PSI - Issue 83

222 Kemal Arslan et al. / Procedia Structural Integrity 83 (2026) 218–228 coefficient, and ௣ , ሶ , ሶ ଴ represent the plastic strain, strain-rate, and reference strain-rate, respectively. Therefore, the MAT_SIMPLIFIED_JOHNSON_COOK (MAT_098) material model was implemented in the numerical model to define the plasticity behavior of the AlSi7Mg alloy Menger fractal structures and the HSLA-350 steel tube. The JC model parameters for the materials are given in Table 1. The striker was modeled by the MAT_RIGID (MAT_020) material model with a mass of 100 kg. For the deformable parts, the Belytschko–Bindeman stiffness-based hourglass formulation [Belytschko and Bindeman (1993)] with a coefficient of 0.03 was defined in the FE model to avoid nonphysical deformation modes since reduced integration was used in the solid element formulation. Table 1. The JC model parameters for the steel tube and the MF structures. Material A (MPa) B (MPa) n C Reference HSLA-350 453 618 0.615 0.0255 Abedrabbo et al. (2009) AlSi7Mg 174 304 0.608 0.0069 Bogahawaththa et al. (2024) Interactions between the FE parts were taken into account by implementing two contact algorithms. The CONTACT_AUTOMATIC_SURFACE_TO_SURFACE algorithm was defined between the striker and the MF structures, and the CONTACT_AUTOMATIC_SINGLE_SURFACE algorithm was described for possible self contacting surfaces, e.g., interaction between folding parts of the structures. The static and dynamic friction coefficients were considered to be 0.3 and 0.2, respectively, in the contact definitions. The striker was allowed to translate only in the vertical direction, and all other translations and rotations were constrained. The MF structures were fixed at their bottom surfaces and subjected to impact velocities of 12 m/s and 18 m/s, corresponding to impact energies of 7.2 kJ and 16.2 kJ, respectively. 4. Validation The FE model was validated by comparing with experimental results reported in the literature [Bogahawaththa et al. (2024)]. The first-order MF cube, having dimensions of 20 mm × 20 mm × 20 mm, was considered for the low velocity crushing analysis. The FE model used for the validation is shown in Fig. 5.

Fig. 5. The FE model of the first-order MF cube for the validation.

The MF cube was made of AlSi7Mg alloy by selective laser melting. The impact velocity is 8 m/s, corresponding to 200 J of impact energy. The force-displacement data for this experiment were extracted from the literature and compared with the present numerical simulation results (Fig. 6). As seen in Fig. 6, the numerical results show reasonable agreement with the experimental results. The peak force and the crushing displacement of the