Fatigue crack initiation from corrosion pits in offshore structural steel: An experimental investigation using thermographic analysis
Elahi, S.A.; Chaudhuri, S.; Mehri Sofiani, F.M.; Krankenhagen, R.; De Waele, W. (2026). Fatigue crack initiation from corrosion pits in offshore structural steel: An experimental investigation using thermographic analysis. International Journal of Fatigue 210: 109660. https://dx.doi.org/10.1016/j.ijfatigue.2026.109660
In: International Journal of Fatigue. Elsevier: Oxford. ISSN 0142-1123; e-ISSN 1879-3452, more
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| Author keywords |
Corrosion fatigue;Pitting corrosion;Crack initiation;Crack propagation;Thermography;Offshore;Structural steel;infrared thermography;damage |
| Authors | | Top |
- Elahi, S.A.
- Chaudhuri, S.
- Mehri Sofiani, F.M., more
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- Krankenhagen, R.
- De Waele, W., more
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| Abstract |
In this study, the authors investigate the detection of fatigue crack initiation from corrosion pits in offshore structural steel. Fatigue tests were conducted on corroded steel specimens that were previously exposed to a marine environment inside the monopiles of two offshore wind farms. The temperature evolution of the test specimens was monitored using infrared thermography. The moment of crack initiation was determined using thermoelastic amplitude and phase signals derived from a thermographic analysis. A thresholding method was applied to identify this moment for each specimen individually, accounting for variability caused by corrosion severity, loading conditions, and thermography configurations. Fractographic analysis was performed to characterize the pits from which fatigue cracks were initiated, revealing strong correlations between pit morphology, corrosion stage, and fatigue crack initiation. To further quantify the role of pit geometry, stress concentration factors (SCFs) were estimated based on pit dimensions, showing systematic trends with exposure height and confirming that sharper isolated pits act as stronger stress raisers than wide valleys. Results show that the proposed approach can reliably detect the onset of stress redistribution in the sample upon crack initiation. The methodology demonstrates high sensitivity to early-stage structural changes under challenging surface conditions and strengthens the understanding of how corrosion pit morphology influences fatigue crack initiation. |
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