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원자력발전소 주요기기의 건전성 평가를 위한 3차원 탄소성 해석 시스템의 개발
허남수,임창주,김영진,표창률,박치용,Huh, Nam-Su,Im, Chang-Ju,Kim, Young-Jin,Pyo, Chang-Ryul,Park, Chi-Yong 대한기계학회 2000 大韓機械學會論文集A Vol.24 No.8
In order to evaluate the integrity of nuclear power plant components, the analysis based on fracture mechanics is crucial. For this purpose, finite element method is popularly used to obtain J-integral. However, it is time consuming to design the finite element model of a cracked structure. Also, the J-integral should be verified by alternative methods since it may differ depending on the calculation method. The objective of this paper is to develop a three-dimensional elastic-plastic J-integral analysis system which is named as EPAS program. The EPAS program consists of an automatic mesh generator for a through-wall crack and a surface crack, a solver based on ABAQUS program, and a J-integral calculation program which provides DI (Domain Integral) and EDI (Equivalent Domain Integral) based J-integral calculation. Using the EPAS program, an optimized finite element model for a cracked structure can be generated and corresponding J-integral can be obtained subsequently.
내압이 작용하는 원주방향 관통균열 배관의 비선형 파괴역학 해석법
허남수,김윤재,김영진,Huh, Nam-Su,Kim, Yun-Jae,Kim, Young-Jin 대한기계학회 2002 大韓機械學會論文集A Vol.26 No.6
This paper provides engineering J-integral and crack opening displacement (COD) estimation equations for circumferential through-wall cracked pipes under internal pressure and under combined internal pressure and bending. Based on selected 3-D finite element calculations for the circumferential through-wall cracked pipes under internal pressure using the idealized power law materials, the elastic and plastic influence functions for fully plastic J-integral and COD solutions are found as a function of the normalized crack length and the mean radius-to-thickness ratio. These developed GE/EPRI-type solutions are then re-formulated based on the enhanced reference stress method. Such re-formulation not only provides simpler equations for J-integral and COD estimations, but also can be easily extended to combined internal pressure and bending. The proposed equations are compared with elastic-plastic finite element results using actual stress-strain data, which shows overall excellent agreement.
허남수(Huh Nam-Soo),조대철(Cho Daechul),권성현(Kwon Sung-Hyun) 한국산학기술학회 2004 한국산학기술학회 학술대회 Vol.- No.-
Filter media are one of themost important choices when bilfiltration is applied. Filter media provide adsorbing microbes with available sites for residence and the residential cells grow to degrade or decompose target waste gases. Up to date, filter media were only qualitatively analyzed. As a quantitative approach to filter material for biofiltration, a simple model based on reaction kinetics and mass action law (Ottengraf’s Model in1983) was presented. Cork, zeolite, and granulated activated carbon were tested in terms of effective surface area, cell covered fraction of adsorbing sites, surface roughness, and pore size distribution. The cell covered fraction, surface roughness and hydrophilicity was found to be closely related to the efficiency of gas degradation in biofiltration. The cork was the best candidate for cell residence and growth in this work.
내압에 의한 원주응력이 관통균열 배관의 J-적분 및 COD 계산에 미치는 영향의 정략적 해석
허남수(Nam-Su Huh),김윤재(Yun-Jae Kim),김영진(Young-Jin Kim) 대한기계학회 2001 대한기계학회 춘추학술대회 Vol.2001 No.8
This paper provides engineering J-integral and crack opening displacement (COD) estimation equations for through-wall cracked pipes under internal pressure and under combined internal pressure and bending. Based on selected 3-D finite element calculations for the through-wall cracked pipes under internal pressure using the idealized power law materials, the elastic and plastic influence functions for fully plastic J-integral and COD solutions are found as a function of the normalized crack length and the mean radius-to-thickness ratio. These developed GE/EPRI-type solutions are then re-formulated based on the enhanced reference stress method. Such re-formulation not only provides simpler equations for J-integral and COD estimations, but also can be easily extended to combined internal pressure and bending. The proposed equations are compared with elastic-plastic finite element results using actual stress-strain data, which shows overall excellent agreement.
