Mechanical Strength Evaluation of A53B Carbon Steel Subjected to High Temperature Hydrogen Attack

Kim, Maan-Won,Lee, Joon-Won,Yoon, Kee-Bong,Park, Jai-Hak The Korean Society of Safety 2007 International Journal of Safety Vol.6 No.2

In this study mechanical strength of A53B carbon steel was analyzed using several types of test specimens directly machined from oil recycling pipe experienced a failure due to hydrogen attack in chemical plants. High temperature hydrogen attack (HTHA) is the damage process of grain boundary facets due to a chemical reaction of carbides with hydrogen, thus forming cavities with high pressure methane gas. Driven by the methane gas pressure, the cavities grow on grain boundaries forming intergranular micro cracks. Microscopic optical examination, tensile test, Charpy impact test, hardness measurement, and small punch (SP) test were performed. Carbon content of the hydrogen attacked specimens was dramatically reduced compared with that of standard specification of A53B. Traces of decarburization and micro-cracks were observed by optical and scanning electron microscopy. Charpy impact energy in hydrogen attacked part of the pipe exhibited very low values due to the decarburization and micro fissure formation by HTHA, on the other hand, data tested from the sound part of the pipe showed high and scattered impact energy. Maximum reaction forces and ductility in SP test were decreased at hydrogen attacked part of the pipe compared with sound part of the pipe. Finite element analyses for SP test were performed to estimate tensile properties for untested part of the pipe in tensile test. And fracture toughness was calculated using an equivalent strain concept with SP test and finite element analysis results.

Pathogenic Upregulation of Glial Lipocalin-2 in the Parkinsonian Dopaminergic System

Kim, Byung-Wook,Jeong, Kyoung Hoon,Kim, Jae-Hong,Jin, Myungwon,Kim, Jong-Heon,Lee, Maan-Gee,Choi, Dong-Kug,Won, So-Yoon,McLean, Catriona,Jeon, Min-Tae,Lee, Ho-Won,Kim, Sang Ryong,Suk, Kyoungho Society for Neuroscience 2016 The Journal of neuroscience Vol.36 No.20

<P>Lipocalin-2 (LCN2) is a member of the highly heterogeneous secretory protein family of lipocalins and increases in its levels can contribute to neurodegeneration in the adult brain. However, there are no reports on the role of LCN2 in Parkinson's disease (PD). Here, we report for the first time that LCN2 expression is increased in the substantia nigra (SN) of patients with PD. In mouse brains, 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP) treatment for a neurotoxin model of PD significantly upregulated LCN2 expression, mainly in reactive astrocytes in both the SN and striatum. The increased LCN2 levels contributed to neurotoxicity and neuroinflammation, resulting in disruption of the nigrostriatal dopaminergic (DA) projection and abnormal locomotor behaviors, which were ameliorated in LCN2-deficient mice. Similar to the effects of MPTP treatment, LCN2-induced neurotoxicity was also observed in the 6-hydroxydopamine (6-OHDA)-treated animal model of PD. Moreover, treatment with the iron donor ferric citrate (FC) and the iron chelator deferoxamine mesylate (DFO) increased and decreased, respectively, the LCN2-induced neurotoxicity in vivo. In addition to the in vivo results, 1-methyl-4-phenylpyridinium (MPP+)induced neurotoxicity in cocultures of mesencephalic neurons and astrocytes was reduced by LCN2 gene deficiency in the astrocytes and conditioned media derived from MPP+-treated SH-SY5Y neuronal enhanced glial expression of LCN2 in vitro. Therefore, our results demonstrate that astrocytic LCN2 upregulation in the lesioned DA system may play a role as a potential pathogenic factor in PD and suggest that inhibition of LCN2 expression or activity may be useful in protecting the nigrostriatal DA system in the adult brain.</P>

Empirical Correlation between Parameters from Small Punch and Tensile Curves of Mn-Mo-Ni Low Alloy Steels by Using Test and FE Analysis

Kim, Min Chul,Lee, Jae Bong,Kim, Maan Won,Lee, Bong Sang Trans Tech Publications, Ltd. 2007 Key Engineering Materials Vol.353-358 No.3

