Experimental fatigue life rule in low cycle fatigue region based on cyclic strain behavior of specimen with notches

The experimental relationship between the strain range at a notch root and the number of cycles to the strain at a notch root of X% before the initiation of microscopic surface cracks in the low cycle fatigue region has been shown as the fatigue life rule. This relationship is based on the characteristic of the cyclic strain behavior at a notch root obtained by the fatigue test of a specimen with notches under the bending deflection control. Strains are measured by strain gages. From the test data, some cyclic strain behaviors at a notch root such as the cyclic maximum strain, the strain range and the mean strain are shown. The cyclic change of the strain distribution near notch roots is also shown. Some special characteristics are mentioned.