Experimental Analysis on the Influence of Supports in Performing Pipes Inspection Using Longitudinal Guided Waves

In the last decades, have been investigated guided waves in pipes, due mainly to their capacity of traveling long distances without substantial attenuation. The long range propagation is however limited, among other causes, by the unavoidable pipe supports. These mechanical structures are supporting the pipe weight and reduce its vibrations. Along a certain length, of several centimeters for small diameter pipes, up to tens of centimeters larger diameters, the pipe is in contact with other structures. For small diameters pipes, especially used in aeronautical industry, a rubber circular layer is placed between the pipe and the metallic support. These supports are reducing the guided waves energy sent through the pipe for inspection purposes. For a particular type of support, the resulting amplitudes of the scattered waves can be obtained as function of frequency. In this paper, a particular ultrasonic signal is sent from one end of the pipe and reflected signals are measured. Comparisons of experimental values with numerical simulations are presented and an acceptable agreement was obtained. These are only preliminary results obtained in our laboratory and further work is necessary to include more parameters in the study and obtain individual mode contribution to the scattered field.