simple drawing process applies membrane element, and spring-back and analysis of stamping process are judged that it is most efficient that apply shell clement. This study, the simulated results for stamping processes are shown and discussed.

• 한국정밀공학회:학술대회논문집
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• 한국정밀공학회 1993년도 추계학술대회 논문집
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• pp.638-643
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• 1993

The three dimensional finite element models for the basic deflection of linear motion guides and ball screws were developed. Form the comparison of the results calculated by the finite element method with those by the experiment, it was proved that the modeling method might be applied to real machine tool structures. Form the structural analysis of the headstock of the machine tool, it was found that the static stiffness was calculated within 6.5% error

• Journal of Advanced Marine Engineering and Technology
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• 제14권4호
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• pp.67-71
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• 1990

The traditional finite element method applied to dynamic problems employs shape functions which are based on a static displacement assumption. The more exact approach uses frequency-dependent shape functions and frequency-dependent mass and stiffness matrices. Such matrices are developed for a torsional vibration of shaft element. Numerical examples are presented for a cantilever beam.

• 대한조선학회논문집
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• 제28권2호
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• pp.195-206
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• 1991

본 논문은 구조부재의 안전성평가에 적용되는 1차 신뢰성해석법들의 비교를 다룬 것으로서, 구조해석 시 재료와 기하학적 변수들의 불확실성을 고려하는 방법과 이를 고려하지 않는 방법으로 편의상 나누어 비교하여 보았다. 전자를 흔히 확율 유한요소법(Stochastic Finite Element Method 또는 Probabilistic Finite Element Method)라고 하는데 이와 구별해 주기 위하여 현재 널리 쓰이는 후자의 방법을 통상적인 신뢰성해석법(Ordinary Reliability Method)이라고 하였다. 이통상적인 방법에서는 구조해석을 단 한번 수행하고 그 결과를 신뢰성 해석과정에 직접 이용한다. 이는 재료 및 기하학적 변수들의 불확실성이 음력이나 변위의 불확실성에 영향을 주지 않고 따라서 그 불확실성의 정도를 하중의 것과 같다는 가정을 이용한다. 본 논문에서는 위의 두방법을 평면 골조구조물의 안전성평가에 적용하였고 그 결과들을 효율성과 응용성 측면에서 비교하였다. 본 논문의 구조모델에 대한 결과에 따르면 재료 및 기하학적 변수들의 불확실성이 비교적 작을때(즉, COV가 약15%이하일 때) 통상적인 신뢰성 해석법은 적용해도 만족할 만한 결과를 주고 효율적인데, 확율유한요소법은 그 COV들이 약15%이상인 구조물에 적용하는 것이 바람직하다.

• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 1992년도 봄 학술발표회 논문집
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• pp.47-52
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• 1992

The entire nonlinear behavior of reinforced concrete frames up to collapse, is analyzed by the displacement control method and the combined layered and nonlayered method. All of the rigidities of section are calculated approximately by a sum over all the layers for the layered method, are used the integral values over the cross section area for the nonlayered method. The spurious sensitivity to the chosen element size in the result of analysis by finite element method for the materials with strain-softening can be overcome by modifying the strain distribution based on the concept of fracture energy at plastic hinge considering the applied axial load.

• Journal of applied mathematics & informatics
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• 제29권1_2호
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• pp.227-245
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• 2011

In this paper, we introduce a new iterative method for finding a common element of the set of solutions for mixed equilibrium problem, the set of solutions of the variational inequality for a ${\beta}$inverse-strongly monotone mapping and the set of fixed points of a family of finitely nonexpansive mappings in a real Hilbert space by using the viscosity and Ces$\`{a}$ro mean approximation method. We prove that the sequence converges strongly to a common element of the above three sets under some mind conditions. Our results improve and extend the corresponding results of Kumam and Katchang [A viscosity of extragradient approximation method for finding equilibrium problems, variational inequalities and fixed point problems for nonexpansive mapping, Nonlinear Analysis: Hybrid Systems, 3(2009), 475-86], Peng and Yao [Strong convergence theorems of iterative scheme based on the extragradient method for mixed equilibrium problems and fixed point problems, Mathematical and Computer Modelling, 49(2009), 1816-828], Shimizu and Takahashi [Strong convergence to common fixed points of families of nonexpansive mappings, Journal of Mathematical Analysis and Applications, 211(1) (1997), 71-83] and some authors.

• Journal of the Korean Society for Industrial and Applied Mathematics
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• 제12권4호
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• pp.249-260
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• 2008

In this work we propose a mixed finite volume method for the Signorini problem which are based on the idea of Keller's finite volume box method. The triangulation may consist of both triangles and quadrilaterals. We choose the first-order nonconforming space for the scalar approximation and the lowest-order Raviart-Thomas vector space for the vector approximation. It will be shown that our mixed finite volume method is equivalent to the standard nonconforming finite element method for the scalar variable with a slightly modified right-hand side, which are crucially used in a priori error analysis.

• 한국공작기계학회논문집
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• 제16권3호
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• pp.75-80
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• 2007

It is necessary to analyze the contact phenomena in order to effectively design the machine components with contact surfaces. In general, the contact action is highly nonlinear and irreversible because we cannot predict the contact regions and conditions. Recently, the finite element method is used to analyze the contact problem. In this paper, the contact element method is applied to avoid the mesh refinement and iterative calculation of general contact algorithms. By use of it, the deformation and stress concentration of turbo compressor rotor are computed. It shown that the contact element is convenient analysis and the results are relatively accurate.

• 한국전산유체공학회지
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• 제4권2호
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• pp.39-46
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• 1999

The FVM(Finite Volume Method) have been used mainly for the flow analyses in the piston-cylinder. The objective of the present study is to analyze numerically the piston-driven intake flows using the FEM(Finite Element Method). The FEM algorithm used in this study is 4-step time-splitting method which requires much less execution time and computer storage than the velocity-pressure integrated method and the penalty method. And the explicit Lax-Wendroff scheme is applied to nonlinear convective term in the momentum equations to prevent checkerboard pressure oscillations. Also, the ALE(arbitrary Lagrangian Eulerian) method is adopted for the moving grids. The calculated results show good agreement in comparison with those by the FVM and the experimental results by the LDA.