• 대한금속재료학회지
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• 제48권1호
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• pp.85-89
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• 2010

The plastic deformation behavior of magnesium alloy is affected simultaneously by deformation temperature and strain rate under warm and/or hot working conditions. The soundness of deformation of AZ31-xCa (x=0. 0.7, 2.0 wt.%) extrudes during compression was strongly affected by processing variables including deformation temperature, strain rate. compression-loading direction, which was related to the activation of available deformation systems. The deformation behavior of AZ31-xCa extrudes was also affected by Ca content, which was related to the change of the sort and fraction of second phase. The complex effects of deformation temperature and strain rate on the deformation behavior of AZ31-xCa extrudes during compression under various conditions could be successfully described by Zener-Hollomon parameter.

• 제어로봇시스템학회논문지
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• 제9권9호
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• pp.700-706
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• 2003

This paper presents a 3D last design system that provides the 3-dimensional last data based on the FFD(Free Form Deformation) method. The proposed system utilizes the control points for deformation factor to convert from the 3D point cloud foot data to the 3D point cloud last data. The deformation factor of the FFD is obtained from the conventional last design technique, and constructed on the FFD lattice based on the bottom view and lateral view of the measured 3D point cloud foot data. In addition, the control points of FFD lattice is decided on the anatomical points of foot. The deformed 3D last obtained from the proposed FFD is saved as a 3D dxf foot data. The experimental results demonstrate that the proposed system have the descent 3D last data based on the openGL window.

• 대한기계학회논문집
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• 제19권4호
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• pp.896-907
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• 1995

Titanium 6242(.alpha. + .betha.) alloy has a good strength/weight ratio and is used for aircraft components such as engine disks and compressor blades. When this material is forged at an elevated temperature, the process parameters should be carefully controlled because the process window of this material is quite narrow. In the present investigation, a rigid-thermoviscoplastic finite element method is used to predict the deformation behavior and temperature/strain distributions in an engine disk during near-net shape hot forging. The purpose of the investigation is to obtain a proper ram speed profile, assuming the hydraulic press used in the forging is capable of varying ram speed during loading. In result, it was found that the ram speed at constant strain-rate of 0.5/sec shows a sound deformation behavior, a relatively uniform deformation and a good temperature distribution. This information is also valuable in predicting resulting microstructures in the disk.

• Corrosion Science and Technology
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• 제22권4호
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• pp.265-272
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• 2023

The aim of this study was to develop a new in-situ observation method and instrument in micro-scale to investigate the mechanism of stress corrosion cracking (SCC) initiation of Ni-base alloys in a high temperature water environment of pressurized water reactors (PWRs). A laser confocal microscope (LCM), an autoclave with diamond window view port, and a slow strain-rate tester with primary water circulation loop system were components of the instrument. Diamond window, one of the core components of the instrument, was selected based on its optical, chemical, and mechanical properties. LCM was used to observe the specimen in micro-scale, considering the experimental condition of a high-temperature primary water environment. Using in-situ method and instrument, it is possible to observe oxidation and deformation of specimen surface in micro-scale through the diamond window in a high-temperature primary water in real-time. The in-situ method and instrument developed in this work can be utilized to investigate effects of various factors on SCC initiation in a high-temperature water environment.

• 한국정밀공학회:학술대회논문집
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• 한국정밀공학회 2001년도 춘계학술대회 논문집
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• pp.235-238
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• 2001

Deformation phase can be obtained by using Least-Square Fitting. In extraction of phase values, Least-Square Fitting is superior to usual method like as 2, 3, 4-Bucket Algorithm. That can extract almost noise-free phase and retain 2$\pi$discontinuities. But more fringe in phase map, 2$\pi$ discontinuities is destroyed when that is filtered and reconstruction of deformation is not reliable. So, we adapted Least-Square Fitting using an isotropic window in dense fringe. using Sine-Cosine filter give us perfect 2$\pi$discontinuities information. We showed the process and result of extraction of phase map and filtering in this paper.

