A novel microstructure-based model validated experimentally for simulating short fatigue crack growth in 3 dimensions in planar slip alloys

A novel microstructure-based model was developed to quantify the 3-D growth behaviors of short fatigue cracks by considering both the local driving force and resistance along their irregular fronts in planar-slip alloys. The driving force at a point on the crack front varied with its distance from and the size of the reference semi-circle which covered the area same as that of the crack, and the total resistance at the point was the summation of the dragging forces as a Gaussian function of distance from those grain boundaries that fell behind the point on the crack front. The resistance of a grain boundary to crack growth was a Weibull function of twist angle of crack plane deflection at the boundary. The growth rate at each point on the crack front was subsequently quantified using a microscopic-scale Paris’ equation using an effective driving force which was the driving force minus the total resistance at the point. The crack growth behaviors simulated by this model was consistent with the growth rate measured on the surface of a naturally occurring short fatigue crack in AA8090 aluminum alloys. The anomalous growth behaviors of short cracks could all be quantitatively explained using the model, for the first time. The model was also able to quantify the relationships between the stochastic behaviors of short crack growth, and the microstructure and texture in the alloys.