High-resolution 3D ultrasonic phased array imaging with 1024-element matrix array transducers for nondestructive evaluation

Ultrasonic phased array (PA) has been widely used for nondestructive evaluation (NDE) in industrial fields. Most PAs employ linear array transducers, producing 2-D images. On the other hand, actual defects can have complex 3-D geometries. Although the use of a 2-D matrix array transducer for 3-D imaging is promising, the number of 2-D matrix array transducers has been limited to 256 or less for NDE applications. The state-of-the-art studies for medical ultrasonics have used 1024-element 2-D matrix array transducers, whereas an appropriate design of a 2-D matrix array transducer for NDE applications differs from that for medical applications because of the difference in diagnosed objects and scattering behaviors. On the other hand, we have developed a high-resolution 3-D imaging method based on the piezoelectric monolithic transmitter and 2-D laser scanning receiver, which is referred to as piezoelectric laser ultrasonic system (PLUS). However, the long acquisition time makes it less pragmatic in a way. In this study, we developed a real-time, high-resolution 3-D PA imaging method by fabricating a 1024-element array transducer dedicated to NDE. We first designed the array transducer using a 3-D numerical simulation and experimental 3-D scattering analysis. Based on the designs, we fabricated 1024-element piezoelectric array transducers. They were applied to metallic samples with internal defects. We will show some high-resolution 3-D imaging results of defects obtained by the 1024ch PA system.