3623 Effect of Surface Roughness on Fatigue strength of Shot Peened Aluminum Alloy

The objective of this research was to determine the effect of surface roughness on fatigue strength in peened 7075-T7351 three point bend (TPB) specimens. Surface roughness of as-received and peened specimens (with four Almen scales (4, 8, 12, 16)) was measured with the laser microscope. All specimens were fatigued to failure at various stress levels, and a S-N diagram was constructed. The fatigue strength of 7075-T7351 was improved by shot peening, and the effect of shot peening on fatigue strength was inversely proportional to the shot intensity. Since the surface roughness in peened TPB specimens was proportional to shot intensity, the fatigue limits of peened specimens were evaluated by equivalent defect size √, which is applied to irregularly shaped surface roughness. The fatigue limits evaluated by √ were agreed with experimental results well.