Development of multi-layered 316l material by additive manufacturing method for orthopedic implants: Experimental/numerical analysis and characterization in terms of mechanical properties

In this thesis, numerical analyzes and experimental studies were carried out on the mechanical properties of porous structures that can represent bone tissue developed in order to improve the mechanical properties of currently used orthopedic implant components. As a result of the studies, porous structures that can represent bone tissue were determined. In addition to mechanical tests, different types of coatings were made in order to reveal the coatability of the structures to be used as implant materials and to test their corrosion resistance. In order to understand the mechanical properties of porous structures, compression, shear and torsion tests of different porous polymer structures were carried out. As a result of the tests, it was seen that the octahedron structure was more flexible than the pillar octahedron structure but its strength was lower. In order to test the effectiveness of the ANSYS 2018 package program to be used for analyzing bone tissue models, the tests of porous polymer materials, whose mechanical tests were carried out, were simulated. A difference of 16% was observed between the elasticity modules obtained with mechanical tests and simulations, 14% between the yield strengths in compression, 3% between the shear modules and 11% between the torsional rigidities. As a result of the tests and analyzes, it was seen that the "Static Structural" module of the ANSYS 2018 package program used can be used in numerical analyzes to obtain the elasticity modulus, shear modulus, yield strength and torsional rigidity. The package program, which was seen to be effective in porous polymer material analyzes, was used in the numerical analysis of porous structures to be determined for the cortical (tight) and trabecular (spongy) parts of the bone tissue. As a result of the analyzes, different structures were produced using the Selective Laser Melting method using 316L steel and subjected to compression tests. As a result of the tests, it was seen that the unit cell of the octahedron structure with a support thickness of 275 µm could represent spongy, and the unit cell of the pillar octahedron structure with a support thickness of 475 µm could represent tight bone tissue. Tensile analyzes of structures with one, two and four intermediate elements were performed for the unit cell that would provide load transfer between the determined tight and spongy bone tissue. As a result of the analysis, it was seen that the pillar octahedron structure with a single intermediate element provided better stress distribution compared to other structures. For this reason, the single pillar octahedron structure was used as the intermediate element. Although it is as biocompatible as 316L steel, various coatings were applied in order to promote bone formation, increase biocompatibility, wear and corrosion resistance. Pure polypyrrole (PPY), pure Hydroxyapatite (HAp), double and quadruple coatings were applied to the samples produced with the Selective Laser Melting method. With XRD analysis, it was seen that the PPY coating formed an amorphous structure on 316L, while the HAp coating was a stable crystal structure. With the EDS analysis performed for pure HAp, PPY+Hap and PPY+HAp+ PPY+HAp coating, it was concluded that the Ca/P ratio on each coating surface was stable and the coatings were distributed homogeneously. In the abrasion tests performed with Ringer solution, it was determined that the corrosion resistance of PPY, HAp and dual coating was higher than that of pure 316L, but the quaternary coating was lower.