Abstract
A method for fatigue damage evaluation was investigated to detect fatigue damage and estimate fatigue life of steels with optical method using laser. In fatigue of mild steels, fatigue damage occurs from material surface, slipbands appear anddensity of the slipbands increases with progress of fatigue damage. In this method, surface change due to slipbands is detected by change in light intensity distribution of diffusion pattern of the reflected laser light from surface of the fatigued steel. Using this method, we are able to detect fatigue damage before crack initiation by observing difiusion pattern change, In this study, we investigated relation between change of difiusion pattern and number of loading cycles and we devised a method to estimate fatigue life of the object material by observing change of the diffusion patterns during fatigue loading.
