牛长骨的动态应力—应变特性和断裂机理研究

发布时间：2018-05-13 02:06

本文选题：骨组织 + 分离式Hopkinson压杆　；参考：《华侨大学》2017年硕士论文

【摘要】：骨组织是生命体重要的组成部分,有保护内脏器官并支撑生命体完成运动的重要作用,在生命体成长、进行运动的过程中骨组织都承受着自身以及外界附加载荷的作用,当施加的外力超过骨组织的极限强度就会造成骨折,因此对骨组织力学特性和断裂机理的研究具有重要的意义。本文以牛长骨密质骨为研究对象,利用电子万能试验机和分离式Hopkinson压杆实验系统,对牛长骨轴、径、切向三个方向的圆柱试样展开力学测试实验,通过得到的应力-应变曲线分析长骨组织三个方向、不同应变率下的应力-应变特性。同时结合高速摄像和扫描电子显微镜对长骨组织的结构特征、宏观和微观断裂特征以及限位环加载之后裂纹扩展进行观察,分析了长骨组织不同方向的断裂特征并结合骨组织结构特点建立骨组织断裂模型。主要研究成果概括如下:(1)长骨组织不同方向的力学特性存在各向异性,长骨组织轴向的极限强度和弹性模量均为三个方向中的最大值,而长骨径向的极限应变为三个方向中的最大值,长骨组织轴向相比于径向和切向有更高的强度而长骨径向则有更大的韧性。(2)长骨组织的应力-应变特性表现出一定的应变率相关性,随着应变率的增大长骨组织的极限强度、极限应变均随着应变率的增大有增大的趋势。高应变率下的极限强度比准静态条件下高约30%-80%,弹性模量为准静态加载的4-10倍大,而准静态加载下的极限应变则远大于高应变率加载。(3)不同加载方式下长骨组织的断裂特性不同,准静态加载下骨组织试样断裂稳定类似均质材料的断裂形式,均呈45-55°剪切型断口的破碎形式,而动态Hopkinson加载时破碎形式多样,受内部微观结构特征影响较大。(4)长骨组织不同方向的断裂特征受骨单元、哈弗氏管、黏合线、椭圆腔隙等表面特征的影响。长骨轴向受内部结构缺陷和骨单元特征影响最大,而径向受骨单元及其内部哈弗氏管影响最大,切向受骨板和内部纤维的影响最大。(5)结合骨组织结构特点和应力-应变特性建立了长骨组织不同方向的断裂模型,可用于骨组织受载时力学特性和断裂机理的分析。
[Abstract]:Bone tissue is an important part of life body. It has the important function of protecting visceral organs and supporting life body to complete the movement. In the process of life body growth and movement, bone tissue bears the function of itself and external additional load. When the applied external force exceeds the ultimate strength of bone tissue, fracture will be caused, so it is of great significance to study the mechanical properties and fracture mechanism of bone tissue. In this paper, using the electronic universal testing machine and the separate Hopkinson pressure bar experimental system, the mechanical testing experiments were carried out on the cylindrical specimens of the bovine long bone in three directions: axis, diameter and tangential direction. The stress-strain characteristics of long bone in three directions and at different strain rates were analyzed by the obtained stress-strain curves. At the same time, the structural characteristics, macroscopic and microscopic fracture characteristics of long bone and crack propagation after limited ring loading were observed by using high speed camera and scanning electron microscope. The fracture characteristics of long bone tissue in different directions were analyzed and the fracture model of bone tissue was established according to the characteristics of bone tissue structure. The main research results are summarized as follows: (1) anisotropy exists in the mechanical properties of long bone tissues in different directions. The axial ultimate strength and elastic modulus of long bone tissues are the maximum values in three directions. And the radial limit strain of the long bone is the maximum in three directions, The axial strength of long bone tissue is higher than that of radial and tangential direction, while the radial direction of long bone has greater toughness. 2) the stress-strain characteristics of long bone tissue show a certain strain rate correlation, and with the increase of strain rate, the ultimate strength of long bone tissue increases. The ultimate strain increases with the increase of strain rate. The ultimate strength at high strain rate is about 30-80 times higher than that under quasi-static condition, and the elastic modulus is 4-10 times larger than that under quasi-static loading, while the ultimate strain under quasi-static loading is much larger than that under high strain rate loading. Under quasi-static loading, the fracture of bone tissue is stable and similar to that of homogeneous material, all of them are in the form of 45-55 掳shear fracture, but the dynamic Hopkinson loading has a variety of fracture forms. The fracture characteristics of long bone tissue in different directions are influenced by the surface characteristics of bone unit, Hafer's tube, adhesive line and elliptical cavity. The axial direction of the long bone was most affected by internal structural defects and bone unit characteristics, while the radial direction was most affected by the bone unit and its internal Hafer's tube. The fracture model of long bone tissue in different directions was established in combination with the characteristics of bone structure and stress-strain. It can be used to analyze the mechanical properties and fracture mechanism of bone tissue under loading.
【学位授予单位】：华侨大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：R318.01

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