• 소성∙가공
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• 제17권1호
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• pp.68-72
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• 2008

In order to investigate the evolution of strain states during screw rolling, the samples of copper rod were rolled in a three-roll screw rolling mill. Microstructure observations and hardness measurements were carried out for examining the deformation history during screw rolling. The finite element method(FEM) was employed to calculate the evolution of strain states during screw rolling. The strain state in the roll gap is quite inhomogeneous through the rod thickness layers. It turned out that shear strain gradients through the thickness layers are reduced by applying a higher reduction.

• 한국소성가공학회:학술대회논문집
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• 한국소성가공학회 2007년도 추계학술대회 논문집
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• pp.158-161
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• 2007

In order to investigate the evolution of strain states during screw rolling, the samples of pure copper rod were rolled in a three-roll screw rolling mill. Microstructure observations and hardness measurements were carried out for examining the deformation during screw rolling. In addition, the finite element method (FEM) was employed to calculate. The strain states reveal that the shear strain plays a dominant role in the deformation during screw rolling.

• 대한설비공학회:학술대회논문집
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• 대한설비공학회 2005년도 동계학술발표대회 논문집
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• pp.300-305
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• 2005

The present experimental study investigates single-phase heat transfer coefficients downstream of support grid in $6{\times}6$ rod bundles. Support grid with split mixing vanes enhance heat transfer in rod bundles by generating it make turbulence. But this turbulence is confined to short distance. Support grid with LSVF mixing vanes enhanced heat transfer to longer distance. The corresponding Reynolds number investigated in the present study is Re=30,000. The heat transfer coefficients are measured using heated and unheated copper sensor.

• 한국세라믹학회지
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• 제35권1호
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• pp.41-47
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• 1998

Cutting and planarization of diamond films have been performed using copper vapor laser under air at-mosphere. Diamond films of about 350${\mu}{\textrm}{m}$ and 800 ${\mu}{\textrm}{m}$ thick have been synthesized with DC plasma assisted chemical vapor deposition. The position of a specimen has been controlled by computer-driven stage. With copper vapor laser beam of 7W cutting depth increases rapidly and saturates with increasing scan number and decreasing scan speed. 8 repetitive scans at scan speed 0.5 mm/sec produce the maximum cutting depth without focus shifting Rod-shape copper vapor laser beam can be made and used effectively in planar-ization of rough diamond surface.

• 조명전기설비학회논문지
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• 제24권1호
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• pp.136-144
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• 2010

봉형접지극은 우리나라 배전계통에 가장 많이 사용하고 있는 접지전극이다. 현재 배전계통에 사용하고 있는 봉형접지극은 접지동봉, 심타용접지봉 그리고 도전성콘크리트접지봉 등이 주로 사용되고 있다. 그러나 접지저항값은 토질에 따라 소정의 접지저항값을 얻기가 어려울 때가 많아 접지저항저감제를 사용하게 된다. 본 연구에서는 봉형접지지전극 중 가장 많이 사용하고 있는 접지동봉에 물을 제공하였을 때 얻어진 접지저항값을 기준으로 접지저항저감제의 사용방법(시공법), 접지저항저감제의 종류 등에 따라 얻어진 초기접지저항값, 시간경과(1년)에 따른 저항값의 변화폭 추이 등을 비교 검토한 연구이다. 본 연구 결과를 요약하면 신공법으로 접지저항저감제를 사용하였을 때 낮은 초기접지저항저감을 얻는 효과뿐만 아니라 시간경과에 따른 접지저항값의 변화폭도 적어 안정됨을 확인할 수 있었다.

• 한국전기화학회:학술대회논문집
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• 한국전기화학회 2005년도 수소연료전지공동심포지움 2005논문집
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• pp.383-390
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• 2005

Effect of applying a DC voltage on the interfacial reaction at the metal to zirconia interface was investigated utilizing an oxygen ionic conductivity of partially stabilized zirconia. The joining of copper rod and zirconia tube was carried out in Ar gas atmosphere at $1000^{\circ}C$. There are two type of the joining. The one is the reaction bond consisting of copper and zirconia was dominated by surface reaction with a undetectable very thin layer. It was found that copper elements were diffused to zirconia side, but that Zr ions were not diffused to copper side. These results mean application of a DC voltage to migrate oxygen to the copper-zirconia interface can oxidize metal at the copper-zirconia interface and the bonding reaction between zirconia and copper oxide may occur. The other is the reaction bonding was dominated by interdiffusion with a very thick interface layer. This result mean application of a DC voltage can reduce zirconia at the interface. The bonding reaction is to be an alloying between Zr and Cu.

