Numerical stress-life curves for the AISI 4340 steel using two sets of materials properties and different bi-axial stress ratios

Abstract Fatigue assessments by the more robust strain-based approach demand the determination of the local strain history from nominal stresses. For notched members, a cyclic constitutive relation, the stress concentration factor (SCF) and a strain concentration rule are used with this aim in some approximate solutions. The plastic part of the cyclic constitutive relations for many materials is well adjusted by a Ramberg-Osgood (RO) type equation. The parameters in the RO equation are the cyclic strength coefficient and exponent (H’ and n’) respectively. These parameters can be experiment...