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The uniaxial cyclic stress-strain curve is frequently used in fatigue analysis of stress concentrations, or notches, under unidirectional loading (tension or bending). However, constraint on transverse strain often causes considerable notch root multiaxiality, even when nominal stresses are uniaxial. A straightforward technique is developed for correcting the uniaxial stress-strain curve to explicitly account for notch root multiaxiality. The corrected curve is then used with a conventional Neuber's Rule analysis to more accurately estimate the state of stress and strain within a notch. Results agree favorably with elastic-plastic finite element results and limited experimental data from a shaft with circumferential notches in bending or torsion. Numerical results from the proposed approach were also in agreement with finite element predictions from a round bar with a through hole in tension.

An analysis method is presented for determining the conventional cyclic material properties from uniaxial strain-life fatigue test data. The method focuses on improving fatigue life predictions for variable amplitude histories when a significant amount of damage is associated with small cycles. Under these conditions, it is necessary to extrapolate the strain-life curve below the constant amplitude endurance limit. This extrapolation requires careful attention to the curve fitting process to avoid the influence of endurance limit affected data. A fitting approach has been developed which identifies structure shifts in the data in order to obtain cyclic material properties not influenced by the endurance limit or other transitions that negatively impact life predictions.