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水牛角角鞘的各向异性研究
Study on the anisotropy of horn sheath of buffalo
投稿时间:2021-04-28  修订日期:2021-07-01
DOI:
中文关键词:  生物材料  力学性能  各向异性  变形损伤
英文关键词:natural materials  mechanical properties  anisotropy  deformation and damage.
基金项目:
作者单位邮编
赵锦红 西南交通大学 材料科学与工程学院 610031
徐明举 西南交通大学 材料科学与工程学院 610031
谢红兰 中国科学院上海应用物理研究所 201204
黄俊宇 西南交通大学 材料科学与工程学院 610031
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中文摘要:
      水牛角角鞘是一种具有优异力学性能的生物材料,本文主要研究其力学性能和变形损伤机理的各向异性。首先利用同步辐射断层成像技术和扫描电镜分别获取了牛角角鞘在初始状态下的三维结构和三个不同方向(纵向、横向和径向)的微观形貌,发现角鞘由波浪状片层沿径向堆叠而成,大量沿纵向生长的长条形孔隙随机镶嵌其中。随后利用自制的微型材料试验机开展了角鞘沿三个方向的准静态压缩实验,并通过准原位扫描电镜表征技术观测试样的变形损伤过程。宏观应力应变曲线表明,角鞘表现出明显的各向异性:纵向具有最高的屈服强度,而径向表现出最大的塑性硬化率。准原位扫描电镜图像揭示了不同方向的裂纹成核和扩展模式存在明显差异。纵向上,片层屈曲诱导初始孔隙沿横向扩张,并沿层间界面相互贯通形成宏观裂纹;横向上,波浪状片层在压缩载荷下会发生显著的弯曲变形,层间易发生滑移开裂;径向上,层间相互挤压将初始孔隙压实,此后试样内出现沿45°方向的“X”形剪切带。变形机制的差异本质上来源于角鞘特殊的微观结构—波浪状片层和单向排布的长条形孔隙,最终导致了宏观力学性能的各向异性。上述结果对澄清牛角优异力学性能的物理基础进而指导仿生材料设计具有较大意义。
英文摘要:
      The horn sheath of buffalo is a type of biomaterial with excellent mechanical properties. The anisotropy of its me-chanical properties and deformation/damage mechanisms is studied in this paper. First of all, the three-dimensional structures and the micro surface morphologies along three different directions (longitudinal, transverse and radial) of the horn sheath are obtained using synchrotron-based computed tomography and scanning electron microscopy, re-spectively. The horn sheath consists of wavy lamellae stacked along the radial direction, and a large number of long strip-shaped pores growing along the longitudinal direction are randomly distributed between them. Then, quasi-static compression experiments are carried out on the horn sheath along three directions by the self-made micro material testing system. The deformation and damage process of the samples are characterized via quasi-in-situ SEM. The macro stress-strain curves show that the horn sheath exhibits obvious anisotropy, i.e. the yield strength is the highest along the longitudinal direction while the maximum plastic hardening rate appears in the radial direction. The SEM images reveal obvious differences in the nucleation and growth of cracks in different directions. In the longitudinal direction, the initial pores are expanded transversely via the buckling of lamellae, and coalesced into macroscopic inter- lamellar cracks. In the transverse direction, the wavy lamellae are bent toward the radial direction under com-pression, which induces inter-lamellae slip and shear cracking. In the radial direction, the initial pores are compacted by mutual extrusion between layers, and X-shaped shear bands along the 45° direction appear in the compacted sam-ple. The difference in deformation mechanisms is essentially attributed to the unique microstructures of horn sheath, i.e., wavy lamellae and long strip-shaped pores arranged in single direction, which consequently leads to the anisot-ropy in macroscopic mechanical properties. The results are of great significance for clarifying the physical basis of excellent mechanical properties of horn sheath and guiding bionic materials design.
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