Relaxation behaviour of laser peening residual stress due to mechanical loading on aluminum alloy

Miyashita, Daisuke*; Takeda, Kazuya*; Oya, Shinichi*; Sano, Yuji*; Saito, Toshiyuki*; Akita, Koichi

The surface residual stress relaxation under tensile loading occurred when the plastic-deformation started at the inside of material where the balancing tensile residual stress existed. Under the compressive loading, the surface residual stress relaxation started due to the plastic deformation beneath the surface where the maximum compressive residual stress existed. The plastic deformation at the inside of material caused the redistribution of the residual stress and resulted in the relaxation of the surface residual stress. For both tensile and compressive loading, the surface compressive residual stress relaxation occurred before the total stress (= (residual stress) + (applied stress)) at the surface reached to the yield condition. The conclusions of this study are thought to be able to apply to the behavior of the residual stress under the mechanical loading on metallic materials treated by any mechanical surface treatment.