The effect of constituent particles in aluminum alloys on fatigue damage evolution: Statistical observations

Constituent particles in aluminum alloys subjected to fatigue cycling contribute substantially to damage evolution. Yet the amount of constituent particles per mm2 in highly stressed regions is orders of magnitude larger than the number of particles that actually contribute significantly to damage growth. In order to accurately model the impact of fatigue cycling on the progression of damage, a better appreciation for the role of certain constituent particles in aluminum alloys is warranted. The purpose of this paper is to statistically characterize particles that directly contribute to fatigue damage evolution. The observations are taken from fatigue cycling experiments subjected to constant amplitude loading and conducted on 7075-T651 aluminum alloy, both of which are representative of the wing skin of military aircraft. The particles that are associated with damage growth are statistically characterized, including their geometrical properties and their locations. Furthermore, the effect of critical particles on crack nucleation is statistically characterized.