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권형도(Hyeong Do Kweon),남덕우(Deok Woo Nam),서정수(Jung Soo Suh) 한국소음진동공학회 2016 한국소음진동공학회 학술대회논문집 Vol.2016 No.4
Natural frequencies of the extension shaft assembly (ESA) of the control element drive mechanism (CEDM) for the advanced power reactor plus (APR+) have been determined by analyzing data obtained from a test and performing a numerical modal analysis. Axial acceleration time history signals of the ESA were obtained from an operational sequence of the CEDM, which produces impact force the same as that of impact tests onto the ESA. FFT analysis for the signals resulted in four natural frequencies. A modal analysis was performed to confirm the reliability of the results from the data analysis. Four natural frequencies for axial mode also resulted from the modal analysis. Maximum difference between two results is within 9%, therefore, the natural frequencies of the ESA from the data analysis are reliable.
인장시험과 유한요소해석을 통한 SA-508 저합금강의 진응력-진변형률 곡선 결정 방법
권형도(Hyeong Do Kweon),허은주(Eun Ju Heo),이도환(Do Hwan Lee),김진원(Jin Won Kim) 대한기계학회 2016 대한기계학회 춘추학술대회 Vol.2016 No.12
It is essential to determine true stress-strain curve of a material for plastic properties input to a numerical analysis. A simple methodology for determining the true stress-strain curve of SA-508 Grade 3 Class 1 low alloy steel using limited information from a general tensile test with finite element analysis is proposed in this paper. Before necking, it is reasonable to simply convert measured engineering stress-strains to true stress-strains under uniform deformation. After necking, it is difficult to know true stress-strains due to nonuniform deformation without any specialized measurement techniques. Five post-necking strain hardening models are taken into account, which are Linear, Swift, Ludwick, Hollomon-Linear, and Hollomon-Linear-Constant equations. The equations can be decided using tensile test results that are true stress-strain value at the maximum load point, corrected true stress-strain value at the fracture point, and Considere Instability Condition. Hollomon-Linear and Hollomon-Linear-Constant models showed that the engineering stress-strains resulted from the finite element analysis best agree with the experimental results.
배관내 열성층이 피크응력강도에 미치는 영향에 관한 연구
권형도(Hyeong-Do Kweon),이강용(Kang-Yong Lee),김종성(Jong-Sung Kim) 대한기계학회 2006 대한기계학회 춘추학술대회 Vol.2006 No.11
Thermal stratification in piping may lead to considerable additive global bending moments and local peak stresses. Numerical analysis is carried out to assess the effect of thermal stratification in piping on peak stress intensity according to ASME Code, Section Ⅲ, NB-3200 under various conditions considering three parameters. As the temperature difference between top and bottom at inner side of piping increases, peak stress intensity increases linearly. On the other hand, peak stress intensity decreases with the increase of boundary layer thickness. Moreover the increase of thermal stratification length causes the increase of peak stress intensity until it approaches to a sustainable value.
엘보우 시편에서의 재료 경화 거동 모델에 따른 최적의 유한 요소 선정
허은주,권형도,Heo, Eun Ju,Kweon, Hyeong Do 한국압력기기공학회 2017 한국압력기기공학회 논문집 Vol.13 No.1
This paper is proposed to select the optimal finite element type in finite element analysis. Based on the NUREG reports, static analyses were performed using a commercial analysis program, $ABAQUS^{TM}$. In this study, we used a nonlinear kinematic hardening model proposed by Chaboche. The analysis result of solid elements by inputting the same material constants was different from the results of the NUREG report. This is resulted from the difference between shell element and solid element. Therefore, the material constants that have similar result to the experimental result were determined and compared according to element type. In case of using solid element for efficient finite element analysis, we confirmed that the use of C3D8I element type(incompatible mode 8-node linear brick element) leads the accurate result while reducing the analysis time.
동적 시간이력 탄소성 지진 해석을 위한 레일레이 감쇠계수 결정방법 고찰
김종성,이석현,권형도,오창영,Kim, Jong Sung,Lee, Seok Hyun,Kweon, Hyeong Do,Oh, Chang-Young 한국압력기기공학회 2017 한국압력기기공학회 논문집 Vol.13 No.2
This paper investigates how to determine the Rayleigh damping coefficients for dynamic time history seismic analysis of piping systems. Three methods are applied. The first one is a conventional method to use the natural frequencies of the mode 1 and 2, derived from dynamic analysis. The second method is to determine the Rayleigh damping coefficients based on frequency range of the acceleration histories. The last one is a iterative transient response analysis method using the transient analysis results without and with damping. It is found that the conventional method and the iterative transient response method yield the same results whereas the acceleration frequency-basis method provides more conservative result than the other methods. In addition, it is concluded that the iterative transient response method is recommended.
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.
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.