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Han, Min-Su;Jeon, Jeong-Il;Jang, Seok-Gi
- Transactions of the Korean Society of Mechanical Engineers A
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- v.31 no.4
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- pp.532-539
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- 2007
The 7075-T651 Al alloy was welded by friction stir welding. Microstructure, macro behaviors and fracture type in the nugget, thermo-mechanically affected zone(TMAZ) and heat affected zone(HAZ) of the welded part were compared to base metal. The microsturctures of nugget zone were compared with tool rotation speeds and various tool transition speed. When the rotation speeds were decreased and transition speeds were increased, the hardness of nugget zone were decreased. Also, the optimal microstructure was observed at the low rotation speed of 800rpm and the high transition speed of 124mm/min. The transgranular dimple and quasi-cleavage at fractured part of nugget zone were investigated.
https://doi.org/10.3795/KSME-A.2007.31.4.532 인용 PDF KSCI

Kwak, Sung-Keun;Kim, Choong-Gon
- Journal of the Korea Organic Resources Recycling Association
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- v.28 no.4
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- pp.69-75
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- 2020
This study was conducted to improve the solid-liquid separation efficiency of clarifiers. To do so, the study did a bio-flocculation experiment simply by controlling the stirring speed (rpm) and baffle angle of a clarifier on a lab scale, but without using a coagulant. For the purpose of the experiment, the feed wall of a clarifier was so improved that a baffle could be installed on the clarifier. Then, it was ensured to change its stirring speed (to 0.0rpm, 0.6rpm, and 1.2rpm), with the angle fixed at 10°. As a result, it was found that concentration efficiency increased by 2.0%, and effluent removal efficiency (SS concentration) by 7.8%, at a stirring speed of 0.6ppm. This indicates the bio-coagulation efficiency of sludge increased with changing stirring speeds. Then, the baffle angle of the sedimentation unit was changed to analyze how the changed baffle angle would affect the sedimentation of sludge. As a result, it was found that the compression of sludge interface was very effective at a baffle angle of 20°. It is hoped that these experimental findings will be useful in improving the sedimentation efficiency of circular clarifiers.
https://doi.org/10.17137/korrae.2020.28.4.69 인용 PDF KSCI

Park, Young-Bin;Koo, Jeong-Seo;Goo, Byeong-Choon
- Journal of the Korean Society for Railway
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- v.12 no.4
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- pp.512-517
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- 2009
Extruded aluminium panels have been widely used for railway vehicle structures because -of their light specific weight and other merits. In the past, GMAW (Gas Metal Arc Welding) and GTAW (Gas Tungsten Arc Welding) were mainly used to join aluminium panels. But recently friction stir welding (FSW) is widely used due to its lots of advantage. In this study aluminium A6005 which is used for car body structures was chosen. The influences of main parameters on mechanical properties such as: pin (tool) rotating speed, pin transition speed, shoulder, diameter, pin length and tilting angle were examined. Optical microscope and scanning electron microscope (SEM) observation, micro hardness tests, and tensile tests were carried out.
PDF KSCI