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

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The effective TPMS lattice thickness was measured by cutting each specimen in two halves and extracting the lattice structure profile by using ImageJ software. The specimens were cut after being subjected to mechanical testing. As the plastic deformation occurs only in limited regions of the specimen, due to the complex shape of the gyroid, the measured post-testing average thickness is precise enough for the scope of this work. The static mechanical properties of the material were determined via tensile testing, employing three cylindrical tensile specimens having a diameter of 5 mm printed in the same job. The calculated properties are listed in Table 2. Hence, the results are in line with a material previously produced in the same conditions (Abruzzo et al., (2024); Macoretta et al., (2023)).

Figure 1: Specimen geometry and dimensions: a) specimen trimetric view, displaying the cutting plane used for lattice thickness estimation post manufacturing; b) specimen X view, c) specimen Y view, d) specimen Z view. All the data are referred to Table 1.

Table 1. Specimen dimensions. W [mm] L [mm] H [mm] D [mm] h [mm] l c [mm] ρ

θ [deg] x 0 [mm] z 0 [mm]

20

20

20

35

7

4

0.25 2

10

10.65

Table 2. Main tensile properties of the studied material, expressed in terms of average values. S y [MPa] S u [MPa] A% E [GPa] 490 915 42 146

2.2. Compression testing Compression testing was performed utilizing a standard servohydraulic testing machine fitted with a 250kN load cell and an external LVDT displacement sensor, as shown in Figure 2. The tests, consisting of 5 macrocycles (S1, S2, S3, S4, S5), were carried out under load control each macrocycle was structured as follows: an initial phase (phase 1) of monotonic compression until reaching progressively the maximum load values specified in the first row of Table 3, followed by a phase of structural relief, reaching the average load (phase 2) that will be used for the final phase, involving 10 cyclic elastic sinusoidal loadings ranging in 5kN of amplitude (phase 3). The relaxation phase was essential for maintaining the maximum force of the cyclical loading at the level attained during the first phase, as shown in Figure 2b. The load amplitude of 10kN peak-to-peak was determined to achieve a maximum strain level below the material's yield point, consistent with both homogenized FE models. The cyclic loading aimed to assess the accumulation of damage within the structure and observe the evolution of the plastic strain under repeated loading. The loading curve steps are outlined in Table 3.