Erosion/corrosion monitoring with dry contact ultrasonic lamb wave transducers

We propose a novel technique that utilizes point source excitation-and detection of Lamb waves through dry, elastic contacts to monitor thickness changes of plate-like structures. A pair of pin transducers ate used to excite and detect the Ao made Lamb wave in a test plate or a pipe wall and the wave velocity is obtained by time of flight measurement. Any change in plate thickness can be detected by the change in the Lamb wave velocity due to the dispersive nature of the Ao mode. Pie demonstrate the power of this approach in ultrasonic pipe erosion/corrosion monitoring and its potential application in aircraft skin defect imaging. We present results of thickness measurements of a test plate with 1% accuracy, and erosion/corrosion monitoring in a section of pipe that was removed from service, as well as imaging of defects in an aluminum thin plate.