Damage Localization in a Residential-Sized Wind Turbine Blade using Subspace Exclusion Zones

Wind turbines are repeatedly exposed to natural loads, which, in general, have a significant influence on the structural lifetime. Therefore, maintenance and manual inspection are of great importance in the attempt to reduce catastrophic failures; both in onshore and offshore scenarios. Vibration-based structural health monitoring (SHM) has the potential to provide information about potential structural deterioration, hence allowing for efficient inspection and, as such, a reduction in operational costs. However, this requires a robust method for each step of the damage identification process, which consists of four subcategories proposed by A. Rytter [1]; namely, detection, localization, assessment and consequence. The process is performed stepwise, hence leading to that detection must be completed before locating the damage. Detecting damages in wind turbines has been solved with reasonable success [2], but a robust solution to the next step in the damage identification process, finding its location, has not been provided. A contribution to the second step is the newly developed method subspace exclusion zone (SEZ), proposed by Bernal and Ulriksen [3]. The SEZ method is a model-based damage localization approach, which facilitates a user-defined localization resolution. The method operates by mapping the damage-induced difference in the kinematic response, from an undamaged and damaged state, to a theoretical model of the structure. The SEZ method has shown promising results in the context of numerical simulations and laboratory experiments with a simple beam structure [4]. Therefore, the focus of this paper is to test the SEZ method on a more complex geometry, here, the residential-sized wind turbine blade in a laboratory environment.