Evaluation of mechanical properties of Ti-25Nb BCC porous cell structure and their association with structure porosity: A combined finite element analysis and analytical approach for orthopedic application

Ti-based alloys have been commonly employed in manufacturing implants for orthopedic applications. Binary Titanium-Niobium (Ti-25Nb) alloy is a promising material for potential applications in orthopedics because of their lower elastic moduli and superior biocompatibility than the conventional Ti-based alloys. Implants with porous structures encourage bone ingrowth and reduce the effect of stress-shielding further. This study is aimed at establishing the relationship between the mechanical performance and structural parameters of porous body-centered-cubic (BCC) structures made up of Ti-25Nb (25% by wt.). Solid models of BCC porous structures were constructed (unit cell size: 2 mm; overall size: 8 x 8 x 8 mm(3)). Finite element analysis (FEA) of the BCC structures with porosity ranging from 29% to 79% (seven porosities) was conducted under tension, bending, and torsional loads. The Gibson-Ashby model and Exponential regression model were also employed to determine the stiffness of the above porous structures. The functional relationships between effective Young's modulus, effective yield strength, and porosity generated from both the models were found to match the FEA results well. Results indicated that porosity in the range of 50%-70% can be used to design graded porous stems to mimic the mechanical properties of cortical bone.