With an objective to understand the effect of the stress-state on the initiation and the growth of nominal defects in structural components under sub-critical fatigue loading, fatigue experiments and simulations are performed. Aluminium alloy has been chosen as the representative material for the study. Three-dimensional finite-element simulations are carried out to analyze the influence of mode-mixity on the parameters that influence fatigue failure mechanism viz. Triaxiality, Equivalent plastic strain, and Crack-opening stress, for a series of crack lengths. Further, a stress-state dependent cohesive zone model with an irreversible damage parameter has been used in the simulation of fatigue crack initiation and continued growth. The cohesive model for a plane-strain modified compact tension geometry is implemented as interface elements. The state of stress of the neighbouring continuum elements is used in the traction-separation behavior of the elements modeled as the cohesive zone. The model is shown to have the ability to reproduce the typical initiation life as well as fatigue crack growth curves. Furthermore, the effects of the cohesive model parameters on the initiation life and crack growth rates are established.