Department of Health and Kinesiology, The University of Texas at Tyler, Tyler, TX, USA.
Bone. 2013 Mar;53(1):1-5. doi: 10.1016/j.bone.2012.11.029. Epub 2012 Dec 4.
Bone fragility depends on its post-yield behavior since most energy dissipation in bone occurs during the post-yield deformation. Previous studies have investigated the progressive changes in the post-yield behavior of human cortical bone in tension and compression using a novel progressive loading scheme. However, little is known regarding the progressive changes in the post-yield behavior of bone in shear. The objective of this short study was to address this issue by testing bone specimens in an inclined double notch shear configuration using the progressive loading protocol. The results of this study indicated that the shear modulus of bone decreased with respect to the applied strain, but the rate of degradation was about 50% less than those previously observed in compression and tension tests. In addition, a quasi-linear relationship between the plastic and applied strains was observed in shear mode, which is similar to those previously reported in tension and compression tests. However, the viscous responses of bone (i.e. relaxation time constants and stress magnitude) demonstrated slight differences in shear compared with those observed in tension and compression tests. Nonetheless, the results of this study suggest that the intrinsic mechanism of plastic deformation of human cortical bone may be independent of loading modes.
骨脆性取决于其屈服后的行为，因为大多数能量耗散发生在屈服后变形过程中。先前的研究已经使用一种新的渐进加载方案，研究了人皮质骨在拉伸和压缩中屈服后行为的渐进变化。然而，关于剪切中骨屈服后行为的渐进变化，人们知之甚少。本短研究的目的是通过在倾斜双切口剪切配置下使用渐进加载方案来测试骨标本，以解决这个问题。研究结果表明，随着施加应变的增加，骨的剪切模量降低，但降解率比以前在压缩和拉伸试验中观察到的要低约 50%。此外，在剪切模式下观察到塑性应变和施加应变之间的准线性关系，与在拉伸和压缩试验中报告的关系相似。然而，与拉伸和压缩试验相比，剪切时骨的粘性响应（即弛豫时间常数和应力大小）表现出细微差异。尽管如此，本研究的结果表明，人皮质骨塑性变形的内在机制可能与加载模式无关。