• 한국정밀공학회지
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• 제19권12호
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• pp.20-26
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• 2002

Deformation phase can be obtained by using Least-Square fitting. In extraction of phase values, Least-Square Fitting is superior to usual method such as 2, 3, 4-Bucket Algorithm. That can extract almost noise-free phase and retain 2 $\pi$ discontinuities. But more fringes in phase map, 2 $\pi$ discontinuities are destroyed when that are filtered and reconstruction of deformation is not reliable. So, we adapted Least-Square fitting using an isotropic window in dense fringe. Using Sine/cosine filter give us perfect 2 $\pi$ discontinuities information. We showed the process and result of extraction of phase map and filtering in this paper.

• 한국추진공학회지
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• 제4권1호
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• pp.1-12
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• 2000

유도탄의 성능 향상을 위해 추진기관의 경량화가 요구되고 있으며 연소관 모타 마개의 경우, Ti 합금 (Ti-6Al-4V)이 사용되고 있다. 제작 과정 중에 열간 형단조 공정이 이용되나 이 과정에서 Ti alloy의 좁은 성형 온도 구간 관계로 단조시 국부적 소성 변형 집중에 의한 결함이 단조품의 다수 생성되며, 심한 경우 전단 파단까지 이르고 있다. 성형 과정에서 금형과의 접촉에 의한 Ti 합금 온도 하강이 전단 파단 발생과 밀접한 관계를 갖고 있으며 따라서 각 단조 조건에 따른 Ti 합금의 내부 및 표면에 대한 변형 및 온도의 분포가 관찰되었다. 아울러 전단 밴드 형성에 대한 별도의 분석도 포함되었다.

• 대한기계학회논문집B
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• 제36권10호
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• pp.1025-1032
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• 2012

플래시 램프 열처리(Flash lamp annealing, FLA) 공정은 저온폴리실리콘의 생산을 위한 기술로써 대면적 기판용 실리콘 결정화 기술로 기대 받고 있는 기술이다. 본 연구에서는 FLA 공정 중 기판에 발생하는 변형의 원인에 대하여 이론적인 해석과 이를 토대로 시뮬레이션을 수행하였다. 상용 FEM 해석프로그램에 고온에서의 유리의 점성에 대한 모델을 적용하여, 고온에서 유리의 구조적인 수축과 응력이완으로 인한 영구변형을 수치적으로 재현하였다. 0 세대 실험시편($2cm{\times}2cm$)의 경우 중력의 영향이 미미하여서, 실험 결과와 일치하는 'U'모양의 변형이 남는 것을 확인하였고, 4 세대 기판($74cm{\times}94cm$)의 경우 중력으로 인하여 'M'모양의 변형이 발생하는 것을 시뮬레이션하였다.

• 한국정밀공학회지
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• 제18권5호
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• pp.90-97
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• 2001

An electronic speckle pattern interferometry (ESPI) system for measuring tensile properties under micro-tensile testing has been developed. The system consists of an optical system and an image processing system. In the optical system, optical components for measurement of in-plane deformation are arranged on the path of He-Ne laser. In the image processing system, the window-based program for acquiring speckle pattern interferometric image was developed and deformation in a small specimen is continuously evaluated during the test. Using this system, tensile strain of copper foil was measured during tensile testing. Tensile specimen had the thickness and width of 22 and 500 ${\mu}{\textrm}{m}$, respectively. Tensile properties, including the elastic modulus, yielding strength and tensile strength, of the copper were evaluated and also plastic exponent and coefficient in the Ramberg-Osgood relationship were evaluated from the stress-strain curve.

• 한국섬유공학회:학술대회논문집
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• 한국섬유공학회 2003년도 The Korea-Japan Joint Symposium
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• pp.75-76
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• 2003

Current efforts to establish links between geometrical features and mechanical performance of nonwoven fabrics in general, and of point-bonded (spot-bonded) nonwovens in particular, would be served significantly by the measurements of Fiber Orientation Distribution Function (ODF) and tensile modulus which occurs during controlled-deformation experiments. Image analysis technique (using the Fast Furier Transform) is used to quantify the fiber orientation distribution. The results suggest that, within a typical window of processing conditions, ODF has a significant influence on the mechanical anisotropy. The data also suggest that mechanical anisotropy of thermally point-bonded nonwovens is likely to be governed by different stress mode according to the applied macroscopic tensile direction.