Relaxation Behaviour of Laser Peening Residual Stress due to Mechanical Loading on Aluminum Alloy

Abstract

The relaxation behavior of residual stress induced by laser peening during mechanical loading was investigated on an aluminum alloy A2024. The residual stress relaxation process was measured by x-ray diffraction method and analyzed by a finite element method (FEM). The plastic deformation behavior was evaluated from the x-ray diffraction peak width and the FEM. 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 the yield condition. All discussions in this study based on the mechanical deformation behaviour of the material. Therefore, 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.