Nanoscale friction characteristics of hydrated montmorillonites using molecular dynamics

• Published in: Applied clay science 2021-09, Vol.210, p.106155, Article 106155
• Main Authors: Wei, Peng-Chang, Zhang, Li-Lan, Zheng, Yuan-Yuan, Diao, Qiu-Feng, Zhuang, Dao-Yang, Yin, Zhen-Yu
• Format: Article
• Language: English
• Subjects: Engineering Sciences; Hydrated montmorillonite; Molecular Dynamics; Nanoscale friction; Normal load; Sliding velocity
• ISSN: 0169-1317; 1872-9053
• DOI: 10.1016/j.clay.2021.106155

The interparticle friction behavior of saturated clay controls its mechanical properties, but remains unclear at nanoscale. As one of major clay minerals, the hydrated montmorillonite (MMT) is selected to investigate the nanoscale friction characteristics using Molecular Dynamics simulation method. Two portions of MMT representing two particles with a water film in the middle are created to simulate an undrained system. A virtual spring is applied on the upper MMT portion to provide the sliding with a constant velocity relative to the bottom portion. The effects of normal load and sliding velocity on the frictional behavior are then investigated. The friction coefficients of hydrated MMT at different cases were measured and compared with other experimental and simulation results for the validation. The evolution of normal load with the number of hydrogen bonds for hydrated MMT was finally analyzed. All simulation results indicated that the friction load fluctuated periodically with a cycle of about 9.10 Å at sliding velocity inferior 0.001 Å•fs−1, which was nearly equal to montmorillonite's lattice constant along the sliding direction; the fluctuation amplitude of the friction load increased with the decreasing sliding velocity; the relationship between the average friction load and the logarithm of sliding velocity followed a power function; the friction coefficient and the cohesion were found to increase approximately linearly with sliding velocity. [Display omitted] •The friction load fluctuates periodically at low sliding velocity.•The cycle equals to montmorillonite's lattice constant along the sliding direction.•Friction coefficient and cohesion increase almost linearly with sliding velocity.•Bound water increases with normal load till a certain level.