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The forming limit diagram of an ultra thin super ferritic stainless steel
Hyuk Jong Bong(봉혁종),Frederic, Barlat,Myung-Gyu Lee(이명규) 한국자동차공학회 2011 한국자동차공학회 부문종합 학술대회 Vol.2011 No.5
The forming limit diagram (FLD) of a 0.1㎜-thick sheet of a ferritic stainless steel was determined using a modified Marciniak test. The conventional ASTM standard test method (ASTM E2218-2) was also tried with almost same conditions. However, the ASTM method produced undesired fracture at upper die radius and draw bead and wrinkling on the sheet specimens. The FLDs determined by the two methods are compared and advantages and disadvantages of the two methods are discussed
롤 본딩된 Ti/Al/Ti 3-ply 다층금속 판재의 접합강도 향상을 위한 최적 후열처리 조건 도출
김민호,봉혁종,김지훈,이광석 한국소성∙가공학회 2022 소성가공 : 한국소성가공학회지 Vol.31 No.4
The influence of post-roll bonding heat treatment conditions such as temperature and time on the variation in the diffusion layer, generated at the bonding interface and the subsequent mechanical properties of the roll-bonded Ti grade 1/Al1050/Ti grade 1 sheets, was systematically investigated. The intermetallic compound (IMC) phase generated by post heat treatment conditions adopted in this study was obviously indexed as monolithic TiAl3. Whereas the thickness of IMC layer generated by annealing at 500 oC was approximately 100 nm scale, it drastically increased above 1.5 m when annealed at 600 oC. Uniaxial tensile and peel tests were then performed to compare mechanical properties. As a result, the bonding strength drastically increased above 7.9 N/mm by annealing at 600 oC, which implies that proper annealing condition was a prerequisite, to improving interface bonding strength as well as global elongation properties for Ti/Al/Ti 3-ply sheet.
유한요소해석을 이용한 금속 판재용 전단 파단 시편 설계
김찬양,봉혁종,이명규 한국소성∙가공학회 2023 소성가공 : 한국소성가공학회지 Vol.32 No.2
In this study, shear fracture specimens are designed using finite element analyses for the characterization of ductile fracture criteria of metal sheets. Many recently suggested ductile fracture criteria require experimental fracture data at the shear stress states in the model parameter identification. However, it is challenging to maintain shear stress states in tension-based specimens from the initial yield to the final fracture, and the loading path can be different for the different materials even with the same shear specimen geometries. To account for this issue, two different shear fracture specimens for low ductility/high ductility metal sheets are designed using the sensitivity tests conducted by finite element simulations. Priorly mechanical properties including the Hosford-Coulomb fracture criterion of the aluminum alloy 7075-T6 and DP590 steel sheets are used in the simulations. The results show that shear stress states are well-maintained until the fracture at the fracture initiation points by optimizing the notch geometries of the shear fracture specimens.