Prediction of the fatigue limit of blunt-notched components

A prediction of the fatigue limit of blunt-notched components of a low carbon steel was made on the basis that the fatigue limit of polycrystalline metals represents the critical conditions for the propagation of nucleated cracks. An expression for the material resistance to crack propagation as a function of the crack length is obtained for the first part of the short crack regime, which defines the blunt notch sensitivity to fatigue. The material resistance curve is modeled from a depth d, given by the position of the strongest microstructural barrier to microstructurally short crack propagation, which defines the plain fatigue limit. A microstructural threshold, ΔKd, is suggested as an intrinsic material resistance to microstructurally short crack propagation, defined by the plain fatigue limit Δσe0 and the position of the strongest microstructural barrier d. The modeled notch sensitivity fits reasonably well the experimental results for a low carbon steel.