Abstract
Laser peening is an emerging surface technology to enhance fatigue properties of metallic materials through imparting compressive residual stress on the surface. Samples of AC4CH cast aluminum alloy were peened with a Q-switched and frequency-doubled Nd:YAG laser. Compressive residual stress was introduced from the surface to the depth of 1mm or deeper. High-cycle fatigue testing by rotating-bending was performed for samples with and without laser peening. In order to visualize fatigue cracks in the samples, computed tomography (CT) was attempted with high-energy synchrotron radiation of SPring-8. Three-dimensional (3D) images of the fatigue cracks were clearly reconstructed by CT with phase contrast effect. The image of a crack in an unpeened sample was obviously larger than that in a laser-peened sample, which strongly suggested that laser peening had retarded the fatigue crack propagation.
