2008 年 57 巻 7 号 p. 648-653
The effect of static and fatigue loading on the residual stress induced by laser peening has been investigated on the aluminum alloy JIS A2024-T3. X-ray diffraction was applied to laser-peened samples to measure surface residual stress before and after subjecting the sample to static tensile or fatigue loading. Plastic deformation of the internal surfaces before and after loading was evaluated from the diffraction peak width associated with the loading. During static tensile loading, the interior of the sample started to deform plastically due to the superposition of external loading and residual tensile stress that compensated for the surface compression by laser peening; this resulted in the relaxation of the surface residual stress after unloading. In the case of fatigue loading, the residual stress on the surface was relaxed during the first loading cycle due to the same mechanism as that observed in the static tensile loading. The degree of the relaxation could be estimated taking the results of the static loading into account. Significant further relaxation was not observed after the first cycle until just before the final fracture.