Application of Phased Array Ultrasonic Transducers for Guided Wave Scanning of Plates Using Multi-point Focusing Technique

Ultrasonic guided waves are extensively used for evaluation of thin structures in different applications. At low frequencies, the non-dispersive modes are often employed to simplify interpretation. However, the evaluation needs to be performed at high frequencies to reach high sensitivity and high probability of detection (POD). Using phased array technology for guided wave evaluation provides the advantages of multi-element phased array transducers and firing control of the elements. However, the optimal setup parameters based on the selected mode and frequency need to be used. In this study, an innovative experimental approach is presented to optimize the phased array setup parameters and enhance the guided wave signals. The received guided wave signals is then employed for detection of surface and in-depth defects, using phased array sectorial scanning. Using a 5 MHz PA transducer, guided wave modes is generated in a 0.63 mm thick steel plate. Along with the experiments, finite element simulation is performed to study the behavior of the propagated guided wave modes in the steel plate. Multi-point focusing technique is employed in sectorial scanning for detection of surface and in-depth defects. The experiments show the guided wave modes can be generated using commercially available phased array ultrasonic systems through setting up the phased array parameters. The POD study demonstrated the selected wave mode detects surface and in-depth defect as small as 2 mm diameter.