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고대철,김병민,강범수 대한기계학회 1994 대한기계학회논문집 Vol.18 No.11
The central burst defects, so-called chevroning, in wire drawing are analyzed by the rigid-plastic finite element method. The occurrence of central burst defects in wire drawing is estimated by the distribution of the hydrostatic pressure around the central part of the workpiece. It has been possible to obtain numerical boundaries which, in reduction in area vs. semicone angle plane, divide the safe and the danger zones, depending on friction factors and material properties. Based on the results of the analysis, it is suggested that the previous criterion derived from the upper bound analysis should be modified for better prediction of the defects. The back tension and the billet with a spherical hole on the central axis are also included in the analysis of the defects.
유한요소해석을 이용한 박판 벤딩용 CO<sub>2</sub> 레이저 성형기 제작
고대철,이찬주,김병민,Ko D.C.,Lee C.J.,Kim B.M. 한국소성가공학회 2006 소성가공 : 한국소성가공학회지 Vol.15 No.4
The laser forming process is a new flexible forming process without forming tools and external force, which is applied to various fields of industry. Especially, applications of the laser forming process focused on cutting, welding and marking process. In this paper, the laser bending process of sheet metal which is heated by laser beam and formed by internal stress is simulated by using thermo elastic-plastic analysis model. Based on the result of FE-analysis, the laser bending machine is made to obtain reliable data for sheet bending. Under the same condition as FE-analysis, the laser bending experiment has been performed to ver 펴 the result of FE-analysis and good agreement has been obtained between FE-analysis and experiments. Additional laser bending experiments have been performed to evaluate the laser bending machine.
고대철,김병민,오세욱,Go, Dae-Cheol,Kim, Byeong-Min,O, Se-Uk 대한기계학회 1996 大韓機械學會論文集A Vol.20 No.11
The Hub is an auto mobile component used as aircon clutch. The important aspects in cold forging of the Hub with complex geometry are the design of an initial shape of the workpiece, the possibility of the forming by one-stage operation and the determination of number of performs, etc. Based on the systematic procedure of process sequence design, in this paper, the forming operation of cold forged part of the Hub is designed by the rigid-plastic finite element method. The two design criterion of geometrical filling without defect and an even distribution of effective strain in final product are investigated in controlling the initial shape of the workpiece and preform configuration. It is noted that one preforming operation is required in order to obtain final product of the Hub.