论文标题
通过反应性MD建模，粘土中的纳米级裂纹在粘土中传播
Nanoscale crack propagation in clay with water adsorption through reactive MD modeling
论文作者
论文摘要
粘土中的原子尺度开裂机制对于在连续尺度上发现粘土的开裂机理至关重要，因为粘土是一种纳米材料。在本文中，我们研究了模式I和模式II裂纹在硫属石和Ca-蒙太尼石中的裂纹传播的机理，并通过用键级力场的反应性分子动力学通过水吸附，并吸附水。通过在粘土表面添加水分子来考虑粘土水的吸附。在平衡阶段，水吸附可能导致预定义的边缘裂纹区域的弯曲变形。相对较小的水分子角度表明在裂纹繁殖过程中形成氢键。吸附水的峰值密度随着菌株的增加而降低。分析了负载下裂纹尖端的原子结构演变，以解释纳米级裂纹传播机制。数值结果表明，裂纹尖端首先被钝化，裂纹尖端的曲率半径显着增加，裂纹长度略有变化。通过在模式I和II裂纹中跟踪四面体SI-O单元中的裂纹尖端开口距离和O-Si-O角度来研究裂纹尖端钝化。我们比较Al-O和Si-O之间的破坏债券行为。发现SI-O键断裂主要负责裂纹繁殖。临界应力强度因子和临界能量释放速率由MD模拟结果确定。
The atomic-scale cracking mechanism in clay is vital in discovering the cracking mechanism of clay at the continuum scale in that clay is a nanomaterial. In this article, we investigate mechanisms of mode I and mode II crack propagations in pyrophyllite and Ca-montmorillonite with water adsorption through reactive molecular dynamics with a bond-order force field. Clay water adsorption is considered by adding water molecules to the clay surface. During the equilibration stage, water adsorption could cause bending deformation of the pre-defined edge crack region. The relatively small orientating angle of water molecules indicates the formation of hydrogen bonds in the crack propagation process. The peak number density of adsorbed water decreases with the increasing strains. The atomistic structure evolution of the crack tip under loading is analyzed to interpret the nanoscale crack propagation mechanism. The numerical results show that the crack tip first gets blunted with a significant increase in the radius of the curvature of the crack tip and a slight change in crack length. The crack tip blunting is studied by tracking the crack tip opening distance and O-Si-O angle in the tetrahedral Si-O cell in mode I and II cracks. We compare bond-breaking behaviors between Al-O and Si-O. It is found that Si-O bond breaking is primarily responsible for crack propagation. The critical stress intensity factor and critical energy release rate are determined from MD simulation results.