참조응력 개념을 이용한 원주방향 관통균열 배관의 파괴역학 해석-실배관 실험 데이터와의 비교
허남수(Nam-Su Huh),심도준(Do-Jun Shim),김윤재(Yun-Jae Kim),김영진(Young-Jin Kim) 대한기계학회 2003 대한기계학회 춘추학술대회 Vol.2003 No.4
This paper presents experimental validation of the enhanced reference stress based J estimates for<br/> circumferential through-wall cracked pipes, recently proposed by authors. Using the pipe test data for<br/> circumferential through-wall cracked pipes, the predicted fracture initiation and maximum moments<br/> according to the proposed enhanced reference stress method are compared with experimental ones as well as<br/> predictions from the R6 method. The results show that both the R6 method and the proposed method give<br/> conservative estimates of initiation and maximum moments for circumferential through-wall cracked pipes,<br/> compared to experimental data. For longer cracks, the proposed method reduces conservatism embedded in<br/> estimated J according to the R6 method, and the resulting predictions are less conservative, compared to those<br/> from the R6 method. For shorter cracks, on the other hand, the proposed method reduces possible nonconservatism<br/> embedded in estimated J according to the R6 method, and the resulting predictions are slightly<br/> more conservative
탄성 유한요소해석을 이용한 동일 평면상에 존재하는 다중 표면균열의 균열상호작용 평가
허남수(Nam-Su Huh),김종민(Jong-Min Kim),최순(Suhn Choi),박근배(Keun-Bae Park),최재붕(Jae-Boong Choi),김영진(Young-Jin Kim) 대한기계학회 2008 대한기계학회 춘추학술대회 Vol.2008 No.5
The crack-tip stress fields and fracture mechanics assessment parameters, such as the elastic stress intensity factor and the elastic-plastic J-integral, for a surface crack can be significantly affected by adjacent cracks. Such a crack interaction effect due to multiple cracks can magnify the fracture mechanics assessment parameters. There are many factors to be considered, for instance the relative distance between adjacent cracks, crack shape and loading condition, to quantify a crack interaction effect on the fracture mechanics assessment parameters. Thus, the current guidance on a crack interaction effect (crack combination rule), including ASME Sec. XI, BS7910, British Energy R6 and API RP579, provide different rules for combining multiple surface cracks into a single surface crack. The present paper investigates a crack interaction effect by evaluating the elastic stress intensity factor of adjacent surface cracks in a plate along the crack front through detailed 3-dimensional elastic finite element analyses. The effects of the geometric parameters, the relative distance between cracks and the crack shape, on the stress intensity factor are systematically investigated. As for the loading condition, only axial tension is considered. Based on the elastic finite element results, the acceptability of the crack combination rules provided in the existing guidance was investigated, and the relevant recommendations on a crack interaction for in-plane surface cracks in a plate were discussed.
유한요소해석을 이용한 노즐 이종금속용접부의 용접잔류응력 예측
허남수(Nam-Su Huh),김종욱(Jong-Wook Kim),최순(Suhn Choi),김태완(Tae-Wan Kim) 대한기계학회 2008 대한기계학회 춘추학술대회 Vol.2008 No.11
The primary water stress corrosion cracking (PWSCC) of dissimilar metal weld based on Alloy 82/182 is one of major issues in material degradation of nuclear components. It is well known that the crack initiation and growth due to PWSCC is influenced by material’s susceptibility to PWSCC and distribution of welding residual stress. Therefore, modeling the welding residual stress is of interest in understanding crack formation and growth in dissimilar metal weld. Currently in Korea, a numerical round robin study is undertaken to provide guidance on the welding residual stress analysis of dissimilar metal weld. As a part of this effort, the present paper investigates distribution of welding resisual stress of a ferritic low alloy steel nozzle with dissimilar metal weld using Alloy 82/182. Two-dimensional thermo-mechanical finite element analyses are carried out to simulate multi-pass welding process on the basis of the detailed design and fabrication data. The present results are compared with those from other participants, and more works incorporating physical measurements are going to be performed to quantify the uncertainties relating to modelling assumptions.