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최영택,변상교 ( Y . T . Choi,S . K . Byoun ) 한국열처리공학회 1992 熱處理工學會誌 Vol.5 No.1
This content is a part of the results of the study on the development of the vacuum carburizing technology. In this study the vacuum carburizing furnace being used was the furnace that developed through the joint project between KIMM and Kyung-Pook Heat Treating Co. from June 1988 to Nov. 1990. And the used carburizing gas was the propane gas and the introducing methods of the gas applied two methods such as pulse and constant pressure. By this study we established the basis of the furnace manufacturing technology and of the processing technology in the vacuum carburizing. Above all in this work there are notable meanings in a viewpoint of the foremost research in home. Hereafter, we are going to industrialize the vacuum carburizing technology by improving the results of the present work and by developing the process for the mass production.
Brazing 과 Metallizing에 의한 세라믹/금속 접합재 잔류응력의 유한요소 해석
최영택(Y.T.Choi),박명균(M.K.Park),박세만(S.M.Bahk),선동주(D.J.Sun) 한국자동차공학회 1997 한국자동차공학회 춘 추계 학술대회 논문집 Vol.1997 No.6_2
In this study finite element method(FEM) is utilized to determine residual stress distributions induced by heat generated during joining processes of ceramics and metals.<br/> The finite element analysis is focused on the joining area. That comprises the interfacial area between a metal and a insert-layer. The inser-tlayer itself and adjoining area between the insert-layer and a ceramic.<br/> The residual stress distributions on the joining area are analyzed as functions of thicknesses and yield stresses of the insert-layer(Brazing Filler Metal). And for different kinds of metals including SUS304 and SM45C.<br/> Two typical joining processes are considered in this investigation: Active Metal Brazing and Metallizing. Stress distributions on the joining areas are computed for both processes and are compared with one another. This comparison can lead to the better joining method in reducing the residual stresses and consequently provide improved joining technologies.<br/>
Al₂O₃/低膨脹合金의 接合强度와 應力特異性에 關한 硏究
주재황(J. H. JOO),최영택(Y. T. CHOI),박명균(M. K. PARK),박세만(S. M. PARK),최승규(S. G. CHOI) 한국자동차공학회 1996 한국자동차공학회 춘 추계 학술대회 논문집 Vol.1996 No.11_1
In this research, both computational and experimental studies are conducted to reveal mechanical natures of bondings and consequences of joining processes for metals and ceramic pairs. In the computational part of this research a FEM analysis was utilized to effectively evaluate stress fields around ceramic-metal interfaces. Special attentions were paid to consider the low yield strength of interlayer alloys(buffer alloys). For the experimental part the effectiveness of active brazing metal methods was investigated. For the test. four different types of ceramic-metal pairs are fabricated. All the ceramic-metal pairs are brazed in vacuum at 850℃, 900℃ and 950℃. Tensile tests were conducted on the fabricated ceramic-metal pairs to evaluate bond strength between ceramics and metals. The test results show temperature effects and increases in bond strengths which is largely due to the inserted buffer layers(Mo-Mn and Ni Layer).
유한요소법을 이용한 단순인장 시험편의 탄소성파괴인성치 예측
선동주(D.J.Sun),박명균(M.K.Park),박세만(S.M.Bahk),최영택(Y.T.Choi) 한국자동차공학회 1997 한국자동차공학회 춘 추계 학술대회 논문집 Vol.1997 No.11_2
In oder to predict the elastic-plastic fracture toughness for metallic materials, Finite Element Method(FEM) was used for analysis of compact tension specimen. ASTM E399 test procedure was adopted for simulation of FEM. The Load-Crack Mouth Opening Displacement curve obtained from this analysis was used to detect the crack initiation point and determine the elastic-plastic fracture toughness J_IC. In order to prove the results, they were compared with the results from previous experiments and they agree with experimental results.
Brazing 과 Metallizing 에 의한 세라믹/금속 접합재 잔류응력의 유한요소 해석
최영택,박명균,박세만,선동주 명지대학교 대학원 1997 대학원논문집 Vol.1 No.-
In this study finite element method(FEM) is utilized to determine residual stress distributions induced by heat generated during joining processes of ceramics and metals. The finite element analysis is focused on the joining area, that comprises the interfacial area between a metal and a insert-layer, the insert-layer itself and adjoining area between the insert-layer and a ceramic. The residual stress distributions on the joining area are analyzed as function of thicknesses and yield stresses of the insert-layer(Brazing Filler Metal), and for different kinds of metals including SUS304 and SM45C. Two typical joining processes are considered in this investigation ; Active Metal Brazing and Metallizing. Stress distributions on the joining areas are computed for both processes and are compared with one another. This comparison can lead to the better joining method in reducing the residual stresses and consequently provide improved joining technologies.
有限要素法을 이용한 열사이클 荷重壯態에서의 세라믹 /金屬 接合材의 强度 平價
최영택,박명균,박세만,선동주 明知大學校 産業技術硏究所 1998 産業技術硏究所論文集 Vol.17 No.-
In this work, variations of residual stresses are investigated by varying thicknesses of copper interlayers inserted for stress relaxations. Futhermore, various modes of stress distributions are evaluated under different assumptions of physical situations. departing from the simple assumption and adopting new assumption is judiciously made to study variations of residual stresses under the simple and new assumption, respectively. The simple assumption dictates that temperature distributions in the ceramic/metal joints are uniform, which amounts to longer cooling time (slow cooling), while the new assumption relaxes the condition of uniform temperature distributions allowing variations of temperatures in the ceramic/metal joints. Especially, the thermal cycles are applied to ceramic/metal joints retaining residual stresses developed during joining processes. Changes in distributions of residual stresses under the applied thermal cycles and the behavior of ceramic/ metal joints formed at elevated temperatures are evaluated from finite element analysis to produce results in good agreement with the existing experimental data.
유한요소법을 이용한 금속재료의 탄소성파괴인성치 결정에 관한 연구
박명균,최영택,박세만,선동주 明知大學校 産業技術硏究所 1998 産業技術硏究所論文集 Vol.17 No.-
In oder to predict the elastic-plastic fracture toughness for metallic materials, Finite element Method(FEM) was used for analysis of compact tension specimen. ASTM E399 test procedure was adopted for simulation of FEM. The Load-Crack Mouth Opening Displacement curve obtained from this analysis was used to detect the crack initiation point and determine the elastic-plastic fracture toughness Jic. In order to prove the results, they were compared with the results from previous experiments and they agree with experimental results.
3차원 탄소성 유한요소법을 통한 금속복합재료와 지르코니아 접합체의 잔류응력해석
주재황,선동주,최영택,박세만,박명균 明知大學校 産業技術硏究所 1996 産業技術硏究所論文集 Vol.15 No.-
Employing a three dimensional finite element method a thermal elasto-plastic stress analysis was conducted to investigate residual stress distributions on the joining area between a ceramic(ZrO₂) and a SiC whisker-reinforced aluminum (Al composite). For purposes of comparisons, residual stresses at the interfaces on the joining area were first analyzed for varying volume fractions of SiC whiskers utilizing two dimensional elasto-plastic models. The results from the 2-D models were compared with those from 3-D models to understand the Practical nature of residual stresses produced during industrial joining processes for ceramics and metal matrix composites. Additionally, the same procedures were applied to compute stress variations along a line passing through the joining area to obtain a physical insight and to offer a plausible explanations for fracture patterns occuring at the interfaces during bending.