基于分子动力学方法,对石英玻璃进行了三维的纳米划痕仿真,用来研究其纳米加工性能。采用熔融-淬火的办法建立了石英玻璃的模型,并通过观察模型的截面图,分析了在制备过程中内部微观孔隙的形成过程和原因。在仿真过程中,观察了石英玻璃的变化和孔隙周围原子的运动,得到了切削力的曲线,重点研究了内部的微观空隙对划痕过程的影响。仿真结果表明: 当石英玻璃冷却时,由于内部共价键的重组,会形成平均半径为0.25 nm的微观的孔隙,而且其降低了石英玻璃的纳米加工性能,使得切削力的曲线发生一定程度的波动。当磨粒划过表面后,会在表面以下形成厚度为2 nm的原子密集堆积区。由于稠密区的原子共价键键长的变化,失去了原有共价键的强度,所以会形成加工的损伤层。因此在对石英玻璃超精密加工时,应采用少量多次的加工方法来提高材料的加工性能。

In order to study the nanoscratch properties of optical quartz glass, a three-dimensional simulation of the fused silica is carried out based on molecular dynamics method. The model of the fused silica is established by using the approach of melting-quenching and the forming mechanism of the microscopic void in the process of preparation is analyzed by observing the sectional view. During the nanoscratch simulation, the change of the fused silica model and the movement of the atoms around the pore are observed and the cutting force curve is drawn. The influence of the void on the nanoscratch performance is obtained. The results show that the gaps in the fused silica are formed in the cooling process due to the restructuring of the covalent bond and their average diameter is about 0.25 nm. The voids will greatly reduce the existence of material mechanical properties, which causes the fluctuations of the cutting force. When the abrasive sweeps away, the atomic dense area, the thickness of 2 nm, is formed beneath the surface because the voids are compressed. The atomic populated area is the damaged layer due to the loss of strength of the original covalent bonds. Therefore the method of small quantities in high frequency can be applied to increasing the mechanical properties in the ultra-precision machining of quartz glass.