Variation in Fatigue Property and Life Prediction for Curved Component of AA 7075-T651 Aluminum Alloy During Damage-Healing Process by Laser Shock Peening

A healing method for fatigue damage was investigated by laser shock treatment with a Nd:YAG nanosecond laser shock device for AA 7075-T651 aluminum alloy. It was found that a stable residual compressive stress field was generated by the improved laser parameters, and this stable residual compressive stress field could be responsible for the improvement in the total fatigue life of the damaged curved structural specimen due to the improved laser treatment. Further analysis is gained from the fracture morphology, and it is concluded that the fatigue crack initiation and early propagation at the notch root may be effectively delayed for the damaged curved specimen by the improved laser treatment. Based on a proposed equivalent stress concentration factor Kteq, a total fatigue life prediction method is established during the damage-healing process for the curved structural specimen manufactured from AA 7075-T651 aluminum alloy. The predicted lives by the proposed method agree well with the experimental results.