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首頁> 外文學位 >Bridging the Gap from Continuum Mechanics to Molecular Dynamics for Nanoscale Systems.
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Bridging the Gap from Continuum Mechanics to Molecular Dynamics for Nanoscale Systems.

機譯：縮小納米系統(tǒng)從連續(xù)體力學到分子動力學的鴻溝。

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Bending nanowires and nanoplates are widely used as flexible beams in Nano-Electro-Mechanical Systems for force and mass sensors. Usually, the vertical deflection and resonant frequencies of the nanowires and plates are the most crucial parameters in these systems. Deriving the mechanical theories specifically applicable to nanoscale materials and enhancing the accuracy of the mechanics of these nanoscale structures is still a bottle neck in designing nanotechnology. Typically, there are two different ways to accomplish the mechanical modeling for nanoscale materials, such as modeling with continuum mechanics by adding size effects and modeling from atomic scale theory. However, both of these methods have some fundamental issues or limitations and cannot be directly applied to accurately achieve accurate mechanical modeling for nanoscale materials. The hypothesis of this dissertation is that the Euler-Bernoulli or Timoshenko beam theory with surface effects, Eringen's nonlocal elasticity and the corresponding nonlocal beam theories, and molecular dynamics simulations results should all be consistent for nanoscale structures with critical dimensions of 1-100nm. First, a more general solution of continuum beam theories with surface effect has been obtained and developed to investigate the surface effect on bending nanowires with the "core-shell" approach. Timoshenko beam theory with surface effects has been applied with consideration of shear effect and rotational inertia effect. Consequently, the limitation of aspect ratio of Euler-Bernoulli beam theory was eliminated. Second, the solutions of the resonant frequencies with surface stress effect and nonlocal effect have been compared. A bridging theory by incorporating surface properties with the nonlocal elasticity theory parameter e0 has been developed to bridge the classical beam theories with nonlocal beam theory at the nanoscale. Finally, molecular dynamics simulations have also been introduced to verify the above conclusions from the theoretical relation between the surface stress and nonlocal parameter. The molecular dynamics simulations found the same trends as the theoretical modeling predicts. An imaginary e0 was also found by calibrating e0 with the resonant frequencies obtained from the molecular dynamics simulations. The future work has been discussed at the end of the dissertation.
機譯：彎曲的納米線和納米板被廣泛用作力和質(zhì)量傳感器的納米機電系統(tǒng)中的柔性梁。通常，納米線和板的垂直偏轉(zhuǎn)和共振頻率是這些系統(tǒng)中最關(guān)鍵的參數(shù)。推導專門適用于納米級材料的力學理論并提高這些納米級結(jié)構(gòu)的力學精度仍然是設(shè)計納米技術(shù)的瓶頸。通常，有兩種不同的方法可以完成納米級材料的機械建模，例如通過添加尺寸效應和原子尺度理論進行建模的連續(xù)介質(zhì)力學建模。但是，這兩種方法都存在一些基本問題或局限性，不能直接應用于為納米級材料準確實現(xiàn)準確的機械建模。本文的假設(shè)是，具有表面效應的Euler-Bernoulli或Timoshenko梁理論，Eringen的非局部彈性以及相應的非局部梁理論以及分子動力學模擬結(jié)果對于臨界尺寸為1-100nm的納米級結(jié)構(gòu)均應是一致的。首先，已經(jīng)獲得并開發(fā)了具有表面效應的連續(xù)光束理論的更通用解決方案，以研究“核殼”方法對彎曲納米線的表面效應。考慮到剪切效應和旋轉(zhuǎn)慣性效應，應用了具有表面效應的季莫申科梁理論。因此，消除了Euler-Bernoulli光束理論的縱橫比的限制。其次，比較了具有表面應力效應和非局部效應的共振頻率解。通過將表面特性與非局部彈性理論參數(shù)e0結(jié)合起來的橋接理論已被開發(fā)出來，以在納米尺度上將經(jīng)典的梁理論與非局部梁理論聯(lián)系起來。最后，還引入了分子動力學模擬以從表面應力和非局部參數(shù)之間的理論關(guān)系驗證上述結(jié)論。分子動力學模擬發(fā)現(xiàn)的趨勢與理論模型預測的趨勢相同。通過用分子動力學模擬獲得的共振頻率校準e0，還發(fā)現(xiàn)了一個虛構(gòu)的e0。論文的最后討論了未來的工作。

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  • 作者

    He, Qilu.;

  • 作者單位

    University of Illinois at Chicago.;

  • 授予單位 University of Illinois at Chicago.;
  • 學科 Mechanical engineering.;Nanoscience.;Mechanics.
  • 學位 Ph.D.
  • 年度 2015
  • 頁碼 157 p.
  • 總頁數(shù) 157
  • 原文格式 PDF
  • 正文語種 eng
  • 中圖分類 遙感技術(shù);
  • 關(guān)鍵詞

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