Measuring and testing – Vibration – By mechanical waves
Patent
1994-07-01
1996-04-02
Williams, Hezron E.
Measuring and testing
Vibration
By mechanical waves
29594, 29598, G01N 2924, G01N 2928
Patent
active
055030203
ABSTRACT:
An improved electromagnetic acoustic transducer (EMAT) for transmitting and receiving signals within an electrically conductive structure, a method of fabricating the same, and a method of generating and detecting acoustic waves in an electrically conductive structure are provided. The EMAT includes a source of magnetic flux for establishing a static magnetic field in the electrically conductive structure, and a multilayered printed circuit board (PCB) positioned within the static magnetic field in close proximity to the surface of the electrically conductive structure. The multilayered PCB includes a plurality of coil layers, an interconnect layer, and a ground plane. When an alternating current is applied, the coil layers induce eddy currents in the conductive structure. The source of magnetic flux and the multilayered PCB are oriented such that the vector product of the magnetic field and the eddy currents produce an instantaneous force field in the electrically conductive structure. The number of coil layers employed in the EMAT and the liftoff distance, the distance between the coil layer furthest from the surface of the electrically conductive structure, are determined so as to increase the amplitude of the received signal while not effecting system noise and to increase the conversion efficiency. The method of generating and detecting acoustic waves in an electrically conductive structure includes establishing a static magnetic filed in the electrically conductive structure, positioning a multilayered PCB within the static magnetic field in close proximity to the surface of the electrically conductive structure, applying an alternating current to said plurality of parallel conductors, and detecting said received signal generated by the instantaneous force field in the electrically conductive structure.
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patent: 4260450 (1981-04-01), Neu
patent: 4434663 (1984-03-01), Peterson et al.
patent: 4593567 (1986-06-01), Isselstein et al.
patent: 4777824 (1988-10-01), Alers et al.
patent: 5319844 (1994-06-01), Huang et al.
Finley Rose M.
Sonic Force Corporation
Williams Hezron E.
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