ADVANCES IN PIEZOELECTRIC MODELING FOR HEALTH MONITORING OF STRUCTURES WITH INTERFACE ELEMENTS
Engineering infrastructures have recently become ubiquitous. However, presence of structural damage and progressive accumulation of material defects can cause catastrophic failures to these infrastructures with huge monetary and life loss. Thus, damage identification and diagnostic methods such as structural health monitoring (SHM) techniques have recently been widely used to ensure the integrity of the structures and assets. The discovery of piezoceramic materials along with recent advances in sensor/actuator technology opened the door to a vast and novel piezo-based SHM technique in the field of damage identification and diagnostics. One important type of piezoceramic transducers which is widely used in SHM and this entire work is Lead-Zirconate-Titanate (PZT). The main body of this dissertation showcases the theory and application of piezoelectric transducers to monitor common, yet critical types of interfaces in infrastructures. The fifth chapter of the dissertation then describes an energy harvesting and power transmission system that can be used to maintain uninterrupted monitoring of structures using piezoelectric transducers installed in remote or inaccessible areas. This dissertation presents the work conducted on four major projects. In the first project, PZT transducers were used to innovatively monitor the interfaces in bolted joints and pin connections. A novel piezo-based wave method and an electromechanical impedance (EMI) technique were proposed to monitor the axial load of bolted joints and pin connections. The second project was focused on the bond-slip detection of concrete-encased composite structures using piezoelectric transducers. First, the shear mode of piezoelectric transducers was used in a PZT-based active sensing approach to correlate the level of bond-slip to the energy of the received signal. Second, the previously proposed EMI technique was used for the bond-slip project as well. The third type of interface analyzed in this study was the crack in metallic structure discussed in the third project. A novel coupled thermo-electro-mechanical analysis with the use of implicit finite element method was used to simulate the vibrothermographic inspection of cracked structures. A low power (10W) piezoceramic-based ultrasonic actuator was used to obtain the corresponding heat generation in a metallic plate with multiple surface cracks. Finally, a method was presented that can remotely charge devices located in inaccessible areas through piezo-generated stress waves that propagate along the structure hosting the device to be charged. The method innovatively applied the time reversal technique for use in energy harvesting to overcome the dispersive and scattering nature of the waves in solid materials.