抄録
A second harmonic YAG laser beam collimated was irradiated on the surface of both ferritic and austenitic steel specimens with various peening conditions. The residual stresses on the laser irradiated surface and the depth profiles of residual stress near the surface of specimens were measured using a characteristic x-ray and a synchrotron radiation source. The microscopic residual stress distributions in the laser single pulse irradiated area and the laser single line irradiated area were also measured using synchrotron radiation in order to clarify the residual stress generation process. Compressive residual stresses are observed in the surface and inner part near the surface after the two dimensional laser peening process, which covers certain area by repeating the single line irradiation. The stress value depends on the scanning direction of laser peening, that is, the stress in the direction of laser scanning is smaller than that in the perpendicular direction. On the other hand, tensile residual stresses were observed in a laser single pulse irradiated area. The value of residual stress in surface gradually changed to the compression side, when the number of laser pulses per unit area or unit length was increased.
