A Finite Fracture Mechanics approach to estimate the fatigue endurance limit of V-notched bars under multiaxial loading

The current study aims to assess the high cycle fatigue strength of sharply V-notched bars under mixed mode I/III loading by applying the coupled Finite Fracture Mechanics (FFM) approach. FFM provides strength predictions by simultaneously satisfying a stress condition and an energy balance. A novel semi-analytical implementation of the FFM criterion is presented for the first time to account for a multiaxial fatigue loading by assuming that fracture early propagates along the notch bisector plane through a circumferential-shaped crack. To validate the model, fatigue strength predictions are then compared with a large variety of experimental data related to several metals, V-notch configurations and different multiaxial loading conditions. Although the adopted hypotheses are simplistic and do not fully encompass all the physical phenomena that occur in the multiaxial fatigue process, the approach reveals to be a reliable tool for obtaining semi-analytical fatigue endurance limit predictions useful for engineering design practice.