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1wt.% Bi 함유 무연황동의 인장강도와 내식특성에 대한 연구
주영석 ( Y S Joo ),이상봉 ( S B Lee ),김시영 ( S Y Kim ),주창식 ( C S Joo ),정병호 ( B H Jung ) 한국열처리공학회 2011 熱處理工學會誌 Vol.24 No.3
This study has been investigated for tensile properties with lead-free brass containing 1wt.% of Bi. And also characteristic of corrosion resistance was analyzed by polarization test. An increase of tempering temperature was found to tend to decrease tensile strength, and percentage of elongation was shown to be the lowest value at 300°C. On the other hand, the elongation was increased with an increase of tempering temperature after 300°C. The change of mechanical properties was closely related with the content and shape of acicular Witmanst?tten α formed at the interface of β phase as well as in β phase. Tensile strength had a tendency to be decreased with an increase of test temperature. The elongation was shown to be the lowest value at around 300°C, while it began to increase as test temperature rose after 300°C. It might be speculated that the reason that elongation was decreased was found to form bismuth film at the interface of α/β phase leading to be easily brittle when loaded by tensile stress. The lead-free brass containing 1wt.% of Bi had similar characteristic of corrosion resistance with a free-cutting brass with 3.4wt.% of Pb in spite of higher fraction of β phase.
진의봉(U. B. Jin),주영석(Y. S. Joo),김시영(S. Y. Kim) 한국동력기계공학회 2004 한국동력기계공학회 학술대회 논문집 Vol.- No.-
The scale correction was analyzed for model to prototype with roughness effects in the pipe. The flow law of log and law of the wall were used by theoretical analysis to calculate the scale correction with surface roughness effects. For the surface roughness in the pipe flow for marine pipe fittings in boiler, heat exchange and the velocity field in the turbulent boundary layer on the wall is determined by scale for law of log and law of the wall. In this study, the calculation for the variation of diameter for roughness effects with variation velocity was investigated to design the facility of the ship. It was shown that the surface roughness effects in scale effects for model to prototype relation could be applied depending on scale ratio in model to prototype.
권중기 (J. K. Kwon ),주영석 (Y. S. Joo ),김시영 (S. Y. Kim ) 한국동력기계공학회 2008 한국동력기계공학회 학술대회 논문집 Vol.2008 No.11
The Mono flex impeller(CR), which is installed inside the bronze housing of the conventional Mono flex pump, is causes the abrasion. Because of the source of breakdown, there is a need to study to prevent the abrasion. In this study, to solve this problem, abrasion test of the rotating impeller equipped with poly-acetal membrane bushing shape between the mono flex housing and impeller were conducted using several approaches. Through the change of oil temperature, rotation speed of the impeller and propulsion pressure, the abrasion test equipped with CR-rubber and actual bushing was intended to contribute to the actual design of the parts by conducting experimental comparison and analysing.