• Proceedings of the Korean Powder Metallurgy Institute Conference
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• 2006.09b
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• pp.754-755
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• 2006

In order to develop the SUS304L housing by powder metallurgy for an optical device useful for the FTTH communication system, the optimum compacting pressure and sintering temperature were investigated using granulated powder as the material to satisfy high air-tightness and high laser-weldability. Then the laser-welding test of specimen made under the optimum condition was carried out to observe welding sputters.

• Proceedings of the Korean Vacuum Society Conference
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• 2012.02a
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• pp.458-458
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• 2012

Fuel Cell is used stacking metal or polymer substrate. This hydro property of substrate surface is very important. Usually, surface property is hydrophilic. The surface oxidation of SUS is investigated through plasma treatments with an atmospheric-pressure dielectric barrier discharge (DBD) for increasing hydrophilic property. The plasma process makes an experiment under various operating conditions of the DBD, which operating conditions are treatment time, plasma gas mixture ratio, the plasma source supply frequency. Two kinds of SUS substrate, SUS-304 and SUS 316L, were used. Discharge frequency has a crucial impact on equipment performance and gas treatment. After the plasma treatment of a SUS plate, highly improved wettability was noted. But, when high oxygen supply, the substrate damaged seriously.

• Transactions of the Korean Society of Mechanical Engineers
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• v.8 no.6
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• pp.569-575
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• 1984

The characteristics of the stress corrosion cracking of SUS 304 stainless steel weldments were studied with the speciments of the constant displacement type under the environment of 42% MgC $l_{2}$ boiled solution (143.+.-.2.deg.C). The susceptibility of initiation and propagation of the stress corrosion crack was quantitatively inspected in the weld metal, heat affected zone and heat affected zone with including the reinforcement shape, respectively. Also, those susceptibility were discussed in connection with the change of mechanical and microstructural characteristics caused by heating cycle of welding. Main results obtained are as follows: (1)Stress corrosion cracking is easiest to initiate and propagate in the heat affected zone of weldment. (2)The susceptibility of stress corrosion cracking of the weldment is largely improved by eliminating the reinforcement part of the weld bead. (3)The dominant factor of the cracking susceptibility of the heat affected zone appeared to be the phenomenon of softening and sensitizing caused by welding heat cycle. (4)Under the low loading conditions, the behavior of stress corrosion cracking of the SUS 304 steel weldment is largely influenced by the pitting phenomenon in the front region of the main crack.

• Transactions of Materials Processing
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• v.23 no.7
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• pp.405-412
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• 2014

As a major type of heat exchanger, the steam generator (SG) produces steam from heat energy of a nuclear power plant reactor. The steam produced by the steam generator flows into a turbine, and plays an important role in electric power generation. The heat transfer tubes in the steam generator consist of approximately 10,000 U-shaped tubes, which perform a structural role and act as thermal boundaries. The heat transfer tubes conduct the thermal energy between the primary coolant (about $320^{\circ}C$, $157kgf/cm^2$) obtained from the reactor and the secondary coolant (about $260^{\circ}C$, $60kgf/cm^2$) as part of the secondary system. Recently, the heat transfer tubes in the steam generator of the pressurized water reactor (PWR) are primarily produced from Alloy 600 and Alloy 690 seamless tubes. As a pilot study to find process parameters for the cold U-bending process using rotary draw bending, numerical and experimental investigations were conducted to produce U-shaped tubes from long straight SUS304L seamless tubes. 3D finite element simulations were run using ABAQUS Explicit with consideration of the elastic recovery. The process parameters studied were the angular speed, the operation period and the bending angle. Experimental verifications were conducted to insure the suitability of the final U-shaped configurations with respect to both ovality and wall thickness.

• Journal of Advanced Marine Engineering and Technology
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• v.34 no.5
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• pp.661-669
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• 2010

The effects of laser peening on metallic materials have been investigated with water-penetrable frequency-doubled Nd:YAG laser. Laser pulses of 200 mJ energy and 8 ns duration focused on samples underwater with 0.8 mm spot diameter. X-ray study showed that compressive residual stress was imparted on SKD61 from the surface to nearly 2 mm depth. Stress corrosion cracking (SCC) was prohibited for sensitized SUS304 even in a severely corrosive environment fatigue lives of SUS316L and SM490A welded samples were prolonged significantly in the high-cycle regime. Since 1999, laser peening has been applied to prevent SCC in operating nuclear power plants in Japan.

• Journal of the Korean Institute of Gas
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• v.2 no.1
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• pp.99-106
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• 1998

In order to investigate the impact properties of structural materials for LNG tank, instrumented Charpy impact tests were carried out at cryogenic temperatures. $9\%$ Ni steel showed a superior fracture resistance because of less degradation in toughness until 77 K. From the load-deflection curve obtained by an instrumented methods it was found that with the decrease of temperature from 173 K to 77 K, the peak load in the curve increased, but the total absorbed energy decreased. In addition, the energy absorbed during the crack growth was larger than one absorbed in the process of crack initiation. In SUS304L material, the energy absorbed in the process of the crack initiation was relatively large, but the energy absorbed in the process of crack growth was small, the behavior of absorbed energy was well agreed with the observations of the fracture surface which showed a relatively smooth fracture surface. The absorbed Charpy impact energy in the case of A5083 alloy was lower as compared with other steels, and some cracks were observed along the crack propagation direction at the fracture surface of 77 K.

• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 2003.05a
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• pp.303-306
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• 2003

To reduce the storage space of spent fuels used at the atomic power plants all over the world, the uranium elements contained in the spent fuels is being extracted and effectively stored. For this, the spent fuel are oxidized and deoxidized. In this study, it is produced conceptual design specification about the spent fuel management technology research and test facilities have been produced. The first considered processes in the facilities is the metal conversion furnace in the dry environment. Since this process is operates at the high temperature range, we have to consider heat-resisting designs for the device. For the heat-resisting designs, we have surveyed and analyzed technical references for material properties. Also, we have determined the temperature distribution condition of the device based on experimental results. We have calculated thermal stress and strain of each devices by the commercial analysis software, I-DEAS. By using the results, we have analyzed design configurations of the point at issue by thermal effects, and suggested alternative design configurations. It is experimented for inspecting confidence rate of heat strain. Based on these results, necessary design specifications for heat-resisting design have been produced.

• Journal of Korean Society of Water and Wastewater
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• v.25 no.5
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• pp.767-775
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• 2011

In this study we verified if the electro-coagulation process can treat properly the nitrate and fluoride that are not removed well in the conventional small water treatment plants which usually employ chlorination and filtration only. As we gave a change of electrode material and gap-distance between electrodes, removal efficiency of the nitrate and fluoride was determined by electro-coagulation process which were equipped with aluminum and stainless steel (SUS304) electrodes. In addition, electrode durability was investigated by determination of electrodes mass change during the repetitive experiments. Removal efficiency was great when aluminum was used as an anode material. Nitrate removals increased as electric density and number of electrodes increased, but fluoride removal was less sensitive to both parameters than nitrate. After 10 minutes of contact time with the current density from $1{\times}10^{-3}$ to $3{\times}10^{-3}A/cm^{2}$, nitrate and fluoride concentration ranged from 9.2 to 1.2mg/L and from 0.02 to 0.01mg/L, which satisfied the regulation limits. Regardless of the repeating number of experiments, removal efficiency of both ions were almost similar and the change of electrode mass ranged within ${\pm}$0.5%, indicating that the loss of the electrode mass is not so much great under the limited circumstances.

• Proceedings of the Korea Water Resources Association Conference
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• 2022.05a
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• pp.397-397
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• 2022

오늘날 급격한 인구증가 및 도시화로 인해 음식물류 폐기물 발생량이 크게 증가하였으며, 음식물류 폐기물에서 발생되는 음폐수의 적절한 처리방안에 대한 관심이 증가하였다. 혐기성 소화(Anaerobic digestion; AD)는 음폐수의 바람직한 처리방법으로 알려졌지만, 긴 처리기간 및 공정 불안정 등의 문제로 개선이 필요하며, 그 중 기존 AD에 보조 반응조를 추가한 보조 미생물전기화학적 혐기성소화(Auxiliary bioelectrochemical anaerobic digestion; ABEAD)가 적절한 개선방안으로 제시되었다. 하지만 아직 20 L 이상 용량에서의 연구는 이뤄지지 않았으며, 따라서 본 연구에서는 100 L의 용량에서 ABEAD의 성능향상을 평가하고 규모증가에 따른 성능변화를 비교하였다. 반응조는 AD와 ABEAD로 구성되었다. 유효용량 100 L, 유기물부하율 4 kg/m³/d, HRT 20 days 및 중온소화(35℃) 조건으로 운전하였으며, AD는 기계적 교반, ABEAD는 기계적 교반 및 펌프를 통한 bulk 용액 순환이 이뤄졌다. ABEAD의 전극재질은 SUS304를 사용하였고, 0.4V의 전압을 공급하였다. 성능비교는 pH, 휘발성지방산(Volatile fatty acids; VFAs), 유기물제거율 및 메탄 생성량을 비교해 수행하였다. 실험결과 AD는 pH 및 VFAs가 각각 평균 7.37 및 3,880 mg/L, ABEAD는 각각 평균 7.5 및 2,870 mg/L로 VFAs의 빠른 처리를 통해 공정안전성 향상되었고, 유기물제거율 및 메탄생성량의 경우 AD는 각각 평균 65.8 % 및 85.1 L/d, ABEAD는 각각 평균 76.1 % 및 108.1 L/d로 유기물의 빠른 처리 및 메탄전환이 이루어져 비교적 큰 규모에서도 ABEAD의 성능향상이 나타남을 확인하였다. 또한 이전 소규모 연구들과 비교를 통해 규모에 따른 성능향상폭을 비교했을 때에도 큰 차이가 나지 않는 것으로 판단되며, 따라서 ABEAD는 BEAD 기술의 상용화 및 적용에 적합한 것으로 사료된다.

• Transactions of Materials Processing
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• v.26 no.1
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• pp.11-17
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• 2017

In this study, process analysis of elbow-shaped tubes using a mandrel has been performed. To reach the final shape within the dimensional tolerance, the process analysis has been performed at various processing parameters such as tube dimensions, the curved cutting surface and the radius of curvature. The area outside the boundary of the target shape was expressed as a quantitative index to analyze the formability. The validation experiments have also been performed in order to increase the reliability of the process analysis. For the processing of elbow-shaped tubes, it is preferable to make the angle of the portion where the punch touches the tube smaller than the opposite angle. And the convex cutting surface is advantageous due to the increased contacts between the punch and the tube ends during the bending process. Elbow tube having larger radius of curvature shows higher dimensional accuracy due to the relatively uniform strain distribution.