Guided Wave Testing

Guided waves can propagate long distances in thin-walled structures, such as pipelines or plates. This allows for the efficient monitoring and testing of large structures and for the detection of hidden or inaccessible defects. Guided wave propagation is dispersive and multi-modal, requiring a thorough understanding of the wave propagation and scattering phenomena from simulations. Guided wave dispersion diagrams, mode shapes, and typical signals are illustrated for the example of isotropic plates. Both low and high frequency guided waves have been used for the testing of plate structures, with different wave modes and applications including tomography and arrays for the detection and localization of defects. For multilayered and anisotropic structures, guided wave propagation becomes more complex, and often the fundamental guided wave modes are employed for defect detection. For pipelines different commercially available testing systems have been developed and long propagation distances up to 100 m have been achieved. Careful selection of guided wave mode and excitation frequency allows the minimization of attenuation due to viscoelastic coatings and in buried pipelines. Synthetic focusing using non-axisymmetric modes improves defect imaging and localization. Experimental methods differ from standard ultrasonic testing, as good control of the excited guided wave mode shape and signal are required to achieve improved sensitivity for small defects. In addition to contact piezoelectric transducers, electromagnetic and laser techniques allow for noncontact measurements. Finite Element Analysis is one of the numerical simulation techniques used to obtain a better understanding of guided wave testing and to improve defect characterization