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Fe-Ni-Cr 코팅층 형성을 위한 SLS 공정변수의 최적화
주병돈(B. D. Joo),장정환(J. H. Jang),임홍섭(H. S. Yim),손영명(Y. M. Son),문영훈(Y. H. Moon) 한국소성가공학회 2009 한국소성가공학회 학술대회 논문집 Vol.2009 No.5
Selective laser sintering(SLS), a kind of rapid prototyping technology, can provide a process to form many types of coatings. Coated layers by selective laser melting are highly influenced by substrate, powder and laser parameters such as laser power, scan rate, fill spacing and layer thickness. Therefore an attempt to fabricate Fe-Ni-Cr coating on AISI H13 tool steel has been performed by selective laser sintering. In this study, Fe-Ni-Cr coating was produced b experimental facilities consisting of a 200W fiber laser which can be focused to 0.08mm and atmospheric chamber which can control atmospheric pressure with Ar. With power increase or energy density decrease, line width was decreased and line surface quality was improved with energy density increase. Surface quality of coating layer was improved with fill spacing optimization or layer thickness decrease.
유한요소해석을 이용한 후판 압연공정의 선단부 롤갭 설정연구
임홍섭(H. S. Yim),장정환(J. H. Jang),최민규(M. K. Choi),서재형(J. H. Seo),문영훈(Y. H. Moon) 한국소성가공학회 2009 한국소성가공학회 학술대회 논문집 Vol.2009 No.5
The roll gap set-up in the finishing mill is one of the most important technologies in the hot plate rolling process. As the target thickness can be obtained by the correct set-up of the roll gap, set up technology is very critical for plate thickness accuracy. The main cause of thickness variation in hot plate mills is the non-uniform temperature distribution along the length of the slab. The objective of this study is to adjust the roll gap set-up for the thickness accuracy of plate in hot rolling process considering top-end temperature drop. Therefore this study has concentrated on determining the correct amounts of roll gap to compensate thickness variation due to top-end temperature drop. The off-line simulation of compensated roll gap significantly decreases top-end thickness variation.
박현규(H. K. Park),임홍섭(H. S. Yim),이혜경(H. K. Yi),김광순(K. S. Kim),문영훈(Y. H. Moon) 한국소성·가공학회 2008 소성가공 : 한국소성가공학회지 Vol.17 No.8
Strain hardening behavior during hydroforming has been experimentally investigated. The variation of flow stress was used as an index of strain hardening during respective processes and the flow stess was estimated from the correlationship between flow stress and effective strain. The local hardness after hydroformig was also predicted by effective strain. By using the inter-relationships between hardness-flow stress-effective strain at variable pre-strains, the strain hardening behavior during hydroforming has been successfully analyzed. The comparison of predicted hardness with measured hardness confirmed that the methodology used in this study was feasible and the strain hardening behavior can be quantitatively estimated.