Phase based guided wave methods for damage mapping In multilayered structures
Darnton, Aaron T.
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This thesis presents two novel methods for mapping damage in plates along with a concept for optical measurement of guided waves in plates. The Two-Dimensional Phase Gradient method is shown to be effective for identifying and mapping cracks. The second method, the Phase Congruency for Damage Mapping is successful at mapping a wider range of damage types including delaminations, geometrical changes in the sample, mass additions and impact damage in addition to cracks. These methods improve robustness by excluding baseline measurements and limiting the use of models as well as increasing the level of information available to a Non-Destructive Evaluation practitioners. The second main contribution of this work is a framework for a novel optical method for acquiring wave signals in plates. This preliminary investigation shows that high speed cameras are capable of capturing full guided wave fields in far less time than a comparable measurement. Analysis of the measured data reveals that the guided wave was in fact captured although at very low signal to noise ratios. Both of these contributions are important steps on the path to developing robust guided wave methods that are suitable for field use.