Fatigue crack detection performance comparison in a composite wind turbine rotor blade

This article presents the detection performance results for multiple detectors or test statistics, using different active-sensing hardware systems in identifying the presence and location of a through-thickness fatigue crack in a 9-m composite wind turbine rotor blade. The rotor blade underwent similar to 8.5 million cycles of fatigue loading until failure, when a 30-cm-long crack surfaced on the leading edge portion of the blade's transitional root area. The rotor blade was cantilevered on a 7-ton test stand and excited using a hydraulically actuated resonant excitation system, which drove the rotor blade at its first natural frequency. Through the course of the test, data were collected using two distinct types of acquisition hardware: one designed for ultrasonic-guided wave interrogation and the other for diffuse wave field interrogation. This article presents the fatigue crack detection performance results for several hardware and test statistic combinations.