Multimodal nature of edge waves in thick plates and shells and their potential applications in non-destructive testing: theory and experimental verification

Wilde, Maria; Saratov State University; Russian Federation

Wilde, M.V.; Saratov State University; Russia
Eremin, A.A.; Kuban State University; Russia
Golub, M.V.; Kuban State University; Russia

ID: ECNDT-0303-2018
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Session: Modelling & data processing - Guided Waves
Room: J2
Date: 2018-06-13
Time: 14:30 - 14:50

Surface elastic waves, first predicted theoretically by Rayleigh in 1885, are widely used in non-destructive testing (NDT). Analogous phenomena described by 2D theories of thin plates are edge waves (EW) guided by the edge of a plate. They are studied since the 1950s, but only in the recent studies on the basis of 3D elastodynamic theory the multimodal nature of EW is revealed. Similar to Lamb waves, there are fundamental edge modes and higher order ones. The latter have wide range of potential applications for the purposes of NDT since they allow detecting defects much smaller than the thickness of a plate and existing in practically all possible cases of boundary conditions on the faces. The intention of the present talk is to review the theoretical results showing properties of fundamental and higher order EW which can be used in NDT and so establish the link between theory and practice. The results of recent studies concerning multimodal EW in shells will be also presented. All the studies are carried out on the basis of 3D linear elastodynamic theory. For the solution of corresponding boundary value problems the semi-analytical method is developed based on the normal modes expansion. In this method, all the relations are satisfied analytically except the boundary conditions on the edge for which the effective numerical procedure is proposed. For the case of a thick plate with free faces, the results of experimental verification are presented. The EW were excited in thick aluminium plate by a piezoelectric transducer and registered by scanning Laser Doppler vibrometer. Comparison of spectral properties and time-space wavefields of computed and measured signals show a good agreement between theory and experiment and confirm the multimodal nature of EW. The effective excitation and registration of higher order EW are discussed.