Recent Advancements in Global-Local Analysis of UGW in Plates

The use of ultrasonic guided waves (UGWs) has increased considerably for NDE and SHM purposes. Analytical solutions are available for few cases only, namely for waveguides of uniform cross-section and in the presence of simple defects. For more complex structural configurations, materials or defects, numerical methods are indispensable. A good compromise is coupling analytical solutions with numerical methods, as in the proposed hybrid Global-Local (GL) method. An eigenvalue problem in the framework of the Semi Analytical Finite Element method (SAFE) is posed to solve for the complex wavenumber and wavemodes, that are then propagated analytically in the wave propagation direction. To include scattering and wave propagation from the UGW interaction with geometrical discontinuities, damages, and any changes along the wave propagation direction, SAFE is coupled with other computational approaches such as full FEM in this work. The complexity of UGW scattering is increased by the presence of propagating and non-propagating modes, the latter becoming significant in the near-field effects, i.e. in the vicinity of defect edges. This work shows the advantages of including the evanescent modes in the accurate modeling of UGWs scattering through applications on isotropic aluminum plates.