Yang S., Li B., Cheng J.

The guided wave measurement gives an estimation of the defects over a long distance in the pipe; therefore, the guided wave is usable for long pipe monitoring. In this paper, we propose an approach using the angle beam transducer to generate the L(0,3) mode of the guided wave in the aluminum test pipe. The angle beam transducers with a 36.6 degree incident angle excited by a tone burst of 2 MHz are used in our experiment. Experiments are carried out for estimating the defect size by measuring the group velocity and time delay of the echoes. The relationship between the group velocity and pipe thickness is shown in the dispersion curve distinctly. The time delay and group velocity changes of L(0,3) mode are measured for the pipe without and with various defects. The results show that the deeper defect induced the faster group velocity. In addition, the wider defect causes a longer time delay of the signal. From the results obtained in this study, we can quantitatively determine the severity of the defects using guided wave along the pipe.