Issue 43

N. Montinaro et alii, Frattura ed Integrità Strutturale, 43 (2018) 231-240; DOI: 10.3221/IGF-ESIS.43.18 236 Figure 6 : Temperature maps through-the-thickness of the sample 2 with the laser before, over and after the defect zone; temperature scale in Kelvin degree. Fig. 6 in particular shows the effect of the subsurface hole defects acting as local thermal barriers against heat flow. This determines a temporary surface redistribution of the trail temperature. Such temperature variation suggests that field parameters such as the Mean or the Standard Deviation calculated in a ROI following the laser spot at a short distance, should be sensitive and affected by the presence of defects of any kind. In Fig. 7 the size and position of five ROIs evaluated in this simulation are presented. ROI 1 is the largest one and includes the other four. ROI 5 is the smallest and the closest to the heat source. Fig. 8 reports plots of the mean temperature values computed on the five ROIs over the face C of the sample. As can be noticed all five curves deviate from their undisturbed trend each time the heat source flies over a defect, generating a local peak. For this reason the detection of such a local peaks, can be regarded as a defect signature. Figure 7 : Geometry definition of five ROIs, respect to the heat source used for the defect signature evaluation.