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유한요소 해석변수가 원자로 배관 노즐 이종금속용접부의 용접잔류응력에 미치는 영향
소나현,오경진,허남수,이성호,박흥배,이승건,김종성,김윤재,Soh, Na-Hyun,Oh, Gyeong-Jin,Huh, Nam-Su,Lee, Sung-Ho,Park, Heung-Bae,Lee, Seung-Gun,Kim, Jong-Sung,Kim, Yun-Jae 한국압력기기공학회 2012 한국압력기기공학회 논문집 Vol.8 No.1
In early constructed nuclear power plants, Ni-based Alloys 82/182 had been widely used for dissimilar metal welds (DMW) as a weld filler metal. However, Alloys 82/182 have been proven to be susceptible to primary water stress corrosion cracking (PWSCC) in the nuclear primary water environment. The formation of crack due to PWSCC is also influenced by weld residual stresses. Thus, the accurate estimation of weld residual stresses of DMW is crucial to investigate the possibility of PWSCC and instability behaviors of crack due to PWSCC. In this context, the present paper investigates weld residual stresses of nuclear reactor piping nozzles based on 2-D axi-symmetric finite element analyses based on layer-based approach using maximum molten bead temperature. In particular, the effect of analysis parameters, i.e., a thickness of weld layer, an initial molten bead temperature, convection heat transfer coefficient, and geometric constraints on predicted weld residual stresses was investigated.
용접부 형상이 협개선 용접부 잔류응력 분포에 미치는 영향
소나현(Na-Hyun Soh),박보람(Bo-Ram Park),허남수(Nam-Su Huh),양준석(Jun-Seok Yang) 대한기계학회 2010 대한기계학회 춘추학술대회 Vol.2010 No.11
It is well known that a conventional welding technique could result in the overheating and welding defects due to the large groove angle of weld. In this context, the narrow gap welding (NGW) technique has been applied to nuclear industry due to its inherent merits, for instance, the reduction of welding time and the shrinkage of weld, and the small deformation of the weld resulting from the small groove angle and welding bead width. In this paper, the distribution of welding residual stress as well as the deformation behavior of ER308L weld due to NGW was predicted through the nonlinear 2-dimensional (2-D) finite element (FE) analysis in which the detailed actual welding process of NGW was simulated. In particular, the effect of shape of weld, the width of weld and the shape of welding groove, on the residual stress are investigated. The present results can be used to assess integrity of defected nuclear components and improve welding process.
용접부 형상이 협개선 용접부 잔류응력 분포에 미치는 영향
소나현(Na-Hyun Soh),양준석(Jun-Seok Yang),표창률(Chang-Ryul Pyo),허남수(Nam-Su Huh) 대한기계학회 2011 大韓機械學會論文集A Vol.35 No.6
일반적인 용접법은 용접 그루브(groove) 각도가 크기 때문에 용접 결함 발생의 원인이 된다. 따라서 원자력 발전소 배관 용접 시, 용접 그루브 각도가 작고 용접부 비드 폭이 좁은 협개선 용접법을 다수 수행하고 있다. 이러한 협개선 용접법은 용접시간 단축, 용접부 변형과 잔류응력의 감소, 용접결함의 감소 등과 같은 장점을 갖고 있다. 본 논문에서는 협개선 용접부의 실제 용접 공정을 모사함으로써, ER308L 용접재의 변형 거동과 용접잔류응력을 비선형 2차원 유한요소해석을 통하여 예측하였다. 특히 용접방법 및 순서가 다른 두 형상에 대한 결과를 비교하고, 용접부 폭 넓이 변화에 따른 잔류응력 분포를 분석하였다. 본 논문의 결과는 향후 협개선 용접부의 용접 개선과 용접부 결함의 건전성 평가 등을 위해 적용될 수 있다. It is well known that conventional welding techniques can result in welding defects due to the large groove angle of the weld. In this context, the narrow gap welding (NGW) technique is applied in the nuclear industry because of its inherent merits such as the reduction in welding time and the shrinkage of the weld, and the small deformation of the weld resulting from the small groove angle and welding bead width. In this paper, the distribution of welding residual stress and deformation behavior of the ER308L weld due to NGW are predicted through nonlinear two-dimensional finite element analysis, in which the actual NGW process is simulated in detail. In particular, the effects of the shape of weld, i.e., the width of the weld and the shape of the welding groove, on the residual stress are investigated. The present results can be used to assess the integrity of defective nuclear components and to improve the welding process.