Fatigue strength improvement of an aluminum alloy with a crack-like surface defect using shot peening and cavitation peening

The effects of shot peening (SP) and cavitation peening (CP) on the bending fatigue strength of the 7075 aluminum alloy with a crack-like surface defect were investigated. Test specimens containing a small semicircular slit were subjected to SP and CP. Bending fatigue tests were conducted on the specimens to determine the fatigue strength and critical depth (ac) of the semicircular slit that can be rendered harmless by peening. The results indicated that fatigue strengths increased by peening and that semicircular slits less than 0.1 and 0.2mm in depth were rendered harmless by SP and CP, respectively. The ac values estimated based on fracture mechanics were similar to experimental values, indicating that ac was affected by the distribution of the compressive residual stress induced by peening.