A Method for Evaluation the Fatigue Microcrack Propagation in Human Cortical Bone Using Differential X-ray Computed Tomography

Abstract

Fatigue initiation and the propagation of microcracks in a cortical bone is an initial phase of damage development that may ultimately lead to the formation of macroscopic fractures and failure of the bone. In this work, a time-resolved high-resolution X-ray micro-computed tomography (CT) was performed to investigate the system of microcracks in a bone sample loaded by a simulated gait cycle. A low-cycle (1000 cycles) fatigue loading in compression with a 900 N peak amplitude and a 0.4 Hz frequency simulating the slow walk for the initialization of the internal damage of the bone was used. An in-house developed laboratory X-ray micro-CT imaging system coupled with a compact loading device were employed for the in situ uni-axial fatigue experiments reaching a 2m effective voxel size. To reach a comparable quality of the reconstructed 3D images with the SEM microscopy, projection-level corrections and focal spot drift correction were performed prior to the digital volume correlation and evaluation using differential tomography for the identification of the individual microcracks in the microstructure. The microcracks in the intact bone, the crack formation after loading, and the changes in the topology of the microcracks were identified on a volumetric basis in the microstructure of the bone.

Computed tomography system with strict real-time synchronization for in-situ 3D analysis of periodically vibrating objects

“…subjected to quasi-static mechanical loading and recently, in-situ computed tomography has been the topic of intensive scientific interest. Using the XCT technique, volumetric investigation of complex phenomena such as crack propagation [1,2], damage development or failure mechanism identification [3][4][5][6] has become possible. Furthermore, X-ray imaging techniques have been adopted for state-of-the-art inspection of nonstationary objects and material samples subjected to dynamic loading [7].…”

VERTEX – versatile in-situ testing rig for X-ray scanners

“…Material characterization based on in-situ X-ray computed tomography (XCT) is becoming very popular experimental technique allowing for an advanced analysis of the internal deformation processes in materials [1,2]. Using this technique, volumetric analysis of strains and investigation of more complex phenomena such as crack propagation [3,4], damage development or failure mechanism identification [5][6][7] are becoming possible. Currently, a number of devices for in-situ mechanical testing in X-ray scanners is available and is developed at both commercial [8,9] and research basis [4,10].…”