A model of initial flaw sizes in aluminum alloys

It has been shown in a previous study that cracked constituent particles constitute the majority of the observed fatigue crack nucleation sites in several aircraft aluminum alloys. Distributions of these particle sizes may be modeled as initial crack sizes and used to predict fatigue life. Lognormal distributions have been fit to the measured lengths and widths of the constituent particles for 2024-T3, 2524-T3, and 7075-T6 aluminum alloys. Choleski decomposition was used to generate pairs of crack width and depth, resulting in a theoretical initial semi-elliptical crack size. The resulting distribution can be used to predict fatigue life distributions.