Tai Kuangshin, Qi Hang J, Ortiz Christine
Department of Materials Science and Engineering, Massachusetts Institute of Technology, Cambridge, MA 02139, USA.
J Mater Sci Mater Med. 2005 Oct;16(10):947-59. doi: 10.1007/s10856-005-4429-9.
In this paper, a multitechnique experimental and numerical modeling methodology was used to show that mineral content had a significant effect on both nanomechanical properties and ultrastructural deformation mechanisms of samples derived from adult bovine tibial bone. Partial and complete demineralization was carried out using phosphoric and ethylenediamine tetraacetic acid treatments to produce samples with mineral contents that varied between 37 and 0 weight percent (wt%). The undemineralized samples were found to have a mineral content of approximately 58 wt%. Nanoindentation experiments (maximum loads approximately 1000 microN and indentation depths approximately 500 nm) perpendicular to the osteonal axis for the approximately 58 wt% samples were found to have an estimated elastic modulus of approximately 7-12 GPa, which was 4-6x greater than that obtained for the approximately 0 wt% samples. The yield strength of the approximately 58 wt% samples was found to be approximately 0.24 GPa; 3.4x greater than that of the approximately 0 wt% sample. These results are discussed in the context of in situ and post-mortem atomic force microscopy imaging studies which show clear residual deformation after indentation for all samples studied. The partially demineralized samples underwent collagen fibril deformation and kinking without loss of the characteristic banding structure at low maximum loads (approximately 300 microN). At higher maximum loads (approximately 700 microN) mechanical denaturation of collagen fibrils was observed within the indent region, as well as disruption of interfibril interfaces and slicing through the thickness of individual fibrils leading to microcracks along the tip apex lines and outside the indent regions. A finite element elastic-plastic continuum mechanical model was able to predict the nanomechanical behavior of all samples on loading and unloading.
在本文中，采用了一种多技术实验与数值建模方法来表明矿物质含量对成年牛胫骨衍生样本的纳米力学性能和超微结构变形机制均有显著影响。使用磷酸和乙二胺四乙酸处理进行部分和完全脱矿质处理，以制备矿物质含量在37重量百分比（wt%）至0重量百分比之间变化的样本。发现未脱矿质的样本矿物质含量约为58 wt%。对于约58 wt%的样本，垂直于骨单位轴进行纳米压痕实验（最大载荷约1000微牛，压痕深度约500纳米），发现其估计弹性模量约为7 - 12吉帕，这比约0 wt%的样本所获得的弹性模量大4 - 6倍。约58 wt%的样本的屈服强度约为0.24吉帕；比约0 wt%的样本大3.4倍。这些结果在原位和死后原子力显微镜成像研究的背景下进行了讨论，这些研究表明，在所研究的所有样本中，压痕后均出现明显的残余变形。部分脱矿质的样本在低最大载荷（约300微牛）下经历了胶原纤维变形和扭结，而特征条纹结构未丧失。在较高的最大载荷（约700微牛）下，在压痕区域内观察到胶原纤维的机械变性，以及纤维间界面的破坏和单个纤维厚度方向的切割，导致沿尖端顶点线和压痕区域外出现微裂纹。一个有限元弹塑性连续介质力学模型能够预测所有样本加载和卸载时的纳米力学行为。
