Fracture of wind turbine blades in operationPart I: A comprehensive forensic investigation

The structural integrity of rotor blades is crucial to ensuring continuous power production of wind turbines. Catastrophic blade fracture can cause significant economic loss and social impact and thereby should be prevented. It is important to understand the structural failure of rotor blades particularly during their normal operation. This study presents a comprehensive forensic investigation into fracture of 2 rotor blades in the field. The investigation is carried out synthetically taking into account interactive aspects associated with operational loads, materials, manufacturing processes, and structural design. The supervisory control and data acquisition data are analyzed to understand the turbine response with damaged blades. A detailed post-mortem investigation is carried out at structural, subcomponent, and material levels both in field and in laboratory from a forensic perspective. Different manufacturing-induced defects are examined using X-ray computed tomography, and they are discussed in the context of the current manufacturing and design practices. Evidences from macroscopic failure features and microscopic fractographic morphologies are collected, analyzed, and correlated in order to identify the underlying mechanisms of blade fracture. Practices are recommended to improve structural integrity of rotor blades during their entire life cycles.