论文简介：

毕业论文-碳纳米管在简单和组合载荷下的屈曲行为研究，正文共58页，19657字。
摘 要
碳元素奇特的性质和多种多样的形态渐渐被人们发现、认识和利用。石墨电极的应用、碳纤维复合材料的开发等都大大推进了人类文明。自从碳纳米管被发现以来，实验研究证明其具有高强度、高刚度等奇异的力学性质以及各种独特的电学性质。在纳米机械、纳米材料等相关领域有着不可估量的应用前景，这些都迫切的要求对碳纳米管的基本力学性能和变形机制有更深入的了解。
本文以单壁碳纳米管和双壁碳纳米管为研究对象，采用分子力学模拟和连续介质理论方法，研究了碳纳米管在各种载荷作用下的变形屈曲行为。加载形式包括轴压、扭转两种简单载荷，以及轴压和扭转组合载荷。分析了碳纳米管应变能随应变的变化，并且讨论了碳纳米管的几何特性对屈曲行为的影响，将分子力学模拟结果与连续介质理论结果进行了比较，验证了连续介质理论的可行性。
在简单载荷下的屈曲行为研究中，得出了碳纳米管的手性、长度、半径对其屈曲变形行为的影响。在双壁碳纳米管的扭转屈曲研究中，提出了双壁碳纳米管等效厚度的概念，使得理论计算大大简化，并且计算结果与分子力学模拟结果吻合。
在复合载荷作用下的屈曲行为研究中，分析了不同轴向载荷下，碳纳米管的临界扭转屈曲，不仅得到了轴向载荷对扭转屈曲的影响，同时也得到了轴向和扭转组合载荷下的临界关系曲线，并且研究了碳纳米管几何特性对临界关系曲线的影响。
本文研究的碳纳米管的屈曲变形规律，对于碳纳米管材料的设计起到了指导作用，对碳纳米管的应用和发展具有重要的理论和现实意义。
关键词： 单壁碳纳米管，双壁碳纳米管，简单载荷，组合载荷，屈曲行为

ABSTRACT
The unique physical properties and many kinds of configurations of carbon element bave been gradually discovered, understood and used. The development of our society has been greatly accelerated by the application of graphite electrodes, the exploration of composites based on carbon fiber etc. Numerous experiments have shown special mechanical properties, such as high strength and high rigidity as well as electrical properties for carbon nanotubes (CNTs) since they were first reported. Nanotubes are considered to be the most promising materials of applications in nano-engineering and nano-materials, which requires a clear understanding of the mechanical properties and deformation mechanism of CNTs.
In this paper, the molecular mechanics simulation and continuum mechanics method are used to investigate the buckling behavior of SWNTs and DWNTs. The paper deals with the deformation and buckling behavior of SWNTs and DWNTs under different types of loads. The simple loads considered are axial compression, axial tension and torsion, and the combined loads involve simultaneous actions of axial compression (or axial tension) and torsion. The molecular mechanics simulation is used to determine the variation of energies with strain. Simulations results also show the buckling behavior is strongly size dependent. Based on the comparison of molecular mechanics simulation results with the continuum mechanics results, we can prove the continuum mechanics method is reliable.
For the buckling of SWNTs and DWNTs under simple loads, the results show that the buckling behavior is depended by the chiral, length, radius of the carbon nanotubes. For the buckling of DWNTs under torsion load, a new concept of equivalent thickness of DWNTs is introduced, and this simple model provides another new and effective mothod of modeling torsional buckling angles of DWNTs with fairly good accuracy.
For the buckling of SWNTs and DWNTs under combined loads, the buckling behavior of DWNTs under different axial loads are determined. It is found that the buckling behavior of SWNTs and DWNTs subjected to combined loads is also size dependent. The interaction buckling curves are obtained for nanotubes under combined loading case of axial compression or tension and torsion. Besides, we also find that the interaction buckling curves are size dependent.
The reseach of buckling behavior and deformation mechanics of CNTs in this paper is helpful to the design of nanotubes materials, and is meaningful for the development and application of CNTs.
Key Word: single-walled carbon nanotubes, double-walled carbon nanotubes, simple load, combined load, buckling behavior

目录
摘 要 I
Abstract II
目录 IV
1 绪 论 1
1.1 碳纳米管结构 2
1.1.1 单壁碳纳米管 2
1.1.2 多壁碳纳米管 4
1.2 碳纳米管的研究现状 5
1.3 本文主要研究内容 7
2 原子间相互作用势以及分子力场 8
2.1 Tersoff-Brenner势 8
2.1.1 非成键原子间的作用势 8
2.1.2 碳-碳共价键作用势 9
2.2 分子力场 10
2.2.1 化学键延伸势能 10
2.2.2 键角的变化能 10
2.2.3晶键的面外弯曲能 11
2.2.4 晶键的扭转能 11
2.2.5 范德华能 11
3简单载荷下碳纳米管的变形屈曲行为 13
3.1扶手型和锯齿型单壁碳纳米管的轴压屈曲行为 13
3.1.1分子力学模拟计算模型 13
3.1.2 分子力学模拟结果 14
3.1.3 连续介质力学计算结果 16
3.1.4 单壁碳纳米管的半径、长度和手性对其压缩屈曲行为的影响 17
3.2扶手型和锯齿型单壁碳纳米管的扭转变形屈曲行为 20
3.2.1 模拟计算模型 20
3.2.2 单壁碳纳米管在扭转载荷下的连续介质理论解 21
3.2.3 分子力学与连续介质理论结果的比较 23
3.3 扭转载荷下双壁碳纳米管的变形屈曲行为 25
3.4 本章总结 28
4. 轴向和扭转组合载荷下碳纳米管的变形屈曲行为 30
4.1 引言 30
4.2 双壁碳纳米管在轴向和扭转组合载荷下屈曲 31
4.2.1 连续介质理论 31
4.2.2 分子力学模型 35
4.2.3分子力学计算结果 35
4.2.4 分子力学于连续力学计算结果比较 37
4.3 单壁碳纳米管在轴压和扭转组合载荷下的临界关系 38
4.3.1 模拟计算模型 38
4.3.2 分子力学模拟结果 39
4.4 本章小结 42
5 全文总结 44
6 展望 46
致 谢 47
参考文献 48

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• 毕业论文-碳纳米管在简单和组合载荷下的屈曲行为研究
• 碳纳米管在简单和组合载荷下的屈曲行为研究.doc  [3.56MB]