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Plasma Enhanced CVD 법으로 증착한 BON박막과 Si-DLC 박막의 산화
김찬우,홍리석,이동복 한국표면공학회 2007 한국표면공학회 학술발표회 초록집 Vol.2007 No.-
Amorphous BON and Si-DLC thin films were synthesized by the RF plasma enhanced CVD method, and their oxidation behavior was studied up to 500°C in air. The oxidation of both films was accompanied by evaporation of volatile species. The oxidation of BON film was preceded by nitrogen escape from the film, and oxygen penetration into the film. The oxidation of Si-DLC film was preceded by carbon escape probably as CO or CO₂from the film, and oxygen penetration into the film. The inwardly transported oxygen simply stayed in the oxidized BON and Si-DLC thin films.
지세인(S. I. Ji),이경훈(K. H. Lee),홍리석(L. S. Hong),정진영(J. Y. Jung),김종성(J. S. Kim),김병민(B. M. Kim) 한국소성가공학회 2014 한국소성가공학회 학술대회 논문집 Vol.2014 No.10
It was investigated that plenty of the processes of shape wire drawing process designed by trial and error relying on experience of industrial experts. In consequence of this process, it is inevitable that the increase of product cost, unnecessary time consuming, and effort. In case of manufacturing the final product with asymmetric section geometry and high aspect ratio, the concentration of strain at a side caused the severe distortion of the wire and low-cycle fatigue resistance is formed. The objective of this study is to design process of multi-pass shape wire drawing from initial round material with consideration of the cross section geometry of the final product. First, the multi-pass shape wire drawing process was designed by equivalent potential line in electric field analysis. The reduction ratio of area was calculated by relationship to the number of pass in multi pass shape wire drawing process determined by capacity of drawing machine and drawing force. In order to take account of concentration of strain of cross section of wire, the process for multi shape wire drawing from initial round material to an intermediate die was redesigned using electric field analysis again. In this study, the either drawing process design was estimated by finite element simulation in which the strain distribution and standard deviation plastic strain of the cross section of drawn wire.
유한요소해석을 통한 선재의 표면 흠이 차량용 엔진 밸브 스프링 수명에 미치는 영향 평가
안남식(Nam-sik Ahn),이경훈(Kyung-hun Lee),김병민(Byung-min Kim),홍리석(Lee-Seok Hong),정진영(Jin-young Jung),임성영(Sung-young Lim) 한국자동차공학회 2012 한국자동차공학회 지부 학술대회 논문집 Vol.2012 No.5-1
Recently, the high surface quality of oil hardened and tempered spring steel wire for valve springs with high fatigue strength has been required for the fuel economy of automobile engines. The aim of this study is to investigate the fatigue life of advance high strength steel(AHSS) springs according to surface flaws of oil hardened and tempered spring steel wire. V-shape surface defects were introduced in the initial workpiece and the evolution of deformation behavior and stress distribution such defects was simulated during the manufacturing spring, The FE-simulations were performed to check the local stress distributions around surface flaws using an AHSS spring, which are determined by analysis results of cold coiling and measured residual stresses. The fatigue lives were predicted in comparison with S-N curves and calculated alternating stress.