Laser Ultrasonics in Cylindrical Rods and Fibers

Cylindrical parts are widely used in industry at very different scales from rotating axis for engines to carbon fibres used in composite materials. Consequently, an increasing demand exists for their nondestructive evaluation. The laser ultrasonics technique providing a non-contact generation and detection process is suited for the study of acoustic waves in cylindrical structures. In previous works, cylinders with a size in the millimetre range have been studied. In this paper, first results obtained on a tungsten micrometric fibre thanks to a pump-probe femtosecond laser technique are presented. Experiments are compared to a two-dimension model for acoustic waves generation and propagation in cylinders taking light penetration depth into account.