2013-01-012024-05-13https://scholars.lib.ntu.edu.tw/handle/123456789/650620摘要：近幾年來，原子尺度模擬如分子動力(Molecular Dynamics, MD) 雖已被廣泛運用於探索材料在奈米尺度的機械性質與微觀機制，但多侷限於特徵長度在20奈米以下的單純材料系統。多尺度模擬如擬連體法 (Quasicontinuum, QC) 雖有極大潛力將MD延伸到微米尺度，但仍有許多理論與模擬方法有待驗證與突破。因此本子計劃的研究目的即為發展可分析多晶與非晶材料之原子尺度與多尺度模擬方法，並將其應用於奈米壓印導致的變形機制對相關機械性質之探索。此目標雖相當具挑戰性，但如能順利完成，便能與奈米壓印實驗的結果做量化連結，闡明微觀機制與微奈米尺度機械性質與現象之關係。 於本子計畫中，我們將專注於：(1) 以大型MD與QC計算模擬單晶、多晶與非晶材料的奈米壓印行為、(2) 擴展QC的擬連體理論以有效應用於多晶與非晶材料、(3) 由MD與QC的結果探索差排、晶界、自由體積等導致的微觀機制、(4) 研究單晶、多晶與非晶材料的尺寸效應、(5) 由MD與QC的量化但簡化結果發展有限元素模擬所需的材料本構關係。最後本子計畫將與其他子計畫充分合作，驗證模擬結果並探索相關現象。我們相信經由本研究所發現的基本機制及其對於材料機械性質的影響，將會對未來尖端材料的發展產生重大衝擊。 <br> Abstract: Atomistic simulations using classical molecular dynamics (MD) have surged recently as a powerful way to elucidate fundamental mechanisms and their consequence on mechanical properties of nanoscale materials and structures. The computational burden however limits the applicability of MD to the phenomena of interest within 20 nm characteristic length. Advances on multiscale modeling such as the quasicontinuum (QC) method have shown a great potential to extend the reach of MD with realistic length and with realistic materials’ representation. The objectives of this subproject are thus to: (1) develop theories and modeling methodologies of atomistic and multiscale simulations for crystalline and amorphous materials and (2) use these simulation tools to study indentation-induced deformation mechanisms and their consequence on mechanical properties of micro-nano scale materials and structures. Both tasks are daunting but with a high reward: once succeeded, we will have very powerful atomistic and multiscale methods and tools to simulate nanoindentation and extract deformation associated microscopic features in more realistic materials’ representations at nano- and micro-scales with desirable atomistic fidelity. In this subproject, research will focus on: (1) perform large-scale MD and QC simulations for crystalline and amorphous materials, (2) extend coarse-grained theories and methodologies in QC for polycrystalline and amorphous materials, (3) develop methodologies to identify and extract microscopic features of interest from MD and QC such as dislocation structures, grain boundary sliding and free volume initiation and propagation, (4) study size effects of crystalline and amorphous materials and their associated mechanisms, and (5) develop constitutive models for finite element analysis with quantitative but reduced input from MD and QC. Finally, by working together with other subprojects and by carefully comparing simulation results with critical experimental observations, significant impact is expected through revealing fundamental mechanisms and their consequence on mechanical properties of the cutting-edge materials.分子動力擬連體法有限元素差排自由體積molecular dynamicsquasicontinuumfinite elementdislocationfree volume