PSI - Issue 68

Hugo Mesquita Vasconcelos et al. / Procedia Structural Integrity 68 (2025) 795–801 Hugo Mesquita Vasconcelos et al. / Structural Integrity Procedia 00 (2025) 000–000

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Fig. 1. – Steps for thermographic field validation

After the acquisition of both thermographic images, the next step involves converting these images into temperature maps. This conversion enables quantification of temperature variations across the blade. Temperature maps provide a precise and interpretable format to observe and analyse the thermal behaviour of the blade, highlighting areas with abnormal thermal signatures that may indicate underlying structural issues. The final stage of the methodology is the post-processing phase, which includes several analytical techniques to enhance the interpretability of the thermal data. Key among these techniques is the creation of a difference map, which is obtained by subtracting the morning temperature map from the noon temperature map. This difference map accentuates the regions with significant thermal variations, thereby revealing potential defects. By comparing these thermal profiles, the methodology enables the identification of anomalies that are consistent with structural defects, facilitating a comprehensive and non-intrusive evaluation of the blade's integrity. A full-scale field test was conducted on a wind turbine in northern Portugal. The turbine tested was a Siemens supplied Izar Bonus 1.3 MW LM 29 model, with a hub height of 60 meters and 29-meter blades equipped with 1.5 meter extensions. The rotor blade used in the field test was manufactured by LM Glasfiber A/S, model LM 29.0P. The DJI Matrice 300 RTK, equipped with the DJI Zenmuse H20T camera, was used for field validation. The camera features a microbolometer sensor for thermal imaging and provides a thermal resolution of 640x512 pixels. Operating in the 8-14 µm spectral band, this spectral range is ideal for identifying thermal anomalies in outdoor conditions, as it corresponds to the infrared region where most thermal emissions from objects at ambient temperatures occur (DJI 2020; Kwan et al. 2021).

Fig. 2. Wind turbine experimental thermal image acquisition with DJI Matrice 300.