INVESTIGATION OF ULTRASONIC TRANSDUCERS USING OPTICAL TECHNIQUES

Laser interferometry and laser-generated ultrasound have been applied to the calibration of contact transducers which are used to detect defects in solids by angled shear-waves. It was found that laser interferometry could readily be used to image the two-dimensional beam generated by each transducer, while laser-generated ultrasound could test its performance as an ultrasonic receiver. The ultrasonic waveforms were also recorded and analysed. The results of optical calibration were compared with traditional methods, i.e. calibration block and water tank. There was good overall agreement. It was confirmed that the refractive index correction which is applied to water tank beam plots is a valid method for predicting the beam in a solid such as aluminum. All the probes and shoes performed satisfactorily and radiated beams with well-defined profile even at the edge of the near-field. There was no evidence of significant side lobes or surface waves.