PSI - Issue 28

3

S. Raghavendra et al. / Procedia Structural Integrity 28 (2020) 517–524 Author name / Structural Integrity Procedia 00 (2019) 000–000

519

Cell topology Structure No. of struts per node Orientation of struts

Cubic Regular

Star-shaped

X-shaped Regular

Trabecular Random

Regular 8 or 10

6

8

4 to 6

Along z-axis Oblique

Along x-, y-, z-axis

Oblique

All directions

Figure 1 Unit cell: (a) Cubic (b) Star-shaped (c) X-shaped (d) Trabecular

Four different unit cells were manufactured with a designed strut thickness value of 200 µm and a pore size of 1500 µm. Pore size was defined as the diameter of the sphere that can be incorporated between the unit cells/struts. The types of unit cell are shown in Figure 1 and named as: Cubic, Star-shaped, X-shaped and Trabecular. Trabecular struts were obtained by joining 4 to 6 struts with random direction and length at each node in order to resemble human trabecular bone.

Figure 2 (a) Cylindrical compression and fatigue test specimen (b) Tensile test specimen with grips

Two types of samples were manufactured as shown in Figure 2. Full-porous cylindrical samples with an L/D ratio >1 used for compression and fatigue test as shown in Figure 2a, and half-porous cylindrical specimens with solid grips and transition zones for avoiding stress concentrations as shown in Figure 2b used for tensile testing.

2.2. Experimental

2.2.1. Porosity analysis Density of the cellular structures ρ c was computed from the ratio between the dry weight of the full-porous cylindrical samples, obtained with an analytical precision balance (Ohaus, adventurer) with an accuracy of 4 decimal digits, and the nominal volume, calculated from the external, nominal values of lengths and diameter measured by means of manual caliper. Density of the cellular structures ρ c and density of bulk Ti6Al4V ρ o (4.42 g/cc) were used to calculate the porosity using equation 1. A total of 10 samples in each batch were used for the porosity measurement. �������� � � ��� � �� � ��� ⁄ ∗ 100% (1)