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공압식 폐쇄다이세트 적용 정밀단조공정 설계 및 해석기술
이광석(K. S. Lee),엄득하(D. H. Eom),강성훈(S. H. Kang),이정환(J. H. Lee) 한국소성가공학회 2009 한국소성가공학회 학술대회 논문집 Vol.2009 No.10
This paper describes design and analysis techniques of cold forging process for precise producing of T-200 type spider made of SCr420H by utilizing pneumatically operated enclosed die set. Since deducing feasible closing force is an important factor to optimize entire pneumatically operated cold forging system, a series of FE analyses with varying the number of gas cylinders has been carried out to investigate the influence of closing force upon the direction of applied load at die surfaces. It also reveals the optimum distribution of the gas cylinders in terms of the flatness of upper/lower plates.
STS-Al-Mg 3-ply 이종금속소재 계면 미세 조직 및 변형 특성에 미치는 열처리의 영향
이광석(K.S. Lee),조유미(Y.M. Jo),윤동현(D.H. Yoon),이수은(S.E. Lee),허진희(J.H. Heo),강남현(N.H. Kang),권용남(Y.N. Kwon),이영선(Y.S. Lee) 한국소성가공학회 2012 한국소성가공학회 학술대회 논문집 Vol.2012 No.10
We present here an exploration of the relationship among post-roll bonding process variables, interfacial and overall mechanical properties of a 3-ply STS-Al-Mg laminated composite. The effect of post-annealing conditions upon the evolution of interface microstructure is first analyzed by means of optical microscope (OM), scanning electron microscope (SEM), transmission electron microscope (TEM) attached with energy dispersive spectroscopy (EDS). Taking the composition and thickness of each intermetallic compound layer into account, results devoted to the interfacial microstructure and overall mechanical properties are also given. Local mechanical properties for the generated diffusion layers were first determined by nanoindentation tests. The mechanism of improvement of interfacial bonding is then verified by means of uniaxial tensile and bending tests. Finally the competitions between two contradictory effects, viz., interface strengthening by the generation of IMCs and the corresponding loose of overall ductility due to the embrittlement, is discussed.
Ni-Fe-Co 합금의 고온 변형 공정 변수와 미세조직 및 열물리적 특성의 상관 관계
이광석(K.S. Lee),정중은(J.E. Jung),장영원(Y.W. Chang),이정환(J.H. Lee) 한국소성가공학회 2011 한국소성가공학회 학술대회 논문집 Vol.2011 No.5
High temperature deformation behavior of a Ni30Fe53Co17 alloy was investigated by conducting a series of compression tests. After constructing empirical process map, the appropriate working temperature-strain rate combination for optimum forming was deduced to be~1423 K, 10<SUP>-2</SUP> s<SUP>-1</SUP> region having relatively high power dissipation efficiency greater than 0.36. Furthermore, open die forging for the 100 mm diameter billets was performed to confirm the variation of thermo-physical properties in relation to microstructure. The coefficient of thermal expansion was found to increase considerably with increasing the open die forging temperature and decreasing the cooling rate, which in turn provides a drastic increase of average grain size.
고주파 유도 열원 적용 선상가열 유기 조선용 후판 이중곡률 성형기술
이광석(K. S .Lee),이정환(J. H. Lee) 한국소성가공학회 2012 한국소성가공학회 학술대회 논문집 Vol.2012 No.5
Line heating-induced permanent deformation behavior of a SS400 thick plate has been investigated through both numerical analysis and experimental testing by applying high frequency induction as a heat source after generating dual-curvature by secondary line heating. Electromagnetic-thermal-structural coupling numerical analysis was first utilized for the prediction of temperature distribution and subsequent permanent deformation over the SS400 carbon steel plate. Also experimental line heating was carried out to validate the feasibility of the numerical analysis by applying newly designed laboratory-scale high frequency (HF) induction heating (IH) equipment. Both the numerical and experimental results indicate that depth and width of the heat affected zone (HAZ), generated by the interaction between I-IF induction heat source and upper surface of the workpiece, tend to increase with the increase in the input power. Also the numerically calculated depth of HAZ coincides well with experimentally obtained HAZ profiles. Permanent vertical deformation is increased with an increase in the input power regardless of both concave and saddle-type doubly curved plates. Transverse curvature determined in both simulation and experiment were investigated, and the results indicate that the transverse curvature after HF IH achieves good agreements between the FE analysis and experimental measurement regardless of input power and shape of plate, indicating the effectiveness of the eco-friendly designed HF IH-based line heating apparatus established in KIMS.
이광석(K.S. Lee),김창원(C.W. Kim),변상윤(S.Y. Pyun),이정환(J.H. Lee) 한국소성가공학회 2011 한국소성가공학회 학술대회 논문집 Vol.2011 No.5
Prediction of temperature distribution and subsequent permanent deformation over the SS400 carbon steel plate during the induction-based line heating process is analyzed by a numerical method by three-dimensional electromagnetic-thermal-structural coupling analysis. The numerical study reveals that the amount of permanent deformation is strongly related to the Joule loss upon different process conditions such as input power and moving speed of the heat source.