PSI - Issue 64

1330 Jie Wang et al. / Procedia Structural Integrity 64 (2024) 1326–1333 Author name / Structural Integrity Procedia 00 (2019) 000–000 5 where ( , , ) are the barycentric coordinates of the point to be interpolated; ( , ) , ( , ) , and ( , ) are the image coordinates of the triangle vertices A, B and C, respectively; and ( , ) are the image coordinates of the point to be interpolated. ( , , ) can be calculated as follows: ( )( ) ( )( ) ( )( ) ( )( ) ( )( ) ( )( ) ( )( ) ( )( ) A C A A C A B A C A B A C A A B A A B A C A B A C A B A 1 y y x x x x y y y y x x x x y y y y x x x x y y y y x x x x y y β γ α β γ − − − − − = − − − − − − − − − − = − − − − − = − − (2) 2.3. Crack detection The global displacement field was visualized as a displacement cloud map. The crack was detected by extracting regions with color change using image processing methods. First, the image was converted from the RGB color space to the HSV color space. Then, a low thresholding with (130, 100, 20) and a high thresholding with (200, 200, 50) were applied to extract the potential crack. Afterward, the image underwent a morphological closing operation followed by dilation, which removed small connected components in each result. Subsequently, a subtraction operation was performed on the image followed by another dilation. This step break connection between cracks and their surrounding areas. 3. CASE STUDY ON A STEEL PLATE The feature matching model was pre-trained on the Scannet dataset, with the total loss function shown in Fig. 3. (3) Using the barycentric coordinates as weights, displacement of the three vertices of the triangle were weighted to calculate displacement of the point to be interpolated.

Fig. 3. Loss function versus training cycles.

Based on the change in the loss function, the training results from the last (37 th ) epoch were chosen as the pre trained model. which was then fine-tuned on steel plate images to obtain the final feature matching model. To validate feasibility of the proposed method for detecting the displacement field and fatigue crack, tensile tests were performed on steel plates.