Fatigue Crack Growth Behavior of 7050-T7451 Aluminium Alloy Attachment Lug with Different Structures

The fatigue crack growth experiments under different loads in different directions were conducted on the straight lug, symmetrical and unsymmetrical tapered lug of 7050-T7451 aluminum alloy, and then the fatigue crack growth curves and crack growth paths were analyzed and compared. The results show that under the same loading direction and peak load, the fatigue lives of the symmetrical tapered lugs were higher than those of the straight lugs and the increase of the oblique angle was in favor to improve the fatigue life. The fatigue life of the symmetrical tapered lug subjected to the vertical load was higher than that under the oblique load. The unsymmetrical tapered lugs with initial cracks at the side of relatively large oblique angle were relatively prone to fatigue fracture. With the increase of the loading angle, the angle between the crack extension direction and the loading direction decreased gradually. The cracks first appeared at the inside lug hole of the tapered lug subjected to the lateral load and the angle between the extension direction and the loading direction was about 45°.