• Structural Engineering and Mechanics
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• 제3권4호
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• pp.325-340
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• 1995

The iterative procedure to use the nonconforming elements in elasto-plastic problems is established and applied to the variable node transition solid element developed for the automated three-dimensional local mesh refinement. Through numerical tests, the validity and performance of the element are examined. As the nonlinear iterative procedure presented in this paper is accomplished for the general three-dimensional case, it can also be easily applied to the two-dimensional elements such as membranes, plates and shells.

• International Journal of Fuzzy Logic and Intelligent Systems
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• 제6권2호
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• pp.144-149
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• 2006

This paper describes a novel automated analysis system for bellows of piping system. An automatic finite element (FE) mesh generation technique, which is based on the fuzzy theory and computational geometry technique, is incorporated into the system, together with one of commercial FE analysis codes and one of commercial solid modelers. In this system, a geometric model, i.e. an analysis model, is first defined using a commercial solid modelers for 3-D shell structures. Node is generated if its distance from existing node points is similar to the node spacing function at the point. The node spacing function is well controlled by the fuzzy knowledge processing. The Delaunay triangulation technique is introduced as a basic tool for element generation. The triangular elements are converted to quadrilateral elements. Practical performances of the present system are demonstrated through several analysis for bellows of piping system.

• 한국정밀공학회:학술대회논문집
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• 한국정밀공학회 2003년도 춘계학술대회 논문집
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• pp.784-787
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• 2003

The present work covers three-dimensional flow simulation and deformation analysis of injection molded plastic lenses using solid elements. A numerical scheme to evaluate part deformation has been proposed from the results of injection molding analysis. Proposed scheme has been applied to the injection molding processes of optical plastic lenses: a spherical lens and an aspheric lens for a photo pick-up device. Through the simulation processes. residual stress is estimated and the final deformed patters are obtained for both products. The reliability of the proposed approach has also been verified in comparison with the results of real experiments.

• 소성∙가공
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• 제11권5호
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• pp.414-422
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• 2002

Most of numerical analyses for injection molding have been based on the Hele Shaw's approximation: two-dimensional flow analysis. In some cases, that approximation causes significant errors due to loss of geometrical information as well as simplification of the flow characteristics along the thickness direction. The present work covers numerical analyses of injection molding using three-dimensional solid elements. The accuracy of the analysis results has been verified through some numerical examples in comparison with the classical shell-based approach. The Proposed approach is then applied to predict product defects and to improve flow characteristics for a precision electronics part. In addition, design of experiment has been utilized in order to find the optimal process conditions for better product quality.

• 한국소성가공학회:학술대회논문집
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• 한국소성가공학회 2002년도 금형가공 심포지엄
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• pp.68-75
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• 2002

Most of numerical analyses for injection molding have been based on the Hele Shaw's approximation: two-dimensional flow analysis. In some cases, that approximation causes significant errors due to loss of geometrical information as well as simplification of the flow characteristics along the thickness direction. The present work covers numerical analyses of injection molding using three-dimensional solid elements. The accuracy of the analysis results has been verified through some numerical examples in comparison with the classical shell-based approach. The proposed approach are then applied to predict product defects and to improve flow characteristics for a precision electronics part. In addition, design of experiment has been utilized in order to find the optimal process conditions for better product quality.

• International Journal of Fuzzy Logic and Intelligent Systems
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• 제6권1호
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• pp.58-63
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• 2006

This paper describes a novel automated analysis system for bellows of piping system. An automatic finite element (FE) mesh generation technique, which is based on the fuzzy theory and computational geometry technique, is incorporated into the system, together with one of commercial FE analysis codes and one of commercial solid modelers. In this system, a geometric model, i.e. an analysis model, is first defined using a commercial solid modelers for 3-D shell structures. Node is generated if its distance from existing node points is similar to the node spacing function at the point. The node spacing function is well controlled by the fuzzy knowledge processing. The Delaunay triangulation technique is introduced as a basic tool for element generation. The triangular elements are converted to quadrilateral elements. Practical performances of the present system are demonstrated through several analysis for bellows of piping system.

• Bulletin of the Korean Chemical Society
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• 제27권10호
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• pp.1557-1561
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• 2006

The use of chemically modified silica-salen$(NEt_2)_2$ was studied for the separation and concentration of the metal ions from an aqueous solution by a solid phase extraction. After the salen(NEt2)2 was synthesized, it was chemically bonded to silica gel by a diazonium coupling reaction. The adsorption capacities and binding constants were obtained with respect to Cu(II), Mn(II), Pb(II) and Zn(II) by a graphical method. Some experimental conditions were optimized for the determination of the trace elements. After the silica-salen(NEt2)2 was pulverized in a sample solution of which the pH was adjusted, the solution was stirred to pre-concentrate the metal ions. The metal ions adsorbed were desorbed with nitric acid solution. And the concentrated analytes were determined by a flame AAS. The method proposed here was so rarely influenced by a sample matrix that the procedure was applied to 3 types of water samples. The reproducible results of less than 10% RSD were obtained at the concentration level of ca. 100 ng/mL and the recoveries of 95-109% were obtained in the spiked samples in which given amounts of analytes were added.

• 열처리공학회지
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• 제15권2호
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• pp.70-75
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• 2002

The depletion of solid solution elements from matrix and the change of carbides during artificial aging of 2.25CrMo steel at $630^{\circ}C$ were investigated. The Mo and Cr elements were found to be depleted drastically in the early stage of aging. The change of carbides was confirmed by analyzing the XRD patterns of electrolytically extracted carbides. Four type of carbides, $M_{23}C_6$, $M_3C$, $M_2C$ and $M_6C$, were found to exist in the specimen before aging. The amount of $M_6C$ carbides increased with aging time, while that of $M_3C$ carbides diminished after short aging time.

• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 2008년도 춘계 학술발표회 제20권1호
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• pp.277-280
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• 2008

본 논문에서는 새로운 교량 형식인 U-Channel Bridge(UCB)의 거동에 관해 연구하였고, 거동을 분석할 수 있는 해석 모델을 제시하였다. 바닥판의 하중을 하면에 위치한 보가 지지하는 형태의 상로교와는 대조적으로 UCB는 바닥판 위쪽에 측보가 위치하는 특징이 있다. 본 논문에서는 프레임 요소를 이용한 모델, 판 요소와 프레임 요소를 혼용한 모델, 실제 구조물과 같은 형태의 솔리드 요소를 적용한 모델의 세 가지 모델을 구성하였으며 솔리드 모델의 결과가 가장 정확하다고 가정하여, 두 가지 요소의 해석 결과를 비교하였다. 비교 결과 판 요소와 프레임 요소를 혼용한 모델이 솔리드 모델과 유사한 결과를 나타내었으며, UCB의 구조해석 모델로 판-프레임 모델을 제시하였다.

• 대한기계학회논문집
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• 제19권3호
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• pp.647-660
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• 1995

Given the tetrahedron-based octree approximation of a solid as described in part(I) of this thesis, in this part(II) a systematic procedure of 'boundary moving' is developed for the fully automatic generation of 3D finite element meshes. The algorithm moves some vertices of the octants near the boundary onto the exact surface of a solid without transforming the topology of octree leaf elements. As a result, the inner octree leaf elements can be used as exact tetrahedral finite element meshes. In addition, as a quality measure of a tetrahedral element, 'shape value' is propopsed and used for the generation of better finite elements during the boundary moving process.