A multiaxial criterion for notch high-cycle fatigue using a critical-point method.

In the present paper, a high-cycle critical plane-based multaxial fatigue criterion, recently proposed by the first two authors to determine the fatigue strength of smooth components, is extended to notched ones by using the so-called point method. Accordingly, once the location of the 'hot spot' (crack initiation point) on the notch surface is determined, the orientation of the critical plane (where to perform fatigue strength assessment) is assumed to be correlated with some averaged principal stress directions in the hot spot itself. Some experimental results related to round bars with a surface circular notch (an artificially drilled surface hole) submitted to three types of cyclic loading (bending, torsion and combined in-phase bending and torsion) are compared with the theoretical predictions of the criterion herein proposed. The comparison, which is instrumental in highlighting the notch size-effect (as the hole diameter varies) under uniaxial and biaxial far-field stress conditions, appears to be quite satisfactory.