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진영관(Young Gwan Jin),강성훈(Seong-Hoon Kang),손일헌(Il Heon Son),임용택(Yong-Taek Im) 대한기계학회 2008 大韓機械學會論文集A Vol.32 No.3
Equal channel angular pressing (ECAP) is one of the effective methods to produce bulk-nano materials by accumulating plastic strain into the workpiece without changing its cross-sectional shape in the multi-pass processing. However, the forming load becomes higher for manufacturing large specimens using conventional solid or split dies because of friction, flash formation, and usage of dummy specimen. In the present investigation, better split die was designed to reduce the forming loads and improve the geometrical accuracy of the specimen in the multi-pass ECAP. The new die exit channel was also designed to reduce the friction effect. Experiments with AA1050 specimens with a square cross-section were carried out to examine the design goal using the proposed split dies for routes A and C up to four passes. The numerical forming simulations were used to determine the effective geometry of various die models in the present work.
연속적 강소성 가공을 위한 스프링 가압형 ECAP 설계
진영관(Y. G. Jin),전병철(B. C. Jeon),임용택(Y. T. Im) 한국소성가공학회 2010 한국소성가공학회 학술대회 논문집 Vol.2010 No.10
Severe plastic deformation processing by equal channel angular pressing (ECAP) has attracted noticeable attention because it is an effective technique to produce the ultrafine-grained materials with enhanced mechanical properties. In the present study, split dies combined with the principle of spring-loaded preform process were newly proposed to provide a solution for the inefficiency of ECAP process. The designed and constructed spring-loaded ECAP set-up was used to make the continuous process feasible. Experiments for a single pass of ECAP were carried out to process aluminum alloy AA6061 by using the multi-stage former at room temperature. Vickers microhardness test was applied to investigate strength increase in the specimen deformed by ECAP. The spring-loaded ECAP proposed might be beneficial in commercializing a continuous application of ECAP to produce a high strength part in industry.
A Study on the Crystalline Boron Analysis in CRUD in Spent Fuel Cladding Using EPMA X-ray Images
정양홍,백승제,진영관 한국부식방식학회 2020 Corrosion Science and Technology Vol.19 No.1
Chalk River Unidentified Deposits (CRUDs) were collected from the Korean pressurized water reactor (PWR)plant (A, B, and C) where the axial offset anomaly (AOA) occurred. AOA, also known as a CRUD-inducedpower shift, is one of the key issues in maintaining stable PWR plant operations. CRUDs were sampledfrom spent nuclear fuel rods and analyzed using an electron probe micro-analyzer (EPMA). This paper describesthe characteristics of boron-deposits from the CRUDs sampled from twice-burnt assemblies from the KoreanPWR. The primary coolant of a PWR contains boron and lithium. It is known that boron deposition occursin a thick CRUD layer under substantial sub-cooled nucleate boiling (SNB). The results of this study aresummarized as follows. Boron was not found at the locations where the existence was confirmed in simulatedCRUDs, in other words, the cladding and CRUD boundaries. Nevertheless, we clearly observed the presenceof boron and confirmed that boron existed as a lump in crystalline form. In addition, the study confirmedthat CRUD existed in a crystal form with a unique size of about 10 μm.