title: Monitoring thickness deviations in planar multi-layer elastic structures using impedance signatures.
abstract: In this letter, a low frequency ultrasonic resonance technique that operates in the 20-80-kHz regime is presented that demonstrates detection of thickness changes on the order of +/-10 mum. This measurement capability is a result of the direct correlation between the electrical impedance of an electro-acoustic transducer and the mechanical loading it experiences when placed in contact with a layered elastic structure. The relative frequency shifts of the resonances peaks can be estimated through a simple one-dimensional transmission model. Separate experimental measurements confirm this technique to be sensitive to subtle changes in the underlying layered elastic structure.
authors.affiliation: Lawrence Livermore National Laboratory, L-333, 7000 East Avenue, Livermore, California 94566, USA. fisher34@llnl.gov
authors.forename: Karl A
authors.initials: KA
authors.lastname: Fisher
mesh_terms: D001307:Auditory Perception; D004548:Elasticity; D006801:Humans; D008962:Models, Theoretical; D013016:Sound; D014465:Ultrasonics