Issue 43

N. Montinaro et alii, Frattura ed Integrità Strutturale, 43 (2018) 231-240; DOI: 10.3221/IGF-ESIS.43.18 233 to the sample in order to reduce geometric distortions. It is worth mentioning that the IR camera selected for this application uses a high thermal resolution cooled detector. The evolution of the generated thermal footprint, while moving the sample at constant speed, is analyzed in the full-filled thermograms acquired with the IR camera. In particular, a sub-window region called ROI is monitored and evaluated offline in the post-processing phase. The ROI is placed in the zone with high temperature gradients behind the heat source, at a certain distance from it. The size of the ROI used in the experimental activity was obtained after the optimization process performed with the numerical model. The scanned surfaces had been preliminary coated with a matt black paint to enhance and uniform the emissivity of radiant energy. Fig. 2 shows the typical defect signature obtained from the temperature profile acquired with the laser thermography analysis. The local bumps occur when the laser flies over a defected zone. As discussed in [13] the detection mechanism in the flying laser inner probe technique (FLIPT) is based on the perturbation of the heat conduction perpendicularly to the scan direction. Figure 1 : Schematic representation of the experimental setup. Parameter set-up Value Distance sample to IR camera ~300 mm Distance laser to sample surface ~200 mm Sample rate IR camera 50 Hz Laser spot on sample surface ~0.5-0.75 mm Table 1 : Main experimental set-up parameters. Figure 2 : Example of the perturbation on the Standard Deviation or Mean values of the temperature in the ROI when approaching a defect along the scanline. Laser control unit Thermo camera Data in/out Sample movement Camera  field of view PC unit Motion control Synchro Standard Deviation or Mean value Distance over scanline                                Begin of defect Begin of defect End of defect End of defect Peak‐to‐peak Peak‐to‐peak