PSI - Issue 41

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

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The main geometric parameters which characterize the unit cells are shown in Fig. 2

Fig. 2 Unit cell geometric parameters

The face size of the unit cell is defined as the minimum space to suit the morphological requirements for the promotion of the osteointegration process (Caliogna et al., 2020). An essential parameter to be determined in the morphological characterization of a lattice structure is its relative density, defined as the ratio between the volume occupied by the strut of the unit cell and the total volume of the geometry (Zadpoor and Hedayati, 2016): � � � � � � � � � (1) The porosity, calculated as percentage value, is defined as the inverse function of the relative density: �%� � �1 � � � � � � ∙ 100 (2) The mechanical characterization was performed by applying the Gibson-Ashby model (Ashby, 2006). In their study, Gibson-Ashby predicted the mechanical properties of a lattice structure based on its relative density. These properties are dependent on the type of response exhibited by the structure (bending or stretch-dominated) and have a positive power relationship with the structure’s relative density (Maconachie et al., 2019): � � � � � � � � � � � � � � � (3) � � � � � � � � � � � � � � � (4) C 1 , n 1 , C 2 , n 2 are constant values, depending on the geometrical features of the lattice structure, that can be calculated by means of experimental tests. The results of the experimental tests can be plotted in the Gibson-Ashby diagrams (Ashby, 2006). In these graphs, relative modulus and relative strength are plotted against relative density on logarithmic scales, and from the data interpolation the constant values con be calculated for a given microlattice structure.