• 대한기계학회논문집A
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• 제20권5호
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• pp.1516-1523
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• 1996

The present study is concerned with the development of anisotropy and deformation texture in polycrystals. The individual grain in an aggregate is assumed to experience the viscoplastic dedformation with crystallographic slip that unsure uniquenessof the active slip systems and shearing rate onthese systems. Two different methods for updating the grain orientation are examined. Texture development for some deformation modes such as plane strain compression, uniaxial tension and simple shear are found. Changes in anisotropic flow potential due to texture development during large deformation are also given. Anisotropic behavior of polycrystals with defferent textures are examined.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2003년도 춘계학술대회
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• pp.1136-1141
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• 2003

Among various methods to manufacture the PDP barrier ribs, the pressing and the roll forming methods are simple and economical because they form the ribs by utilizing the plastic flow of the green tape in a relatively short time without generating air-polluting dusts. In the present study, the roll forming method was investigated by experiments as well as numerical analyses and in result the groove roll and the preform were designed. The effect of draft angle, comer radius, and initial thickness of the green tape on the plastic flow was examined by a series of parametric studies. The preform was recommended to ease the plastic flow into the grooves and to avoid the occurrence of crack during rolling and sintering processes.

• 한국정밀공학회:학술대회논문집
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• 한국정밀공학회 1996년도 춘계학술대회 논문집
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• pp.546-550
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• 1996

A fully automatic computer simulation technique of axisymmetric multi-stage compound forging processes was presented in this paper. A penalty rigid-viscoplastic finite element method was employed together with an improved looping method for automatically remeshing with quadrilateral finite-elements only. An application example of six-stage axisymmetric forging processes involving one cold and two hot forging processes, two piercing processes and a sizing process was given with emphasis on automatically tracing the metal flow lines through the whole simulation.

• 한국공작기계학회논문집
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• 제10권2호
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• pp.73-78
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• 2001

In this study, the friction weldability and properties of inconel alloy(IN738LC) to stainless steel (STS304) was investigat-ed. Upset length increased according to increment of friction pressure and time. The tensile strength of the friction weld-ing reached 85% of the STS304 base metal strength under the conditions of 8 sec friction time, 50MPa friction pressure and 150 MPa upset pressure. From the result of fracture surface analysis, IN738LC section can be joined with STS 304 materials in shape of a convex lens. Also, the temperature of welded interface was measured with k-type thermocouple. Finally the plastic flow confirmed at the welded interface STS304 by micro test.

• 한국정밀공학회지
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• 제14권8호
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• pp.82-91
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• 1997

The major objective of this study is to establish analytical technique in order to analyze the behaviour of semi-solid material considering induction heating of the billet. Induction heating process is analyzed by using commerical finite element software. ANSYS. The finite element program, SFAC2D, for the simulation of deformation in semi-solid state is developed in the present study. The semi-solid behaviour is described by a viscoplastic model for the solid phase, and by the Darcy's law for the liquid flow. Simple compression and closed-die compression process considering induction heating are analyzed, and also it is found that the distribution of initial solid fraction of the billet has an important effect on deformation behaviour of semi-solid material. In order to verify the effectiveness of proposed analytical technique the simulation result is compared with experimental result.

• 대한지질공학회:학술대회논문집
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• 대한지질공학회 2004년도 암반의 조사와 적용(단행본)
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• pp.24001-24056
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• 2004

