Experimental investigation of the effect of spin on traction in elastohydrodynamically lubricated contacts
Tests were conducted to determine the effect of spin on traction using elastohydrodynamically lubricated spheres, three driving and two driven, at maximum Hertzian contact pressures of 300 KSI, 333 KSI, 400 KSI, and 450 KSI. The angle between the axis of the driven ball and the normal to the plane of contact was varied from 40° to 50° and data were taken to determine the relation between coefficient of traction and percent slip for various rolling velocities ranging from 7.08 in/sec to 30.08 in/sec. For the percentages of slip ranging from 0 to 20 the coefficient of traction was found to increase as the angle between the axis of the driven ball and the normal to the plane of contact deviated from 45°. The cause of this increase was possibly due to the spin component of velocity across the contact area. However, this effect was reversed in the 20 to 100 percent slip range. The coefficient of traction increased as the maximum Hertzian pressure was increased for percent slips ranging between 0 to 20. The effect of maximum Hertzian pressure on coefficient of traction was reversed for percent slip values ranging between 20 to 100. An inflection point was incurred in the 16 to 20 percent range. The coefficient of traction increased with the rolling velocity after the inflection point. The traction curves also went to a maximum and then decreased as the percent slip was increased.