Effect of microstructural configurations on the mechanical responses of porous titanium: A numerical design of experiment analysis for orthopedic applications

The reduced stiffness, weight and open porosity of microporous titanium makes it an attractive material possibility for engineering applications ranging from medical implants to impact tolerant structures. To facilitate the design and application of this material, it is necessary to develop an understanding of the relationship between the porous microstructure and mechanical responses of the material. A factorial design of experiment methodology (DOE) is therefore used to systematically compare the effects that several microstructural features have on the mechanical responses via 2D and 3D finite element (FE) simulations. The FE models for the DOE study are all based on a titanium matrix of 12% porosity and the application to orthopedic implants. Five microstructural features are varied to create 32 test cases to study the effects of pore shape, size, orientation, and arrangement, and bone infiltration. The quantitative effects of the features are used to screen their relative importance for elastic modulus, yield stress, and stress concentration factor. The results of the DOE studies of both 2D and 3D numerical simulations demonstrate that bone infiltration into the pores is the most dominant factor for elastic modulus and yield stress. A random arrangement of pores has great effect on local stress concentrations where the local stress fields are primarily concentrated in the regions around closely spaced pores. Bone infiltration greatly reduces the stress concentration in such regions indicating an advantage of bone ingrowth beyond improved interface and attachment. Compared to bone infiltration and pore arrangement and orientation, relative pore size and shape have relatively small effect on the mechanical responses.