Laser–ultrasonic absorption measurements in low carbon steels

Ultrasonic resonance measurements were performed on interstitial-free and commercial carbon steels subjected to plastic deformation. Specimens had a trapped-mode cylindrical geometry which localized resonant vibrations and minimized acoustic losses into the grips of a mechanical testing machine that was attached to the ends of the specimens. Deformation induced an increase in Q-1 and a corresponding decrease in velocity that partially recovered with time. The frequency dependence and relative magnitude of velocity changes during recovery are found to be inconsistent with a single Debye form of the GranatoLücke overdamped dislocation model. A distribution of Debye functions arising from a random distribution of pinning points also fails to explain the experimental results.