Under this project , a phase-field based fatigue damage model coupled to elasto-plasticity is being proposed to accurately correlate the fatigue crack growth rates in residual stress field for different cyclic strain ratios. Additionally, a multi-time scale methodology will be developed to enable crack growth simulations for large number cycles. In order to calibrate the phase field fatigue damage model, low cycle fatigue experiments of standard samples will be performed under various strain ratios. The findings from these experiments will be used to validate the phase field fatigue damage model.