Speaker: Andrew Downs, ECpE Graduate Student
Advisor: Jiming Song
Title: Phased Array Implementation of High Frequency, Multi-mode Dispersion Compensation for Ultrasonic Guided Wave Nondestructive Evaluation
Abstract: Ultrasonic guided wave inspections offer significant advantages over their bulk-wave counter parts. Owing to the boundary conditions, guided waves propagate relatively great distances and carry important information for flaw characterization. Unfortunately, the boundary conditions also make them multi-modal and dispersive. At any frequency, there are at least two modes propagating independently according to unique, frequency dependent, phase velocities. Energy scattered from flaws is divided between the propagating modes, and signals which are spatially and temporally compact on transmission become spatially, and temporally dispersed. This dispersion makes it difficult to characterize flaws in terms of their quantity, location, size and orientation. In this presentation, a method by which the deleterious effects of multi-mode dispersion may be removed is discussed. I begin with a brief history of guided wave inspection techniques and the current approaches to solve the problem. A discussion of our approach is given which includes the dispersion compensation algorithm and our method for extracting individual mode contributions. Results from simulation and measurement are presented, and the robustness of the method for locating a flaw in the presence of multi-mode dispersion is demonstrated. The presentation concludes with a discussion of future work and remaining research questions.