구속효과를 고려한 원자로 압력용기 균열선단에서의 응력분포 예측

김진수,최재붕,김영진,Kim, Jin-Su,Choe, Jae-Bung,Kim, Yeong-Jin 대한기계학회 2001 大韓機械學會論文集A Vol.25 No.4

In the process of integrity evaluation for nuclear power plant components, a series of fracture mechanics evaluation on surface cracks in reactor pressure vessel(RPV) must be conducted. These fracture mechanics evaluation are based on stress intensity factor, K. However, under pressurized thermal shock(PTS) conditions, the combination of thermal and mechanical stress by steep temperature gradient and internal pressure causes considerably high tensile stress at the inside of RPV wall. Besides, the internal pressure during the normal operation produces high tensile stress at the RPV wall. As a result, cracks on inner surface of RPVs may experience elastic-plastic behavior which can be explained with J-integral. In such a case, however, J-integral may possibly lose its validity due to constraint effect. In this paper, in order to verify the suitability of J-integral, tow dimensional finite element analyses were applied for various surface cracks. A total of 18 crack geometries were analyzed, and $\Omega$ stresses were obtained by comparing resulting HRR stress distribution with corresponding actual stress distributions. In conclusion, HRR stress fields were found to overestimate the actual crack-tip stress field due to constraint effect.

가압열충격 사고시 결함 이상화 방법이 구조물 건전성 평가에 미치는 영향

김진수,최재붕,김영진,박윤원,Kim, Jin-Su,Choe, Jae-Bung,Kim, Yeong-Jin,Park, Yun-Won 대한기계학회 2001 大韓機械學會論文集A Vol.25 No.2

The reactor pressure vessel is usually cladded with stainless steel to prevent corrosion and radiation embrittlement. Number of subclad cracks may be found during an in-service-inspection due to the presence of cladding. It is specified, in ASME Sec. XI, that a subclad crack is characterized as a surface crack when the thickness of the clad is less than 40% of the crack depth. This condition is provided to keep the crack integrity evaluation conservative. In order to refine the fracture assessment procedures for such subclad cracks under a pressurized thermal shock condition, three dimensional finite element analyses are applied for various subclad cracks existing under cladding. A total of 36 crack geometries are analyzed, and the results are compared with those for surface cracks. The resulting stress intensity factors for subclad cracks are 6 to 44% less than those for surface cracks. It is proven that the flaw characterization condition as specified in ASME Sec. XI can be overly conservative for some subclad cracks.

PBTI에 의한 무접합 및 반전모드 다중게이트 MOSFET의 소자 특성 저하 비교 분석

김진수,홍진우,김혜미,이재기,박종태,Kim, Jin-Su,Hong, Jin-Woo,Kim, Hye-Mi,Lee, Jae-Ki,Park, Jong-Tae 한국정보통신학회 2013 한국정보통신학회논문지 Vol.17 No.1

본 연구에서는 다중게이트 구조인 나노 와이어 n-채널 무접합(junctionless)와 반전모드(inversion mode) 다중게이트 MOSFET(Multiple-Gate MOSFET : MuGFET)의 PBTI에 의한 소자 특성 저하를 비교 분석하였다. PBTI에 의해서 무접합 및 반전모드 소자의 문턱전압이 증가하는 것으로 관측되었으며 무접합 소자의 문턱전압 변화가 반전모드 소자보다 작음을 알 수 있었다. 그러나 소자특성 저하 비율은 반전모드 소자가 무접합 소자보다 큰 것으로 관측되었다. 특성저하 활성화 에너지는 반전모드 소자가 무접합 소자보다 큰 것을 알 수 있었다. PBTI에 의한 소자 특성 저하가 무접합 소자보다 반전모드 소자가 더 심한 것을 분석하기 위하여 3차원 소자 시뮬레이션을 수행하였다. 같은 게이트 전압에서 전자의 농도는 같으나 수직방향의 전계는 반전모드 소자가 무접합 소자보다 큰 것을 알 수 있었다. In this paper, a comparative analysis of PBTI induced device degradation in nanowire n-channel junctionless and inversion mode Multiple-Gate MOSFET(MuGFETs) has been performed. It has been observed that the threshold voltage is increased after PBTI stress and the threshold voltage variation of junctionless device is less significant than that of inversion mode device. However the degradation rate of junctionless device is less significant than that of inversion mode device. The activation energy of the device degradation is larger in inversion mode device than junctionless device. In order to analyze the more significant PBTI induced device degradation in inversion mode device than junctionless device, 3-dimensional device simulation has been performed. The electron concentration in inversion mode device is equal to the one in junctionless device but the electric field in inversion mode device is larger than junctionless device.

