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지진 하중조건에서 배관 건전성 평가를 위한 실험적 연구 현황
김진원,김종성,김윤재,권형도,Kim, Jin Weon,Kim, Jong Sung,Kim, Yun Jae,Kweon, Hyeong Do 한국압력기기공학회 2017 한국압력기기공학회 논문집 Vol.13 No.1
This paper reviewed and summarized the experimental studies conducted during last three decades to evaluate the structural integrity and to establish the acceptance criteria for piping system of nuclear power plants (NPPs) under seismic loading condition. These experimental studies contain the results of large-scale piping system tests under excessive seismic loading as well as standard specimen tests, simplified piping specimen tests, and piping components tests under simplified dynamic and cyclic loading. These would be useful as a basis for establishing integrity assessment procedure and acceptance criteria for piping systems of NPPs under beyond design basis earthquake (BDBE) conditions, and also could be used in planing the scope and direction of further related researches.
김진원,박치용,이성호,Kim, Jin-Weon,Park, Chi-Yong,Lee, Sung-Ho 대한기계학회 2007 大韓機械學會論文集A Vol.31 No.10
This study performed a series of burst tests at ambient temperature using real-scale elbow specimen containing a local wall-thinning defect at it's intrados or extrados and evaluated failure pressure of locally wall-thinned elbows. In the experiment, a 90-degree 100A, Sch. 80 standard elbow was employed, and various wall-thinning geometries, such as length, depth, and circumferential angle, were considered. From the results of experiment, the dependences of failure pressure of wall-thinned elbows on the defect geometries and locations were investigated. In addition, the reliability of existing models was examined by comparing the tests data with the results predicted from existing failure pressure evaluation models for locally wall-thinned elbow.
반복 응력-변형률 시험을 통한 반복하중 조건에서 원전 주요 구조재료의 변형거동 평가
김진원,김종성,권형도,Kim, Jin Weon,Kim, Jong Sung,Kweon, Hyeong Do 한국압력기기공학회 2017 한국압력기기공학회 논문집 Vol.13 No.1
This study investigated deformation behavior of major nuclear structural materials under cyclic loading conditions via cyclic stress-strain test. The cyclic stress-strain tests were conducted on SA312 TP316 stainless steel and SA508 Gr.3 Cl.1 low-alloy steel, which are used as materials for primary piping and reactor pressure vessel nozzle respectively, under cyclic load with constant strain amplitude and constant load amplitude at room temperature (RT) and $316^{\circ}C$. From the results of tests, the cyclic hardening and softening behavior, stabilized cyclic stress-strain behavior, and ratcheting behavior of both materials were investigated at both RT and $316^{\circ}C$. In addition, appropriate considerations for cyclic deformation behavior in the structural integrity evaluation of major nuclear components under excessive seismic condition were discussed.
김진원,이성호,Kim, Jin Weon,Lee, Sung Ho 한국압력기기공학회 2011 한국압력기기공학회 논문집 Vol.7 No.1
The objective of this study is to classify the geometry of wall-thinning defect that causes a circumferential crack in the pipe elbows subjected to internal pressure. For this objective, first of all a criterion to determine the occurrence of circumferential cracking at wall-thinned area was developed based on finite element simulation for burst tests of pipe elbow specimens that showed axial and circumferential cracking at wall-thinned area. In addition, parametric finite element analysis including various wall-thinning geometries, locations, and pipe geometries was conducted and the wall-thinning geometries that initiate circumferential crack were determined by applying the criterion to the results of parametric analysis. It showed that the circumferential crack occurs at wall-thinning defect, which has a deep, wide, and short geometry. Also, it is indicated that the pipe elbows with larger radius to thickness ratio are more susceptible to circumferential cracking at wall-thinned area.
상온과 343℃에서 Alloy 690 증기발생기 전열관의 인장물성치 평가
김진원(Jin Weon Kim),엄기현(Ki Hyeun Eom) 대한기계학회 2013 대한기계학회 춘추학술대회 Vol.2013 No.12
This study conducted tensile tests on Alloy 690 SG tube material at RT and 343℃ in air environment. In the tests tube and ring specimens were used to obtain axial and circumferential properties at both temperatures, respectively. The tensile properties and deformation behaviors were investigated at different temperatures. Yield point phenomena appeared at both temperatures, and serrated flow appeared at 343℃. The yield and tensile strengths were reduced at 343℃ compared with RT, but the change of elongation and hardening behavior with test temperature was not significant. Also, it showed that the reduction of yield and tensile strengths at 343℃ was more significant in comparison with that suggested by ASME code Sec.II. This means that the prediction of yield and tensile strengths at 343℃ for Alloy 690TT by ASME code Sec.II. is not conservative.
