Researchers at the Federal Institute for Materials Research and Testing (BAM) have demonstrated that specialised welding filler metals can significantly improve the fatigue strength of welded components used in offshore wind turbines.
The research focused on welds in high-strength steel components, which are among the most heavily stressed areas of offshore wind turbines due to continuous exposure to wind and wave loads. According to BAM, fatigue strength increased by between 50% and 140% compared with conventional welds, depending on component design and weld geometry.
The study examined Low-Transformation-Temperature (LTT) filler metals, which alter the microstructure of welds during cooling. This reduces tensile residual stresses generated during welding and, in some cases, creates compressive residual stresses that help inhibit fatigue crack formation.
Researchers tested reinforced high-strength steel components similar to those used in offshore wind turbine towers and support structures. The greatest improvements were achieved through the addition of a strategically positioned LTT weld pass in highly stressed areas.
BAM said the findings could support greater use of high-strength steels in offshore wind applications, potentially enabling lighter structures while maintaining required safety standards.
The results are being reviewed by industry expert groups and standards committees for possible inclusion in future regulations. The findings may also have applications in mechanical engineering, steel construction, automotive manufacturing and heavy-lift cranes used for wind farm construction.
The project was coordinated by BAM in collaboration with the Fraunhofer Institute for Mechanics of Materials (IWM) and the Research Association of the German Society for Welding and Related Processes (DVS). It was funded by the German Federal Ministry for Economic Affairs and Energy through the Industrial Collaborative Research programme.
