Effects of Surface Roughness and Spin Motion on Surface Durability and Traction Coefficient.

The durability (pitting limit) of through-hardened steel rollers (about 500 HB) whose surfaces have Rmax ranging from 0.2 to 6μm is examined using a rolling contact fatigue testing machine. Then, the torque of a driving shaft and duration of full EHL conditions between two rollers are measured during running. The greater the surface roughness is, the larger the traction coefficient, and the smaller the surface durability. When a pair of tapered rollers is used, a spin motion is induced. However a surfacc durability is not markably decrcased. If a pit might occur on a pair of rollers, it has occurred on the contact surface with minus sliding ratio of a following roller. The effective traction coefficient between rollers with a spin motion is calculated from those obtained in the absence of the spin motion.