Numerical modeling of fatigue crack propagation based on the theory of critical distances

• The model is based on the theory of critical distances.
• Stage I and stage II crack growth rates can be quantitatively simulated.
• The effect of R-ratio on crack propagation curve is correctly predicted.
• The critical distance is related to the microstructural length and the cyclic plastic zone size.

A numerical model based on the theory of critical distances has been developed to simulate the fatigue crack propagation for cast aluminum alloys under mode I loading. The accumulated plastic energy density at the critical distance point ahead of the crack tip is used as a measure of the fatigue damage. The effect of different R-ratios on the crack propagation rate is correctly predicted using the proposed methodology. For the 319 cast aluminum alloys investigated in the present paper, the critical distance is of the same order of magnitude as the secondary dendrite arm spacing (SDAS).