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허용학(Y.-H Huh),김동진(D.J. Kim),이해무(H.M. Lee),홍성구(S.G. Hong),박준협(J.H. Park) 대한기계학회 2009 대한기계학회 춘추학술대회 Vol.2009 No.5
Fatigue limit of the copper film coated by Sn was estimated by using Goodman diagram and Gerber diagram. To obtain the high cycle fatigue life S-N curve of the film, the high cycle fatigue test was carried out by applying the constant amplitude load to the film specimen with three different stress ratio of 0.1, 0.3 and 0.5 and the frequency of 40 ㎐ at room temperature in air. The film specimen 15.26㎛ thick was fabricated by etching process. The fatigue limits and S-N curves at the respective stress ratios were determined from the experimental works. It was shown that the S-N curves were dependent on the stress ratio and the fatigue limit was increased with decreasing the stress ratio. The dependency of the fatigue behavior was presented in empirical relationship. Using these relationships, the fatigue limit was predicted.
수리모형 실험에 의한 선박 부착형 오탁방지막의 거동특성 구명
홍성구 ( S. G. Hong ),강구 ( K. Kang ) 한국농공학회 2012 한국농공학회 학술대회초록집 Vol.2012 No.-
Silt curtains are constructed for minimizing pollution of sediment dispersion in water bodies. In spite of wide uses of the silt curtains, there are few studies for analyzing the effectiveness of them with respect to their dimension and hydraulic characteristics. Currently, the market of silt curtains does not provide the various dimension of them due to the limit of information regarding its effectiveness on reducing sediment pollution. In this study, a series of experiments was conducted to investigate hydraulic characteristics around the silt curtains under the different flow conditions. The information to be obtained will provide information required to design appropriate dimension of silt curtains in various water environment such as velocity and water depths. For this study, a silt curtain was fabricated and an open channel with 30cm of width and 40cm of depth was used. The results indicated that the silt curtain was not effective in preventing dispersion at flow velocities over 6 cm/s. Based on the experimental results, it is required that approaching velocity be minimized and the weight of bottom be increased in order to reduce deformation angles.
{10-12} 쌍정 특성이 AZ31 마그네슘 합금 압연재의 변형거동에 미치는 영향
박성혁(S. H. Park),홍성구(S. G. Hong),이종수(C. S. Lee) 한국소성가공학회 2010 한국소성가공학회 학술대회 논문집 Vol.2010 No.5
The active twin variants during {10-12} twinning of magnesium alloys were dependent on the activation mode (i.e., compression perpendicular to the c-axis or tension parallel to the c-axis) and their section mechanism was governed by the Schmid law. The activation of specific twin variants depending on the activation mode induced a significant difference in twinning characteristics, such as twin morphology, volume fraction of twins with strain, and twin texture, and consequently gave rise to a totally different effect on the deformation. The differences in the deformation characteristics (flow stress and strain hardening) between both activation modes were explained in relation with activation stresses for twinning and slips, activities of twinning and slips in the deformation, Hall-Petch effect by twinning-induced grain size change, and twinning-induced change in activities of slips.