Outline

  • Abstract
  • Keywords
  • 1. Introduction
  • 2. Model and Method of Molecular Dynamics Simulation
  • 2.1. Potential and Simulation Method
  • 2.2. Model of Tensile Deformation
  • 3. Results and Discussion
  • 3.1. Stress–strain Curves at 300 K and Loading Rate 10 M/s
  • 3.2. Atoms Snapshot of Tensile Deformation
  • 3.3. Strain Rate Effects
  • 3.4. Tensile Deformation at Different Temperatures
  • 3.5. Potential Energy Curves at Different Temperatures
  • 4. Conclusion
  • Acknowledgements
  • References

رئوس مطالب

  • چکیده
  • 1. مقدمه
  • 2. مدل و روش شبیه سازی دینامیک مولکولی
  • 2.1. روش پتانسیل و شبیه سازی
  • 2.2. مدل تغییر شکل کششی
  • 3. نتایج و بحث
  • 3.1. نمودارهای تنش-کرنش در 300 کلوین و بارگذاری 10 متر بر ثانیه
  • 3.2 snapshot اتمها در تغییر شکل کششی
  • 3.3. اثرات نرخ کرنش
  • 3.4 تغییر شکل کششی در دماهای مختلف
  • 3.5. منحنی های انرژی پتانسیل در دماهای مختلف
  • 4. نتیجه گیری

Abstract

In order to research the mechanisms of tensile deformation at nanometer, molecular dynamics (MD) was employed to simulate the tension process of nano-single crystal aluminum (Al) under different temperatures. The results show that the stress–strain curves decrease after a linear increase up to the maximum abruptly because the first transition from elastic to plastic deformation and the slip take place. Then the multiple slips on the (1 1 1) planes continue to occur after the yield. At last, the plastic deformation causes ductile shear fracture. Atomistic simulations of tension at nanometer give results that agree with the phenomenological attributes of plasticity observed in macroscale experiments. The lower strain rate results in the lower yield stress. The tensile strength decreases at higher temperatures.

1. Introduction

Now the emergence of nano-electro-mechanical systems (NEMS) [1] and the development of micro-electro-mechanical systems (MEMS) are urgently required to understand the micro- mechanism of materials deformation behavior at nanometer level. In addition, the micro-structural elements used in micro- electro-mechanical systems (MEMS) are almost devoid of defects [2]. So an investigation of the deformation and fracture process of defect-free materials at nanometer level is indispens- able. While tension tests are very common in determining the mechanical properties at macrolevel, such tests at nanoscale are extremely difficult, if not impossible to realize. An alternative approach is molecular dynamics (MD) simulation.

At present, MD simulation has been proposed to study the micro-mechanism of tensile deformation at nanometer. Sasaki et al. [3] adopted the two-dimensional L–J potential to simulate the tensile deformation of a-Fe single crystal under a constant tensile stress. The temperature was controlled by the velocity scaling method and the comparison of deformation mechanisms with or without temperature scaling was investigated

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