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해수배관 내부 에폭시 코팅재의 캐비테이션 및 침지 열화에 따른 압입인장특성
정민재 ( M. J. Jung ),김수현 ( S. H. Kim ),전종모 ( J. M. Jeon ),김영식 ( Y. S. Kim ),김영천 ( Y. C. Kim ) 한국부식방식학회 2023 Corrosion Science and Technology Vol.22 No.6
Seawater has been used to cool devices in nuclear power plants. However, the pipes used to transport seawater are vulnerable to corrosion; hence, the inner side of pipelines is coated with an epoxy layer as prevention. Upon coating damage, the pipe becomes exposed, and corrosion progresses. The major cause is widely known as cavitation corrosion, causing the degradation of mechanical properties. In this study, corroded specimens were prepared using cavitation and immersion methods to clarify the degradation trend of mechanical properties with corrosion. Three different types of epoxy coatings were used, and accelerated cavitation procedures were composed of amplitudes of 15 μm, 50 μm, and 85 μm for 2 h, 4 h, and 6 h. The immersion periods were 3 and 6 weeks. We conducted instrumented indentation tests on all degradation samples to measure mechanical properties. The results showed that higher cavitation amplitudes and longer cavitation or immersion times led to more degradation in the samples, which, in turn, decreased the yield strength. Of the three samples, the C coating had the highest resistance to cavitation and immersion degradation.
피칭운동을 하는 대형 우주발사체 형상의 천음속 비정상 유동해석
김동현(D. H. Kim),김요한(Y. H. Kim),김동환(D. H. Kim),윤세현(S. H. Yoon),김광수(G. S. Kim),장영순(Y. H. Jang),김수현(S. H. Kim) 한국전산유체공학회 2010 한국전산유체공학회 학술대회논문집 Vol.2010 No.11
In this study, steady and unsteady aerodynamic analyses of a huge rocket configuration have been conducted in the transonic flow region. Launch vehicle structural response can couple with transonic flow state transitions at the nose of payload fairing. Before doing fluid-structure coupled transonic aeroealstic simulations for a huge rocket configuration, transonic aerodynamic characteristics are investigated for pitching motions of the rocket with angle-of attack. Unsteady CFD analysis method with moving grid technique based on Reynolds-averaged Navier-Stokes equations with κ-ω SST transition turbulence model is applied to accurately predict the transonic loads of the rocket with pitching motion. It is importantly shown that the fluctuated amplitude of lateral aerodynamic loads imposed on the rocket due to pitching motion can be significantly increased in the transonic region when the rocket has certain angle-of-attack.
피칭운동을 고려한 우주발사체 형상의 천음속 비정상 유동해석
김동현(D.H. Kim),김요한(Y.H. Kim),김동환(D.H. Kim),윤세현(S.H. Yoon),김광수(G.S. Kim),장영순(Y.H. Jang),김수현(S.H. Kim) 한국전산유체공학회 2011 한국전산유체공학회지 Vol.16 No.1
In this study, steady and unsteady aerodynamic analyses of a huge rocket configuration have been conducted in a transonic flow region. The launch vehicle structural response are coupled with the transonic flow state transitions at the nose of the payload fairing. Before performing the coupled fluid-structure transonic aeroealstic simulations transonic aerodynamic characteristics are investigated for the pitching motions of the rocket at finite angle-of-attack. An unsteady CFD analysis method with a moving grid technique based on the Reynolds-averaged Navier-Stokes equations with the k-w SST transition turbulence model is applied to accurately predict the transonic loads of the rocket at pitching motion. It is shown that the fluctuating amplitude of the lateral aerodynamic loads imposed on the rocket due to the pitching motion can be significantly increased in the transonic flow region.
생사정량산정(生絲正量算定)에 있어서 연감후(練減後) 무수량(無水量)의 도입(導入)에 관(關)한 연구(硏究)
김수현 ( S. H. Kim ),이상근 ( S. K. Lee ),김영진 ( Y. J. Kim ) 한국잠사학회 1971 한국잠사곤충학회지 Vol.13 No.1
본 시험은 공정거래를 기할 수 있도록 진섬유량으로부터 생사의 거래중량을 산정할 수 있는 정량거래방법을 구명하기 위한 연구로서 다음과 같은 결과를 얻었다. 1. 거래중량인 정량은 원량에서 연감후무수량을 감한 연감수분량의 원량에 대한 백분율인 연감수분률로부터 산정하면 생사의 진섬유량을 잘 나타낼 수 있고 재현성이 있어 현행검사보다 합리적이다. 2. 연감수분률로부터 정량을 산정함에 있어서 연감후무수량에 대한 공정가산률은 44%로 함이 적당하다고 판단된다. 3. 섬도검사 잔사인 섬도사의 연감률과 하구의 연감률을 대표할 수 있을 것으로 생각되는 시료사(24타래)의 연감률 사이에 통계적인 유의차가 없었으므로 섬도사의 연감률은 하구의 연감률을 대표할 수 있다. 4. 우리나라는 연감수분율검사에 의한 정량검사를 실시하면 약 2억원의 이득을 얻을 수 있다. The purpose of this study is to find out the method of conditioned weight test by which the dealing weight of raw silk can be calculated from true fiber in order to do the fair trading. The results of this study were as follows. 1. It is more reasonable than the current test that conditioned weight as a dealing weigh can be calculated by boil-off and moisture regain which is a percentage of boil-on and moisture regain to net weight. Because the boil-off and moisture regain can show directly the amount of true fiber and reproductibility in raw silk. In this study the boil-off and moisture regain is to take dry weight after boiling-off from net weight. 2. To calculate the conditioned weight from boil-of and moisture regain it would be proper that the standard additional ratio is 44 per cent of dry weight after boiling-off. 3. Boil-of percent of the sizing sample skein used in the size test did not show a statistical significance comparing with the boil-off percent of sample skeins (24 skeins) which may represent that of a lot. To observe this result boil-off percent of the sizing sample skein may represent that of a lot. 4. In Korea if conditioned weight test substitute for test of boil-off and moisture regain, we make a profit of two billion won in a year at the current market-price.