Abstract
We investigated a method to evaluate fatigue damage of steels with optical method by detecting surface change caused by fatigue. In the earlier stage of fatigue in a low-carbon steel, slipbands appear on the specimen surface and then density of the slipbands increases with progress of fatigue damage. When a laser illuminates surface of the fatigued steel, light intensity distribution of the diffusion pattern of the reflected light changes with the change of surface properties caused by slipbands. Using this method, we are able to detect fatigue damage before crack initiation by observing diffusion pattern change during fatigue test. In this study, we investigated relation between change of surface properties and diffusion pattern. We also investigated a method to estimate fatigue life of the object material by observing change of the diffusion patterns during fatigue loading.
