| Summary: | 碩士 === 國立臺北科技大學 === 機電整合研究所 === 100 === Due to its importance in safety concerns, failure analysis of the LNG (Liquefied Natural Gas) tank has been a key task in the design process. Probabilistic failure analysis mainly aims to determine the failure mode and safety by employing fracture mechanics associated with the probabilistic size distribution of defects. This study focused on using the simulated loading-unloading history of the LNG tank to calculate the structural stresses due to temperature change and the liquid pressure variations. Then, the local mechanical stress and thermal stress analysis at weld lines of the LNG tank due to the first filling and subsequent fatigue loading-unloadings were analyzed. The stress results, especially those at hot spots of the loaded tank, provided the information needed in the safety evaluation of the tank regarding the weld’s fracture and catastrophic rupture. The finite element analysis was carried out by using ANSYS. Shell and solid elements were both employed in the analysis based on the meshing feasibility and computation efficiency. The structural stress of the tank in different loaded conditions supplied part of the information for failure analysis. Finally, the reliability of the inner tank under normal operation was calculated accordingly.
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