Wave energy trapping and localization in a plate with a delamination

Abstract

The research aims at an experimental approval of the trapping mode effect theoretically predicted for an elastic plate-like structure with a horizontal crack. The effect is featured by a sharp capture of incident wave energy at certain resonance frequencies with its localization between the crack and plate surfaces in the form of energy vortices yielding long-enduring standing waves. The trapping modes are eigensolutions of the related diffraction problem associated with nearly real complex points of its discrete frequency spectrum. To detect such resonance motion, a laser vibrometer based system has been employed for the acquisition and appropriate visualization of piezoelectrically actuated out-of-plane surface motion of a two-layer aluminum plate with an artificial strip-like delamination. The measurements at resonance and off-resonance frequencies have revealed a time-harmonic oscillation of good quality above the delamination in the resonance case. It lasts for a long time after the scattered waves have left that area. The measured frequency of the trapped standing-wave oscillation is in a good agreement with that predicted using the integral equation based mathematical model.

Laminate Element Method and Its Application to the Study of Guided Wave Resonance Phenomena in Layered Elastic Structures With Defects

“…Examples of such localization are shown in Fig. 3 Analytically based simulation In the transient GW diffraction, natural frequenciesf n pronounce themselves with prolonged oscillations being localized at the obstacle region (trapping modes) [6]. The duration of such motion depends on the imaginary part of the corresponding eigenfrequency δ n = 2πImf n through the factor exp(−δ n t).…”

“…The resonance trapping mode effect [5] is featured by the capturing of incident wave energy and its prolonged localization in the defect's vicinity in the form of weakly decaying oscillations at the resonance frequencies [6]. The latter coincide with the spectral points of the corresponding boundary value problem (BVP) in the complex frequency plane.…”

Continuous wavelet transform application in diagnostics of piezoelectric wafer active sensors

“…At the same time Figure 5 reveals that the amplitude of the debonded actuator on the central frequency f 0 = 180 kHz is higher in comparison with fully glued PWAS. We think that it is caused by standing waves near resonance frequencies f n of the debonded PWAS, when the signal is trapped in the PWAS similar to the case of a crack [9].…”

Impact induced delamination detection and quantification with guided wavefield analysis

“…When guided waves propagate in a delaminated composite, multiple reflections within the delamination region can occur, as shown in references [18,[22][23][24][25]. Hence, a considerable amount of ultrasonic energy is "trapped" above and below the delaminated region until eventually the energy dissipates.…”