As the increase of operating times of petro-chemical facilities, possibility of flaw occurrences has been rapidly increased also. From a recent in-service inspection, three different sized surface cracks (crack depths of 4.5, 9.9 and 14.2 mm) were detected in welding parts of a spherical shell in Korea. While API579 code provides corresponding assessment procedures to determine crack driving forces, in the present work, numerical analyses are carried out for the cracked spherical shell to investigate effects of complex geometry, analysis model and residual stress. From detailed finite element analysis, stress distributions are determined for the full three-dimensional model. Then, stress intensity factors are calculated for simplified model by employing the well-known influence stress function technique. Finally, parametric structural integrity evaluation of the cracked spherical shell is conducted by using failure assessment diagram method. And the numerical results reflecting different geometry, analysis model and residual stress are fully discussed.

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