Assessment of ultrasonic guided wave inspection methods for structural health monitoring

Structural health monitoring (SHM) has the potential to significantly increase safety and reduce manufacturing and maintenance costs of industrial structures. The use of piezoelectric material such as Lead-Zirconate-Titanate (PZT) in exciting and sensing ultrasonic guided waves for damage detection has become popular since its allows the rapid inspection of large areas in a structure using non-intrusive sensors. Ultrasonic guided waves interact with discontinuities in the structure, giving information about the potential presence of a damage, its size and location.;The main concerns about using such methods is that PZT sensors and guided waves are affected by environmental conditions. The performance of the PZT sensors, in terms of their ability to detect damage, degrades over time and varies depending on current environmental conditions and surrounding, resulting in inconsistent measurements. This work gives a novel formulation of a model-based probability of detection method, which is able to quantify the performance of guided wave inspection in a stochastically varying environment. An analytically and experimentally verified finite element model is used to generate data that represent the effects of varying environmental conditions. Then the stochastic approach is used to evaluate the probability of detection of cracks in riveted aluminum plates and delaminations in composite plates. Also, the performance of guided wave imaging algorithms under degrading PZT conditions is examined.;Another concern is the ability to transfer data from the PZT sensors, which are per-manently located on the structure, to a computer where the data could be processed in real-time or near real-time. Wireless sensor networks (WSN) use low footprint smart sensor nodes that are permanently mounted on the structure. The sensor nodes have their own power supply and wireless communication devices to communicate with other sensor nodes or a base station. Wireless sensor node for guided waves require an actuation interfaces and high frequency sampling of the guided wave measurements. A proof-of-concept wireless sensor node prototype is developed for the data acquisition and actuation using PZT sensors and guided waves.