PSI - Issue 68

M. Álvarez et al. / Procedia Structural Integrity 68 (2025) 272–278 M. Álvarez et al. / Structural Integrity Procedia 00 (2025) 000–000

276

5

Fig. 4. Postmortem observation of CF specimens: a) Appearance after failure, b) Crack initiation site identification in optical microscope, c) Detail of crack initiation defect (SEM image).

3.2. Experimental corrosion-fatigue results Expected range for experimental CF life results (Fig. 5) was defined using DNV-GL-RP-C203 [Det Norske Veritas and Germanischer Lloyd (2019)] and BS 7608:2014 [BSI (2014)] S-N design curves as lower bound, and S355 S-N curve in air [Gkatzogiannis et al. (2019)] as upper bound. These S-N design curves (97.7% survival probability) correspond to plates with pitting corrosion subjected to free corrosion environmental condition.

Fig. 5. Experimental CF life results under wet and wet-dry conditions

As depicted in Fig. 5, fatigue life reduction was observed in wet and wet-dry CF conditions when compared to S355 S-N curve in air, due to material degradation induced by CF process. This life reduction was more severe in the case of wet-dry cycling with an estimated degradation in the range of 61-74%, in comparison with an approximate 34-69% degradation under wet condition. Fatigue limit is typically absent in CF because corrosion is a continuous process along the entire test [Sonsino et al. (2007)], hence S-N curve for wet-dry cycling was considered as a linear curve without knee point.