Crack Retardation of Damage Through Enhanced Crack Closure Effect Induced by Laser Peening

Abstract

The effect of laser peening (LP) on damage is of great significance to recover the service life of damaged material. However, it is still unclear for the reason behind to introduce this effect by high-dynamic loading of LP. In this study, experiments are conducted to investigate the retardation of pre-crack growth by LP treatment. Pre-cracks fabricated by cyclic loading are introduced on CT specimens of aluminum alloy 2024-T351 to act as initial fatigue crack damage. LP treatment is performed to cover the specimen surface with pre-crack. Fatigue crack propagation (FCP) experiments are conducted to demonstrate the crack retardation effect following LP treatment. Digital image correlation (DIC) method is also employed to obtain the full field displacement around the crack tip to evaluate the enhancement of crack closure level behind pre-crack tip. The results show that crack arrest and retardation and hence a significant fatigue life promotion are observed for the pre-cracked specimen with LP treatment. It even sustains more loading cycles than the undamaged specimen with LP treatment. DIC analysis reveals that the immediate enhancement of crack closure level is introduced behind the crack tip due to high-dynamic loading of LP treatment. Plastic deformation produced by the high dynamic loading of LP, is possibly dominant to introduce crack retardation behind the pre-crack tip.