Continuous Line Laser Thermography for Damage Imaging of Rotating Wind Turbine Blades

This paper proposes a continuous line laser thermography technique for damage visualization of wind turbine blades under rotating condition. Although a number of non-destructive testing techniques have been proposed for damage inspection of wind turbine blades under stationary condition, a few prior studies on the operating blade monitoring have been reported due to technical challenges associated with actual implementation issues. The proposed continuous line laser thermography technique is able to inspect wind turbine blades with fully noncontact mechanism, no couplant requirement, data acquisition without spatial scanning mechanism and intuitive data interpretation. First, thermal waves are generated by a continuous line laser beam targeted onto the rotating wind turbine blades, and the corresponding thermal responses are simultaneously measured by an infrared camera. Then, a new pixel tracking and statistical pattern recognition algorithms are developed and applied to the measured thermal images in the time domain so that only damage features can be extracted even under the rotating condition of wind turbine blades. The performance of the proposed continuous line laser thermography technique is verified through scaled wind turbine model tests under varying rotating speed.