시편두께 및 균열깊이 영향을 고려한 비표준시편의 J 시험법 및 구속효과의 정량화

김진수,조수만,김윤재,김영진,Kim, Jin-Su,Cho, Soo-Man,Kim, Yun-Jae,Kim, Young-Jin 대한기계학회 2003 大韓機械學會論文集A Vol.27 No.9

This paper compiles solutions of plastic $\eta$ factors and crack tip stress triaxialites for standard and nonstandard fracture toughness testing specimens, via detailed three-dimensional (3-D) finite element (FE) analyses. Fracture toughness testing specimens include a middle cracked tension (M(T)) specimen, SE(B), single-edge cracked bar in tension (SE(T)) and C(T) specimen. The ligament-to-thickness ratio of the specimen is systematically varied. It is found that the use of the CMOD overall provides more robust experimental J estimation than that of the LLD, for all cases considered in the present work. Moreover, the J estimation based on the load-CMOD record is shown to be insensitive to the specimen thickness, and thus can be used for testing specimen with any thickness. The effects of in-plane and out-of-plane constraint on the crack tip stress triaxiality are also quantified, so that when experimental J value is estimated according to the procedure recommended in this paper, the corresponding crack tip stress triaxiality can be estimated. Moreover, it is found that the out-of-plane constraint effect is related to the in-plane constraint effect.

배관에 존재하는 원주방향 표면균열에 대한 파괴거동 해석 (I) -J-적분 예측식 -

김진수,김윤재,김영진,Kim, Jin-Su,Kim, Yun-Jae,Kim, Yeong-Jin 대한기계학회 2002 大韓機械學會論文集A Vol.26 No.1

This paper provides the fully plastic J solutions for circumferential cracked pipes with inner, semi- elliptical surface cracks, subject to internal pressure and global bending. Solutions are given in the form of two different approaches, the GEF/EPRl approach and the reference stress approach. For the GE/EPRl approach, the plastic influence functions for fully plastic J are tabulated based on extensive 3-D FE calculations using the Ramberg-Osgood (R-O) materials, covering a wide range of pipe and crack geometries. The developed GEf/EPRl-type fully plastic J estimation equations are then re-formulated using the concept of the reference stress approach for wider applications. Based on the FE results, optimized reference load solutions for the definition of the reference stress are found for internal pressure and for global bending. Advantages of the reference stress based approach over the GE/EPRl-type approach are fully discussed. Validation of the proposed reference stress based J estimation equations will be given in Part II, based on 3-D elastic-plastic or elastic creep FE results using typical tensile properties of stainless steels and generalized creep- deformation behaviours.

PTS 사고하에서 J-Q해석법을 이용한 표면균열의 구속효과 고찰

김진수,최재붕,김윤재,김영진,Kim, Jin-Su,Choe, Jae-Bung,Kim, Yun-Jae,Kim, Yeong-Jin 대한기계학회 2002 大韓機械學會論文集A Vol.26 No.1

In recent years, the integrity of reactor Pressure Vessel(RPV) under pressurized thermal shock (PTS) accident has been treated as one of the most critical issues. Under PTS condition, the combination of thermal and mechanical stress by steep temperature gradient and internal pressure causes considerably high tensile stress at the inside of RPV wall. As a result, cracks on inner surface of RPV may experience elastic-plastic behavior which can be characterized by J-integral. In such a case, however, J-integral may possibly lose its vapidity due to the constraint effect. The degree of constraint effect is influenced by the loading mode, crack geometry and material properties. In this paper, in order to investigate the effect of clad thickness and crack geometry on constraint effect, three dimensional finite element analyses were performed for various surface cracks. Total of 27 crack geometries were analyzed and results were presented by a two-parameter characterization based on the J-integral and the f-stress.

