集成纳米HAP晶体影响的牙釉质多级微结构跨尺度建模和有效模量预测方法

发布时间：2018-01-03 20:37

本文关键词：集成纳米HAP晶体影响的牙釉质多级微结构跨尺度建模和有效模量预测方法　出处：《西南交通大学》2017年硕士论文　论文类型：学位论文

【摘要】：作为典型的多级生物复合材料,牙釉质位于牙齿最外层,是动物体中钙化程度最高的坚硬矿物组织。它通常兼具高强度、强韧性、耐疲劳等优异特性,主要原因在于其经自然选择而形成的多级优化微结构及特定比例的材料组成。深入探索牙釉质固有力学等性能与多级微/纳结构组成、材料特性等的定量关系,不仅有助于揭示多级生物组织宏观优异特性的产生机理,更可指导新型高性能仿生材料合成和已有非均质材料及结构性能优化。本论文主要研究内容及结果概述如下:第一章,以天然生物材料为例,阐述了常见多级结构及其性能特点。结合已有文献,综述了牙釉质多级微结构建模方法、弹性模量预测等研究的国内外现状,并进一步给出了本论文的研究内容及选题意义。第二章,为了准确描述微米釉柱和纳米HAP晶体的非规则轮廓,采用水平集函数法建立了二者的显式表达式,并基于已有试验数据进一步拟合获得了釉柱不同位置晶体角度模型。基于课题组建立的自动建模方法,实现了规则及非规则纳米和微米尺度代表性单元模型自动重构。第三章,简要介绍了细观力学均匀化方法和常见的牙釉质等效本构关系。通过开发的模拟方法计算了牙釉质代表性单元模型的有效模量矩阵,发现:随着间质层厚度减小,预测结果逐渐接近已有模拟数据,说明建立的模型和模拟方法是有效的。在此基础上,进一步讨论了纳米尺度晶体形状及材料组成对牙釉质宏观模量的影响。第四章,结合牙釉质微米尺度代表性单元和第二章的HAP晶体倾斜函数,采用静态凝聚技术开发了牙釉质宏观模量跨尺度预测方法,可直观反映微观釉柱形状和纳米HAP晶体组织方式等因素的影响。同时,进一步分析了晶体大小、形状及体积分数对牙釉质有效模量的影响。本文主要结论包括:(1)通过多项式函数分段逼近釉柱轮廓,建立了牙釉质复杂微结构重构方法;采用水平集法和单元自动分割策略,实现了牙釉质微-纳尺度模型的自动建模,极大地简化了复杂多级生物非均质材料建模过程。(2)鉴于牙釉质宏观模量与其独特的微/纳结构组织方式及材料组成等密切相关,本文采用静态凝聚技术进一步开发了牙釉质宏观模量跨尺度计算方法,定量反映了微观釉柱形状和纳米HAP晶体组织方式等影响。(3)牙釉质微观釉间质特性对宏观模量影响显著。随着釉间质刚度增加,牙釉质宏观模量显著增大,且D11、D22和D33较其他模量增加更快。(4)牙釉质纳米HAP晶体的体积分数和蛋白质层模量对宏观模量影响较大,晶体形状和尺寸对其影响较小。
[Abstract]:As a typical multistage biological composite, enamel is the hardest mineral tissue with the highest degree of calcification in the outer layer of teeth. It usually has high strength, toughness, fatigue resistance and other excellent properties. The main reason lies in the multi-level optimization microstructure and the specific proportion of materials formed by natural selection. The quantitative relationship between the intrinsic mechanical properties of enamel and the composition of multi-stage micro / nano structure and the material characteristics is deeply explored. It is not only helpful to reveal the mechanism of macroscopical excellent properties of multistage biological tissue. It can also guide the synthesis of new high-performance biomimetic materials and the optimization of existing heterogeneous materials and structural properties. The main contents and results of this paper are summarized as follows: chapter 1, natural biomaterials as an example. The common multilevel structure and its performance characteristics are described. Combined with the existing literature, the research status of the modeling method of multilevel microstructure of enamel and the prediction of elastic modulus at home and abroad are summarized. In chapter 2, in order to describe the irregular profile of micron glaze column and nanocrystalline HAP crystal, the explicit expressions of the two crystals are established by using the level set function method in order to accurately describe the irregular contour of the nanocrystalline glaze column and nanocrystalline HAP crystal. Based on the existing experimental data, the crystal angle model of different positions of the glaze column is obtained, and the automatic modeling method based on the research group is established. It realizes the automatic reconstruction of regular and irregular nanoscale and micron scale representative cell models. Chapter 3. The mesomechanical homogenization method and the common equivalent constitutive relation of enamel were briefly introduced. The effective modulus matrix of the enamel representative unit model was calculated by the developed simulation method. It is found that with the thickness of mesenchymal layer decreasing, the prediction results are close to the existing simulation data, which shows that the established model and simulation method are effective. The effects of nanoscale crystal shape and material composition on the macroscopic modulus of enamel were further discussed. Chapter 4th combined with the micron-scale representative unit of enamel and the tilt function of HAP crystal in Chapter 2. The cross-scale prediction method of macroscopic modulus of enamel was developed by static coagulation technique, which can directly reflect the influence of the shape of micro-glaze column and the structure of nano-sized HAP crystal. At the same time, the crystal size was further analyzed. The effect of shape and volume fraction on the effective modulus of enamel. The level set method and the unit automatic segmentation strategy are used to realize the automatic modeling of enamel micro-nano scale model. The modeling process of complex multistage biological heterogeneous materials is greatly simplified. (2) since the macroscopic modulus of enamel is closely related to its unique micro / nano structure and material composition. In this paper, a cross-scale calculation method of macroscopic modulus of enamel was developed by static coagulation technique. Quantitative analysis shows that the microstructure of enamel post and the microstructure of nanometer HAP crystal have significant influence on the macroscopic modulus of enamel, and with the increase of the stiffness of enamel, the microstructure of enamel has a significant effect on the macroscopic modulus of enamel. The macroscopic modulus of enamel increased significantly, and D11D22 and D33 increased more rapidly than other moduli.) the volume fraction of enamel nanocrystalline HAP crystal and the modulus of protein layer greatly affected the macroscopic modulus. The shape and size of the crystal have little effect on it.
【学位授予单位】：西南交通大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：TB33

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