Investigation of Acoustic Coupling Phenomena in FBG Lamb Wave Detectors
Abstract
GRANT13517290 12/14/2021-Monitoring the level of corrosion or other damage during service is a critical need for the US Navy. Accura,te assessments of the health of critical structural components would enable better management of the naval fleet through data driven, maintenance and replacement of components, rather than schedule based maintenance and replacement. The propagation of guided waves, through these structuresis one of the best approaches to collecting accurate data, particularly over the large size of complex nava,l structures. FBG sensornetworks are excellent detectors for guided Lamb waves in structures used for monitoring of damage initiatio,n and progression. Collecting sufficient energy of the guided ultrasonic waves presents challenges, due to the fact that the guided, waves have extremely low amplitudes.The goal of this project is to numerically and experimentally compare the efficiency of extract,ing Lamb wave energy from the surface of a structure to a FBG sensor using a discrete or continuous bonding approach. Both cases wil,l utilize remote bondingto enhance the signal amplitude at the FBG sensor. Once the physics of both approaches are understood and co,mpared, the acoustic energy extracted from a structural plate into an optical fiber detector for structural health monitoring applic,ations can be maximized. The general question to be answered is which method converts more energy into a longitudinal mode in the op,tical fiber: extractingthe energy into a solid lens and focusing it into a point in the lens prior to coupling it into the optical f,iber; or coupling it into an array of discrete optical fibers and then coupling the signals from multiple fibers into a signal fiber,? These two approachescreate quite different mechanisms that produce loss and signal distortion in the final signal arriving at the, FBG sensor. These loss and distortion mechanisms will also be investigated quantitatively in this research and will be considered, as losses to the energy efficiency. In particular, the physics of coupling, losses and signal distortion in each approach will be p,robed numerically and experimentally in the proposed research plan.The proposed research would increase the energy collected by opti,cal fiber Lamb wave detectors for structural health monitoring of naval structures. As a result the collected waveforms could be bet,ter resolved increasingthe accuracy of damage detection and prognostics, as well as permitting earlier detection of fatigue or corro,sion induced damage. Alternatively, the same amount of information could be collected with fewer sensors than in current systems, re,ducing the complexity of cost of structural health monitoring systems. The sensor data and the related interpretation of structural, performance could alsoserve as useful data for the future design of high performance naval vehicles.
Document Details
- Document Type
- DoD Grant Award
- Publication Date
- Jul 13, 2022
- Source ID
- N000142212365
Entities
People
- Kara Peters
Organizations
- North Carolina State University
- Office of Naval Research
- United States Navy