Advisor: Chancellor Henry Yang Title: "Response of Cortical Bone under Cone and Wedge Indentation" Abstract: Cortical bone provides unique challenges as a material for indentation testing – especially in live patients. It has a hierarchical composite structure, a dependence on hydration, and it is situated underneath layers of soft tissue in-vivo. The ability to determine its properties or quality in-vivo, with minimal damage to the overall, living patient, holds large value in biomechanics and medicine, including assessment treatment of osteoporosis, diagnosing human and equine fracture risk, and development of orthopaedic instruments. This talk will examine deformation and fracture in cortical bone underneath axisymmetric cone indentation and plane strain prismatic wedge indentation, using finite element modeling, pre-and-post mortem cortical bone experiments in human, bovine, and equine bone, and high-speed microscopy. Initial work to clarify mechanical links to indentation data will be discussed, followed by current efforts and challenges in modeling indentation fracture behavior under the effects of wedge apical angle and osteonal microstructure orientation. Computational and experimental results show indentation response, including penetration depth, fracture initiation, and crack propagation behavior; may be modeled and predicted within an elastic-plastic based brittle indentation framework, where both prismatic wedge angle and bone microstructural orientation relative to load direction play large roles in the ability of cortical bone to resist deformation and fracture. Complimentary work on finite element modeling of machining is discussed as well, informing future research.