以分子動力學研究雙金屬之拉伸行為

本研究是以分子動力學理論進行金屬結構的力學模擬分析。模擬的方法是使用Tight-Binding勢能函數來描述過渡金屬分子間的作用力；並用Gear五階預測修正法計算系統中原子因外力產生位移後的位置、速度及加速度，同時以Verlet鄰近表列法簡化計算以進行分析。主要分析內容分為兩部分：第一部分探討理想單晶金屬銅與鋁，以位移控制進行拉伸後之應力應變等力學性質之分析。由單晶銅的應力應變分析結果可發現，在到達最大應力值之前有一應力值的巨大落差，此時試件外側局部原子朝特定角度排列、移動，這是單晶銅巨觀拉伸實驗所沒有觀察到的現象。分析結果顯示：單晶銅與單晶鋁的應力應變圖得知，單晶鋁結構的應變率大於單晶銅，此一特性與巨觀結果相符；第二部分則探討理想的銅/鋁雙金屬結構在外力作用下的拉伸行為。由應力應變分析圖可知，Cu/Al/Cu/Al層狀排列結構有較佳的抗拉強度、而Cu/Al/Al/Cu層狀結構則有較佳的應變率，但兩種層狀結構在達到最大應力前，幾乎有相同的彈性模數。

關鍵字

銅/鋁雙金屬層狀結構； Tight-Binding多體勢能

並列摘要

In this study the molecular dynamics simulation method was utilized to predict the mechanical behaviors of metals structure. Two issues had been discussed in this article. The first is to study the mechanical behaviors of ideal single crystal copper/aluminium structure deformed under tensile. The second is to study the fatigue behaviors of that ideal copper/aluminium bimetal structure under cyclic loading. The interaction force of Cu/Al atoms were predicted by the Tight-Binding potential energy theory. And the Gear’s fifth order predictor-corrector method is adopted to calculate the positions, velocities and accelerations of the atoms of the structure after deformation by the applied step force; meanwhile, the calculations are simplified by Verlet’s neighbor lists. The analytic results shows that the single crystal copper has a drop before the maximum on stress-strain curve. At the same time, a parts of atoms slipped along slip directions on sample’s outsides. On compare of Cu/ Al stress-strain curves, the strain of the single crystal Al sample is better than another one. In the parts of Cu/Al bimetal structure, the stress-strain curve show that the tensile strength of Cu/Al/Cu/Al structure is better than Cu/Al/Al/Cu’s. On the other hand, the strain of Cu/Al/Al/Cu structure is better than the other one. Besides, the elastic modulus of them nearly the same before the maximum on stress-strain curve.

並列關鍵字

Cu/ Al bimetal structure ； Tight-Binding potential function

參考文獻

[27] 李弘智與陳立仁, “淺談分子模擬,” 化工, 編號 2, 2006.

[1] R.Car and M. Parrinello, "Unified Approach for Molecular Dynamics and Density-Funational Theory," Physical Review Letters, vol. 55, no. 22, pp. 2471-2474, 1985.

[2] J. H. Irving and J. G. Kirkwood, "The Statistical Mechanical Theory of Transport Propeties. IV. The Equations Hydrodynamics," Journal of Chemical Physics, vol. 18, pp. 817-823, 1950.

[3] J. E. Lennard-Jones , "The Dtermination of Molecular Fields. I. From The Varation of The Viscosity of A Gas with Temperature," Proceedings of the Royal Society, no. 106, pp. 441-462, 1924.

[4] L. A. Girifalco and V. G. Weizer, "Application of The Morse Potential Function to Cubic Metals," Physical Review, vol. 114, no. 3, 1959.

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以分子動力學研究雙金屬之拉伸行為

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