Finite Element Modeling and Vibration Simulation of a 5-MW 61.5-Meter Composite Wind Turbine Blade for Debonding Damage Inference

  • Author / Creator
    Yang, Junbo
  • The renewable and clean energy industry highly relies on wind turbine blades (WTBs) to generate electricity from wind. However, WTBs can suffer from a variety of damage, including spar cap-shear web debonding, which can lead to crack initiation and propagation, and in turn, cause wind turbine structural collapse. As such, this study focuses on spar cab-shear web debonding by comparing the dynamic behaviors of WTBs with and without debonding via finite element simulations, aiming to shed light on vibration-based damage detection for WTBs. Specifically, this study performed debonding and vibration simulations of the 61.5 m 5-MW blade developed by the National Renewable Energy Laboratory (NREL) in the United States. The objectives of this study are two-fold: (1) to identify the hotspot for cap-web debonding and demonstrate the crack-propagation behavior with an existing crack in the hotspot under increasing aerodynamic loads; (2) to investigate and compare the vibration behaviors of wind turbine blades with and without debonding damage (via free vibration and impact load analysis) to better inform future development of vibration-based diagnostic techniques. It is found that the cap-web connection within a 9-10.25 m span of the studied WTB is more vulnerable to debonding damage and thus determined as the debonding hotspot. The vibration simulation results indicate that the cap-web debonding is less likely to be uncovered by vibration signals, particularly via free vibration testing. However, when impact load testing is used for WTB with relatively large debonding cracks, adequate hitting points and signal collection points (i.e., near crack) can reveal the hidden damage. It is found that when the hitting point is closer to the potential debonding location, more signal discrepancy between the defective WTB and the intact WTB can be observed. Since it is possible to have debonding damage at the following 4 locations in the transverse direction, i.e., within the connection joints between the shear webs and the spar cap located at LE-BOT, LE-TOP, TE-BOT, TE-TOP (herein, LE, TE, BOT, and TOP refer to the leading edge, trailing edge, bottom surface, and top surface of the WTB, respectively), hitting points in impact load tests (e.g., flapwise on the BOT or TOP surfaces, edgewise on the LE or TE) should be located at those 4 locations in the transverse direction. In the spanwise direction, the hitting points within the debonding area, particularly around 10.25 m from the WTB root, are found to be effective for damage detection. Furthermore, the signal collection points should be as close as possible to the hitting points. Such pre-knowledge regarding the debonding hotspot, the relative effectiveness of vibrations methods,
    and the impact and vibration signal collection points can potentially increase the effectiveness of vibration-based detection techniques for cap-web debonding in practical applications.

  • Subjects / Keywords
  • Graduation date
    Fall 2023
  • Type of Item
  • Degree
    Master of Science
  • DOI
  • License
    This thesis is made available by the University of Alberta Libraries with permission of the copyright owner solely for non-commercial purposes. This thesis, or any portion thereof, may not otherwise be copied or reproduced without the written consent of the copyright owner, except to the extent permitted by Canadian copyright law.