상온과 316℃에서 SA508 Gr.1a 저합금강 배관과 TP316 스테인리스강 배관의 변형거동에 미치는 하중속도의 영향
김진원(Jin Weon Kim),최명락(Myung Rak Choi) 대한기계학회 2015 大韓機械學會論文集A Vol.39 No.4
본 논문에서는 원전 배관 재료의 변형거동에 미치는 하중속도의 영향을 파악하기 위해서, SA508 Gr.1a 저합금강과 SA312 TP316 스테인리스강 배관재를 대상으로 상온과 원전 운전온도인 316℃에서 다양한 변형률 속도로 인장시험을 수행하였다. 시험 결과, 상온에서는 두 배관재의 변형거동이 일반적인 하중속도 의존성을 보였다. 즉, 하중속도가 증가함에 따라 강도는 증가하고 연성은 감소하는 경향을 보였다. 그러나, 316℃에서는 하중속도가 증가함에 따라 SA508 Gr.1a 저합금강의 강도와 연신률이 모두 감소하였고 단면수축률은 감소 후 증가하는 비선형 거동을 보였다. SA312 TP316 스테인리스강의 강도, 연신률, 그리고 단면수축률은 하중속도에 관계없이 거의 일정한 값을 보였다. 시험 온도에 관계없이 SA508 Gr.1a 저합금강의 가공경화능력은 하중속도에 거의 영향을 받지 않았으나, SA312 TP316 스테인리스강에서는 하중속도가 증가함에 따라 가공경화능력이 감소하였다. This study conducted tensile tests on SA508 Gr.1a low alloy steel and SA312 TP316 stainless steel piping materials under various strain rates at room temperature (RT) and 316°C to investigate the effects of loading rate on the deformation behavior of nuclear piping materials. At RT, the deformation behavior for both pipe materials showed a typical loading rate dependence, i.e., the strength increased and the ductility decreased as the loading rate increased. At 316°C, however, the strength and elongation of SA508 Gr.1a low alloy steel decreased as the loading rate increased, and its reduction of area non-linearly varied with the loading rate. For SA312 TP316 stainless steel, the strength, elongation, and reduction of area at 316°C were almost the same regardless of the loading rate. At both temperatures, the strain hardening capacity was nearly independent of the loading rate for SA508 Gr.1a low alloy steel, while it decreased with increasing loading rate for SA312 TP316 stainless steel.
원전 배관 감육 결함 검사를 위한 IR 열화상시험 조건 결정
김진원(Jin-Weon Kim),윤경원(Won-Kyung Yun),정현철(Hyun-Chul Jung),김경석(Kyeong-Suk Kim) 한국비파괴검사학회 2012 한국비파괴검사학회지 Vol.32 No.1
본 논문에서는 적외선 열화상 기법을 원전 배관에 적용하여 감육결함을 검사하기 위한 시험 조건을 파악하기 위해서, 인공 결함이 가공된 배관 시편과 평판 시편을 이용하여 적외선 열화상 시험을 수행하였다. 시험에는 할로겐램프를 사용하여 시편을 가열하였으며, 램프의 출력과 시편과 램프의 거리를 변수로 실험을 수행하였다. 시험 결과 시편과 램프의 거리가 1∼2 m 이고 램프의 출력이 정격출력의 60 % 이상일 때, 적외선 열화상 기법은 1회 촬영으로 최소한 500 mm 범위 내에 존재하는 원주방향 폭이 2θ = 90˚이고 깊이와 길이가 각각 d/t = 0.5와 L/D<sub>o</sub> = 0.25인 배관내 인공 감육 결함들을 검출하였다. 평판 시편과 배관 시편에서 시편과 램프의 거리에 관계없이 램프 출력이 높을수록 결함에 대한 이미지가 선명하였다. 평판 시편과 배관 시편에서 적외선 열화상 방법의 결함 검출 능력은 유사하지만, 최적의 시험 조건은 시편에 따라 다르게 나타났다. This study conducted infrared (IR) thermography tests using pipe and plate specimens with artificial wall-thinning defects to find an optimal condition for IR thermography test on the wall-thinned nuclear piping components. In the experiment halogen lamp was used to heat the specimens. The distance between the specimen and the lamp and the intensity of halogen lamp were regarded as experimental parameter. When the distance was set to 1∼2 m and the lamp intensity was above 60 % of full power, a single scanning of IR thermography detected all artificial wall-thinning defects, whose minimum dimension was 2θ = 90˚, d/t = 0.5, and L/D<sub>o</sub> = 0.25, within the pipe of 500 mm in length. Regardless of the distance between the specimen and the lamp, the image of wall-thinning defect in IR thermography became distinctive as the intensity of halogen lamp increased. The detectability of IR thermography was similar for both plate and pipe specimens, but the optimal test condition for IR thermography depended on the type of specimen.