20 C.-H. Wang et al. 4.2 Experimental Setup In this study, a typical 3D DIC configure composed with a laser triangulation setup were implemented for in-plane displacement measurement, as shown in Fig. 4.1. The laser triangulation setup consisted of a laser source and a cylindrical lens which were integrated as an unit and then mounted right at the center in between left- and right- cameras; based on the experimental setup, two cameras can be used to take image-pairs for determining in-plane displacement by using 3D DIC method; at the same time, the left- and right- cameras can also capture a bright curve introduced by the projected laser light-sheet intersects with the specimen. The heading angles of the left- and right- cameras are rotated to be about ˙10.5ı with respect to the specimen. The baseline distance of the two cameras is set to be about 188.6 mm. A three-step aluminum block was used as the test specimen, the change of height indicates the geometrical change of the experimental setup which can be used to monitor the change of the geometrical setup. The sizes of the three-step specimen are 10 10 mm2, 30 30 mm2 and 60 mm 70 mm2 with respect to the front surface, the middle surface and the rear surface, and the offsets of front-to-middle surface and middle-to-rear surface are 10.18 mm and 20.25 mm respectively. For 3D DIC in-plan study, the three-step-height specimen was moved by a manual linear-stage along x-axis away 3, 6, 9, 12, 15, 18, 21 and 24 mm with respect to its origin. As shown in Fig. 4.2, the displacements were extracted from three Fig. 4.1 Experimental setup consists of the 3D DIC and the laser triangulation method Fig. 4.2 A three-step aluminum block is moved in plan along x-direction and the displacement is evaluated from remarked regions of the block by 3D DIC method
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