Molecular dynamics simulation of traction fluid molecules under EHL condition

A new molecular dynamics (MD) code was developed to simulate the dynamic behaviour of traction fluid molecules kept between 2 solid surfaces under the shear condition. In this methodology, one of the surfaces is slid with a constant velocity in a given direction, while a constant pressure is applied on the 2 solid surfaces vertically in order to provide a normal load. We have applied this new MD code and computer graphics technique to the investigation of the dynamic behaviour of benzene and cyclohexane molecules kept between 2 Fe(001) planes at 400 K. Significant differences were observed between the dynamic behaviour of benzene and cyclohexane molecules. The 2nd cyclohexane layer on the sliding surface moved almost together with the 1st cyclohexane layer, whereas the 2nd benzene layer moved slower than the 1st benzene layer. These differences can be explained by the interlocking of cyclohexane molecules due to their chair conformation as opposed to the plane-shape of the benzene molecules. Moreover, the traction coefficient of benzene and cyclohexane molecules were estimated; they qualitatively agreed with the experimental results.