Contact Conformity Effects on Spinning Torque and Friction

Lubricated and unlubricated tests were conducted in the NASA spinning friction apparatus with SAE 52100 steel specimens with ball-race conformities of infinity (a ball on a flat), 60, 55, and 51-percent. For a constant conformity under lubricated conditions, the coefficient of spinning friction decreased from approximately 0.5 to 0.05 with increasing load and stress. At a constant stress, the coefficient of spinning friction increased with decreasing conformity (increasing percent conformity). Under unlubricated conditions, the coefficient of spinning friction remained relatively constant regardless of load, stress, or conformity, having values within a scatter band of 2.5 to 6.0. For a constant stress under both lubricated and unlubricated conditions, the greater the conformity (the smaller the percent conformity), the higher the torque.