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이경수,이정근,이성호,박재학,Lee, Kyoung-Soo,Lee, Jeong-Keun,Lee, Seong-Ho,Park, Jae-Hak 한국압력기기공학회 2011 한국압력기기공학회 논문집 Vol.7 No.1
Primary water stress corrosion cracking (PWSCC) has been found in the weld region of the nuclear power plant. Welding can produce tensile residual stress. Tensile residual stress contributes to the initiation and growth of PWSCC. It is important to estimate weld residual stress accurately to predict or prevent the initiation and growth of PWSCC. This paper shows the results of finite element analysis and measurement experiment for weld residual stress. For the study, four kinds of specimen were fabricated with the materials used in the nuclear power plant. Residual stresses were measured by four kinds of methods of hole drilling, x-ray diffraction, instrumented indentation and sectioning. Through the study, numerical analysis and measurement results were compared and the characteristics of each measurement technique were observed.
기계가공이 이종용접부의 잔류응력에 미치는 영향에 관한 연구
이경수,이정근,이성호,박치용,이승건,박재학,Lee, Kyoung-Soo,Lee, Jeong-Geun,Lee, Seong-Ho,Park, Chi-Yong,Lee, Seung-Geon,Park, Jai-Hak 대한용접접합학회 2011 대한용접·접합학회지 Vol.29 No.2
his paper aimed to understand the residual stress in the dissimilar metal welds of nuclear power plant. Two kinds of residual stress were considered, which caused by welding and machining. Residual stress due to mechanical machining was measured by hole-drilling technique and x-ray diffraction method for the SA508 and F316L. Weld residual stress at dissimilar metal weld between SA508 and F316L was evaluated by FEA. Residual stress profiles were obtained for the inside surface and through thickness of welds. Machining effect was also analyzed by FEA. According to the residual stress measurement, it was observed that mechanical machining can generate tensile stress on the surface of the test material. However, FEA results showed that mechanical machining did not increase the tensile stress on the surface of weld region. Further study with more elaborate measurement and numerical analysis is required to identify the effect of machining on residual stress in the dissimilar metal weld region.
원자로 상부헤드 관통노즐 균열에 대한 원인분석 및 건전성 평가
이경수,이성호,이정석,이재곤,이승건,Lee, Kyoung-Soo,Lee, Sung-Ho,Lee, Jeong-Seog,Lee, Jae-Gon,Lee, Seung-Gun 한국압력기기공학회 2013 한국압력기기공학회 논문집 Vol.9 No.1
This paper presents the results of integrity assessment for the cracks happened in reactor vessel upper head penetration nozzles. The crack morphology for a boat sample from crack area was analyzed through microscope. The stress condition including weld residual stress around crack was analyzed using finite element analysis. From the results of crack morphology and stress condition, the crack was concluded as primary water stress corrosion cracking. The integrity of the cracked nozzle was assessed by the methodology provided in ASME Section XI. According to the assessment results, the remaining life of the cracked nozzle was 1.43 yrs. and the plant decided to repair it.
이경수,한상을,Lee, Kyoung-Soo,Huque, Ziaul,Kommalapati, Raghava,Han, Sang-Eul 한국공간구조학회 2014 한국공간구조학회지 Vol.14 No.4
This paper presents the structural model development and verification processes of wind turbine blade. The National Renewable Energy Laboratory (NREL) Phase VI wind turbine which the wind tunnel and structural test data has publicly available is used for the study. The wind turbine assembled by blades, rotor, nacelle and tower. The wind blade connected to rotor. To make the whole turbine structural model, the mass and stiffness properties of all parts should be clear and given. However the wind blade, hub, nacelle, rotor and power generating machinery parts have difficulties to define the material properties because of the composite and assembling nature of that. Nowadays to increase the power generating coefficient and cost efficiency, the highly accurate aerodynamic loading evaluating technique should be developed. The Fluid-Structure Interaction (FSI) is the emerging new way to evaluate the aerodynamic force on the rotating wind blade. To perform the FSI analysis, the fluid and structural model which are sharing the associated interface topology have to be provided. In this paper, the structural model of blade development and verifying processes have been explained for Part1. In following Part2 paper, the processes of whole turbine system will be discussing.
미사일-타깃해석법에 의한 콘크리트돔의 항공기 충돌해석에 관한 연구
이경수,하크 지아올,한상을,Lee, Kyoung-Soo,Huque, Ziaul,Han, Sang-Eul 大韓建築學會 2014 大韓建築學會論文集 : 構造系 Vol.30 No.6
In this paper, the authors performed the missile-target interaction analysis for B747 airplane against prestressed concrete dome structure. The aircraft model was developed and verified from the previous researches that were done by the authors. Therefore, the FE aircraft model can be used for the aircraft impact loading case. The development of aircraft FE model is theoretically based on the Riera function which was proposed by Riera derived from the rigid wall impact hypothesis. When the aircraft impact to the freeform or circular section shaped structure, the resulting impact force and it's integral impulse force may be different from the theoretical values. In this paper, the authors developed the artificial prestress concrete dome structure which has circular section shape and usually using for the nuclear power plant containment building structure. And the aircraft impact analyses were performed using missile-target interaction method. The commercial Hydrocode AUTODYN was used for FE modelling and simulations. From the comprehensive numerical studies, the shape of target structure significantly affects the aircraft impact load and decreases it compared to the Riera function and rigid wall impact simulation.
