Effect of the geometrical defectiveness on the mechanical properties of SLM biomedical Ti6Al4V lattices

Metallic lattice biomaterials can be very complex structures that are often impossible to be fabricated with other manufacturing technologies than additive manufacturing (AM). Residual stresses and geometric defects such as severe notches and distorted struts are inevitably introduced into the printed structures and these can affect the mechanical and biological properties. Micro X-ray Computed Tomography (µCT) has been proven to be a very powerful tool for accurately measuring the mismatch between the as-designed CAD model and the SLM structure. In this work, selective laser melting (SLM) Ti6Al4V lattices were measured using a metrological µCT system to identify and classify the geometrical distortions introduced by the printing process. The µCT measurements have also been used to build Finite Element (FE) models based on beam elements that make possible a quantification of the effect of these defects on the elastic modulus of the lattice by comparison with FE models based on the ideal geometry. Moreover, solid FE models of the junctions between the struts have been built by importing the CT data in Ansys® to calculate the stress concentrations caused by the severe notches.