Effect of Tangential Traction and Roughness on Crack Initiation/Propagation During Rolling Contact

Rolling-fatigue tests of 0.45 percent carbon steel rollers were carried out using a four-roller-type rolling-contact fatigue tester. Tangential traction and surface roughness of the harder mating rollers were varied and their effect was studied. The results of the study indicate that the fatigue life decreases when traction is applied in the same direction as that of rolling. When the direction of traction is reversed, the life increases over that obtained with zero traction. The roughness of harder mating rollers also has a marked influences on life. The smoother the mating roller, the longer the life. Microscopic observation of specimens revealed that the initiation of cracks during the early stages of life is more strongly influenced by the surface roughness, while the propagation of these cracks in the latter stages is affected mainly by the tangential traction.