PSI - Issue 41

Fabio Distefano et al. / Procedia Structural Integrity 41 (2022) 470–485 Author name / Structural Integrity Procedia 00 (2019) 000–000

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SEM observation was performed before carrying out the experimental tests, to evaluate the matching of the geometric parameters between designed and real structure. Visual testing and SEM observations were performed to analyse the failure modes induced by compression tests.

Table 2. Geometric properties of the specimens

G7 specimens

ρ c /ρ m

0.05

0.1

0.2

Mass [g]

7.40 3.68 1.65 19.43 14.41 10.42 17.59 12.42 8.41 17.57 12.40 8.41

Height [mm] Width [mm] Length [mm]

2.3. Finite element analysis FE models of the single unit cells were developed to evaluate via numerical solution the compressive behaviour and the failure modes of the structures and to determinate the influence of the cell shape and size on the mechanical properties. The FE analyses were conducted on both G7 and IWP unit cells. Thin-walled TPMS structures show higher fatigue strength and higher structural performance than lattice structures (Refai et al., 2020). Therefore, authors introduced IWP unit cell because is considered a reliable solution for possible application in the biomechanical field. Three different levels of relative density were investigated, and for each relative density two cell sizes were analysed. MATLAB R2021a (MathWorks, MA) MS Lattice toolbox was used to obtain IWP cell configurations. IWP cell diameters were imposed equal to the G7 ones, while cell thicknesses were changed to obtain the selected relative densities. The unit cells geometric parameters are summarised in Table 3 and Table 4.

Table 3. Geometric parameters of G7 unit cell for FE analysis

G7 unit cells

ρc/ρm

0.05

0.1 90 2.1 0.2

0.2 80 1.4 0.2

0.05

0.1 90

0.2 80 3.5 0.5

Porosity [%]

95 2.9 0.2

95 7.3 0.5

D [mm] t [mm] L [mm] A [mm]

5

0.5

2.28 1.70 0.07

1.59 0.98 5.75 3.76 2.46 1.14 0.65 4.29 2.68 1.63 0.10 0.14 0.07 0.10 0.14

t/D

Table 4. Geometric parameters of IWP unit cell for FE analysis

IWP unit cell

ρc/ρm

0.05

0.1 90 2.1

0.2 80 1.4

0.05

0.1 90

0.2 80 3.5

Porosity [%]

95 2.9

95 7.3

D [mm] t [mm] L [mm] A [mm]

5

0.04

0.06 0.08 0.11 0.15 0.21

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1.15 0.02

0.81 0.51 2.90 1.94 1.29

t/D 0.03 0.06 0.02 0.03 0.06 The FE model was developed by using Altair HyperWorks 14.0 (Altair Engineering, MI) software package and RADIOSS as explicit solver. The model was validated by taking in consideration the results of tensile tests carried out on Ti6Al4V ELI alloy specimens in a previous work (Epasto et al., 2019b). The Johnson-Cook material model