<P>A load-displacement curve from a small punch test includes several useful information that is related to standard test properties such as the tensile property, fracture toughness and ductilebrittle transition temperature. In this study, the empirical relationship between the material property factors in SP curves and the tensile curves has been investigated by comparing test results and finite element analysis results. SP and tensile tests and finite element analyses were performed for several Mn-Mo-Ni low alloy steels with different manufacturing processes. It was found that the yield loads (Py) in the SP curves, if they were adequately defined, were linearly related to the yield strength (σ0). The yield loads defined from the intersection point of two lines tangent to the elastic bending region and plastic bending region showed a better relation with the yield strength than those from the offset line. The slope of the SP curves from the simulation results had a close correlation with the hardening coefficient and strength constant as well.</P>

Mechanical Strength Evaluation of A53B Carbon Steel Subjected to High Temperature Hydrogen Attack

( Maan Won Kim ),( Joon Won Lee ),( Kee Bong Yoon ),( Jai Hak Park ) 한국안전학회(구-한국산업안전학회) 2007 International Journal of Safety Vol.6 No.2

In this study mechanical strength of A53B carbon steel was analyzed using several types of test specimens directly machined from oil recycling pipe experienced a failure due to hydrogen attack in chemical plants. High temperature hydrogen attack (HTHA) is the damage process of grain boundary facets due to a chemical reaction of carbides with hydrogen, thus forming cavities with high pressure methane gas. Driven by the methane gas pressure, the cavities grow on grain boundaries forming intergranular micro cracks. Microscopic optical examination, tensile test, Charpy impact test, hardness measurement, and small punch (SP) test were performed. Carbon content of the hydrogen attacked specimens was dramatically reduced compared with that of standard specification of A53B. Traces of decarburization and micro-cracks were observed by optical and scanning electron microscopy. Charpy impact energy in hydrogen attacked part of the pipe exhibited very low values due to the decarburization and micro fissure formation by HTHA, on the other hand, data tested from the sound part of the pipe showed high and scattered impact energy. Maximum reaction forces and ductility in SP test were decreased at hydrogen attacked part of the pipe compared with sound part of the pipe. Finite element analyses for SP test were performed to estimate tensile properties for untested part of the pipe in tensile test. And fracture toughness was calculated using an equivalent strain concept with SP test and finite element analysis results.

소구경배관 소켓용접부 클램프 설치중량에 따른 영향평가

김만원(Maan-Won Kim),신인환(In-Hwan Shin),주용선(Yong-Sun Ju) 대한용접·접합학회 2018 대한용접학회 특별강연 및 학술발표대회 개요집 Vol.2018 No.4

소형 모듈형 원자로의 원자로용기 파손확률에 대한 민감도 분석

김만원(Maan-Won Kim),문호림(Ho-Rim Moon),박치용(Chi-Yong Park) 대한기계학회 2021 대한기계학회 춘추학술대회 Vol.2021 No.4

