Effect of Residual Stress and Surface Roughness of Hole Inner Face on Fatigue Life of 7050 Aluminum Alloy Fastener Hole Sample

The ϕ2.6 mm fastener hole with different surface roughness and residual stress were prepared on 7050-T7451 aluminum alloy fatigue samples by drilling and reaming under different cutting speed (4, 8, 12, 16, 20, 40, 80 mm · min⁻¹ ), milling under different feed speed (0.02, 0.04 mm · r⁻¹ ) or electrical discharge machining respectively. The effect of hole surface roughness and residual stress on fatigue life was studied by high cycle fatigue test, and the correlation between hole surface roughness and residual stress and fatigue life was established. The results show that among three kinds of processed holes, the surface quality of drilling and reaming holes was the best; increasing the cutting speed could improve the residual compressive stress and maintain a small surface roughness. Surface roughness and residual stress jointly affected the fatigue life. When the surface roughness was small, the fatigue life was extended with the increase of residual compressive stress. When the surface roughness increased, the proportion of stress concentration effect on fatigue life increased, while the proportion of residual stress effect decreased, resulting in the decrease of fatigue life. When the cutting speed was 16 mm · min⁻¹, the fatigue life of the drilling and reaming hole was the longest. The hole surface quality influence coefficient comprehensively considering the influence of surface roughness and residual stress could correlate the fatigue life well in the ±2.5 times data dispersion band.