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김명균(Myoung Gyun Kim),성시영(Si Young Sung),김영직(Young Jig Kim) 한국주조공학회 2002 한국주조공학회지 Vol.22 No.2
N/A The main objectives were to investigate the suitability of CaO crucible for melting TiAl alloys and to develop investment mold for investment casting of TiAl alloys. TiAl alloy specimen were prepared by plasma arc furnace under argon atmosphere. After melting of TiAl alloy using CaO crucible, the results showed that there is little contamination of oxygen in the TiAl bulk. Conentional vacuum induction furnaces can be readily adaptable to produce cast parts of TiAl without high skilled techniques. The determination of optical metallography and microhardness profiles in investment cast TiAl alloy rods has allowed the gradation of the relative thermal stability of the oxides examined. The mold used for the present study were ZrO_2, Al_2O_3, CaO stabilized ZrO_2 and ZrSiO_4. Even although high temperature of mold preheating, Al_2O_3 mold is a promising mold material for investment casting of TiAl alloys in terms of thermal stability, cost and handling strength. It is important to take thermal stability ancpreheating temperature of mold into consideration for investment casting of TiAl alloys.
Sr 개량처리된 사형주조 Al-7Si-0.35Mg 합금의 열처리에 따른 공정 Si상 변화거동 및 특성평가
김명균 ( Myoung-gyun Kim ),황석민 ( Seok-min Hwang ) 한국주조공학회 2018 한국주조공학회지 Vol.38 No.2
In this study, we focused on the correlation between the solidification structure, heat treatment and mechanical properties of the A356 alloy according to the conditions of Sr modification. The microstructural evolution of the eutectic Si and α-Al phase in the A356 alloy castings depending on the amount of Sr were investigated during solid solution heat treatment using an optical microscope, a scanning electron microscope and an image analyzer. In addition, tensile tests on the heat treated materials examined the relationship between the microstructure and the fracture surface. The as-cast A356 alloys under 40 ppm Sr showed an undermodified microstructure, but that of the added 60-80 ppm Sr had well modified structure of fine fibrous silicon. After solid solution treatment, the microstructure of the undermodified A356 alloy exhibited a partially spheroidized morphology, but the remainder showed the fragmentation of fibrous shaped silicon. The spheroidization of the eutectic silicon in the modified A356 alloys was completed during heat treatment, which was very effective in increasing the elongation. This is supported by the fracture surface in the tensile test.
Sr 개량처리된 사형주조 Al-7Si-0.35Mg 합금의 열처리에 따른 공정 Si상 변화거동 및 특성평가
김명균 ( Myoung-gyun Kim ),황석민 ( Seok-min Hwang ) 한국주조공학회 2018 한국주조공학회지 Vol.38 No.1
In this study, we focused on the correlation between the solidification structure, heat treatment and mechanical properties of the A356 alloy according to the conditions of Sr modification. The microstructural evolution of the eutectic Si and α-Al phase in the A356 alloy castings depending on the amount of Sr were investigated during solid solution heat treatment using an optical microscope, a scanning electron microscope and an image analyzer. In addition, tensile tests on the heat treated materials examined the relationship between the microstructure and the fracture surface. The as-cast A356 alloys under 40 ppm Sr showed an undermodified microstructure, but that of the added 60-80 ppm Sr had well modified structure of fine fibrous silicon. After solid solution treatment, the microstructure of the undermodified A356 alloy exhibited a partially spheroidized morphology, but the remainder showed the fragmentation of fibrous shaped silicon. The spheroidization of the eutectic silicon in the modified A356 alloys was completed during heat treatment, which was very effective in increasing the elongation. This is supported by the fracture surface in the tensile test.
반용융 성형가공한 SiCp / AZ91HP Mg 복합재료의 피로 및 내마모 특성
하홍수,김명균,안선규,임병수,김영직 ( Hong Soo Ha,Myoung Gyun Kim,Sun Kyu Ahn,Byeong Soo Lim,Young Jig Kim ) 한국주조공학회 1997 한국주조공학회지 Vol.17 No.5
N/A The effect of size and mass fraction of SiC particulate on the fatigue and wear have been investigated for semi-liquid formed SiCp/AZ91HP Mg composites. In the study, different particulate sizes of 7, 20, 50 ㎛ were prepared with various mass fraction for sample preparation. By tension-tension fatigue tests, whose procedures are standardized in ASTM standard 647E-93, the da/dN vs. ΔK curves were obtained. Also, the crack propagation paths were observed by optical microscope. As a result of wear test, specific wear loss is decreased with increasing mass fraction and particulate size. Specific wear loss of 30 mass% 50 ㎛ SiC reinforced Mg composite is compared to SKD11. (Received July 21, 1997)
스캔 환경에서 간접 유추 알고리즘을 이용한 경로 지연 고장 검사 입력 생성기
김원기(Kim Won Gi),김명균(Kim Myoung Gyun),강성호(Kang Sung Ho) 한국정보처리학회 1999 정보처리학회논문지 Vol.6 No.6
The more complex and large digital circuits become, the more important delay test becomes which guarantees that circuits operate in time. In this paper, the proposed algorithm is developed, which enable the fast indirect implication for efficient test pattern generation in sequential circuits of standard scan environment. Static learning algorithm enables application of a new implication value using contrapositive proposition. The static learning procedure found structurally, analyzes the gate structure in the preprocessing phase and store the information of learning occurrence so that it can be used in the test pattern generation procedure if it satisfies the implication condition. If there exists a signal line which include all paths from some particular primary inputs, it is a partitioning point. If paths passing that point have the same partial path from primary input to the signal or from the signal to primary output, they will need the same primary input values which separated by the partitioning point. In this paper test pattern generation can be more effective by using this partitioning technique. Finally, an efficient delay fault test pattern generator using indirect implication is developed and the effectiveness of these algorithms is demonstrated by experiments.