Absorption measurements on creep damaged samples using the reverberation technique

Ultasonic absorption measurements have been performed on creep damaged samples using the reverberation technique by laser ultrasonics. The materials investigated were low alloy ferritic steels widely used for piping systems in fossil plants. The experiments show that the absorption increases with increased creep damage. It is interpreted that this behaviour follows the altered dislocation structure that leads to a larger contribution to the dislocation damping. During the experiments an oscillation behaviour of the reverberation signals was observed which was not yet reported previously. This paper also presents some additional experiments performed at different materials to investigate this oscillation behaviour