One critical issue in the integrity assessment of pressurised vessels to be addressed is characterising the influence of initial residual stresses (arising from fabrication processes especially around welds, where the appearance of cracks is also a likely event) on cleavage fracture. Using a specific crack configuration, this paper explores the stress state at crack tip area under similar loading conditions with and without the presence of initial stresses as well as their interaction and compares the stress fields in the context of stress based statistical modelling of cleavage fracture toughness. A recently developed local stress based approach to failure probability prediction for cleavage fracture of ferritic steels is used to predict toughness distributions. It is found that the presence of initial residual stresses dramatically change the final fracture conditions.

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