ROLLING FRICTION TORQUE IN LUBRICATED CONTACTS FROM MICRO TO MACRO SCALE

Using a modified axial ball bearing with three balls and a new analytical methodology, this paper investigates, both theoretically and experimentally, the variation of the rolling friction torque in a ball-race contact in dry and lubricated conditions. It was determined that for the microballs having 1.588 mm in diameter, the rolling friction torque determined with the help of the proposed methodology in lubricated conditions is higher with one order of magnitude than the rolling friction torque determined with the help of Biboulet-Houpert equation. Increasing the diameter of the balls to 7.938 mm, the rolling friction torque determined by the proposed methodology corresponds to the values obtained by Biboulet-Houpert equation. Also, when the maximum Hertzian contact pressure between a ball and a race in pure rolling motion has low values (0.1-0.4 GPa), it was shown that in a ball-race contact operating from dry conditions to fully flooded lubricated conditions, both in micro scale and macro scale, the rolling friction torque has a continuum increases, dry conditions realizing the minimum friction torque.