A phase transformation based method to predict fatigue crack nucleation and propagation in metals and alloys

The fatigue failure of metallic materials contains of dislocations, lattice defects accumulation and interactions. Fatigue is a dynamically changing process of the Gibbs free energy, and the change of defects in the materials could be considered to be a generalized form of phase transformation. In the current work, phase transformation theory has been applied to predict fatigue crack nucleation and propagation. An updated fatigue crack nucleation model based on phase transformation theory and micromechanics is developed and compared with experiments. The proposed approach is also extended for predicting fatigue crack propagation in metallic materials. A new energy parameter is proposed and its relationship with the stress intensity factor is studied. The predicted fatigue crack propagation rates are compared with experimental data for different metallic materials, and the results show that the proposed model can predict fatigue crack nucleation and propagation with reasonable accuracy.

Theoretical predictions of fatigue crack propagation rate dA/dN (m/cycle) compared with experimental data for Al2024-T351 and Ti-6Al-4V under different conditions.199