Diagnostic lamb waves in an integrated piezoelectric sensor/actuator plate: Analytical and experimental studies

The objective of this study is to model the diagnostic transient waves in an integrated piezoelectric sensor/actuator plate with a view as a first step to establish an entire structural health monitoring system and to provide experimental verification to the proposed models. PZT ceramic disks are surface mounted on an aluminum plate acting as both actuators and sensors to generate and collect A₀ mode Lamb waves. Mindlin's plate theory is adopted to model the propagating waves by taking both transverse shear and rotary inertia effects into account. Actuator and sensor models are both proposed. The interaction between actuator and the host plate is modeled based on classical lamination theory. The converse piezoelectric effect of the actuator is treated as an equivalent bending moment applied to the host plate. The sensor is acted as a capacitor that converts the sensed strain change into voltage response. An analytical expression for the sensor output voltage in terms of the given input excitation signal is derived and then experimental work is performed to verify accuracy of the analytical model. Experimental results show that single mode Lamb waves in the plate can be successfully generated and collected through the integrated PZT disks. The experiment also shows that the predicted sensor output for both amplitude and phase agrees well with experimentally collected data.