이경수,신동진,고중혁,Lee, Kyoung-Soo,Shin, Dong-Jin,Koh, Jung-Hyuk 한국전기전자재료학회 2012 전기전자재료학회논문지 Vol.25 No.4
In this paper, we have proposed piezoelectric energy harvester employing the pillar structure with the diameter size of 500 um. So we have selected the Su-8 photo-resist and modified lithography process to manufacture the pillar structure with height above the $500{\mu}m$. Simultaneously, we tried to make a comparative study to use ceramic bulk - polymer structure In this paper, we will report the process and properties of micro pillar structure based on the PMN-PZT ($Pb(Mg_{1/3}Nb_{2/3})O_3-PbZrTiO_3$) materials. Finally, We will propose a method for generating electrical energy with a piezoelectric element using vibration, an energy source can be obtained from the "clean" energy.
이경수,하크 지아올,전두진,한상을,Lee, Kyoung-Soo,Huque, Ziau,Jeon, Doo-Jin,Han, Sang-Eul 大韓建築學會 2014 大韓建築學會論文集 : 構造系 Vol.30 No.8
In this paper, the aircraft impact force models of large commercial B747 aircraft were developed by using so called Missile-Target Interaction Method. The Lagrangian meshfree SPH concept was adopted to the fuel mass for impact force calculation. 240ton, 320ton, 420ton of aircraft mass were considered to meet with the previously proposed aircraft impact force model by OECE/NEA(2002) and Arros & Doumbalski(2007). The model of present studies are based on the model of OECE/NEA originally, and extended to the model of Arros & Doumbalski. To calculate and evaluate the aircraft impact force, the impact analyses were simulated by using commercial Hydrocde AUTODYN considering the fuel mass effect. The resultant reaction force of symmetric rigid wall is considered as the impact force of aircraft. The preparation of refined FE mesh and impact simulation were done by using AUTODYN. The aircraft and fuel debris and secondary trajectory effects were considered by the eroding effect on the FE shell element and the explicitly modeled fuel mass. To evaluate and verify the impact force of aircraft, the Riera approach were used for the reference impact time history graph. The rigid wall impact test shows that the finite element model of a B747 which considering the explicit fuel mass effect is good agreement with reference values and the applicability of fuel modelling approaches of this study.
수압시험 및 운전조건이 가압기 안전노즐의 용접잔류응력에 미치는 영향 평가
이경수,이성호,김완재,Lee, Kyoung Soo,Lee, Sung Ho,Kim, Wan Jae 한국압력기기공학회 2012 한국압력기기공학회 논문집 Vol.8 No.1
This paper presents the results of finite element analysis for the effects of hydrostatic test and operating condition on the weld residual stress at dissimilar metal weld of a pressurizer safety nozzle in a nuclear power plant. For the study, the weld residual stress at ambient condition was analyzed using ABAQUS in the first place. After the weld residual stress analysis, the hydrostatic test condition and operating condition was applied to the same model one after another. The weld residual stress was observed to change due to the successive hydrostatic test and operating condition. The axial residual stresses on inner surface of the dissimilar metal weld and HAZ region were decreased by hydrostatic test and operating condition, which gives beneficial effect on preventing primary water stress corrosion cracking.
자발성 뇌지주막하 출혈 환자에서 뇌동맥류 검출에 대한 고식적 혈관조영술과 3차원 전산화 단층 혈관조영술의 비교
이경수,강창구,허륭,이상훈,정의화,Lee, Kyoung Soo,Kang, Chang Gu,Huh, Ryoong,Lee, Sang Hoon,Chung, Ui Wha 대한신경외과학회 2001 Journal of Korean neurosurgical society Vol.30 No.6
Objectives : Three-dimensional computed tomographic angiography(3D-CTA) is recently developed diagnostic imaging modality. We have studied this noninvasive method for possible role in replacing conventional angiography( CA) in the detection of aneurysms of the circle of Willis in patients with subarachnoid hemorrahge(SAH). Methods : We studied retrospectively, the 100 patients with SAH or unruptured aneurysms admitted to our hospital from October 1997 to December 1998. Among there, 85 patients underwent CTA, 82 patients underwent CA and 67 patients underwent both of CTA and CA. 3D-CTA was obtained using maximum intensity projection(MIP) and shaded-surface display(SSD) reconstruction. Results : Total 107 aneurysms were detected in 92 patients, and 64 aneurysms were detected in 67 patients underwent both CTA and CA. In five cases of those 67 cases, aneurysms were detected by CA but not by 3D-CTA. The detection rate of aneurysms(91.8%) and the detection rate of parent artery in cases of anterior communicating artery aneurysms(86.9%) with total 3D-CTA were relatively compatible with that of CA. But 3D-CTA was not enough in detection of posterior communicating artery aneurysms, internal carotid artery aneurysms as well as small sized aneurysm(<3mm). Conclusion : We consider CTA is valuable in as a screening test for cerebral aneurysm and follow-up test. And it is also valuable in early surgery for patients with aneurysmal rebleeding because of simple, quick, non-invasive method.