A comprehensive numerical study has been carried out to investigate and to explore the impact of the presence of part through surface cracks of various size and orientation in a thick welded ferritic steel cylindrical vessel, on the bene- ficial effect of autofrettage loading. It is well known that autofrettage loading en- hances the load carrying capacity of defect free pressure vessels. The results of this study suggest that in presence of cracks, the localised near crack tip residual stress fields interact with in service stresses and influence the enhancement in load carry- ing capacity of autofrettaged vessel. Furthermore it is concluded that depending on the crack/loading configuration the impact of crack presence on post-autofrettage performance of the vessel varies from noticeable in some cases to marginal in others to negligible for cases where the crack tip stress field is not significantly disturbed by the service loads.

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