Empirical rule for predicting mechanical properties of Ti-6Al-4V bone implants with radial-gradient porosity bionic structures

The focus of this study was the design of implants related to the tibia bone. Most of the pressure loads applied on the tibia bone by the human body are normal forces. An orthogonal structure has been introduced in porous implants because it can support higher normal stress than other porous structures. Human bone is composed of an outer cortical bone and an inner cancellous bone, varying in gradient. Based on the characteristics of human bone, the design in this study applied a radial-gradient structure. Samples were fabricated using additive manufacturing (3D printing) via selective laser melting. Two different structural design methods were proposed for the radial-gradient structure, namely same region thickness and same region volume. The relationship between the porosity-gradient structure designs and mechanical properties was systematically examined and analyzed in detail. The resulting porosity-gradient materials were demonstrated to exhibit similar Young's moduli but higher strength in comparison with those of the human bone structure.