DEFECT DETECTION IN PLATE STRUCTURES USING COUPLED RAYLEIGH-LIKE WAVES

The use of coupled Rayleigh-like waves has been investigated for the nondestructive inspection of aircraft structures. Rayleigh-like waves transfer energy between the plate surfaces and have good sensitivity for the detection and localization of small defects on both surfaces. The beating phenomenon allows for the remote detection of defects in areas where access is restricted by structural features, such as stiffeners and stringers. By selecting appropriate excitation frequency and position, a significant part of the energy can be transmitted past the obstacles and reflected at the defect, allowing detection. This has been shown experimentally and verified from numerical Finite Difference simulations, where surface slots were detected behind multiple stiffeners from standard pulse-echo measurements using angle-beam transducers.