Microstructure-based characterization and modeling of trabecular bone deformation and failure

Abstract

In this research, a robust and reliable compression testing technique ("two-camera two-mirror" technique) for anisotropic, heterogeneous, and porous materials is developed for both nondestructive uniaxial loading in different orthogonal directions and destructive uniaxial loading over the yield point. The whole specimen strain can be measured using the video extensometer technique that provides a prompt evaluation method for strain measurement; and the full-field three-dimensional (3D) surface strain can be measured using the digital image correlation (DIC) technique that provides abundant information about the mechanical properties. In addition, the volumetric strain can be measured from micro-computed tomography (μCT) scans before and after the testing. Possible errors of this compression testing technique are calibrated. This technique was also validated using a variety of biological materials and biomaterials, such as birch wood blocks, solid rigid polyurethane (PU) foams, open-cell aluminum foams, and customized Ti-6Al-4V ELI lattice structures.

Several trabecular bone specimens from porcine cervical spines are tested nondestructively or destructively using the experimental technique. Elastic and post-yield behaviors of trabecular bone specimens are measured. Besides the nominal stress-strain curve, more mechanical properties of these specimens such as Poisson’s ratio and the local strain mapping are obtained. The 3D full-field measurements based on μCT data from one of the specimens are demonstrated as well.

A variety of micro-finite element (μFE) modeling meshes and tissue material models are investigated using ANSYS. An elasto-plastic μFE model of trabecular bone based on μCT reconstruction is validated and verified. The tissue material model of trabecular bone is predicted using the method of fitting the experimental nominal stress-strain curve. More measurements could be performed from μFE model, and a few examples are demonstrated.