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U-bending에서의 Spring-back 제어에 관한 연구
현경환,김종호 서울産業大學校 2005 논문집 Vol.54 No.1
Spring-back has been one of key factors to influence the quality of stamped parts in the U-bending process. It is generally caused by residual stress of the sheet during sheet metal forming processes, and measured as the amount of deformation after the sheet is released from dies. Since such deformation has a bad effect onf the accuracy of the product, evaluation of the spring-back is necessary for the reduction of the lead time and cost in the die development. Three type of sheet materials have been used in the present work : STS304, SPCC and C1201. As for the C1201 sheet, the spring-in has been detected for the bending along the rolling ditrction with a bottoming punch. On the other hand, for the STS304 sheet, the sheet direction, a bending along the transverse direction shows more amount of spring-back than the rolling direction. In case of SPCC, there is a negligiale change for the variation of relative blankholding forces. It is expected that the experimental results can play a role as a guideline in the U-bending design process. Additional systematic approaches can be implemented considering more processing factors as future work.
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박동환,현경환,이명준 한국소성∙가공학회 2020 소성가공 : 한국소성가공학회지 Vol.29 No.2
Wire drawing is a metalworking process used to reduce the cross-section of a wire by pulling the wire through multi-stage drawing dies. The aim of this study is to fabricate a drawing wire using 2 stage drawing process. The finite element analysis of wire drawing was conducted to validate the efficiency of the designed process and the experiment was performed to validate the designed wire drawing process using 2 stage tungsten carbide die. Dry lubricant with powder was applied for producing a wire of desired diameter. Finally, a drawing wire using 2 stage die for cold rolling mill was developed.
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고온 진공 브레이징을 이용한 초경합금과 스테인리스강의 접합 계면 특성
박동환,현경환,권혁홍 한국소성∙가공학회 2020 소성가공 : 한국소성가공학회지 Vol.29 No.6
The cemented carbide and stainless steel were bonded using a hot-vacuum brazing method to analyze the bonding interface. Since it is suitable for the hot vacuum brazing, nickel metal was used as a binder among the main components of the cemented carbide, and a new cemented carbide material was developed by adjusting the alloy composition. The paste, which is one of the important factors affecting the hot vacuum brazing bonding, was able to improve brazing adhesion by mixing solder as Ni powder and a binder as an organic compound at an appropriate ratio. Division of the stainless steel yielded a dense brazing result. This study elucidated the interfacial characteristics of wear-resistant parts by bonding stainless steel and cemented carbide via hot vacuum brazing.
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후판 소재를 적용한 파인 블랭킹 금형 수명에 관한 연구
박동환,현경환 한국소성∙가공학회 2021 소성가공 : 한국소성가공학회지 Vol.30 No.3
Fine blanking is a high-precision process combining principles of metal stamping and cold forming. Unlike conventional metal stamping, fine blanking uses a special triple action such as V-ring force, counter force, shearing force. This study performed the effect of pocket-shaped compression molding on the mold life of the fine blanking using the 7.4mm thick SM45C material. In order to determine the lifespan of the punch and die in the fine blanking molds, a trial mold was manufactured and various punch materials were selected to perform the mold life test. A study on the life of a fine blanking mold by applying a thick plate material was experimentally performed through a mold test.
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고함량의 Mg을 함유한 Al-Mg 합금의 이축교번단조 변형에 따른 미세조직 및 인장특성 변화
신영철,하성호,윤영옥,김세광,최호준,현경환,현승균 한국소성∙가공학회 2019 소성가공 : 한국소성가공학회지 Vol.28 No.6
Microstructure evolution and tensile properties of Al-8mass%Mg alloy casting billet by biaxial alternative forging were investigated in this study. An alternative forging system tailored in this study was used to allow continuous strain accumulations on the alloy workpiece. A finite element (FE) simulation results revealed that the strain was mainly concentrated in the core and that the shear bands developed into a form with an X shape in the cross-section of workpiece after the alternative forging using octangular rod shaped dies. With increasing the forging passes, it was observed that the Al-8mass%Mg alloy workpieces were significantly deformed, and cracks began to form and propagate on the both ends of the forged workpieces after five passes at room temperature. In as-forged microstructures taken by microscopes, twins, clustering of dislocations, and fine subgrains were found. Tensile strengths of the forged specimens showed significant increases depending on the number of forging passes, and a trade-off relationship was observed between the elongation and strength. At room temperature and 100 ℃, the workpieces showed similar behaviors in microstructural evolution and tensile properties depending on forging passes, while the increase range in strength was reduced at 200 ℃.
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