Analyses of the growth of a plane strain crack subject to remote mode-I cyclic loading under small scale yielding were carried out using discrete dislocation dynamics. Plastic deformation was modelled through the motion of edge dislocations in an elastic solid with the lattice resistance to dislocation motion, dislocation nucleation, dislocation interaction with obstacles and dislocation annihilation being incorporated through a set of constitutive rules. An irreversible relation was specified between the opening traction and the displacement jump across a cohesive surface ahead of the initial crack tip in order to simulate cyclic loading in an oxidizing environment. Calculations were carried out with different material parameters so that values of yield strength, cohesive strength and elastic moduli varying by factors of three to four were considered. The fatigue crack growth predictions were found to be insensitive to the yield strength of the material despite the number of dislocations and the plastic zone size varying by approximately an order of magnitude. The fatigue threshold scales with the fracture toughness of the purely elastic solid, with the experimentally observed linear scaling with Young's modulus an outcome when the cohesive strength scales with Young's modulus.

Scaling of Discrete Dislocation Predictions for Near-Threshold Fatigue Crack Growth. V.S.Deshpande, A.Needleman, E.Van der Giessen: Acta Materialia, 2003, 51[15], 4637-51