Issue 43

N. Montinaro et alii, Frattura ed Integrità Strutturale, 43 (2018) 231-240; DOI: 10.3221/IGF-ESIS.43.18 238 Figs. 10a and 10b present the plot of the MT values computed over the ROI versus the ROI position along face A and face B, respectively, on sample 1. As shown in Fig. 10, the four defects of sample 1 are correctly identified. In this case, the FLIPT technique is only able to detect the position of the defect but not its extension, that is overestimated. Figure 10 : Plots of MT values computed over the ROI versus the ROI position along face A (a) and face B (b) on sample 1. Fig. 11 shows the plot of MT and SD values computed over the ROI versus the ROI position along face C of sample 2. The perturbations on the MT and SD value along the scanline over the sample 2 allow to spot the three defects correctly. Even in this case, the FLIPT technique is only able to detect the position of the defects but not their extension, that is overestimated. In particular, it is observed that the abscissa corresponding to the defect initiation is well correlated with the initiation of the defect signature. Therefore, the technique is more effective in detecting the beginning of the defect, but less effective in establishing its extension. This is due to thermal inertia effects which remain in the temperature distribution of the ROI which do not allow a clear identification of the instant when the laser spot overcomes the defected zone. Figure 11 : Plot of MT (a) and SD (b) value computed over the ROI versus the ROI position along face C on the sample 2. Experimental/Numerical Comparison In Fig. 12 the MT curves referred to the experimental and numerical outcomes for the scan of face C on sample 2 are compared. One noteworthy outcome from the above comparison is that both peaks and valleys are well aligned and the relative distances between peaks and valleys of the three defects are similar. In general, the trend of the defect signature is similar between experimental and numerical predictions. The peak-to-peak amplitude is significantly different (the left scale in Fig. 12 refers to the experimental results, while the right scale to the numerical) and is higher for the numerical case, especially for the defect 2/2 and 3/2. 35 35,5 36 36,5 37 5 10 15 20 25 30 35 40 45 MT [°C] Distance [mm] MT Defect 1/1 Defect 2/1 36,0 36,5 37,0 37,5 38,0 5 10 15 20 25 30 35 40 45 MT [°C] Distance [mm] MT Defect 3/1 Defect 4/1 (a) (b) 33 33,5 34 34,5 35 35,5 5 10 15 20 25 30 35 40 45 MT [°C] Distance [mm] MT 0,2 0,3 0,4 0,5 0,6 0,7 0,8 0,9 1 1,1 5 10 15 20 25 30 35 40 45 SD [°C] Distance [mm] SD Defect 1/2 Defect 2/2 Defect 3/2 Defect 1/2 Defect 2/2 Defect 3/2 (a) (b) (a) (b) (a) (b)