Understanding thermal-mechanical fatigue crack growth: A microscopic mechanical model

In the present paper, an original fatigue crack growth model is employed and further developed. Based on it, a new microscopic mechanical model of thermal-mechanical fatigue crack growth is proposed. The model is based on the dislocation-free zone (DFZ) theory and cohesive zone model. The process of thermal-mechanical fatigue crack growth is viewed as the intermittent quasi-cleavage fracture of the DFZ. A simple relation is employed to evaluate the thermal-mechanical fatigue crack growth rate. The calculated crack growth rate curve (dc/dN curve) exhibits different regimes after initiations of the crack (Δk > Δkth), which is in agreement with the propagation pattern of creep-fatigue crack. The model gives a reasonable explanation for thermal-mechanical fatigue crack growth.