Acoustic Emission for Structural Integrity Assessment of Wind Turbine Blades

Over the last 16 years, pioneering research work has resulted in significant progress in the area of acoustic emission condition monitoring of wind turbine blades. From laboratory static tests on small blades to laboratory full-scale fatigue tests, then to static field tests on actual wind turbines, we are now in the position to instrument and monitor in real time the structural integrity of rotating blades on operating machines with multichannel acoustic emission systems, via the Internet. This chapter provides an overview of the research conducted, the various types of tests carried out, and the milestones in developing the application, and summarizes the recent developments on in-service monitoring of wind turbine blades during operation. Emphasis is given to the difficulties faced, the means these were overcome, the challenges that still need to be dealt with, and propositions for future work and research. Apart from summary results from the initial and subsequent laboratory experiments, characteristic results from recent long-term health monitoring of the blades of an operating machine with acoustic emission are presented. The importance of fusion of acoustic emission data with operational data from the wind turbine (wind speed, torque, RPM, etc.), for the proper assessment of the blade's condition, is also demonstrated.