The energy turnaround represents a societal challenge. Currently, the amount of renewable energy reaches 29 % of the gross electricity production in Germany with nearly half of the renewable energy generated by wind turbines. The number of onshore wind turbines in operation is already considerable today. But beyond that, a continuous and consolidated increase of new wind turbines is expected to meet the government’s target of 65 % of gross renewable energy production by 2030.

Operators of wind turbines can achieve remarkably high efficiency by extending operation of the wind turbine for as long as possible and even over the original service life. This requires reliable lifetime prediction models. The research project FutureWind aims at developing damage models and fracture mechanic models for the prediction and evaluation of the service life of typical construction details of onshore wind turbines. The phenomenological models capture crack initiation and crack growth and allow a stress-optimized design and an optimization of components and construction details under operating loads. Moreover, the advanced models lead to an accurate prediction of the service life of wind turbines. Finally, the research project provides simple rules for next generations of assessment guides.

Wind turbines are exposed to highly dynamic variable load conditions during their lifetime of at least 20 years and can be subjected to up to 10⁹ cycles. Therefore, they are assigned to the very high-cycle-fatigue regime. With respect to the huge amount of load cycles in this regime, conventional models do not accurately represent the influence of load cycles below the endurance limit. Furthermore, sequence effects, the influence of manufacturing accuracy, material properties and stress distribution in notches are not considered adequate in conventional models. Hence, there are many opportunities for optimization regarding steel tower design of wind turbines.

Bissing, H.; Knobloch, M.; Rauch, M. (2021). Improving economic efficiency of wind energy using data-based fatigue assessment methods. In: IABSE Congress Ghent 2021 - Structural Engineering for Future Societal Needs. DOI: https://doi.org/10.2749/ghent.2021.1537

Bissing, H.; Knobloch M. (2021). Data-based fatigue assessment - Application of the Incremental Step Test and the Strain-Life Approach. In: Workshop SimFat 2021 Large-scale testing & advanced numerical simulation in fatigue and fracture. DOI: https://doi.org/10.13154/294-7938

Bissing, H.; Knobloch, M.; Rauch, M. (2021). Advanced fatigue assessment - the future of wind turbine towers. FATIGUE DESIGN 2021, 9th Edition of the International Conference on Fatigue Design. In: Procedia Structural Integrity, Vol. 38, 2022, pp. 372-381, DOI: https://doi.org/10.1016/j.prostr.2022.03.038

Schulze Spüntrup, H., Rauch, M., & Knobloch, M. (2019). Comparative study on the fatigue assessment concepts for horizontal butt welds of wind turbine towers. In J. Jönsson (Hrsg.), Nordic Steel Copenhagen 2019: 18th to 20th September ; The 14th Nordic Steel Construction Conference (S. 773–778). https://doi.org/10.1002/cepa.1132

The research project IGF 20987 N / P 1398/04/2020 "Prediction models for the service life and further operation of wind turbines" from the Research Association for steel Application (FOSTA), Düsseldorf, was supported by the Federal Ministry of Economic Affairs and Climate Action through the German Federation of Industrial Research Associations (AiF) as part of the programme for promoting industrial cooperative research (IGF) on the basis of a decision by the German Bundestag. The project was carried out at Chair of Steel. Lightweight and Composite Structures.