Traction behavior and mechanism of molecular level with effects of molecular structure and sliding velocity in boundary lubrication regime: A molecular dynamics study

The traction mechanism in power transmission systems with effects of sliding velocity and molecular structure are revealed at high temperature and pressure through molecular dynamics approach. Firstly, the simulated traction coefficients agree well with the experimental values, and the linear correlation between traction coefficient and bond energy is created to predict the coefficient. The molecule with higher bond energy and more –CH₃ groups between two terminal cyclohexane rings shows higher traction coefficient. Then, the typical shear localization is found from the layered structure of alicyclic molecules confined between Fe₂O₃ slabs. The increase of sliding velocity has a very week effect on the velocity profile but benefits the slip length shrinkage on the whole. The traction coefficient increases fast and then converges toward a plateau with increasing velocity. Finally, the power transmission mechanism in molecular level is discussed and attributed to three effects, i.e., the interlocking effect between alicyclic rings in layer, the cross-linkage effect between layers, and the rotation resistance effect of alicyclic structure. This mechanism is desirable to be achieved with low degrees of slip, and thus maximize the efficiency of the device and help designing new traction fluids.