Structural health monitoring of 52-meter wind turbine blade: Detection of damage propagation during fatigue testing

Abstract

This work is concerned with damage detection in a commercial 52-meter wind turbine blade during fatigue testing. Different artificial damages are introduced in the blade in the form of laminate cracks. The lengths of the damages are increased manually, and they all eventually propagate and develop into delaminations during fatigue loading. Strain gauges, acoustic emission sensors, distributed accelerometers, and an active vibration monitoring system are used to track different physical responses in healthy and damaged states of the blade. Based on the recorded data, opportunities and limitations of the different sensing systems for blade structural health monitoring are investigated.

A full-scale wind turbine blade monitoring campaign: detection of damage initiation and progression using medium-frequency active vibrations

“…The purpose of the present blade test was to collect sensor data with multiple different damages of increasing size, enabling the study of blade SHM. Multiple sensing systems were utilized, as documented by the authors in 14 . The present study focuses on vibration-based methods, investigating both monitoring of lower-order natural vibration modes as well as a medium-frequency active vibration system.…”

“…In a previous study, the authors used OMA to estimate the modal parameters of the lower-order natural vibration modes of a 52-meter wind turbine blade mounted on a test stand 14 . Neither eigenfrequencies nor mode shapes showed significant changes resulting from manually induced transverse laminate cracks of lengths up to approximately 1% of the blade length.…”

“…From the AE data, it was also apparent at which point in time critical failure of the blade was imminent. AE sensors were used by the authors during fatigue testing of a 52-meter blade with manually induced transverse laminate cracks 14 . The AE sensors were used to conduct localized monitoring of fatigue-driven damage propagation, where a detection range of 0.5 meters was obtained for damage propagation in the shear web and spar cap laminate.…”

Feasibility study on a full‐scale wind turbine blade monitoring campaign: Comparing performance and robustness of features extracted from medium‐frequency active vibrations

“…In the low‐frequency range, monitoring of large structures is commonly concerned with global modal parameters, being natural frequencies, mode shapes, and damping estimates. Vibration‐based methods relying on monitoring of low‐frequency natural vibrations of wind turbine blades are insensitive for detection of small damages 18,35,36 . For low‐frequency natural vibration modes to serve as reliable features for SHM, damages need to affect the global stiffness of the structure.…”

“…Our previous work investigated the use of an electrodynamic vibration shaker for excitation with active vibrations in the medium‐frequency range for wind turbine blade SHM. Using accelerometer outputs, the power spectral density estimate was selected as a feature for detection of damage initiation and propagation 18,43 . A 52‐meter wind turbine blade was used for studying the utilization of the active vibration monitoring system.…”