Coupling of phase field and viscoplasticity for modelling cyclic softening and crack growth under fatigue

A coupled phase field-viscoplasticity approach was developed to model the deformation and crack growth in a nickel-based superalloy under fatigue. The coupled model has an advantage in predicting the cyclic softening behavior of the alloy caused by fatigue damage, overcoming a major limitation of the original cyclic viscoplasticity model. The coupled approach is also highly effective in predicting fatigue crack propagation under varied dwell times at peak load, an important behavior for crack growth under dwell fatigue. By incorporating the stress state factor, the coupled model is further utilized to investigate the growth behavior of 3D cracks under fatigue. Both the geometrical feature of the 3D crack front and the overall crack growth rate are well captured, confirming the predicative capability of the coupled model.