Segmented rotor blades: advancing damage detection in wind turbine bolted joints via low-/high-frequency sensing and data fusion

Wind energy is proving to be the backbone of the transition to sustainable electricity generation. However, due to the permanent increase in wind turbine rotor blade length to achieve higher capacities, the already challenging transportation process of rotor blades becomes even more difficult, which can be addressed by segmenting the parts. This work presents several measurement campaigns of bolted connections used to couple the structural parts of wind turbine blades, monitored by both passive low-frequency strain measurements and active high-frequency ultrasonic waves. The comprehensive test concept enables gaining insight into the degradation process of the connection type under different loading conditions. Moreover, the monitoring systems are analyzed separately, and the impact of data fusion by combining the obtained scores is thoroughly investigated. The results reveal the strong need for more reliable analysis of the individual measurement systems. Particularly challenging is the high number of false positives due to the ultrasonic guided wave’s high sensitivity. The additional strain measurements incorporated at the decision level address this endeavor, despite their lower sensitivity, thereby increasing the reliability of the results at the macroscopic level. Overall, the study presents extensive test results for bolted connections under various loading conditions and demonstrates the reliable monitoring of the system employing decision-level data fusion.