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열성층 및 냉각재 환경이 오스테나이트 배관의 피로수명에 미치는 영향 평가
최신범(Shin-Beom Choi),우승완(Seung-Wan Woo),장윤석(Yoon-Suk Chang),최재붕(Jae-Boong Choi),김영진(Young-Jin Kim),이진호(Jin-Ho Lee),정해동(Hae-Dong Chung) 대한기계학회 2008 大韓機械學會論文集A Vol.32 No.8
During the last two decades, lots of efforts have been devoted to resolve thermal stratification phenomenon and primary water environment issues. While several effective methods were proposed especially in related to thermally stratified flow analyses and corrosive material resistance experiments, however, lack of details on specific stress and fatigue evaluation make it difficult to quantify structural behaviors. In the present work, effects of the thermal stratification and primary water are numerically examined from a structural integrity point of view. First, a representative austenitic nuclear piping is selected and its stress components at critical locations are calculated in use of four stratified temperature inputs and eight transient conditions. Subsequently, both metal and environmental fatigue usage factors of the piping are determined by manipulating the stress components in accordance with NUREG/CR-5704 as well as ASME B&PV Codes. Key findings from the fatigue evaluation with applicability of pipe and three-dimensional solid finite elements are fully discussed and a recommendation for realistic evaluation is suggested.
손상모델의 온도의존성을 고려한 SA508 탄소강의 취성파괴 평가
최신범(Shin-Beom Choi),정재욱(Jae-Uk Jeong),최재붕(Jae-Boong Choi),장윤석(Yoon-Suk Chang),고한옥(Han-Ok Ko),김민철(Min-Chul Kim),이봉상(Bong-Sang Lee) 대한기계학회 2012 大韓機械學會論文集A Vol.36 No.5
본 연구의 목적은 손상모델의 온도의존성을 고려하여 압력용기강의 취성파괴 거동을 평가하는 것이며, 이를 위해 다중 섬유전자알고리즘과 와이블 응력모델을 연계하여 대표적 취성파괴 손상모델의 재료상수 결정절차를 개선하였다. 벽개파괴가 예상되는 -60℃, -80℃, -100℃ 온도에서 수행한 SA508 탄소강 재료의 파괴 인성 실험 데이터를 사용하여 개선된 절차에 따른 재료상수를 결정하였고, NUREG/CR-6930과 동일한 결과인 재료상수의 온도의존성을 확인하였다. 최종적으로는 손상모델 재료상수의 온도의존성에 따른 2-매개변수와 이블 응력모델과 3-매개변수 와이블 응력모델의 차이를 정량화하였으며, 공학적으로 활용 가능한 관계식을 제안하였다. The aim of this study was to determine the brittle fracture behavior of reactor pressure vessel steel by considering the temperature dependence of a damage model. A multi-island genetic algorithm was linked to a Weibull stress model, which is the model typically used for brittle fracture evaluation, to improve the calibration procedure. The improved calibration procedure and fracture toughness test data for SA508 carbon steel at the temperatures -60℃, -80℃ and -100℃ were used to decide the damage parameters required for the brittle fracture evaluation. The model was found to show temperature dependence, similar to the case of NUREG/CR-6930. Finally, on the basis of the quantification of the difference between 2- and 3-parameter Weibull stress models, an engineering equation that can help obtain more realistic fracture behavior by using the simpler 2-parameter Weibull stress model was proposed.
극저온 환경에서 운용되는 배관의 구조 거동에 관한 연구
김유경(Yu-Gyng Kim),최신범(Shin-Beom Choi),최재봉(Jae-Boong Choi),이홍철(Hong-Chul Lee),황인주(In-Ju Hwang) 대한설비공학회 2009 대한설비공학회 학술발표대회논문집 Vol.2009 No.-
As the LNG(Liquefied Natural Gas) has been recognized as sustainable energy resources, many researches to evaluate structural safety of equipments related on LNG plant were performed. Expecially, the cryogenic effect on structural integrity of cold box which is on of major components in LNG plant should be considered. The aim of this study is to describe structural behavior by considering cryogenic environment. To do this, the pipe used in ASU is analyzed by CFD(Computational Fluid Dynamics) and structural analyses. The result shows that elbow region is the most frailty by stress concentration due to the cryogenic environment. Thus, these effects should be considered when main devices such as heat exchanger, valves, pipes and etc in cold box are designed. This results will be useful to assess structural integrity of LNG plant.