최근 소형 모듈형 원자로에 대한 연구가 국내외에서 활발히 추진되고 있다. 소형 모듈형 원자로는 원자로용기의 크기가 작고 원자로용기 내에 증기발생기, 가압기, 내부구조물 등이 포함되어 있으며, 장수명으로 설계되는 것이 특징이다. 소형 모듈형 원전의 운전환경 특성을 반영한 가압열충격 민감도 분석을 통해 원자로용기 파손확률에 미치는 변수들의 영향을 살펴보는 것도 초기 설계과정에서 의미가 있다. 본 논문은 확률론적 파괴역학 건전성평가 프로그램인 VISA-II 를 사용하여 소형 모듈형 원자로압력용기 파손 확률에 대한 민감도 분석을 수행하였다. 민감도 분석 변수로는 장수명 운전에 따른 재료가 받는 영향(중성자조사량, 재료 내 구리 함량), 균열의 방향(원주방향과 축방향 균열), 균열 형상비(깊이와 길이의 비), 가동중검사 데이터 적용 여부이며, 원자로용기의 두께 및 반경 크기의 영향도 분석하였다. 분석을 위한 대상 노형은 국내외 노형을 각각 1 개씩 선정하였다. 분석 결과, 선정된 두 노형에서 각각의 고유 사고 시나리오를 적용하는 경우, 60 년 운전 동안 원자로용기 파손확률은 거의 발생하지 않은 것으로 평가되었다. 파손확률이 무시할 정도로 낮은 이유는 고유 사고 시나리오의 온도 압력 변화가 작고, 중성자 조사취화로 인한 재료의 파괴인성 값에 영향을 주는 재료 내 구리 함량이 작기 때문인 것으로 판단된다. 한편, 원자로용기 반경의 영향 보다는 두께의 영향이 더 크게 나타났으며, 원주방향 균열보다 축방향 균열인 경우 파손확률이 크게 나타남이 관찰되었다. Recently, small module reactors (SMRs) have being actively researched and developed. SMR has some structural features such as small reactor vessel (RV), in which installed main components like as steam generator and pressurizer. Generally in the large light water reactor(LWR), the initial event of reactor vessel rupture (RVR) has a significant impact on the core damage frequency and the large early release frequency. However, as SMRs have different operation environments and features compared to the large PWR plants, the investigation of reactor vessel rupture has a meaning review in the aspect of probabilistic safety analysis during SMR initial design. This paper’s goal is to analyze the probability of RV failure due to SMR’s accident event transient load using VISA-II, which is one of software to probabilistic fracture mechanics. The sensitivity analysis have been evaluated in various valuables as to material impact parameters (e.g., neutron fluence and weight percent of copper in RV material) during plant life-time, inner diameter of reactor vessel and crack directions (e.g., circumferential, axial). The estimated failures of RVR at the selected two SMRs would not be occurred during the RV’s life. From sensitivity analysis, the effects of a crack of thickness or circumferential direction were investigated and analyzed.

유한요소 교호법을 이용한 이방성 재료내의 꺽인 균열 및 원호균열 해석

김만원(Maan Won Kim),박재학(Jai Hak Park) 한국항공우주학회 2000 韓國航空宇宙學會誌 Vol.28 No.7

원자로압력용기의 가압열충격평가 시 조사된 재료의 파괴인성 적용 방법에 대한 고찰

김만원(Maan-Won Kim),이재곤(Jae-Gon Lee) 대한기계학회 2020 대한기계학회 춘추학술대회 Vol.2020 No.12

균열 및 재료 비선형을 고려한 파단전누설(LBB) 평가

김만원(Maan-Won Kim),김성환(Sung-Hwan Kim),강용철(Yong-Chul Kang) 대한기계학회 2010 대한기계학회 춘추학술대회 Vol.2010 No.11

According to the increase of thermal power output of recently developing nuclear power plants, the applied forces and moments are should be increased in some piping systems so that the leak-before-break (LBB) application criteria could not be satisfied in those pipes. In this paper a method to obtain additive LBB margin in the pipes is presented by considering the nonlinearity of the crack and material properties. Finite element analysis and moment-rotation equation of beam theory were used to calculate the nonlinearity of the crack and material properties. Stability analysis of LBB crack was performed using the method proposed in this study. The LBB margin could be increased effectively by considering the nonlinearity of crack and material properties in the pipe.

스크래치가 존재하는 파열판의 소성변형률 기반 파열압력 평가

김만원(Maan-Won Kim),신인환(In-Hwan Shin),부명환(Myung-Hwan Boo) 대한기계학회 2018 대한기계학회 춘추학술대회 Vol.2018 No.12

The rupture disc is an important part for safely protecting the pressure vessel by bursting when the pressure vessel reaches a preset pressure. The failure pressure of the rupture disc can be predicted through engineering evaluation equation or numerical analysis such as finite element analysis at the design stage. The designed ruture pressure is verified by the test. However, a careful approach must be taken to apply existing evaluation methods to the disc which has scratches on its surface made during installation process because scratch makes a local stress concentration and disc material has usually a large deformation capability. In this study, the burst pressure was calculated by elastic plastic finite element analysis according to the position, shape, and depth of the scratch. The difference between the strength-based evaluation method and the plastic strain-based evaluation method was examined. It is appeared that the plastic strain-based evaluation method predicts more accurately the burst pressure of the rupture disc with scratches than the strength-based approach. The plastic strain-based finite element analysis results were compared with the burst test results and confirmed to be in good agreement.