Koudelka Petr, Kytyr Daniel, Fila Tomas, Sleichrt Jan, Rada Vaclav, Zlamal Petr, Benes Pavel, Bendova Vendula, Kumpova Ivana, Vopalensky Michal
Institute of Theoretical and Applied Mechanics, Czech Academy of Sciences, Prosecka 809/76, 19000 Praha 9, Czech Republic.
Materials (Basel). 2021 Mar 11;14(6):1370. doi: 10.3390/ma14061370.
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 μ2μm 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.
皮质骨中微裂纹的萌生和扩展是损伤发展的初始阶段，最终可能导致宏观骨折的形成和骨的失效。在这项工作中，进行了时间分辨高分辨率X射线微计算机断层扫描（CT），以研究在模拟步态周期加载下骨样本中的微裂纹系统。使用了低周（1000次循环）压缩疲劳加载，峰值幅度为900 N，频率为0.4 Hz，模拟慢走以引发骨的内部损伤。一个内部开发的实验室X射线微CT成像系统与一个紧凑的加载装置相结合，用于原位单轴疲劳实验，有效体素尺寸达到2μm。为了获得与扫描电子显微镜相当质量的重建3D图像，在进行数字体积相关和使用差分断层扫描评估以识别微观结构中的单个微裂纹之前，进行了投影级校正和焦点漂移校正。在骨的微观结构中，基于体积识别了完整骨中的微裂纹、加载后的裂纹形成以及微裂纹拓扑结构的变化。
