Asessment of a local S/N curve theory for the fatigue life calculation on experimental data

ABSTRACT: A theory for the fatigue life calculation based on local S/N curves, computed from the finite element results, has been analysed by the comparison with experimental data. In a first analysis, a good agreement in the general trend of data as function of the relative stress gradient, c’, has been observed. This means that an exponential decreasing of the slope K and the number of cycle at the fatigue limit ND over the stress gradient was observed. Nevertheless, an absolute error following an exponential low came out from the comparison of the experimental versus the predicted values of K and ND. This low should be computed for each analysed data set, requiring, however, more than two generally data set as indicated in the original theory, and used to refine the proposed formulas to calculate K and ND.