DIRECTIVITY PATTERNS OF A MOVING THERMOELASTIC SOURCE IN SOLID MEDIA

Generation of ultrasonic displacements under thermoelastic effect has the advantage to be contactless and nondestructive. Unfortunately, directivity and energy of the sound field of such a source are limited. In order to change these parameters we use a moving thermoelastic source by moving the laser beam on the solid surface. Moving the laser beam allows to control the ultrasonic beam directivity and to increase the energy of the sound field. For this purpose, a large impulse dye laser deflected by an acousto-optic cell working under the Bragg mode is used. Experimental results in an aluminum sample give good agreement with the theoretical prediction.