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아닐링처리에 따른 NbTi초전도 선재의 RRR거동에 미치는 피로손상의 영향
신형섭,오상엽 安東大學校 工業技術硏究所 2000 공업기술연구논문집 Vol.7 No.1
9본으로 구성된 Cu-Ni/NbTi/Cu 복합선재의 RRR에 대한 피로손상의 영향을 연구하기 위하여 상온에서 피로시험을 실시하고, 12K에서 잔류저항을 측정하였다. 피로시험은 아닐링열처리한 초전도 선재를 사용하였다. 피로시험시 소선간의 fretting이 발생한 가능성이 높았지만, 9본 Cu-Ni/NbTi/Cu 복합선재의 피로시험을 통하여 S-N선도를 구살 수 있었다. 피로시험후 NbTi소선의 저항을 측정한 결과, 아닐링한 선재의 RRR값이 처녀재보다 3배가 높았으나, 피로 반복수가 증가함에 따라 격자결함과 Cu안정화재 내부에 전위와 같은 손상의 누적 원인으로 RRR값이 감소하였다. In order to investigate how the fatigue damage influences on the RRR of a 9 strand Cu-Ni/NbTi/Cu composite cable, the fatigue test at room temperature and the residual resistivity measurement test at 12K were carried out. The annealing treated superconducting cable was used in the fatigue test. A conventional S-N curve could be obtained through the fatigue test of the 9 strand Cu-Ni/NbTi/Cu composite cables, despite a high possibility of fretting among strands. From the resistivity measurement of a NbTi strand after fatigue tests, it was found that the RRR for annealed cables was 3 times higher than that for as received one, but with increasing the repeated number the RRR decreased which was resulted from the accumulation of damage such as lattice defects and dislocations within the Cu stabilizer.
신형섭,이규호,박종화,Shin, Hyoung-Sub,Lee, Kyu-Ho,Park, Jong-Hwa 한국농공학회 2009 한국농공학회논문집 Vol.51 No.3
The objective of this study was to investigate the basic relationships between spectral reflectance and varying concentrations of sediment in surface waters. An experimental method for determining suspended sediment concentration (SSC) in the water by use of a spectroradiometer above the water surface, in visible and near-infrared (NIR) wavelengths, is applied. The main advantage of the method is the direct comparison of spectral reflectance and the SSC, but it requires an accurate knowledge of the water body and sediment. Therefore numerous spectroradiometric measurements are carried out in situ measurements, for SSC, ranging from zero to 100 percentage and two types of sediment applied in the water tank. The results indicate that the suspended sediment causes increasing spectral reflectance response in waters. We observed that spectral reflectance increases with SSC, first at the lower wavelengths (430-480 nm), then in the middle wavelengths (570-700 nm), and finally, in the NIR domain (800-820 nm); a characteristic maximum reflectance appears at 400-670 nm. Relationships between the wavelength, integral value, and the SSC were evaluated on the basis of the regression analysis. The regression curve for the relation between the wavelength, integral value, and the SSC were determined ($R^2$>0.98). Finally, the specular wavelength can be estimated to recognize the sediment and to improve SC estimation accuracy in the water.
마그네슘합금(AZ31B) 판재의 마찰교반 점용접시 접합특성에 미치는 툴 속도의 영향
신형섭,정윤철,최광,Shin, Hyung-Seop,Jung, Yoon-Chul,Choi, Kwang 대한용접접합학회 2011 대한용접·접합학회지 Vol.29 No.2
In this study, the friction stir spot welding (FSSW) of Mg alloy sheets has been tried using an apparatus devised with a CNC milling machine to give the precise control of joining condition including tool speed. The probe tool used is made of hard metal and composed of cylindrical shoulder and pin parts. The variation of morphologies formed after the friction stir spot welding depending on the plunge speed of the tool were investigated at each rpm of tool. The history of the temperature distribution and the vertical load induced during the spot welding with friction time were measured by using an Infrared Thermal Imager (THERMA CAMTM SC2000) and a loadcell located below the specimen fixture, respectively. Tensile-shear tests were also performed to evaluate the fracture load of welded specimens. In order to characterize the friction stir spot welding of Mg alloy sheets, the variation of the fracture load was discussed on micrographic observations, temperature distribution during the FSSW according to the plunge speeds of tool.