A microscopic mechanism model and quantitive description of fatigue crack growth

In the present paper, a new microscopic mechanism model of fatigue crack growth is presented based on the dislocation-free zone (DFZ) theory. A cohesive zone model is developed to determine the stress field of the DFZ under cyclic loading. The process of fatigue crack growth is viewed as the intermittent quasi-cleavage fracture of the DFZ. A simple relation is derived to evaluate the fatigue crack growth rate. The calculated dc/dN curves exhibit three different regimes of fatigue crack growth, which is in agreement with the general propagation pattern of fatigue crack. The model gives a reasonable explanation for both the crack growth and striation formation.