Mustansar Zartasha, McDonald Samuel A, Sellers William Irvin, Manning Phillip Lars, Lowe Tristan, Withers Philip J, Margetts Lee
Research Centre for Modelling and Simulation, National University of Science and Technology, Islamabad, Pakistan.
School of Earth and Environmental Science, University of Manchester, Manchester, UK.
PeerJ. 2017 Jun 23;5:e3416. doi: 10.7717/peerj.3416. eCollection 2017.
This paper uses X-ray computed tomography to track the mechanical response of a vertebrate (Barnacle goose) long bone subjected to an axial compressive load, which is increased gradually until failure. A loading rig was mounted in an X-ray computed tomography system so that a time-lapse sequence of three-dimensional (3D) images of the bone's internal (cancellous or trabecular) structure could be recorded during loading. Five distinct types of deformation mechanism were observed in the cancellous part of the bone. These were (i) cracking, (ii) thinning (iii) tearing of cell walls and struts, (iv) notch formation, (v) necking and (vi) buckling. The results highlight that bone experiences brittle (notch formation and cracking), ductile (thinning, tearing and necking) and elastic (buckling) modes of deformation. Progressive deformation, leading to cracking was studied in detail using digital image correlation. The resulting strain maps were consistent with mechanisms occurring at a finer-length scale. This paper is the first to capture time-lapse 3D images of a whole long bone subject to loading until failure. The results serve as a unique reference for researchers interested in how bone responds to loading. For those using computer modelling, the study not only provides qualitative information for verification and validation of their simulations but also highlights that constitutive models for bone need to take into account a number of different deformation mechanisms.
本文利用X射线计算机断层扫描技术追踪脊椎动物（黑雁）长骨在轴向压缩载荷作用下的力学响应，该载荷逐渐增加直至骨失效。将加载装置安装在X射线计算机断层扫描系统中，以便在加载过程中记录骨内部（松质骨或小梁骨）结构的三维（3D）图像的时间序列。在骨的松质部分观察到五种不同类型的变形机制。这些机制分别是：（i）开裂，（ii）变薄，（iii）细胞壁和支柱撕裂，（iv）缺口形成，（v）颈缩，以及（vi）屈曲。结果表明，骨经历了脆性（缺口形成和开裂）、延性（变薄、撕裂和颈缩）和弹性（屈曲）变形模式。利用数字图像相关技术详细研究了导致开裂的渐进变形。所得应变图与在更精细长度尺度上发生的机制一致。本文首次捕捉了整个长骨在加载直至失效过程中的时间序列3D图像。研究结果为对骨如何响应载荷感兴趣的研究人员提供了独特的参考。对于使用计算机建模的人员来说，该研究不仅为其模拟的验证和确认提供了定性信息，还强调了骨的本构模型需要考虑多种不同的变形机制。
