Cyclic plasticity and fatigue crack growth threshold

Fatigue crack growth threshold is predicted based on material's cyclic plasticity. The model proposed emphasizes the influence of material s cyclic plasticity on fatigue crack growth. The value of J-integral within cohesive zone under cyclic loading is determined based on dislocation-free zone (DFZ) and cohesive zone theory. Then, the value of J-integral is regarded as fracture parameter and a criterion of crack growth is set up. The calculated curve of fatigue crack growth rate is in agreement with the general propagation pattern and the predicted threshold accords with the experiment threshold well. A prominent character of the present model is that the near threshold characteristics are most determined by the cyclic deformation behavior of the material, and are theoretically determinable from the standard cyclic loading test. This study should be of practical importance in engineering design.