Assessing fatigue endurance limit of pitted specimens by means of an integrated fracture mechanics approach

From an operator/engineering perspective, the correct assessment of the severity of corrosion defects (e.g., pits) can have enormous economic, social and environmental benefits; therefore the development of a generally applicable and simple to apply procedure for fatigue assessment of key components is recognised as a valuable tool, seeking to reduce the current overly conservative procedures whilst maintaining structural integrity. The critical condition for a crack emanating from a pit (pit-to-crack transition) to start to propagate is analysed in this paper. The pit-crack configuration is re-characterized into that of a hemispherical crack of length equal to the pit depth, and this assumption is analysed by detailed 3D FEA. A propagation threshold approach is used to estimate the fatigue resistance from intrinsic material properties. The proposed approach is validated by comparison with experimental results available in the open literature.