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

Abstract

• Cavitation peening and shot peening was applied to an aluminum alloy with a crack-like surface defect. • The fatigue strengths of an aluminum alloy were improved by peening. • A detrimental surface defect could be rendered harmless by peening. • The sizes of the surface defect rendered harmless by peening were successfully estimated based on fracture mechanics. 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 ( a c ) 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 0.2 mm in depth were rendered harmless by SP and CP, respectively. The a c values estimated based on fracture mechanics were similar to experimental values, indicating that a c was affected by the distribution of the compressive residual stress induced by peening.