A microstructural model for biaxial fatigue conditions

This paper presents the extension to biaxial proportional loads of a short crack growth model based on the blocking of dislocations at grain boundaries. The model considers a small inclined crack and its associated plastic zones blocked in a grain boundary and within a plane biaxial stress field. Two distributions of dislocations are employed to account for the climb and glide components of displacements. The conditions for activation of dislocations sources in the neighbouring grain are established and this leads to a biaxial criterion which reproduces the well-known Gough and Pollard ellipse.

Research highlights
► Derivation of biaxial in-phase bending–torsion fatigue limit locus.
► Takes into account in a quantitative manner the existence of microcracks.
► An exact derivation of the Gough and Pollard ellipse arc criterion is provided.