Abstract
A simplified method was proposed for predicting the threshold value of small fatigue cracks, which is based on the concept of the cyclic resistance-curve (R-curve) method. In this simplified method, the resistance curve can be determined by using only one material data, either the hardness or the tensile strength. The threshold condition of crack initiation was given by the constant value of the effective stress intensity range, which is assumed to be equal to the threshold value for long cracks. The threshold value of the crack opening stress intensity factor was formulated as a function of the hardness, the applied stress and the amount of crack extension. The fatigue limits for the crack initiation and the fracture and the length of arrested crack were predicted. The predicted values agreed well with the experimental results.