실린더에 존재하는 축방향 표면균열에 대한 공학적 J-적분식 (II) - 최적참조응력에 기초한 방법-

김진수,김윤재,김영진,Kim, Jin-Su,Kim, Yun-Jae,Kim, Young-Jin 대한기계학회 2002 大韓機械學會論文集A Vol.26 No.11

This paper provides an reference stress based J estimation equation fur cylinders with finite internal axial surface cracks under internal pressure. In part 1, the J estimation equation based on deformation plasticity using Ramberg-Osgood (R-0) materials is proposed. In this paper, the developed CE/EPRI -type solutions ale then re-formulated based on the reference stress concept. Such a re-formulation provides a simpler equation for J. estimation are then further extended to combined internal pressure and bending. The proposed reference stress based J estimation equation is compared with elastic-plastic 3-D FE results using actual stress-strain data for a Type 304 stainless steel. Good agreement between the FE results and the proposed reference stress based J estimations provides confidence in the use of the proposed method to elastic -plastic fracture mechanics of pressurised piping.

학교 이전적지의 적정활용 방안에 관한 연구 - 서울시 은평구 'A' 초등학교를 중심으로 -

김진수,김창신,김현호,동재욱,이화룡,Kim, Jin-Su,Kim, Chang-Shin,Kim, Hyoun-Ho,Dong, Jae-Wook,Lee, Hwa-Ryong 한국교육시설학회 2011 敎育施設 Vol.18 No.1

ent years, the change of urban function and the decrease in birth rate have given rise to merge, abolition and relocation of the existing schools. This study explores the possibilities for various land utilizations of relocated school sites, using the trial case of 'A' elementary school in Eun-pyeong gu, Seoul. 'A' elementary school has happened transfer plan due to the urban development project of the redevelopment area, Eun-pyeong gu in Seoul. Firstly, it studies the land use categories and the development methodologies of 7 relocated school sites happened in Seoul. In addition, it analyzes the land utilization after relocation, development principals, area, building usage and changes in land use regulation. Finally, it proposes the commercial exploitation of school site targeting 'A' elementary school site. Throughout the profit analysis, this study concludes that it is available to exploit the relocated school sites by the variety of development methodologies, especially in a metropolis like Seoul.

강우시 광역논으로부터의 영양염류의 유출 특성

김진수,오승영,김규성,이종진,오광영,Kim, Jin-Su,O, Seung-Yeong,Kim, Gyu-Seong,Lee, Jong-Jin,O, Gwang-Yeong 한국수자원학회 2000 한국수자원학회논문집 Vol.33 No.1

실린더에 존재하는 축방향 표면균열에 대한 공학적 J-적분식 (I) - 변형소성에 기초한 방법-

김진수,김윤재,박영재,김영진,Kim, Jin-Su,Kim, Yun-Jae,Park, Yeong-Jae,Kim, Yeong-Jin 대한기계학회 2002 大韓機械學會論文集A Vol.26 No.8

This paper provides an engineering J estimation equation for cylinders with finite internal axial surfacecracks under internal pressure. The proposed equation is the J estimation equation based on deformation plasticity using Ramberg-Osgood (R-O) materials. Based on detailed 3-D FE results using deformation plasticity, plastic influence functions for fully plastic J components are tabulated for practically interesting ranges of the mean radius-to-thickness ratio, the crack depth-to-length ratio, the crack depth-to-thickness ratio. the strain hardening index for the R-O material, and the location along the semi-elliptical crack front. Based on tabilated plastic influence functions, the J estimation equation along the crack front is proposed and validated for R-O materials. Good agreements between the FE results and the proposed J estimation provide confidence in the use of the proposed method to elastic-plastic fracture mechanics of pressurized piping.