On the Excitation of Time Harmonic Cylindrical Surface Acoustic Waves

Abstract

Reciprocity theorem is used to study the excitation of time harmonic cylindrical surface acoustic waves in a semi-infinite isotropic medium. Excitations by point and partial ring sources with applica- tions to laser generated ultrasound are investigated. It is verified that the ablation and thermoelastic cylindrical SAW signals in a CW op- eration are 180 out of phase provided that the sources of excitation are in phase. Asymptotic expressions for acoustic fields, excited by par- tial ring sources, near and far from the ring center are calculated. The asymptotic solutions show that far from the focal region, the fields are essentially converging, diverging, or standing waves. Furthermore, it is established that there is a 90 phase difference between the converg- ing and diverging SAW's.