Shear-wave focusing and beam steering by a thermoelastic source array: application to nondestructive testing

A phased array of 16 thermoelastic line sources has been implemented to focus shear-waves by time delaying the laser generated ultrasound pulses. The focusing parameters have been optimized by computations. Directivity patterns of the array have been probed on a duraluminum sample by using a piezoelectric transducer. The shear-beam characteristics versus the focusing direction are discussed. Two applications of nondestructive testing are presented. A hole is detected by a transducer by scanning a duraluminum sample with the narrow shear-beam. The same kind of defect is located by an optical probe by analysing the transmitted shear-beam diffracted by the hole