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基于同步辐射原位CT的水牛角结构性能关系研究
Investigations on the structure-property relationship of buffalo horn based on in situ synchrotron CT
投稿时间:2020-02-25  修订日期:2020-04-09
DOI:
中文关键词:  水牛角  同步辐射原位CT  力学性能  微观结构  变形损伤
英文关键词:buffalo horn  in situ synchrotron CT  mechanical properties  microstructure  deformation and damage
基金项目:国家自然科学基金(No.11802252)
作者单位E-mail
徐明举 西南交通大学 材料先进技术教育部重点实验室 xmj18380202683@163.com 
柴海伟 顶峰多尺度科学研究所  
谢红兰 中国科学院上海应用物理研究所  
黄俊宇 西南交通大学 材料先进技术教育部重点实验室 jyhuang@pims.ac.cn 
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中文摘要:
      为探究水牛角的结构性能关系,基于上海同步辐射光源搭建了高分辨原位CT系统,对牛角角鞘进行初始表征和准静态压缩下的三维实时表征。三维表征结果显示,牛角孔隙率在1%左右,椭圆柱状孔洞沿牛角生长(纵向)方向排列成线,在纵向上首尾相连却并未完全连通;孔洞特征椭球的轴长分布满足对数正态分布,长轴和短轴的长度均值分别约为7 ?m和3 ?m。原位CT结果表明,牛角在发生屈服之后,初始孔洞首先开始扩张并逐渐发展成微裂纹。随后同一片层内的微裂纹由外向内发生桥接,片层发生局部屈曲和层间开裂,牛角内部出现尺寸较大的宏观裂纹,导致牛角内裂纹密度急剧上升。但片层之间存在大量纤维粘接(提高了层间拉伸/剪切强度),而且管状孔洞互不连通,这些抑制了层间裂纹在横、纵向上的快速传播,使得各处裂纹只能独立缓慢发展而无法贯通样品;同时波浪状片层使裂纹传播路径更加曲折,层间屈曲增加了片层摩擦耗能。这些使得牛角表现出加工硬化,也是牛角在纵向方向呈现优良韧性的主要原因。
英文摘要:
      In order to explore the structure-property relationship of buffalo horn, a high-resolution in-situ CT system is implemented based on the Shanghai Synchrotron Radiation Source. Three-dimensional (3D) microstructural evolution of the buffalo horn under quasi-static compression including the initial microstructures is characterized. Quantifications on the 3D images show that the porosity of the horn is about 1%. Cylindroid holes are arranged in a line along the growth or longitudinal direction. They are connected end to end but not through each other in the longitudinal direction. The axis length distributions of the characteristic ellipsoids of the pores satisfy a lognormal distribution, and the mean lengths of the major and minor axes are about 7??m and 3??m, respectively. In situ CT shows that the initial pores begin to expand and develop into microcracks after yielding. Then, the microcracks in the same layer are bridged from the outward to inward followed by local buckling of laminates and interlaminar cracking, leading to macro cracks and a sharp increase of the crack density in the sample. However, there is a lot of fiber bonding (which improves the interlaminar tensile/shear strength) between the layers, and the tubular pores are not connected with each other, which prohibits the rapid propagation of the interlaminar cracks in the transverse and longitudinal direction, making cracks develop independently and slowly and unable to penetrate the sample. Meanwhile, the wavy layers deflect the crack propagation path, and the laminar buckling increases the friction dissipation. These contribute to the work hardening, and excellent toughness of the horn in the longitudinal direction.
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