Title :
The excitation and detection of Lamb waves with planar coil electromagnetic acoustic transducers
Author :
Wilcox, Paul D. ; Lowe, Michael J S ; Cawley, Peter
Author_Institution :
Dept. of Mech. Eng., Bristol Univ., UK
Abstract :
Planar coil electromagnetic acoustic transducers (EMATs) are investigated for the excitation and detection of Lamb waves in nonferromagnetic metallic waveguides. Such EMATs are attractive for certain applications due to their omni-directional sensitivity to wave modes with predominantly in-plane surface displacement, such as the S/sub o/ Lamb wave mode. A model is developed that enables the modal content of the radiated Lamb wave field from a transmitting EMAT to be calculated, and the output voltage from a receiving EMAT to be predicted when a Lamb wave mode is incident on it. The predictions from this model are compared with experimental data obtained from 12 different EMATs tested on a 5-mm thick aluminum plate, and good agreement is obtained. The model then is used to analyze the different effects that contribute to the overall Lamb wave modal sensitivity of an EMAT. The relationship between coil geometry and wavelength is examined.
Keywords :
acoustic transducers; coils; electromagnetic devices; surface acoustic waves; Lamb wave modal sensitivity; aluminum plate; coil geometry; inplane surface displacement; nonferromagnetic metallic waveguides; omnidirectional sensitivity; planar coil electromagnetic acoustic transducers; Acoustic signal detection; Acoustic transducers; Acoustic waveguides; Coils; Electromagnetic scattering; Electromagnetic waveguides; Planar waveguides; Predictive models; Surface acoustic waves; Voltage; Acoustics; Computer Simulation; Computer-Aided Design; Equipment Design; Equipment Failure Analysis; Magnetics; Models, Theoretical; Reproducibility of Results; Sensitivity and Specificity; Transducers; Ultrasonography;
Journal_Title :
Ultrasonics, Ferroelectrics, and Frequency Control, IEEE Transactions on
DOI :
10.1109/TUFFC.2005.1563281
