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감육형상 및 내압이 원자력 감육배관의 파단에 미치는 영향 -내압과 굽힘모멘트가 동시에 작용하는 경우-
심도준,임환,최재붕,김영진,김진원,박치용,Shim, Do-Jun,Lim, Hwan,Choi, Jae-Boong,Kim, Young-Jin,Kim, Jin-Won,Park, Chi-Yong 대한기계학회 2003 大韓機械學會論文集A Vol.27 No.5
Failure of a pipeline due to local wall thinning is getting more attention in the nuclear power plant industry. Although guidelines such as ANSI/ASME B31G and ASME Code Case N597 are still useful fer assessing the integrity of a wall thinned pipeline, there are some limitations in these guidelines. For instance, these guidelines consider only pressure loading and thus neglect bending loading. However, most Pipelines in nuclear power plants are subjected to internal pressure and bending moment due to dead-weight loads and seismic loads. Therefore, an assessment procedure for locally wall thinned pipeline subjected to combined loading is needed. In this paper, three-dimensional finite element(FE) analyses were performed to simulate full-scale pipe tests conducted for various shapes of wall thinned area under internal pressure and bending moment. Maximum moments based on true ultimate stress(${\alpha}$$\sub$u,t/) were obtained from FE results to predict the failure of the pipe. These results were compared with test results, which showed good agreement. Additional finite element analyses were performed to investigate the effect of key parameters, such as wall thinned depth, wall thinned angle and wall thinned length, on maximum moment. Also, the effect of internal pressure on maximum moment was investigated. Change of internal pressure did not show significant effect on the maximum moment.
복합하중을 받는 평판에 존재하는 반타원 표면균열의 공학적 탄소성 파괴해석법
심도준,김윤재,최재붕,김영진,Shim, Do-Jun,Kim, Yun-Jae,Choi, Jae-Boong,Kim, Young-Jin 대한기계학회 2002 大韓機械學會論文集A Vol.26 No.6
The present paper provides an engineering J estimation equation for surface cracked plates under combined bending and tension. The proposed equation is based on the reference stress approach, and the most relevant normalising loads to define the reference stress for accurate J estimations are given for surface cracked plates under combined bending and tension. Comparisons with J results from extensive 3-D FE analyses, covering a wide range of crack geometry, plate geometry and loading combination, show overall good agreement not only at the deepest point but also at arbitrary points along the crack front. for pure tension, agreement between the estimated J and the FE results is excellent, even at the surface point. On the other hand, for pure bending and combined bending and tension, the estimated J values become less accurate for locations close to the surface point. Thus the results in this paper will be useful to assess short-term fracture or low cycle fatigue of surface defects in plates under combined bending and tension.
심도준,김윤재,김영진,박치용,Shim Do-Jun,Kim Yun-Jae,Kim Young-Jin,Park Chi-Yong 대한기계학회 2005 大韓機械學會論文集A Vol.29 No.10
Recently authors have proposed a new method to estimate failure strength of a pipe with local wall thinning subject to either internal pressure or global bending. The proposed method was based on the equivalent stress averaged over the minimum ligament in the locally wall thinned region, and the simple scheme to estimate the equivalent stress in the minimum ligament was proposed, based on the reference stress concept. This paper extends the new method to combined internal pressure and global bending. The proposed method is validated against FE results for various geometries of local wall thinning under combined loading. The effect of internal pressure is also investigated in the present study. Comparison of maximum moments, predicted according to the proposed method, with published full-scale pipe test data fur locally wall-thinned pipes under combined internal pressure and global bending, shows good agreement.
복합하중을 받는 평판에 존재하는 반타원 표면균열의 공학적 탄소성 파괴해석법
심도준(Do-Jun Shim),김윤재(Yun-Jae Kim),최재붕(Jae-Boong Choi),김영진(Young-Jin Kim) 대한기계학회 2001 대한기계학회 춘추학술대회 Vol.2001 No.8
The present paper provides an engineering J estimation equation for surface cracked plates under combined bending and tension. The proposed equation is based on the reference stress approach, and the most relevant normalising loads to define the reference stress for accurate J estimations are given for surface cracked plates under combined bending and tension. Comparisons with J results from extensive 3-D FE analyses, covering a wide range of crack geometry, plate geometry and loading combination, show overall good agreement not only at the deepest point but also at arbitrary points along the crack front. For pure tension, agreement between the estimated J and the FE results is excellent, even at the surface point(?) On the other hand, for pure bending and combined bending and tension, the estimated J values become less accurate for locations close to the surface point. Thus the results in this paper will be useful to assess short-term fracture or low cycle fatigue of surface defects in plates under combined bending and tension.
반타원 표면균열 형상측정을 위한 유한요소 전기장 해석에 기초한 직류전위차법의 개발
심도준(Do-Jun Shim),최재붕(Jae-Boong Choi),김영진(Young-Jin Kim) 대한기계학회 2001 대한기계학회 춘추학술대회 Vol.2001 No.3
One of major problems in analyzing failure mechanism of real components is the accurate measurement of crack size and shape. The DCPD(Direct Current Potential Drop) method has been widely used for the crack measurement of a structure and finite element analysis has been used for the derivation of calibration equations, which relates the potential drop with the crack depth. In this paper, finite element analyses were performed for semi-elliptical surface cracks with various crack shapes(a/c) and crack depths(a/t). As a result, a calibration equation has been derived for the measurement of a semi-elliptical surface crack in wide plates. Analytical results are compared with experimental results to evaluate the validity and the applicability of the derived equation. The proposed method is expected to provide efficient and accurate measurement of a surface crack during crack growth.
