Simulation of the Lamb wave interaction between piezoelectric wafer active sensors and host structure

Piezoelectric wafer active sensors (PWAS) are small, inexpensive, unobtrusive devices capable of generating and detecting Lamb waves in thin-wall structures. PWAS are directly attached to the surface of a metallic structure or inserted between the layers of a composite structure. PWAS interact with the structure through surface shear stresses that couple the in-plane motion of the PWAS with the in-plane motion of the structure undergoing Lamb wave motion. The paper will present a simulation of the Lamb wave interaction between PWAS and host structure using analytical solutions in axisymmetric formulation. The Bessel function solutions are used to model the Lamb waves emanating from the PWAS. The time domain Fourier transform is used to process the excitation signal into its frequency components. The frequency domain excitation is used to modulate the Fourier transform of the Bessel function solution in the frequency domain. Inverse Fourier transform is used to return from the frequency domain in to the time domain. Simulations will be presented for symmetric and antisymmetric Lamb-wave modes at various frequencies and mode numbers. The influence of the mode number and frequencies upon the efficiency of the Lamb wave interaction between PWAS and host structure is studied and exemplified with numerical solutions and visualizations. Experiments on different kind PWAS and plate material, thickness, and dimension, will be illustrated and compared with the simulations. It will be shown that the experimental data are in good agreement with the theoretical values. The aim of the paper will be then to evidence that the illustrated method is able to predict the Lamb-wave tuning with PWAS transducers in different structures.