Investigation of effects of design variables on physical and mechanical properties in graded porous structures produced by selective laser melting

With additive manufacturing, the production of bone-like functionally graded porous structures that can be used in implants has become much easier and research in this area has gained momentum. In this study, a total of nine functional graded porous structures with three different unit cell structures and three different column thicknesses were produced using a selective laser melting (SLM) machine and Ti6Al4V powder. The porosity of the specimens was measured by Archimedes and dry weighing methods. Deviations up to 20% occurred between design and production porosities (dry weighing) due to thickening and sagging in the columns. As a result of the compression tests, it was observed that the fracture behavior of the structures was affected by the angles of the columns with the direction of the force. The modulus of elasticity of unit cell structures with the same porosity was found as cubic, octahedroid, and diamond in descending order, respectively. In the three-point bending test, this order was found as diamond, octahedroid, and cubic. Manufacturing errors, deviations in measurements and analysis, and fracture behavior in experiments were interpreted with micro-CT, optical microscope, and SEM images. With the mathematical models created from the unit cell structure, generalized mathematical models that give the porosity and modulus of elasticity depending on the unit cell size and column thickness, which are the design variables, are derived. It is aimed to increase compatibility in personalized implant design with mathematical models.