Converting Lamb modes into shear horizontal waves using a resonance-based metamaterial

In this paper, an elastic metamaterial is presented to achieve complete conversion from Lamb modes into the fundamental shear horizontal mode. Modal analysis with Bloch-Floquet boundary condition is performed to obtain the dispersion features of the metamaterial system. By analyzing the resonant modes of the unit cell, a complete SH0 mode generation band within the A0 and S0 modes bandgap can be formed in a wide frequency range. Thereafter, finite element model (FEM) harmonic analyses for an elastic metamaterial plate are carried out to explore the mode conversion efficiency. Finally, a coupled field transient dynamic FEM is constructed to acquire the response of the structure. A 30- count tone burst incident wave containing both A0 and S0 modes is excited to propagate into the elastic metamaterial system. The frequency-wavenumber analysis results demonstrate the achievement of the mode conversion behavior, manifested by the strong coupling between guided waves and resonant modes of the composite stubs. The proposed mode conversion behavior may possess great potential in future Structural Health Monitoring (SHM) and Nondestructive Evaluation (NDE) applications. The paper finishes with summary, concluding remarks, and suggestions for future work.