Influence of Grain Size on Notch Sensitivities in Fatigue of Carbon Steel

In order to investigate the influence of grain size on notch sensitivities in fatigue of a fine-grained carbon steel, rotating bending fatigue tests were carried out using specimens with a V-grooved circumferential notch of commercial fine-grained carbon steel with grain size of 6.5µm. The results were compared with those of a larger grain sized carbon steel (grain size: 20 µm) and the notch sensitivities were evaluated based on Linear notch mechanics proposed by Nisitani. Notch sensitivities for both of fatigue limits for a crack initiation and its propagation of the fine grained steel were high. The results were discussed from the view points of the size of area related to crack initiation and the crack growth resistance.