Local unified probabilistic model for fatigue crack initiation and propagation: Application to a notched geometry

• A procedure to generate probabilistic S–N fatigue fields is proposed.
• Fatigue crack initiation and propagation are integrated in an unified approach.
• Fatigue crack propagation is a process of continuous crack re-initializations.
• Experimental data shows the accuracy of the proposed P–S–N fields.

Traditionally, fatigue crack initiation has been modelled based on strain-life relations whereas fatigue crack propagation has been modelled using fracture mechanics concepts. Recently, new fatigue crack growth models, based on elastic–plastic stress–strain histories at the crack tip region, along with strain-life damage models have been proposed, which constitutes a class of local fatigue crack propagation models. Therefore, a unified local approach is feasible to model both crack initiation and crack propagation. An application of such a unified local approach to fatigue is presented in this paper. In particular, a notched rectangular plate, made of P355NL1 steel is modelled in order to generate S–N curves for distinct stress R-ratios. The predictions are compared with available experimental data. The required strain-life data of the P355NL1 steel is also presented in the paper, in a probabilistic form, using adequate fatigue damage parameters. Finally, the probabilistic S–N field is proposed for the notched detail and a good correlation of the available experimental data is observed.