LONGITUDINAL-WAVE GENERATION IN LASER ULTRASONICS

The purpose of this work is to conduct a detailed investigation of wav e generation by thermal dipoles in laser-generated ultrasound. A simpl ified description of ultrasound generation is used to provide a clear explanation as to how longitudinal waves are generated by thermal dipo les. The effects of the shape and time dependence of the temperature d istribution on the waveforms are illustrated. Studies such as this are needed in order to explain the shapes of laser-generated ultrasound w aves for nondestructive materials testing, and to enable researchers t o select optimum laser pulse parameters for specific applications. fn particular, this work identifies the physical origins of the precursor . (C) 1998 Elsevier Science B.V.