SUBJECT: Ph.D. Proposal Presentation
BY: Aaron Darnton
TIME: Friday, August 28, 2015, 10:00 a.m.
PLACE: Knight Bldg, 317
TITLE: Phase Based Guided Wave Methods for Damage Mapping in Multilayered Structures
COMMITTEE: Dr. Massimo Ruzzene, Chair (AE/ME)
Dr. Karim Sabra (ME)
Dr. Michael Leamy (ME)
Dr. Jennifer Michaels (ECE)
Dr. Andrew Hull (Naval Undersea Warfare Center, Division Newport)


This work develops a method for mapping internal or external damage in plate-like specimens utilizing wavefields induced by Guided Waves. The approach is novel in that phase from the spatial domain of the propagating wavefield will be the primary input of the method. This approach has been selected since the spatial wavenumber and consequently space dependent phase are sensitive to changes in material properties, boundary conditions and geometry. This is in contrast with temporal frequencies, which are not affected by these parameters as long as the monitored systems behave linearly. Further phase is insensitive to attenuation and spreading. Mapping damage is an important component of non-destructively assessing the integrity of structures, in particular composites and laminated structures, which is a growing concern for many industries including marine, aerospace and automotive. This research will focus on two wavefield processing methods. The first, the Phase Gradient approach, utilizes the phase of the wave reflected by damage. By isolating the reflected wave, the phase field can be unwrapped. Identifying discontinuities in the unwrapped phase field will lead to identification of the damage boundary. The second method is the Phase Congruency method. This is an image processing method that will be adapted to detecting discontinuities in the wavefield indicating the presence of damage. By considering the underlying physics of the propagating waves and their interaction with damage, the Phase Congruency method can be recast in a form suitable for damage mapping. This method may have the potential for some level of classification of the damage type by utilizing the angle where the phase components align as well as the wavenumber spectrum. The results of this work will contribute to robust and efficient methods that aid inspectors in evaluating the integrity of composite and laminated structures.