A link-up resulted fatigue crack branching in Al-Cu-Mg alloy

Fatigue crack branching phenomena in Al-Cu-Mg alloy 2324-T39 are studied. Both spectrum and constant amplitude loading cases are examined. A novel type of crack branching process and mechanism is present, which results from the link-up of the secondary crack with the main crack. The grain shapes in 2324-T39 are different from those in the 2024 and 2524 alloys, and their interaction with the plastic zone size contributes to the appearance of this type of crack branching. FE analysis shows that the surface secondary crack is located near the plastic zone boundaries of the main crack.