• Weijtjens, Wout
• Sadeghi, Negin
• Noppe, Nymfa
• Devriendt, Christof

Abstract

Wind and sea waves are the principal sources of variable amplitude fatigue loading for offshore wind turbines. Additionally, corrosion might play a role in reducing the fatigue tolerance capabilities of the structure at its critical locations. On this purpose, the OWI-lab MAXWind Project aims to understand the interactive effects and the impact of corrosion and fatigue on crack initiation and propagation at welded joints. This shall be done by the development of a reliable fatigue analysis tool to update the failure life at critical locations.<br/>The focus of MAXWind will be on monopile foundations, as these are currently the most used type of foundation in Belgian waters and there is a large amount of data available on these types of foundations. However, the established<br/>methodology can be extended to include other foundation types like jacket<br/>structures and floating foundations.<br/>For current research within the field of fatigue assessment of offshore wind<br/>turbines OWI-lab considered the standard Rainflow counting algorithm, and a<br/>linear damage accumulation rule. As part of the MAXWind project, the<br/>improvement and extension of the existing fatigue toolbox is necessary. This<br/>contribution will give an introductory overview of the possibilities to achieve this<br/>goal, giving the benefits and the drawbacks of existing techniques for the specific application in offshore wind.<br/>First the paper will give an overview of potential improvements of the<br/>deterministic method already included in the current toolbox e.g.mean stress<br/>effect correction models, the usage of the D’Antuono-Ciavarella amplification<br/>factors for continuous corrosion assessment, the use of the Kitagawa-Takahashi<br/>diagram and the Murakami-Endo method for short-crack/defects.<br/>In the end the paper will also discuss the non-deterministic approaches to variable amplitude fatigue life prediction and the characterization of corrosion metrics.

Topics

• impedance spectroscopy
• corrosion
• crack
• fatigue