Effect of Shot Peening on the Fatigue Life of AA 7050-T7451

Author:  Charles Bianchetti, Martin Lévesque, Myriam Brochu
Source:  ICSP-13
Doc ID:  2017072
Year of Publication:  2017
Introduction: Fatigue is a common cause of failure. A structure that undergoes fluctuating mechanical loadings becomes locally damaged. This weakness is caused by the nucleation and the growth of cracks at the microstructural scale. These cracks propagate until final fracture, when the material’s toughness is reached. Shot peening is a surface treatment well-known to increase fatigue life. This process consists in impinging shots at high velocity onto a metal surface. The impacts strengthens the structure by delaying the initiation and growth of cracks through the introduction of residual stress,local hardening, and grain distortion [1, 2]. However, shot peening also introduces surface deterioration, which may accelerate crack initiation and growth. Even if the shot peening process has an overall beneficial effect on fatigue life, a potential increase of fatigue dispersion exists due to the stochastics nature of the process. Moreover, process reliability and its influence on fatigue dispersion remain unreported in the literature. The project described herein involves aerospace companies, for which reliability is an important criteria. Therefore, a probability study of shot peening effect on the fatigue life of AA 7050-T7451 at two stress amplitudes was undertaken.

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