중수로 압력관의 크리프 처짐 해석 기법 및 프로그램 개발
심도준(Do-Jun Shim),허남수(Nam-Su Huh),박보규(Bo-Kyu Park),장윤석(Yoon-Suk Chang),김윤재(Yun-Jae Kim),김영진(Young-Jin Kim),정현규(Hyun-Kyu Jung) 대한기계학회 2004 대한기계학회 춘추학술대회 Vol.2004 No.4
Estimation of the CANDU pressure tube deflection is important since the deflection may cause significant structural failure due to hydrogen diffusion and blister. However, there is no appropriate engineering model to estimate it exactly. The purpose of this paper is to propose a new analysis method and program to resolve this issue. For development of proper analysis method, a series of finite element analyses has been carried under elastic-creep condition. In addition, for effective estimation of the creep deflection, an analysis program named PC-DAS was developed based on the proposed method. Comparison of simple case study results with corresponding reference ones showed good agreement. Therefore, the proposed method and program can be utilized as one of valuable toolkit for integrity assessment of CANDU pressure tube.
인장하중이 작용하는 평판에 존재하는 반타원 표면균열의 J-적분 계산식
심도준(Do-Jun Shim),김윤재(Yun-Jae Kim),최재붕(Jae-Boong Choi),김영진(Young-Jin Kim),박윤원(Youn-Won Park) 대한기계학회 2001 대한기계학회 춘추학술대회 Vol.2001 No.3
This paper provides a simplified engineering J estimation method for semi-elliptical surface cracked plates in tension, based on the reference stress approach. Note that the essential element of the reference stress approach is the plastic limit load in the definition of the reference stress. However, for surface cracks, the definition of the limit load is ambiguous (local or global limit load), and thus the most relevant limit load (and thus reference stress) for the J estimation should be determined. In the present work, such limit load solution is found by comparing reference stress based J results with those from extensive 3-D finite element analyses. Validation of the proposed equation against FE J results based on actual experimental tensile data of a 304 stainless steel shows excellent agreements not only for the J values at the deepest point but also for those at an arbitrary point along the crack front, including at the surface point. Thus the present results provide a good engineering tool for elastic-plastic fracture analyses of surface cracked plates in tension.
유한요소한계해석에 기초한 균열이 존재하는 배관에 대한 소성한계압력식
심도준(Do-Jun Shim),허남수(Nam-Su Huh),김윤재(Yun-Jae Kim),김영진(Young-Jin Kim) 대한기계학회 2002 대한기계학회 춘추학술대회 Vol.2002 No.5
Based on detailed FE limit analyses, the present paper provides tractable approximations for plastic limit<br/> pressure solutions for axial through-wall cracked pipe; axial (inner) surface cracked pipe; circumferential<br/> through-wall cracked pipe; and circumferential (inner) surface cracked pipe. Comparisons with existing<br/> analytical and empirical solutions show a large discrepancy in circumferential short through-wall cracks and<br/> in surface cracks (both axial and circumferential). Being based on detailed 3-D FE limit analysis, the present<br/> solutions are believed to be the most accurate, and thus to be valuable information not only for plastic<br/> collapse analysis of pressurised piping but also for estimating non-linear fracture mechanics parameters based<br/> on the reference stress approach.
표면균열배관의 파괴역학 해석을 위한 참조하중의 영향 분석
심도준(Do-Jun Shim),손범구(Beom-Goo Son),김윤재(Yun-Jae Kim),김영진(Young-Jin Kim) 대한기계학회 2003 대한기계학회 춘추학술대회 Vol.2003 No.11
To investigate relevance of the definition of the reference stress to estimate J and C<SUP>*</SUP> for surface crack problems, this paper compares FE J and C<SUP>*</SUP> results for surface cracked pipes with those estimated according to the reference stress approach using various definitions of the reference stress. Pipes with part circumferential inner surface crack and finite internal axial crack are considered, subject to internal pressure and global bending. The crack depth and aspect ratio are systematically varied. The reference stress is defined in four different ways using (ⅰ) the local limit load, (ⅱ) the global limit load, (ⅲ) the global limit load determined from the FE limit analysis, and (ⅳ) the optimised reference load. It is found that the reference stress based on the local limit load gives overall excessively conservative estimates of J and C<SUP>*</SUP>. Use of the global limit load clearly reduces the conservatism, compared to that of the local limit load, although it can provide sometimes non-conservative estimates of J and C<SUP>*</SUP>. The use of the FE global limit load gives overall non-conservative estimates of J and C<SUP>*</SUP>. The reference stress based on the optimised reference load gives overall accurate estimates of J and C<SUP>*</SUP>, compared to other definitions of the reference stress. Based on the present finding, general guidance on the choice of the reference stress for surface crack problems is given.