High contrast air-coupled acoustic imaging with zero group velocity Lamb modes

Date
2003-07-01
Authors
Holland, Stephen
Holland, Stephen
Chimenti, Dale
Major Professor
Advisor
Committee Member
Journal Title
Journal ISSN
Volume Title
Publisher
Altmetrics
Authors
Research Projects
Organizational Units
Aerospace Engineering
Organizational Unit
Journal Issue
Series
Department
Aerospace Engineering
Abstract

The well known zero in the group velocity of the first-order symmetric (S1) plate wave mode has been exploited in air-coupled ultrasonic imaging to obtain significantly higher sensitivity than can be achieved in conventional air-coupled scanning. At the zero group velocity point at the frequency minimum of the S1mode, a broad range of wavenumbers couple into the first-order symmetric mode at nearly a constant frequency, greatly enhancing transmission at that frequency. Coupled energy remains localized near the coupling point because the group velocity is zero. We excite the mode with a broadband, focussing, air-coupled transducer at the frequency of the zero group velocity point in the S1 mode. By exploiting the efficient coupling at the zero group velocity frequency, we have easily imaged a single layer of Scotch tape attached to a 6.4-mm thick Plexiglas plate and 3.2-mm Teflon inserts in a composite laminate.

Comments

This is a post-print of a proceeding from Ultrasonics, 42, no. 1–9 (April 2004): 957–960, doi: 10.1016/j.ultras.2003.12.009.

Description
Keywords
Citation
DOI
Source