Electromagnetic generation of electronically steered ultrasonic bulk waves

Abstract

The frequency dependence of the propagation direction of ultrasonic shear and longitudinal waves generated by a meander-line electromagnetic transducer (EMAT) at MHz frequencies has been determined. The results are found to agree well with theory and demonstrate that electronic beam steering is possible using EMAT’s. The relative efficiency of generation in aluminum was also studied and, for a specific meander-line geometry with a permanent magnet providing the necessary static magnetic field, it was found to be relatively flat versus frequency. Efficiency for shear-wave generation (frequency range, 5–9 MHz) was about 4 dB per conversion less than the Rayleigh-wave generation efficiency at 4.6 MHz, and for longitudinal waves (frequency range, 10–24 MHz) about 10 dB less.

Weld defect detection using PPM EMAT generated shear horizontal ultrasound

“…These Lorentz forces generate the SH wave in the sample. For conditions under which the SH wave can be treated as a bulk wave, the propagation angle of a PPM EMAT can be varied by using the pulse frequency [28,29,27] (this cannot be done with SV waves as they do not satisfy the free-surface boundary conditions [15]), but this is not exploited in this work.…”

Micro-stereolithography as a transducer design method

“…The above measurements all used the spiral-coil EMAT geometry, whereas interesting directivity effects can be produced using meander-line geometries [11] (Figs. 1b and 4b).…”

Effect of Coil Configuration on Conversion Efficiency of EMAT on 7050 Aluminum Alloy

“…The electromagnetic acoustic transducer (EMAT) technique was developed in the early 1970s [1][2][3][4]. As a potential method of non-destructive testing and evaluation, EMAT has attracted great attention [5][6][7][8][9] due to its advantages, such as the liquid coupling and the surface preconditioning being not required, which consequently render this method useful in many areas of modern technology [10][11][12][13][14].…”