Dispersion Curve Extraction of Lamb Waves in Metallic Plates by Matrix Pencil Method

Lamb wave dispersion curves for isotropic plates are extracted from measured sensor data by matrix pencil (MP) method. A piezoelectric wafer emits a linear chirp signal as broadband excitation to generate Lamb waves in metallic plates. The propagating waves are measured at discrete locations along a wave ray direction with a sensor 1-D laser Doppler vibrometer (LDV). The out-of-plane velocities are first Fourier transformed into either space-frequency x-omega domain or wavenumber-time k-t domain. The matrix pencil method is then employed to extract the dispersion curves for various wave modes simultaneously. In addition, the phase and group velocity dispersion curves are deduced by the relation between wavenumber and frequency. In this research, the inspections for dispersion relations on isotropic plates are demonstrated and compared by two-dimensional Fourier transform (2-D FFT) and MP method. The results are confirmed by theoretical curves computed numerically. It has demonstrated that the MP method is robust in recognining/differentiating different wave modes, including higher order ones.