PSI - Issue 42

C. Boursier Niutta et al. / Procedia Structural Integrity 42 (2022) 1449–1457 Author name / Structural Integrity Procedia 00 (2019) 000 – 000

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4.1 FE model validation The validation of the numerical model has been carried out by comparing the two representative cases of collapse of the lattice structure in experimental tests. Indeed, according to the beam diameter and size of unit-cell, a progressive crushing failure and foam-like collapse have been observed in the experimental campaign [5]. The comparison of the experimental and numerical results for the progressive crushing collapse is shown in Fig. 5.

(a)

(b)

(c) Fig. 5. Comparison of the experimental and numerical results of the lattice structure with d =1.1mm, l =8.35 mm and n =3: a) force displacement curves; b) comparison for the intrusion of 8.5 mm; c) comparison for the intrusion of 15 mm [5]. In this configuration, the diameter of the cell was equal to 1.1 mm, the size of the cell was 8.35 mm and the number of cell replications was 3. As shown, the FE model is able to correctly predict the failure, where each layer of cells progressively collapses. This can be appreciated also through the plastic strain, which flows from one layer of cells to the other as the crushing process proceeds, as shown through the blue beams in Fig. 5. As a result of this, the force displacement curve is characterized by peaks and valleys. Also, the FE model well captures the maximum force, while the discrepancy between the length of the peaks and valleys can be attributed to the presence of defects within the specimen which facilitated the collapse. The foam-like collapse is instead characterized by the global failure of the specimen. Comparison of the experimental and numerical results are reported in Fig. 6, where the retained lattice structure has d =1.65 mm, l =6.38 mm and n =4.