Robot-assisted crack detection on complex shaped components using constant-speed scanning infrared thermography with laser line excitation

Infrared thermography (IRT) using a focused laser is effective for surface defect detection. Nevertheless, testing complex-shaped components remains a challenging task. The state-of-the-art focuses on testing a limited region of interest rather than the full sample. Thus, detection and location of surface defects has been less researched. Most attempts require a manual scan of the full sample, which makes it hard to reconstruct the full scanned surface. Here, we introduce a reliable workflow for crack detection and semi-automated inspection of complex-shaped components using IRT excited with a laser line. A 6-axis robot arm is used for moving the sample in front of the setup. This approach has been tested on a section of a rail and a gear, both containing defects due to heavy use. Crack detection is based on the segmentation of thermograms obtained by Fourier transform of sorted temperatures. Moreover, texture mapping is used to visualize a reconstructed thermogram on the 3D model of the sample. Our approach illustrates a reliable process towards the digitalization of thermographic testing.