Ultrasonic guided wave detection of U-shaped pipeline

The guided waves in the elbow was analyzed using semi- analytical finite element method, which was used to calculate the dispersion curves, along with the vibration deformation and energy flow density distribution of the elbow cross-section. The L(0,1) mode guided wave was used to detect different defects in the U-shaped pipeline in experiment. The average experimental velocity of L(0,1) mode in U-shaped pipeline was between the theoretical velocities of the straight pipe and the elbow, due to the different velocities in the two parts. The detection sensitivity difference of L(0,1) mode guided wave to defects in intrados and extrados of the elbow was analyzed, the experimental result showed that the reflected signal amplitude of defect in extrados was significantly larger than the defect in intrados, which was consistent with the energy flow density distribution in elbow cross-section.