Fatigue crack propagation in notched and unnotched round bars

As is well-known, the stress field in a structural component depends on the possible presence of a notch, and fatigue life may strongly be affected by geometric discontinuities. A circular-arc circumferential notch is considered in a round bar, and the Stress Concentration Factors (SCFs) related to both tension and bending are determined. Then, an elliptical-arc surface flaw is assumed to exist at the notch root and, for different values of SCF, the Stress-Intensity Factor (SIF) along the crack front is computed through a three-dimensional finite element analysis. The effect of the stress concentration on the SIF values is discussed for the considered crack configurations. Finally, the surface crack propagation under cyclic loading is examined through a numerical procedure which takes into account the computed SIF values.