• Transactions of the Korean Society of Mechanical Engineers A
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• v.26 no.1
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• pp.105-112
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• 2002

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.

• Journal of the Korean Institute of Gas
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• v.25 no.6
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• pp.14-21
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• 2021

Inner shell material of LNG storage tanks that store ultra-low temperature LNG at -162℃ requires structural integrity assessment of a crack-like defect. From the viewpoint of conventional fracture mechanics, the assessment has mainly performed by single parameter using stress intensity factor K, J-integral and CTOD. However, the stresses in a material of crack tip are not unique caused by constraint loss due to size and geometry of the structure. Various attempts have been made to complement a single parameter fracture mechanics, typically with Q-stress. In this paper, we have performed a two-parameter approach by deriving the Q-stress coupling with J-integral suitable for the evaluation of the crack tip stress field in the non-linear elastic region. A quantitative evaluation of the constraint effect has performed by using the J-Q approach. It was evaluated that the SENB type specimen had a crack ratio of 0.1 to 0.7 and the wide type specimen had a crack ratio of 0.2 to 0.6.

• Proceedings of KOSOMES biannual meeting
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• 2006.05a
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• pp.65-70
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• 2006

The regulation of HNS has been intensified by the international trends including OPRC-HNS Protocol and '96 Convention which was driven by the high amounts of cargo. Due to the characteristics of HNS that would possibly bring potential damage with personnel and assets, effective management and prompt actions are required definitely. In order to respond effectively against HNS accidents, Korea Coast Guard (KCG) is in the process q development of HNS accident response manual and information system which allows On-Scene Coordinator(OSC) and personnels for rescue including an information for hazardous materials, sensitive area to be affected, solution methods and more. Furthermore, KCG is also building up establishment of national and local contingency plans for HNS in accordance with OPRC-HNS Protocol. It is also advised to proceed for the government to solve the anticipated obstacles that include protection equipments to get close to the site, experts allowing to manage accidents and organizations specialized for overall HNS related matters. The proposed issues described above are planned to conducted on basis of government.