獾牙与狗牙的微观结构及摩擦学特性

以獾牙和狗牙为研究对象,采用摩擦磨损试验机进行摩擦磨损试验,考察了獾牙和狗牙的摩擦学性能,利用纳米压痕仪进行力学性能试验,测试了獾牙和狗牙的纳米硬度和弹性模量。试验表明:牙齿的摩擦磨损行为同其微观结构密切相关,獾牙釉质磨斑表面划痕和擦伤痕迹相对轻微,磨损深度为(13.521±1.034)μm,狗牙釉质磨斑表面有较多的裂纹,犁削和擦伤较为严重,磨损深度为(15.429±1.337)μm;牙齿的摩擦磨损性能与其硬度以及显微组织和结构密切相关;獾牙釉质的耐磨性和纳米硬度、弹性模量高于狗牙釉质。该研究为以獾的牙齿为原型将仿生耦合原理应用于刀具的开发提供了理论依据。

Micro-structure and tribological properties of badger teeth and dog teeth

Abstract: Taking the teeth of badgers and dogs as the research object, the friction and wear behavior of the two different animals was investigated systematically in this paper. The wear resistance of the two surfaces was estimated by a wear tester and a roughness tester. The structure of different worn surfaces was characterized by scanning electron microscopy (SEM), and mechanical properties such as hardness and elastic modulus were also evaluated by using a nano-test apparatus. The results showed that the friction and wear performance of these teeth closely related with microstructure. The surface of badger teeth appeared with less scrap, and slight wear and tear happened with some little peeling pits. Compared with the worn surface of badger teeth, the worn surface of the canine tooth enamel had more cracks, and the observed plough cut and bruises were relatively more serious accompanied by massive spalling. Friction and wear properties of different teeth are determined by hardness and microstructure to a large extent. The wear resistance, hardness, and elastic modulus of badger tooth enamel is better than that of dogs. Research results show that badger teeth have apparently better performance such as tribological characteristics and mechanical properties, which suggests greater potential for developing cutters based on badger teeth. This phenomenon could be due to the fact that the surface roughness of the polished teeth sample, which contacts with Si3N4 ceramic ball, is small at first. Badger enamel and dog enamel therefore have a low initial friction coefficient. After a period of time, due to fatigue damage in the enamel surface and associated with brittle cracking, the friction coefficient rapidly increases in the enamel material from peeling. The friction coefficient of the two different samples changed with time and presented different trends. The friction coefficient of badger enamel showed a rapid increase after 1 100 s, while the time for dog enamel is 350 s. As can be seen, the brittle surface flaking of dog enamel appeared earlier than that of badger enamel, which may be affected by the different degree of mineralization and crystal density. As time continues, from the enamel surface of badger and dog tooth, spalling flake enamel is repeatedly squeezing and make the size small. These tiny particles of enamel played an important role in lubrication, reducing the wear between the enamel and a Si3N4 ceramic ball. Then friction and wear went into the stable phase, and the friction coefficient remained constant. The nano-hardness and elastic modulus of badger enamel are higher than that of dog tooth enamel. The reasons for the above findings are mainly that the mechanical properties of the tooth enamel are closely related with its microstructure. Enamel rod is the basic structure of the enamel. The density of the fiber bundles which is within the column is non-aligned and has a certain gap. Therefore, under the effect of an external force on the enamel rod, a single fiber bundle is less restrictive by other fiber bundles around. The effect of a single fiber bundle to resist external forces is not obvious and easily deformed. The density of dog enamel fiber bundle is lower than the badger enamel; therefore, its mechanical properties are inferior to those of the badger tooth enamel.