PSI - Issue 68

Ivan Senegaglia et al. / Procedia Structural Integrity 68 (2025) 610–618 Ivan Senegaglia at al. / Structural Integrity Procedia 00 (2025) 000–000

614

5

Figure 3: Gyroid unit cell PBCs: a) cells lying in the central region of the specimen; b) cells closer to the specimen base and machine interface (all DOFs) .

3. Results and discussion 3.1. Post-testing specimen analysis

The initial analysis focused on the specimen's macroscopic permanent deformation. Initially, the cutting plane in the specimen was estimated at a 2° inclination to the x-z plane and passing through (10 mm, 10.65 mm) in the x-z plane, as shown in Figure 1c. After preprocessing the image to eliminate the background, the identification of border pixels was carried out, highlighted in blue in Figure 4a. Subsequently, polynomial interpolation was performed to assess the variations in the specimen width along the loading direction (with the same notation used in Figure 1d). According to Figure 4b, even a 7-degree polynomial was inadequate to model the boundary region deformation in a millimeter radius from the bottom interface, due to its high curvature. This outcome can be attributed to the constraint imposed by the base, which restricts both linear and rotational degrees of freedom (DOFs). In the upper part of the specimen, where the contact constraint is unilateral, the curvature is milder, allowing a good representation in a polynomial interpolation. It is worth noting that the initial angle is close to 0 degrees, which can be explained by local rotational constraints due to unilateral contact. The maximum width variation is in the center of the specimen, which was estimated as 107.40% of the initial width.

y

Figure 4: Stereo image of the sliced specimen. a) Reconstructed boundaries of the compressed lattice; b) Specimen width interpolation in percentage from rigid bottom section; c) extracted angle of the boundaries calculated from vertical direction.