NARROW-BAND HYBRID PULSED-LASER EMAT SYSTEM FOR NONCONTACT ULTRASONICINSPECTION USING ANGLED SHEAR-WAVES

Angled, shear wave ultrasonic testing using piezoelectric transducers has been used in industry for years to inspect the plate welds of stee l vessels. This method's reliance on viscous surface couplants limits its reproducibility as well as its applicability for testing surfaces at elevated temperatures. In this work, a pulsed laser/meander line EM AT (electromagnetic acoustic transducer) system was demonstrated to pe rform testing using vertically polarized, angled, shear waves. This ca pability was augmented with a narrow-bandwidth laser excitation techni que to increase signal-to-noise ratio. The system was tested on both a luminum and steel plates containing saw cuts to mimic cracks. Finally, a steel weld specimen with known defects was tested with good results .