The effects of multiple re-shot peening on fretting fatigue behavior of Al7075-T6

Fretting fatigue is a consequence of small oscillatory movement between two contacting parts. This type of damage may give rise to significant reduction in fatigue life of the components. The resistance of materials against fretting fatigue can be improved by surface treatment such as shot-peening. In this work, the effect of multiple re-shot peening on resistance of Al7075-T6 against fretting fatigue was investigated. After each re-shot peening, the specimen was subjected to 80% of the fatigue life corresponding to the cycles to failure of the specimen after re-shot peening. This process continued until the effect of any further re-shot peening became insignificant. The results showed almost a 100% enhancement in fatigue life for the first re-shot peening. The enhancement, however, reduced logarithmically for the next re-shot peenings such that for the 4th re-shot peening the increase of fatigue life fell below 2% which was negligible. On the whole, the fretting fatigue life increased by 600% after shot peening and 4 times re-shot peenings.