兰州大学机构库 >土木工程与力学学院
耦合作用下线材结构力电性能分析
Alternative TitleAnalysis on mechanical/electrical properties of wire-structures under coupling effects
乔力
Thesis Advisor郑晓静
2011-06-06
Degree Grantor兰州大学
Place of Conferral兰州
Degree Name博士
Keyword金属纳米线材 ZnO 纳米线材 Nb3Sn 复合超导线材 杨氏模量 临界电流密度 上临界磁场 临界温度 表面效应 电场效应 自平衡应变场
Abstract在纳米器件、纳机电系统以及热核聚变实验反应堆超导磁体系统等中,涉及大量线材结构力学性能尺度效应、力电耦合作用问题,其直接关系到实际装置的性能指标和可靠运行。为此,本文针对金属纳米线材力学性能,金属纳米线材、ZnO 纳米线材应用中的电场效应,以及复合超导线材临界电流密度的应变效应开展了理论研究工作。首先,从原子结合能出发,对有广泛用途的 fcc 金属纳米线材,建立了基于原子间相互作用规律并便于实际应用的表征其弹性的杨氏模量解析模型。通过考察表面原子弛豫导致的原子键强度的变化,得到了与fcc 金属纳米线材杨氏模量,尺寸效应相关的尺度函数,给出了估算fcc 金属纳米线材杨氏模量的简单公式,该式表明了表面原子弛豫导致的键强化在金属纳米线材杨氏模量尺寸效应中的主导作用,理论模型与实验结果定性吻合;与基于连续介质的建模方法相比,本文分析简化了描述低维材料力学性能尺寸效应所需的材料参数个数。其次,结合经典的分子动力学模拟和连续介质电动力学,定量给出了外加侧向电场对金属纳米线材力学性质的影响,模拟结果表明:表面电场负压的存在会导致纳米线材杨氏模量的减小和泊松比的增大。同时,这种电场效应随着表面电势的增大而增大、随着纳米线材直径及其与基面距离的增大而减小。
Other AbstractWire structures have wide application prospects in varied fields, including nanodevices, nanoelectromechanical systems (NEMS), and thermonuclear experimental reactor magnet system. The size dependent mechanical properties, and electro-mechanical coupling effects of which are involved in the applications due to gaining relevance in the operation performance criteria and controlling functionality of the actual device. Therefore, theoretical studies on the mechanical properties of metal nanowires, the electric field effects in the metal nanowire/ZnO nanowire based NEMS, and the strain effects in the critical current density of composite superconducting wires are carried on in this thesis. Firstly, from the viewpoint of the atom binding energy, a Young’s modulus model is proposed for the widely used fcc metal nanowires, which allows for an analytical study on the elastic behavior from the perspective of atomic interactions and easy application in engineering practice. By examining the bond-strength enhancing arising from the spontaneous bond relaxation, a scale function is obtained and a simple formula characterizing the Young’s modulus of the fcc metal nanowires is given, which indicate the key role the bond-strength enhancing plays in the size-dependent elastic properties. There is good qualitative agreement between theoretical predictions and experimental observations. The number of material parameters needed for the low dimensional material Young’s modulus modeling in this paper is reduced by comparing with the continuum modeling approach. Secondly, elastic properties of metal nanowires in a transverse electric field are investigated using molecular dynamics simulations and classical electrostatics theory.The negative pressure on the surfaces stemmed from the transverse electric field modifies the Young’s modulus and Poisson’s ratio of nanowires significantly. The simulation results reveal the decrease in Young’s modulus and the increase in Poisson’s ratio as a result of the negative pressure. With the increase of the applied voltage and decreasing the distance between the nanowire and the ground plane, the electromechanical coupling effect on elastic properties of nanowires becomes more remarkable.
URL查看原文
Language中文
Document Type学位论文
Identifierhttps://ir.lzu.edu.cn/handle/262010/226057
Collection土木工程与力学学院
Recommended Citation
GB/T 7714
乔力. 耦合作用下线材结构力电性能分析[D]. 兰州. 兰州大学,2011.
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