K-0815 大塑性変形繰返しにおける表面き裂材の構造安全性(S11-4 構造健全性評価(4))(S11 構造健全性評価)

概要

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It is quite an important problem to estimate the safety against the large earthquakes in large oil tank. Especially, up-lift behaviors of oil tank bring plastic strains of several percentage to shell to annular joint. TDM committee in High Pressure Institute of Japan have discussed such problems to establish an estimation technique of the fracture behaviors and the criterion of maintenance under cyclic plastic strains to prevent or minimize fatal accidents. Authors have reported that crack growth under ultra low cycle fatigue can be estimated by using a parameter related to J-integral and suggested equations which express the crack growth at shell to annular joint. This paper discusses an analytical procedure to estimate ultra low cycle fatigue life of the shell to annular joint. The crack growth equations obtained by 3-dimensional FEM were modified to take into account an effect of a thickness reduction of annular plate and critical defect sizes ware shown in a diagram.
2001-08-22