Notch fatigue behaviour of shot peened high-strength aluminium alloys: Role of the residual stress field ahead of the notch root

The present paper is aimed at investigating the effect of shot peening on the fatigue behavior of A1-7075-T651 samples carrying different types of notches. The Wohler S-N curves were determined by pulsating bending for the different experimental conditions. A different improvement of the fatigue strength was found, i.e. a different effectiveness of the treatment for different notch geometries: the more critical notches received the larger beneficial effect by shot peening treatment in terms of reduction of the notch fatigue sensitivity and increment of the notch fatigue strength. The fatigue improvements with respect to the unpeened condition were discussed accounting for the residual stress effects. The residual stress field ahead of the notch root was evaluated by means of a numerical technique, making use of XRD measurements on the plain peened specimens. The numerical predictions were then compared with the results of XRD measurements conducted in the vicinity of the notch root of the peened notched samples.