

Combining Guided Waves and Electromechanical Impedance Method for SHM Applications
Abstract
In this paper the simultaneous use of ultrasonic testing and impedance-based technique to monitor the health of waveguides is proposed. Methods based on the propagation of guided waves are increasingly used in all those structural health monitoring (SHM) applications that benefit from built-in transduction, moderately large inspection ranges, and high sensitivity to small flaws. In the meantime, impedance-based SHM has shown promising success in assessing structural integrity of local areas. Leveraging the fact that both wave-based and impedance-based approaches can be used by deploying piezoelectric transducers (PZT) bonded or embedded to the structure being monitored, this paper describes a unified SHM paradigm where these techniques are employed simultaneously, using the same sensing/hardware/software. Specifically, we propose to use two PZTs controlled by a National Instrument PXI running under LabView. An ad hoc LabView Virtual Instrument controls signal output and input as well as processing and storage. To assess the feasibility of this unified system an aluminum plate was monitored. Damage was simulated by changing the boundary conditions of the plate. The results show that the proposed system is robust and can be developed further to address the challenges associated with the SHM of complex structures.