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THE INFLUENCE OF GRAIN SIZE AND TEMPERATURE ON THE MECHANICAL DEFORMATION OF NANOCRYSTALLINE MATERIALS: MOLECULAR DYNAMICS SIMULATION 总被引:2,自引:0,他引:2 下载免费PDF全文
Nanocrystalline (nc) materials are characterized by a typical grain size of 1-100nm. The uniaxial tensile deformation of computer-generated nc samples, with several average grain sizes ranging from 5.38 to 1.79nm, is simulated by using molecular dynamics with the Finnis-Sinclair potential. The influence of grain size and temperature on the mechanical deformation is studied in this paper. The simulated nc samples show a reverse Hall-Petch effect. Grain boundary sliding and motion, as well as grain rotation are mainly responsible for the plastic deformation. At low temperatures, partial dislocation activities play a minor role during the deformation. This role begins to occur at the strain of 5%, and is progressively remarkable with increasing average grain size. However, at elevated temperatures no dislocation activity is detected, and the diffusion of grain boundaries may come into play. 相似文献
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纳米晶铜单向拉伸变形的分子动力学模拟 总被引:13,自引:0,他引:13
纳米材料是由尺度在1-100nm的微小颗粒组成的体系,由于它具有独特的性能而备受关注。本文简要地回顾了分子动力学在纳米材料研究中的应用,并运用它模拟了平均晶粒尺寸从1.79-5.38nm的纳米晶体的力学性质。模拟结果显示:随着晶粒尺寸的减小,系统与晶粒内部的原子平均能量升高,而晶界上则有所下降;纳米晶体的弹性模量要小于普通多晶体,并随着晶粒尺寸的减小而减小;纳米晶铜的强度随着晶粒的减小而减小,显示了反常的Hall-Petch效应;纳米晶体的塑性变形主要是通过晶界滑移与运动,以及晶粒的转动来实现的;位错运动起着次要的、有限的作用;在较大的应变下(约大于5%),位错运动开始起作用;这种作用随着晶粒尺寸的增加而愈加明显。 相似文献
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Numerical solutions for the transient flow in the homogenous closed circle reservoirs 总被引:2,自引:0,他引:2
There are many fault block fields in China. A fault block field consists of fault pools. The small fault pools can be viewed
as the closed circle reservoirs in some case. In order to know the pressure change of the developed formation and provide
the formation data for developing the fault block fields reasonably, the transient flow should be researched. In this paper,
we use the automatic mesh generation technology and the finite element method to solve the transient flow problem for the
well located in the closed circle reservoir, especially for the well located in an arbitrary position in the closed circle
reservoir. The pressure diffusion process is visualized and the well-location factor concept is first proposed in this paper.
The typical curves of pressure vs time for the well with different well-location factors are presented. By comparing numerical
results with the analytical solutions of the well located in the center of the closed circle reservoir, the numerical method
is verified. 相似文献
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The nearest-neighbour Lennard-Jones potential from the embedded-atom method is extended to a form that includes more than nearest neighbours.The model has been applied to study melting with molecular dynamics.The calculated melting point,fractional volume change on melting,heat of fusion and linear coefficients of thermal expansion are in good agreement with experimental data.We have found that the second and third neighbours influence the melting point distinctly. 相似文献