암반 기초에서 발생 가능한 파괴형태로는 $\circled1$전단파괴(Shear failure) $\circled2$관입파괴(punch failure) $\circled3$붕락(Collapse) $\circled4$균열파괴 (cracking) $\circled5$분쇄상파괴 (crushing) $\circled6$쐐기상파괴 (wedging)를 들 수 있다. 그림 2.4-1에서 (a)는 연암층 내에서의 전형적인 전단파괴를 나타내고, (b)는 소성암반 상부에 강성암반이 놓였을 때의 전단파괴를 보여준다. (c)는 2층으로 구성된 지반에서의 전단파괴 양상이며, (d)는 편심하중이 작용할 때의 전단파괴이다. (e)는 사면 상에서의 활동에 의한 파괴유형이다. (f)는 절리가 발달한 풍화된 암반내로 진행되는 관입파괴를 보여주고 있다. (e)는 연암지반 내부로 강성암반이 관입되어 파괴된 모습이다. (h)는 풍화된 화강암에서의 관입파괴 유형이다. (i)는 석회암층 내부의 지하공동에 의한 붕락현상을 보여주고 있으며, (j)는 지하수의 유동에 의해 형성된 공동으로 인한 붕락파괴를 나타낸다. (k)는 균열파괴, (l)은 분쇄상 파괴, (m) 쐐기상 파괴, (n)은 단층선을 따른 파괴 유형이다. (중략)

• 한국지반공학회논문집
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• 제17권2호
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• pp.95-101
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• 2001

연약한 점토 지반에 안벽을 축조하고 매립하는 경우, 안벽의 기초로서 케이슨 기초공법이 종종 쓰이고 있다. 케이슨 기초는 안벽의 연직 하중을 지지층에 전달할 뿐만 아니라, 매립하중에 의한 연약 점토의 횡방향 소성 유동에 대하여는 매우 효과적인 공법으로 호안공사에서 그 사용 빈도가 증가하고 있는 추세이다. 반면 매립하중에 의해 점토지반에서 장기간에 걸쳐 발생하는 압밀침하에 대해서는 아무런 역할을 하지 못하는 단점이 있다. 따라서 본 연구에서는 기존 케이슨 기초의 배면에 다수의 강관 배수공을 설치함으로써 과잉간극수압의 횡방향 소산을 촉진시켜 압밀 시간을 단축시키는 \"매립측 연약점토 압밀촉진 케이슨 기초공법\"을 제안하였다. 이 새로운 케이슨 공법의 압밀촉진 효과를 분석하기 위하여 2차원 압밀방정식의 해석해를 유도하였다. 연구결과, 등방성 점토에서 압밀촉진 케이슨 사용시 ξ=0.1인 단면에서 평균압밀도 50%, 90%에 이르는 시간이 기존 케이슨을 사용한 것에 비해 각각 약 7배, 3.5배 단축되는 것으로 나타났다. 것으로 나타났다.

• 한국해양공학회지
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• 제14권2호
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• pp.70-75
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• 2000

In this paper a new constitutive model for ductile materials was proposed. This model can describe the material degradation due to the evolution of isotropic damage during elasto-platic deformation. The plastic flow rule was derived under the framework of thermodynamic approach of continuum damage mechanics(CDM) in which plastic strain hardening parameters and isotropic damage were taken as thermodynamic state variables. And the process to determine material constants for constitutive model using an experimental data was presented.

• 한국산학기술학회논문지
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• 제4권1호
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• pp.36-41
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• 2003

열간단조 밀폐금형의 수명연장을 위한 빌릿의 소성변형 유동해석을 유한 요소법에 의하여 실시한 결과 임프레션 형상에 대한 수정설계를 수행하였고, 임프레션 표면 마멸부위의 보수방법을 육성용접에 의한 방법으로 금형을 재생하여 사용한 결과 개발 전의 3,0(H개 생산에서 개발 후 5,000개 양산되었을 때 임프레션 표면을 관찰하였더니 3,000개 정도에서 나타났던 마멸보다 얕은 마멸이 나타났다.

• 대한기계학회논문집A
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• 제20권12호
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• pp.3715-3727
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• 1996

Compression behavior of semi-solid aluminum alloys with controlled solid fractions was investigated in the present study. The stress and strain relationships were obtained from the compression test. Variations of the solid fraction distribution and the material behaviour were investigated for various friction coeffieiants and die speedsd. For a finite element analysis, the semi-solid material was described by a compressible regid viscoplastic model for the solid region and darcy's law for the liquid region. The computed results were compared with experimental data for the validity of the yield criteria.