Fatigue Properties of Aluminum Alloy Hole Structure Strengthened byHigh Interference Fit Bushing Technique

7050 aluminum alloy hole structure was strengthened by high interference fit bushing technique with single-side expansion and both-side expansion processes. The residual stress and fatigue properties of the hole structure were studied. The fatigue crack initiation life and growth life were derived quantitatively from fatigue fracture by the trapezoidal accumulation method. The results show that the residual compressive stress field with the depth of 12 mm was formed in the hole structure. The residual stress on the in-side of the single-side expansion strengthening sample was higher than that on the out-side, while the residual stresses on the in-side and out-side of the both-side expansion strengthening sample were almost the same. Compared with non-expansion strengthening sample, the average fatigue lives of single-side expansion strengthening and both-side expansion strengthening samples increased by 770% and 1 500%, respectively; the high interference fit bushing technique had obvious fatigue strengthening effects, and that of the both-side expansion strengthening process was better. The high interference fit bushing technique could both increase the fatigue growth life and initiation life of the hole structure, and the increase of initiation life was greater.