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AZ31B 마그네슘합금의 피로균열성장에 미치는 응력비 및 이방성의 영향
김명근(M. K. Kim),김귀식(K. S. Kim) 한국동력기계공학회 2008 한국동력기계공학회 학술대회 논문집 Vol.2008 No.11
In This study, fatigue was to investigate the effects of R Ratio and anisotropy on Fatigue Crack Propagation(FCP) Behavior of AZ31B Magnesium alloy. The experimental materials were magnesium alloys AZ31B. The FCP test was conducted on compact tension specimen by a servo-hydraulic fatigue testing machine under the load control amplitude in laboratory air at ambient temperature. Compact specimens were prepared from the extruded parallel and vertical direction. The test condition was frequency of 10Hz, sinusoidal load, and a load ratio of 0.1 and 0.7. The FCP was automatically measured by a compliance method. In the case of the FCP of AZ31B, the FCP of both direction of LT and TL by anisotropy of specimens are almost same value. In lower stress ratio, the FCP of the LT, TL specimens are increased in lower △K region but higher △K regions are almost same value. Finally, the result of observed the surface crack, it expressed the quasi-cleavage fracture in lower △K region and straight mark on the aspect of the facet in high △K region.
복합표면처리된 CrZrN 박막의 밀착력에 미치는 스퍼터링 효과에 관한 연구
김명근(M.K. Kim),김은영(E.Y. Kim),이상율(S.Y. Lee) 한국표면공학회 2006 한국표면공학회지 Vol.39 No.6
In this study, effect of sputtering on the plasma-nitriding substrate and before PVD coating on the micros-tucture, microhardness, surface roughness and the adhesion strength of CrZrN thin films were investigated. Experimental results showed that this sputtering process not only removed surface compound layer which formed during a plasma nitriding process but also induced an alteration of the surface of plasma nitrided substrate in terms of microhardness distribution, surface roughness. This in turn affected the adhesion strength of PVD coatings. After sputtering, microhardness distribution showed general decrease and the surface roughness became increased slightly. The critical shear stress measured from the scratch test on the CrZrN coatings showed an approximately 1.4 times increase in the adhesion strength through the sputtering prior to the coating and this could be attributed to a complete removal of compound layer from the plasma nitrided surface and to an increase in the surface roughness after sputtering.
복합표면처리된 CrN박막의 밀착력에 미치는 스퍼터링 효과에 관한 연구
김명근(M.K. Kim),김은영(E.Y. Kim),김정택(J.T. Kim),이상율(S.Y. Lee) 한국표면공학회 2006 한국표면공학회지 Vol.39 No.1
In this study, effect of sputtering after plasma nitriding and before PVD coating on the microstucture, microhardness, surface roughness and the adhesion strength of CrN thin films were investigated. Experimental results showed that this sputtering process not only removed surface compound layer which formed during a plasma nitriding process but also induced an alteration of the surface of plasma nitrided substrate in terms of microhardness distribution and surface roughness, which in turn affected the adhesion strength of PVD coatings. After sputtering, microhardness distribution showed general decrease and the surface roughness became increased slightly. The critical shear stress measured from the scratch test on the CrN coatings showed an approximately twice increase in the binding strength through the sputtering prior to the coating and this could be attributed to a complete removal of compound layer from the plasma nitrided surface and to an increase in the surface roughness after sputtering.