Effect of Backing Plate Hole Diameter on Residual Stress Distribution around 7A04-T6 Aluminum Alloy Hole after Cold Expansion

A split sleeve cold-expansion model of 7A04-T6 aluminum alloy plate with hole was carried out with a finite element software, the split sleeve cold-expansion process was simulated, the hoop residual stress distribution around the hole after cold expansion was predicted, and the prediction results was compared with the measured results. The hoop residual stress distribution around the hole after cold expansion at different backing plate hole diameters was discussed finally. The results show that the simulated residual stresses around the hole was accordance with the measured results. The residual compressive stress in the entrance layer of the plate exhibited an increase trend with the increase of the backing plate hole diameter. When the backing plate hole diameter was smaller than 11.74 mm, lug boss was formed in the exit layer, which lead the residual compressive stress changed sharply, and the residual compressive stress peak in the exit layer located in the backing plate hole edge. The hoop residual stress tended to change more smoothly with the increase of the backing plate hole diameter, and the lug boss vanished gradually.