PSI - Issue 64

Jie Wang et al. / Procedia Structural Integrity 64 (2024) 1326–1333 Author name / Structural Integrity Procedia 00 (2019) 000–000

1332

7

The input images were divided into 391 patches with 320×240 resolution. 25% overlap rate was set between adjacent patches. Dense matching of feature points was performed on pairs of patches. A total of 560,000 matched point pairs were acquired. Coordinates of the matched point pairs were used to calculate displacement of the matched points, which were then interpolated to obtain the global displacement field in y direction (perpendicular to the initial cracks), as shown in Fig. 7(a). Images obtained from DIC were also postprocessed to generate the y -direction displacement field within the ROI, as illustrated in Fig. 7(b). Calculated by the proposed method, the maximum and the minimum displacement of ROI at load of 150 kN were 0.387 mm and 0.242 mm, respectively, while those by the DIC method were 0.333 mm and 0.271 mm. Therefore, the displacement cloud map based on the proposed method generally agreed well with that of DIC method.

(a)

(b)

Fig. 7. Y -direction displacement cloud map of ROI by two methods (a) by the proposed method; (b) by the DIC method

3.3. Crack detection Color change was extracted from the displacement cloud map to identify the crack. It was compared with the actual crack and is marked in Fig. 8. The hole diameter was 5 mm, which was equivalent to 244 pixels in the image. The total length of the crack derived based on the image was 2069 pixels. Thus, the total length was converted to be 42.4 mm, which was corresponding to a deviation of 3.9% in comparison with the real crack length of 44.1 mm.

Fig. 8. Detected crack and actual crack