Experimental Phased Array Focusing in Pipe Using Ultrasonic Guided Waves

The phased array focusing technique is being developed with the intent to inspect hundreds of feet of pipeline from a single array position. The single array position is beneficial if access to a pipe is limited, e.g. steam pipes onboard U.S. Naval ships, nuclear power plants, oil and gas pipelines, etc. From a single array position, ultrasonic guided waves propagate down the length of the pipe and return information about potential defects. Focusing the ultrasonic energy at a predetermined location along the length of the pipe enhances the ability to detect defects that current state of the art inspection systems cannot detect. In this paper, theoretical time delays are used to focus torsional ultrasonic guided waves in the frequency ranges of 30 to 130 kHz and 200 to 800 kHz. Results of the focusing experiments are presented along with some concluding remarks and future work.