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김형종,최만호,최우천 한국비파괴검사학회 1993 한국비파괴검사학회지 Vol.13 No.3
포항가속기 저장링 진공챔버는 진공도가 10(-10)Torr로 유지될 수 있도록 설계되었고, 초고진공에 적합하도록 TIG용접을 하여 헬륨에 대한 누설률이 1×10(-10)Torr·ℓ/sec 이하의 기밀성이 요구되고 있다. 저장링 진공챔버에 적용된 TIG용접방법과 결함에 대해 논하고 누설검사에 사용된 헬륨누설검사기의 원리 및 검사방법에 대해서 보고자 한다. The storage ring vacuum system for the Pohang Light Source (PLS) has been designed to maintain the vacuum pressure of 10(-10) Torr which requires UHV welding to have helium leak rate less than 1×10(-10) Torr·ℓ/sec. In order to develop new technique (PLS) welding technique), a prototype vacuum chamber has been welded by using Tungsten Inert Gas welding method and all the welded joints have been tested with a non-destructive method, so called helium leak detection, to investigate the vacuum tightness of the weld joints. The test was performed with a detection limit of 1×10(-10) Torr·ℓ/sec for helium and no detectable leaks were found for all the welded joints. Thus, the performance of welding technique is proven to meet the criteria of helium leak rate required in the PLS Storage Ring. Both the principle and the procedure for the helium leak detection are also discussed.
최우천, 최우영, 송대준, 이건상 한국레이저가공학회 2000 한국레이저가공학회지 Vol.3 No.1
Selective Laser Sintering(SLS) can produce three-dimensional objects directly from a CAD solid model without part-specific tooling. In this study, a simple rapid prototyping through selective laser sintering on brass powder is investigated using a Nd:YAG laser. Experiments are conducted to produce single lines on a powder-packed bed for various process parameters. Also, temperature distribution in the powder bed and the thickness of a melted line are predicted by finite element analysis. In the numerical analysis, the thermal conductivity of the brass powder which is obtained as a function of state and temperature is used.