• 소성∙가공
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• 제7권1호
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• pp.66-71
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• 1998

The present study is concerned with the hydrostatic extrusion process of copper-clad aluminium bar to investigate the bonding conditions as well as the basic flow characteristics. Considering the bonding mechanism of bi-metal contact surface as cold pressure welding the normal pressure and the contact surface expansion are selected as process parameters governing the bonding conditions, in this study the critical normal pressure required for the local extrusion-the protrusion of virgin surfaces by the surface expansion at the interface-is obtained using a slip line method and is then used as a criteron for the bonding. A rigid plastic finite element method is used to analyze the steady state extrusion process. The interface profile of bi-metal rod is predicted by tracking the paths of two particles adja-process. The interface profile of bi-metal rod is predicted by tracking the paths of two particles adja-cent to interface surface. The contact surface area ration and the normal pressure along the interface are calculated and compared to the critical normal pressure to check bonding. It is found that the model predictions are generally in good agreement with the experimental observations. The compar-isons of the extrusion pressure and interface profile by the finite element with those by experi-ments are also given.

• 한국소성가공학회:학술대회논문집
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• 한국소성가공학회 2001년도 제4회 압출 및 인발가공 심포지엄
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• pp.55-62
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• 2001

An electrolytic copper rod was drawn up to $90\%$ in area reduction and annealed under various conditions. The EBSD measurement of the drawn wire showed that in the center region the <111> + <100> fiber duplex texture was dominant, while in the middle and surface regions relatively defused textures developed with a little higher density in <11w>//wire axis. The inhomogeneous texture in the deformed wire gave rise to the inhomogeneous microstructure and texture after annealing. The annealing texture could be classified into the recrystallization texture developed during low temperatures and at the early stage at a high temperature and the growth texture developed after a prolonged annealing at the high temperature. The recrystallization temperature could be explained by the strain energy release maximization model and the growth texture was discussed based on the grain boundary mobility anisotropy.

• 한국표면공학회지
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• 제45권2호
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• pp.75-80
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• 2012

A sputter-sublimation source was tested for high rate deposition of protective coating of PEMFC(polymer electrolyte membrane fuel cell) with high electrical conductivity and anti-corrosion capability by DC biasing of a metal rod immersed in inductively coupled plasma. A SUS(stainless steel) tube, rod were tested for low thermal conductivity materials and copper for high thermal conductivity ones. At 10 mTorr of Ar ICP(inductively coupled plasma) with 2.4 MHz, 300 W, the surface temperature of a SUS rod reached to $1,289^{\circ}C$ with a dc bias of 150 W (-706 V, 0.21 A) in 2 mins. For 10 min of sputter-sublimation, 0.1 gr of SUS rod was sputter-sublimated which is a good evidence of a high rate deposition source. ICP is used for sputter-sublimation of a target material, for substrate pre-treatment, film quality improvement by high energy particle bombardment and reactive deposition.

• 대한설비공학회:학술대회논문집
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• 대한설비공학회 2006년도 하계학술발표대회 논문집
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• pp.188-193
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• 2006

In present study, the thermal-hydraulic characteristics of the subchannels are investigated as measuring single-phase heat transfer coefficients and the cross sectional velocity field using LDV in the downstream of support grid in $6{\times}6$ rod bundles. Support grid with mixing vanes make enhancing heat transfer in rod bundles by generating turbulent flow. But this turbulent flow only is reserved in a short distance. Support grid with LSVF mixing vanes keep the turbulent flow a long distance. The experiments are performed at the nominal Reynolds number 30,000 and 50,000. The heat transfer coefficients are measured using heated and unheated copper sensor. In this study, the comparison of local heat transfer coefficients for LSVF mixing vane and split mixing vane is represented.