PSI - Issue 33

Panagiotis N. Lymperopoulos et al. / Procedia Structural Integrity 33 (2021) 818–823 Panagiotis Lymperopoulos, Efstathios Theotokoglou / Structural Integrity Procedia 00 (2021) 000–000

820

3

Table 1. Pentamodes Properties (Hedayati et al. (2017)) Ti 170-500

Ti 170-450

Ti 230-500

Porosity, dry weighing (%) Porosity, Archimides (%) Pososity, micro-CT (%) Pore size, nominal (μm) Pore size-micro-CT (μm) Strut size, nominal (μm) Strut size, micro-CT (μm)

77.1±0.5 76.8±0.5

70.1±0.3 69.7±0.3

66.4±0.3 65.8±0.3

77.68

71.20

68.45

500

450

500

608±182

486±162

560±186

170

170

230

218±62

216±64

251±76

In the sequel, the material that was used is Titanium for bioengineering purposes (Table 2).

Table 2. Material Properties (Hedayati et al. (2017))

Elastic modulus, GPa Tangent modulus, GPa

113.8 1.25 1000

Yield Stress, MPa

3. Computational Analysis In order to computationally analyze the specimen, an axisymmetric analysis was performed. Thus, the half of the specimen was implemented. Then, the volume was filled with pentamodes, in compliance with the properties in the Table 1.After, each rod was meshed, and finally the boundary conditions were applied. Concerning the meshing, 4 cases were tested, using the BEAM189 with 3 nodes per element in ANSYS (ANSYS (2019)).

Table 3. Meshing cases Case

Elements at each rod

Total Elements

1 2 3 4

1 2 3 4

14496 28992 43488 57984

The boundary conditions were, 

Fully constrain the nodes in the left side

 Apply symmetric conditions in the nodes at the upper nodes  Displacement at the centre of the circle The applied displacements were chosen to be 0.1, 0.2, 0.3, 0.4, 0.5, 1.0, 1.5, 2.0 mm. In addition, small and large displacement analyses were performed. Choosing the case of Ti 170-500, and applying a displacement of 0.2mm, the convergence of the algorithm has taken into account, and the results are presented in the following Fig. 3.