Abstract
In this paper, a time-lapse micro-tomography (micro-CT) analysis has been used for identifying of fatigue microcracks in human cortical bone. A custom designed table-top loading device was employed for in-situ fatigue loading in an X-ray scanner. The initial defects (thin microcracks) in the bone were induced by the first loading step with a peak force sufficient for crack initiation. Then, the in-situ fatigue loading was performed to induce propagation of the microcracks. Loading increments of several thousand load cycles, with period of approximately four seconds were used to investigate the crack propagation phenomena. The fatigue testing was finished after approximately 13,000 cycles. The micro-CT scans were performed using a modular X-ray imaging device. During the entire experimental procedure, the in-situ loading device was mounted on a rotary stage of the X-ray scanner. The tested specimen was scanned using the high-resolution micro-CT in the representative loading steps (before initiation of the microcracks, directly after the initiation and each time after a defined increment of fatigue cycles was reached). The individual micro-CT reconstructions of the specimen were processed using differential tomography for the identification of the individual microcracks in the microstructure and for the investigation of the crack propagation phenomena. The micro-tomography results were compared with the data recorded by the in-situ loading device during the fatigue testing and the damage development identified from the mechanical data was connected to the changes in the microstructure identified in the micro-tomography results.
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