Transmission of Lamb waves and resonance at an adhesive butt joint of plates

Abstract

The transmission behavior of Lamb waves and the possible occurrence of resonance at an adhesive butt joint of plates are studied experimentally. To this purpose, two 2.5-mm thick aluminum alloy plates are bonded at their edges using cyanoacrylate-based adhesive. Bonded plate specimens with different joint conditions are prepared by changing the bonding procedure. The measurements are performed for the transmission characteristics of the lowest-order symmetric (S0) and antisymmetric (A0) Lamb modes for the frequency range of 0.4-0.6MHz below the cut-off frequency of the higher-order modes. The experimental results show that the transmission coefficients of the S0 and A0 modes exhibit different frequency-dependent characteristics depending on the joint condition. Furthermore, for the incidence of the S0 mode at the center frequency of 1MHz, the transmitted S0 mode in weakly bonded specimens shows a long oscillation tail due to the resonance effect. The experimental results are discussed in the light of the theoretical results based on the spring-type interface model. The interfacial stiffnesses identified from the transmission coefficients are shown to be correlated with the bonding condition of the joint and give reasonable estimates of the resonance frequencies of weakly bonded specimens.

Harmonic Generation at a Nonlinear Imperfect Joint of Plates by the S0 Lamb Wave Incidence

“…To this purpose, the imperfect joint is modeled as a nonlinear spring-type interface, which expresses interfacial stresses as functions of the displacement gaps [34,35]. The interaction of Lamb waves with a linear spring-type interface has been reported in the previous papers [36][37][38][39]. Recently, the second-harmonic generation behavior for the incidence of the lowest-order symmetric (S0) Lamb wave has been shown by the perturbation analysis in the frequency domain using the hybrid finite element method (HFEM) [40].…”

Transmission characteristics of the S0 and A0 Lamb waves at contacting edges of plates

“…The method for the measurement of the transmission coefficients of the S0 and A0 Lamb modes has been described in Ref. [18] where it was applied to adhesive butt joints of aluminum alloy plates of the same size as those used here. As schematically shown in Fig.…”

“…A Gaussian-modulated tone-burst signal with the center frequency of 0.5 MHz was used to excite the emitting transducer. The wedge angle θ was chosen in order to excite and detect a particular Lamb mode dominantly, i.e., θ = 30 deg and θ = 60 deg for the incidence of the S0 and A0 modes, respectively [18].…”

“…Furthermore, Mori and Biwa [17] showed that the imperfect joint of plates exhibits resonance for the S0 mode incidence at two frequencies which depend on the interfacial stiffnesses. Based on these theoretical findings, the transmission of Lamb waves and the resonance at butt-type adhesive joints of plates were investigated experimentally [18]. It is also of high interest to examine the corresponding behavior at a butt-type contacting interface of plates as it can represent the local interaction of Lamb waves with a closed crack.…”

Damage Imaging in Lamb Wave-Based Inspection of Adhesive Joints

“…The ability of Lamb waves to interact with any kind of defect makes them particularly useful in the diagnostics of various elements of engineering structures, including adhesive joints. In previous studies, guided waves have been proven to be an effective technique for the inspection of adhesive lap joints [15][16][17][18], adhesive bonds between composites [19][20][21], adhesive butt joins of plates [22], or the detectability of the adhesion level [23].…”