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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.
김만원,신인환,이경수,Kim, Maan-Won,Shin, In-Hwan,Lee, Kyoung-Soo 한국압력기기공학회 2015 한국압력기기공학회 논문집 Vol.11 No.1
The purpose of this study is to evaluate structural integrity of a weldment which is partially screwed and then welded. Two finite element models are constructed and solved: operating temperature and internal pressure are considered in the first simple model, and welding process and normal operating condition including heat-up process are simulated in the second model. Structural integrity assessment criteria are satisfied with both finite element models, therefore the repair weldment finely sustains structural integrity of this assembly and prevents leakage. Stresses are dramatically increased when weld residual stress is considered, but it should be considered as a secondary stress.
유효탄성계수를 이용한 균열 비선형 및 재료 비선형을 고려한 파단전누설(LBB) 평가 방법
김만원(Maan-Won Kim),김성환(Sung-Hwan Kim),이의종(Eui-Jong Lee) 대한기계학회 2011 大韓機械學會論文集A Vol.35 No.6
최근 열출력이 향상된 신규 원자력발전소의 개발이 증가하고 있으며 배관계에 가해지는 모멘트 및 하중의 크기도 증가하는 경향이므로 배관의 파단전누설(LBB) 적용조건 여유도가 작아질 수 있다. 본 논문에서는 이러한 배관에서 LBB 적용조건을 만족시키기 위한 추가적인 여유도 확보의 한 방법으로써 균열의 비선형과 재료물성치를 고려하는 방법을 제시하였다. 균열 및 재료의 비선형을 고려하기 위하여 유한요소해석과 보(beam) 이론을 병용하였다. 원자력 배관을 모델로 하여 본 논문에서 제안한 방법으로 LBB 균열안정성 해석을 수행하였으며, LBB 여유도가 낮은 위치에서 균열 및 재료 비선형을 고려함으로써 추가적인 LBB 여유도를 확보할 수 있음을 확인하였다. With the increase in the thermal power output of recently developed nuclear power plants, the applied forces and moments are increased in some piping systems, so that the leak-before-break (LBB) application criteria would not be satisfied in those pipes. In this paper, we present a method for obtaining the additive LBB margin in the pipes by considering the nonlinearity of the crack and material properties. Finite element analysis and the moment-rotation equation of beam theory were used to calculate the nonlinearity of the crack and material properties. Moreover crack stability analysis was performed using the method proposed in this study. The LBB margin was increased effectively through consideration of the nonlinearity of the crack and material properties in the pipe.