On the Excitability of Zero-Group Velocity Lamb Modes Using Normal Mode Expansion Method

Abstract

This study employs the normal mode expansion (NME) method to investigate both symmetric and anti-symmetric zero-group velocity (ZGV) modes. Since a general loading case can always be decomposed into the superposition of the symmetric and anti-symmetric parts corresponding to the symmetric and anti-symmetric modes. The research considers a general loading case and the shear lag model for an adhesive bonding layer to calculate the amplitudes of the generated Lamb modes within and outside of the loading zone. By targeting symmetric (S-) and anti-symmetric (A-) type ZGV modes, the study uses exact analytical solutions and numerical results to validate the effectiveness of the model, ensuring a comprehensive understanding of the behavior of ZGV modes. The influence of the piezoelectric patches’ length on the excitability of S- and A-type ZGV modes is also examined. The length of the PZT is a significant factor in determining how effectively the energy can be captured by the targeted modes. Numerical simulations are conducted to observe the behavior of these modes outside the loading zone, providing a broader perspective on their dynamics. Additionally, the study utilizes 2D fast Fourier transform (2D-FFT) results to verify the resonance characteristics of the ZGV modes at the aiming frequency. These results are essential in confirming the theoretical predictions and understanding the practical implications of the ZGV modes. This approach offers valuable insights into the physical behavior of ZGV Lamb modes and their potential applications in various fields.