Abstract
Extensional edge waves propagate along the edges of plates, with low attenuation in the propagation direction and amplitude decreasing rapidly (within one or two wavelengths) in the direction perpendicular to the plate edge. This makes them an ideal candidate for inspecting the edges of plate-like structures. Here, finite-element models and experiments are used to investigate the propagation and scattering of extensional edge waves in composite plates and application to damage detection is demonstrated. Piezoceramic transducers attached to the edge of a 4-mm-thick carbon-fibre-reinforced polymer (CFRP) plate were used to excite 140-kHz edge waves and damage detection demonstrated using two experimental configurations: pitch-catch and two-transducer pulse-echo. Damage due to edge-on impacts of 5 J and 10 J were detected in both configurations. A mass-addition damage model was used to investigate the effect of damage location. Detection was specific to damage within 33 mm (1.5 wavelengths) of the plate edge with propagation unaffected by features beyond that distance. The time of arrival of reflected signals in pulse-echo mode was accurately predicted using the edge-wave group velocity indicating that this configuration can be used for locating damage on edges. The localisation of edge waves means that they can specifically detect damage at the edges of structures, and attenuation measurements indicate that their useful propagation distance is large (5.5 m).
Highlights
IntroductionPropagating edge waves can have symmetric and antisymmetric (referring to the symmetry of the material motion through the thickness of the plate) modes of various orders in a manner similar to Lamb waves in plates
Propagating edge waves can have symmetric and antisymmetric modes of various orders in a manner similar to Lamb waves in plates
The following results start with comparison of the predicted group-velocity dispersion curves with those obtained experimentally to ensure that the correct mode is detected (Sect. 5.1). This is followed by numerical prediction of the shape of the edge wave and its penetration depth in the carbon-fibre-reinforced polymer (CFRP) sample (Sect. 5.2)
Summary
Propagating edge waves can have symmetric and antisymmetric (referring to the symmetry of the material motion through the thickness of the plate) modes of various orders in a manner similar to Lamb waves in plates. At low frequencies only the zeroth-order modes are present and, as the ratio of thickness to wavelength tends to zero, they become the thin-plate extensional edge waves and flexural edge waves, respectively. In each case the wave propagates in the positive x-direction (parallel to the plate edge) with elliptical motion in the x y-plane that decreases with increasing distance, y, from the edge
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