NONCONTACT OPTICAL-FIBER PHASED-ARRAY GENERATION OF ULTRASOUND FOR NONDESTRUCTIVE EVALUATION OF MATERIALS AND PROCESSES

The use of non-contact laser techniques for the generation of ultrasou nd has extended the limits of the application of traditional ultrasoni c techniques. This paper focusses on the use of one such non-contact l aser technique, know as 'optical fibre array, to generate shear and su rface waves. The shear wave experimental directivity pattern results a re presented and compared with the theoretical results of a single sou rce and an array source. The experimental directivity results for the surface wave are also presented, and compared with the theoretical res ults. The data show that the array enhances signal generation in the f orward direction for both shear and surface waves. The array gain is a lso discussed. The receiver for the directivity measurements was a con tact piezoelectric transducer.