Characterization of Progressive Fatigue Damage in Solid Plates by Laser Ultrasonic Monitoring of Zero-Group-Velocity Lamb Modes

Abstract

Many engineered objects endure stress throughout their lifetimes, typically leading to material fatigue and failure, which can turn to tragedy, as in the Versailles rail accident of 1842. Thus quantitatively assessing the level of cumulative fatigue damage is of great interest in many contexts, and should promote our insight into the underlying physics at the several stages of fatigue. The authors find that the frequency of a particular surface-acoustic-wave elastic Lamb mode is a reliable indicator of the fatigue level in a thin metal film. This technique should also work for other systems in which these Lamb modes are observable, including alloys, composites, glasses, and polymers.