PSI - Issue 56

Vasilica Ioana Cimpoies et al. / Procedia Structural Integrity 56 (2024) 49–57 Author name / Structural Integrity Procedia 00 (2019) 000–000

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The structures have shown that by increasing the number of cells the structure gains significant elasticity. In the graph below (Fig. 6) are presented the compressive load vs compressive extension curves generated by the progressive load for all three models. The extension was captured on the graph up to plastic deformation. Until that point, the structures have an instant recovery behaviour. 2.6. Numerical Analysis After conducting the physical experiments, the same samples in virtual manner have been tested using the finite element method (as captured in Fig. 7) in Ansys Workbench 2022 (Ansys Inc., USA).

Fig. 7. Samples subjected to compressive tests with FEM (right - M1X1, center - M3X1, left - M3X3)

First the samples have been subjected to the maximum loads resulting from physical experiments by recreating the conditions of the compressive tests. When creating the finite element (FE) models, the material constants were incorporated, including a Young's modulus of 1703 MPa, a Poisson's ratio of 0.3, and a tensile strength derived from experimental testing, amounting to 28.75 MPa. Only geometrical nonlinearities have been considered in the simulation. Subsequently, all FE models were subjected to a uniform load of 150 N, a choice made to ensure elastic behavior and avoidance of the contact interactions between the spiral arms. The focus of the finite element analysis (FEM) was restricted to computing initial stiffness of the metamaterial, including only a liner elastic material model. The results deviation between the experimental test and FEM was around 3%. Considering that the observed deviation falls within the margin of 5%, signifying a close alignment in results, it can be inferred that the two methods mutually validate each other.

Fig. 8. Directional displacement on Y-axis inside M3X3 model.

Fig. 9. Graph of the directional displacement on Y-axis