Influence of external load on the frictional characteristics of rotary model using a molecular dynamics approach

[Display omitted] •The rotary model is studied with the molecular dynamics simulation.•A computational method is proposed to calculate the frictional force.•Effect of external load on the frictional characteristics is investigated.•Coefficient of friction has close relationship with the real contact area. Based on the swash plate–slipper in water hydraulic axial piston pump, a rotary model is built using the molecular dynamics approach to study the frictional characteristics in the perspective of atoms. The model consists of a diamond rotator and a copper substrate and the diamond rotator rotates around the cooper substrate at different external loads. The frictional force is calculated by summing all the atomic forces of diamond rotator along the opposite direction of linear velocity and the real contact area is defined by the number of atoms that interact chemically across the contact interface. Influences of external load on the frictional force and coefficient of friction are analyzed. The simulation results show that the total atomic force varies with rotary cycle according to the sine law with a periodic cycle of 2π in the rotary model. However, the frictional force is basically not a periodic signal. It fluctuates around the average frictional force which is linearly dependent on the real contact area. Besides, it is demonstrated that the coefficient of friction decreases with the increase of external load, which is due to the nonlinear increase of real contact area. As a result, the present work will have an important impact on the fundamental understanding of the wear mechanism of rotary model.