Transmission detection of internal defects in billets using shear ultrasonic waves

Abstract

We used ultrasonic shear waves for nondestructive defect detection in a billet using transmitted waves. We utilized the deviation the time-of-flight (TOF) obtained by cross-correlation of transmitted waves of a defect-free reference plane and that of a measurement plane containing a defect. We compared the performance of longitudinal waves and shear waves at different wavelengths in detecting the diameter of a circular defect in two-dimensional (2D) simulation and the TOF for a cylindrical defect while changing the vibration direction of shear waves in three-dimensional (3D) simulation. Shear waves detected defects better than longitudinal waves in the 2D simulation, especially at wavelengths of 1.4–2.4 mm. In the 3D simulation, the maximum TOF was larger when the vibration direction was perpendicular to the defect’s major axis than when it was parallel in the measurement using shear waves. This suggests a defect’s shape can be estimated by measurement using shear waves.