Effect of Defect on Fatigue Property of EA4T Axle Steel

In order to accurately evaluate the effects of different size defects on the fatigue property of EA4T axle steel, the drilling method was used to artificially introduce defects on the surface of the smooth specimen, and the fatigue test was carried out to obtain the fatigue limits on the smooth specimens and the specimens with different size defects by the rotary bending fatigue machine. The fracture morphology was observed by a scanning electron microscopy (SEM). Finally, the fatigue limits of specimens with defects were assessed using Neuber's formula (based on notch sensitivity) and a modified El-Haddad model (based on fracture mechanics). The result show that when the defect size of the specimen is less than 59.64 μm, the fatigue limit is the same as the smooth specimen, both of which are 360 MPa, however, when the defect size is larger than 59.64 μm, the defect will reduce the fatigue limit of the smooth specimen, and the larger the introduced defect size, the lower the fatigue limit. Fatigue strength prediction based on the Neuber formula is conservative, however, the modified El-Haddad model can better predict and evaluate the effect of different size of 3D hole defects on the fatigue strength of EA4T axle steel.