2004 Volume 53 Issue 5 Pages 487-492
Fatigue strength and crack initiation depth were investigated in carburized SCM415 steel under rolling contact fatigue (RCF). RCF tests were carried out until the number of cycles reached 1.2×108. The fatigue strength of carburized SCM415 was found to be more than 4000MPa. Observation of a flaking surface showed that the crack initiated around an inclusion or a defect, the depth of which was about 50μm. Based on the observations, we concluded that the subsurface crack was propagated when its shape remained circular. We evaluated the crack growth behavior in terms of contact stresses and stress intensity factors. The contact stresses and the stress intensity factors were calculated by using Hanson and Fabrikant's analytical method. It is found that the absolute values of KIImax and KIImin were larger than other stress intensity factors and the subsurface crack was dominantly propagated in mode II. The flaking depths vary depending on the KII peak curbing slightly. The friction between crack faces causes the flaking failure which is shallower than predicted by the maximum shear stress.
