PSI - Issue 64

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

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3.1. Experimental set-up The specimen was a Q345 steel plate with dimensions of 1170 mm in length, 90 mm in width, and 10 mm in thickness (Fig. 4). A hole of 5 mm in diameter and two initial cracks of 0.3 mm wide in the center was manufactured to simulate the initial damage. As show in Fig. 5, The y direction was parallel to the direction of length, while the x direction was parallel to the direction of width. The steel plate was subjected to a certain number of cyclic loads, resulting in fatigue cracks extending approximately 7mm from each end of the initial cracks. The total length of the hole, initial cracks, and fatigue cracks is 44.1 mm. One side of the steel plate was sprayed with speckles, and two DIC cameras were placed in front of it. Supplementary lights were mounted on both sides of the cameras to illuminate the ROI. On the other side of the steel plate, a Sony AX60 camera was positioned to capture 4K (3840×2160 resolution) RGB images. The test was performed on an Instron 8802 servo hydraulic testing machine with a dynamic load capacity of 250 kN. The sample was loaded from 0 to 150 kN at a constant speed of 0.75 kN/s.

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Fig. 4. Steel plate specimen (a) drawing of steel plate; (b) initial cracks and fatigue cracks under microscope camera.

Fig. 5. Image coordinate system

Fig. 6. Experiment conditions.

3.2. Detection of the displacement field At load of 0 kN, DIC cameras took photos of the speckled side of the steel plate, and meanwhile, Sony AX60 took photos of the other side. After the load reached 150 kN, two kind of cameras took photos again as mentioned above. Two images by Sony AX60 at load of 0 kN and 150kN were regarded as the input images of the proposed method.