Measurement of near-surface ultrasonic absorption by thermo-emissivity

It is generally recognized that ultrasonic absorption, i.e. the relaxation of mechanical energy into heat is related to mechanical properties for several materials. In particular, in polycrystalline metals and within the frequency range generally used in ultrasonic testing, absorption is mainly caused by thermoelastic losses, inter-granularthermal currents, magnetic domain wall motion, the relaxation of interstitials and the interaction with dislocations.1,2 Among these different mechanisms, the last three can be related (to a variable extent) to the strength of the metal and its state of stress or fatigue.Peer reviewed: YesNRC publication: Ye