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Acoustic Beamforming for Damage Detection in Plate-like Structures

Shibu Thomas, Nikhil
http://rave.ohiolink.edu/etdc/view?acc_num=ucin1721397533346671

Abstract Details

2024, MS, University of Cincinnati, Engineering and Applied Science: Mechanical Engineering.
Acoustic pressure measurement (beamforming) is an emerging structural health monitoring (SHM) technique that can localize defects based on the sound field generated or transmitted through these defects. It can detect damage initiated with small physical irregularities like cracks, holes and worn out material thickness which ultimately lead to deformation and breakdown. Compared to other SHM techniques, acoustic beamforming has the advantages of being a non-contact method, having improved signal quality and precise directional sensitivity for localizing sound sources. State of the art acoustic measurement setups are limited to sealed hollow structures where an acoustic source is placed inside and a microphone array outside the structure captures the acoustic signal leaking through defects and gaps. This work extends the use of acoustic beamforming using the delay and sum algorithm to open structures and studies (numerically and experimentally) the ability of acoustic beamforming to detect defects in plates actively excited by sound in an open environment. Our numerical results, using the finite element method, show that sound diffraction around the plate is the main limiting factor for detecting defects in this configuration. To address the problem of diffraction, two solutions are proposed. An insulation material is used as a barrier around the plate to reduce diffraction around the plate and the directivity of the exciting sound source is improved by introducing a frustum-shaped enclosure to focus sound onto the plate. Subsequently, the beamformer is able to accurately identify the location of the defect, down to a defect size of 5 mm numerically and 7 mm experimentally. The minimum detectable defect size is identified as a function of diffraction pressure and a metric is developed for the detectability of a given defect size based on pressure measurements. Our results show that acoustic beamforming is a viable solution for detecting defects in open structures and identifying key directions that can enable smaller defects/cracks to be detected.
Ahmed Allam, Ph.D. (Committee Chair)
Jay Kim, Ph.D. (Committee Member)
Yongfeng Xu, Ph.D. (Committee Member)
70 p.
Acoustics
Acoustic beamforming; source localization; damage identification; plate structure; diffraction; directional acoustic source excitation

Recommended Citations

Citations

  • Shibu Thomas, N. (2024). Acoustic Beamforming for Damage Detection in Plate-like Structures [Master's thesis, University of Cincinnati]. OhioLINK Electronic Theses and Dissertations Center. http://rave.ohiolink.edu/etdc/view?acc_num=ucin1721397533346671

    APA Style (7th edition)

  • Shibu Thomas, Nikhil. Acoustic Beamforming for Damage Detection in Plate-like Structures. 2024. University of Cincinnati, Master's thesis. OhioLINK Electronic Theses and Dissertations Center, http://rave.ohiolink.edu/etdc/view?acc_num=ucin1721397533346671.

    MLA Style (8th edition)

  • Shibu Thomas, Nikhil. "Acoustic Beamforming for Damage Detection in Plate-like Structures." Master's thesis, University of Cincinnati, 2024. http://rave.ohiolink.edu/etdc/view?acc_num=ucin1721397533346671

    Chicago Manual of Style (17th edition)

ucin1721397533346671
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© 2024, all rights reserved.
This open access ETD is published by University of Cincinnati and OhioLINK.