Corrosion Monitoring of Airframe Structures Using Ultrasonic Arrays and Guided Waves

Guided Lamb waves offer important inspection potential due to the range of available propagating wave modes. Compared to localized conventional point‐by‐point ultrasonic wave testing, they can be launched over long distances where larger and non accessible areas can be inspected using single pulse excitation. In this work, Lamb modes are excited using 2D linear array probes to detect corrosion/cracks in airframe‐like structures. A Lamb wave phase velocity variation technique was developed to evaluate material thinning caused by corrosion. First order antisymmetric At mode was used in a substantially dispersive region, yielding important phase velocity variation to characterize corrosion. To simplify phase variation calculations, we assumed either no mode conversion or a complete mode conversion occurring from mode interaction with defects. For defect separation, results were averaged and images were reconstructed using synthetic artificial focusing technique.