Improving accuracy of dual-axial resonance fatigue testing for wind turbine blades by using predicted equivalent test loads caused by combined loading

The dual-axial resonance fatigue test provides for accurate and efficient testing of wind turbine blades through optimizations. However, the existing dual-axial test optimization does not yield an accurate test design because it compares the test loads that correspond to the mode shapes with the target loads that are aligned to the local chord axes. Therefore, this paper proposes equivalent applied loads to predict the flatwise and edgewise test loads by transferring the mode shapes to the local chord axes and using the linear damage accumulation rule. The application of the equivalent applied loads helps the dual-axial test optimization yield satisfactory test schemes without much additional computing time.