Development of a divided-ring array for three-dimensional beam steering in ultrasonic nondestructive testing - theoretical and experimental results of a prototype

This paper focuses on a newly developed device based on a 2 MHz divided-ring array for nondestructive testing (NDT) application with two rings, 48 elements, and an aperture of 30 mm. With this array, it is possible to steer an ultrasound beam three-dimensionally in space within a range of +- 45 degrees (longitudinal-wave excitation) and +- 30-70 degrees (shear-wave excitation). Computations of the directivity pattern, the process of the theoretical optimization, experiments, and a defect reconstruction will be described. One example of a defect reconstruction has been performed representatively, illustrating that the image quality of the first prototype is improved when compared to linear array images because of the higher lateral resolution in elevation direction. (-z-)