Squeeze film characteristics of circular contacts at impact and rebound motion with micropolar lubricants

In this paper, pure squeeze elastohydrodynamic lubrication (EHL) motion of circular contacts with micropolar lubricant is explored at the impact and rebound processes from a lubricated surface. On the basis of micro-continuum theory, the transient modified Reynolds equation is derived. Then it is solved simultaneously with the elasticity deformation, rheology, and ball motion equations in order to obtain the transient pressure profiles, film shapes, normal squeeze velocities, and accelerations. The simulation results reveal that the effect of the micropolar lubricant is equivalent to enhancing the lubricant viscosity, which would also enlarge the damper effect. Therefore, as the characteristic length (L) and coupling number (N) of the micropolar lubricants increase, the pressure spike and the dimple form earlier, the maximum pressure and the film thickness increase, the diameter of the dimple decreases, the rebounding velocity and the maximum acceleration decrease, and the maximum relative impact force decreases. Furthermore, the secondary peak of central pressure occurred at the rebound end is greater than the first peak of central pressure occurred at maximum impact force. As the effects of micropolar lubricants increase, the first and second peaks form earlier, the total impact time decreases, and the first and the second peaks increase.