Experimental and numerical investigation of material heterogeneity in shot peened aluminium alloy AA2024-T351

Shot peening is a mechanical surface treatment that consists of projecting numerous small particles onto a ductile surface. Repeated and random hammering leads to compressive residual stresses as well as work-hardening near the surface resulting in a potentially significant improvement of the fatigue performance. On the other hand, shot peening also increases surface roughness and can produce surface damage which are detrimental to fatigue properties. Fatigue life prediction models have been proposed to predict the combined influence of these factors. Most of these models assume that shot peening leads to a uniform material state parallel to the surface. The current work investigated the heterogeneities present in peened aluminium alloy AA2024-T351 after repeated random impacts in terms of residual stresses, work-hardening, surface roughness, and damage while also considering the initial non-uniformities in the material. Experimental and numerical methods were combined to obtain a detailed description of the material state at various length scales. The implications of the heterogeneities in terms of fatigue performance as well as the potential contributions of numerical simulation were also discussed.