纳米薄膜润滑及其改性的分子动力学模拟

研究了纯正十三烷和含有摩尔分数为10％的多面体倍半硅氧烷材料T8H8的正十三烷两种润滑膜在不同剪切速率下的纳米薄膜润滑行为。首先建立了长链分子间的作用力模型,接着运用分子动力学模拟的方法得到了两种润滑膜分别在1 m／s、5 m／s、10 m／s和20 m／s四种不同剪切速率下所受到的平均剪应力以及沿着膜厚方向的速度、密度和平均温度分布,考察了一些特殊的物理现象。结果表明:分层和层间滑移现象在两种润滑膜的各种剪切速率下都会发生,是纳米薄膜润滑中的普遍现象;随着剪切速率的不断增加,两种润滑膜内部的温度都在不断升高。在各种剪切速率下,润滑膜中心层的温度总是达到最高值;T8H8加入到纯正十三烷中能显著降低润滑膜所受到的剪切应力和内部产生的温度,达到改善润滑剂润滑效果的作用。

MOLECULAR DYNAMICS SIMULATION OF NANO-SCALE THIN FILM LUBRICATION AND ITS MODIFICATION

The nano-scale thin film lubrication of two kinds of lubricants, pure tridecane and tridecane with polyhedral oli-gomeric silsesquioxanes material T8H8 added (the mole fraction of T8H8 is 10%), at different shear velocities are studied. Firstly, the interaction model of long chain molecules is built. Then the average shear stresses, the distribution of velocities, densities and temperatures of two kinds of lubricates at four different shear velocities, 1 m/s, 5 m/s, 10 m/s, 20 m/s, are obtained by the molecular dynamics simulations. Some special physical phenomena were investigated also. The results indicate that the phenomena of delamination and slippage between layers appear at each shear velocity of the two kinds of lubricants. These phenomena generally occur in nano-scale thin film lubrication. Along with the unceasing increase of the shear rate, the temperatures of the two kinds of lubricants increase continuously. At each shear velocity, the central layers of the two kinds of lubricates get the maximum temperatures always. The results also show that the shear stresses and the temperatures decreased observably after the T8H8 is added into the tridecane. The T8H8 can greatly improve the lubrication effect of the tridecane lubricant.