Peña Fernández Marta, Kao Alexander P, Witte Frank, Arora Hari, Tozzi Gianluca
Department of Engineering Mechanics, School of Engineering Sciences, KTH Royal Institute of Technology, Stockholm, Sweden; Zeiss Global Centre, School of Mechanical and Design Engineering, University of Portsmouth, Portsmouth, UK.
Zeiss Global Centre, School of Mechanical and Design Engineering, University of Portsmouth, Portsmouth, UK.
J Biomech. 2020 Dec 2;113:110105. doi: 10.1016/j.jbiomech.2020.110105. Epub 2020 Oct 28.
As a composite material, the mechanical properties of bone are highly dependent on its hierarchical organisation, thus, macroscopic mechanical properties are dictated by local phenomena, such as microdamage resulting from repetitive cyclic loading of daily activities. Such microdamage is associated with plastic deformation and appears as a gradual accumulation of residual strains. The aim of this study is to investigate local residual strains in cortical bone tissue following compressive cyclic loading, using in situ X-ray computed tomography (XCT) and digital volume correlation (DVC) to provide a deeper insight on the three-dimensional (3D) relationship between residual strain accumulation, cortical bone microstructure and failure patterns. Through a progressive in situ XCT loading-unloading scheme, localisation of local residual strains was observed in highly compressed regions. In addition, a multi-scale in situ XCT cyclic test highlighted the differences on residual strain distribution at the microscale and tissue level, where high strains were observed in regions with the thinnest vascular canals and predicted the failure location following overloading. Finally, through a continuous in situ XCT compression test of cycled specimens, the full-field strain evolution and failure pattern indicated the reduced ability of bone to plastically deform after damage accumulation due to high number of cyclic loads. Altogether, the novel experimental methods employed in this study, combining high-resolution in situ XCT mechanics and DVC, showed a great potential to investigate 3D full-field residual strain development under repetitive loading and its complex interaction with bone microstructure, microdamage and fracture.
作为一种复合材料，骨的力学性能高度依赖于其层次结构，因此，宏观力学性能由局部现象决定，例如日常活动中反复循环加载导致的微损伤。这种微损伤与塑性变形相关，并表现为残余应变的逐渐积累。本研究的目的是通过使用原位X射线计算机断层扫描（XCT）和数字体积相关技术（DVC），研究皮质骨组织在压缩循环加载后的局部残余应变，以更深入地了解残余应变积累、皮质骨微观结构和破坏模式之间的三维（3D）关系。通过渐进式原位XCT加载-卸载方案，在高度压缩区域观察到了局部残余应变的定位。此外，多尺度原位XCT循环试验突出了微观尺度和组织水平上残余应变分布的差异，在血管通道最细的区域观察到了高应变，并预测了过载后的破坏位置。最后，通过对循环加载后的试件进行连续原位XCT压缩试验，全场应变演化和破坏模式表明，由于大量循环加载导致损伤积累后，骨的塑性变形能力降低。总之，本研究采用的结合高分辨率原位XCT力学和DVC的新颖实验方法，在研究反复加载下的3D全场残余应变发展及其与骨微观结构、微损伤和骨折的复杂相互作用方面显示出巨大潜力。
