A phased array ultrasonic-based enhanced strategy of critically refracted longitudinal (LCR) wave technique

Conventional critically refracted longitudinal (LCR) wave technique seriously relies on the first critical angle (θCR), showing poor adaptability to the wave velocity variations of materials in defect and stress characterization. We propose an enhanced strategy based on the phased array ultrasonic, termed PA-LCR. Three typical beam profiles, deflection, focusing and their combination, are studied on the excitation of LCR wave. With one fixed wedge and time delay law, the wave can be excited within a wild angle range relative to θCR, about ±7° for −6 dB amplitude, and the adaptable longitudinal wave velocity is ranged about 6000 m/s. In addition, a calculation method of the LCR wave velocity is also proposed and verified.