LAUSR.org creates dashboard-style pages of related content for over 1.5 million academic articles. Sign Up to like articles & get recommendations!

EMAT phased array: A feasibility study of surface crack detection

Photo from wikipedia

HIGHLIGHTSThe first low‐power (24 Vpp and 200 mA), pulse‐echo EMAT phased array is reported.An 8‐element array can image defects with a cross‐section of 0.2 × 0.8 mm2 at 1 MHz.Coil… Click to show full abstract

HIGHLIGHTSThe first low‐power (24 Vpp and 200 mA), pulse‐echo EMAT phased array is reported.An 8‐element array can image defects with a cross‐section of 0.2 × 0.8 mm2 at 1 MHz.Coil design enables crosstalk of ˜−15 dB and a sub‐wavelength array pitch.Coils with sub‐wavelength width mainly generate shear waves at ˜60° angle. ABSTRACT Electromagnetic‐acoustic transducers (EMATs) consist of a magnet and a coil. They are advantageous in some non‐destructive evaluation (NDE) applications because no direct contact with the specimen is needed to send and receive ultrasonic waves. However, EMATs commonly require excitation peak powers greater than 1 kW and therefore the driving electronics and the EMAT coils have to be bulky. This has hindered the development of EMAT phased arrays with characteristics similar to those of conventional piezoelectric phased arrays. Phased arrays are widely used in NDE because they offer superior defect characterization in comparison to single‐element transducers. In this paper, we report a series of novel techniques and design elements that make it possible to construct an EMAT phased array that performs similarly to conventional piezoelectric arrays used in NDE. One of the key enabling features is the use of coded excitation to reduce the excitation peak power to less than 4.8 W (24 Vpp and 200 mA) so that racetrack coils with dimensions Symbol can be employed. Moreover, these racetrack coils are laid out along their shortest dimension so that 1/3 of their area is overlapped. This helps to reduce the crosstalk between the coils, i.e., the array elements, to less than −15 dB. We show that an 8‐element EMAT phased array operating at a central frequency of 1 MHz can be used to detect defects which have a width and a depth of 0.2 and 0.8 mm respectively and are located on the surface opposite to the array. Symbol. No caption available.

Keywords: array; phased arrays; surface; phased array; emat phased

Journal Title: Ultrasonics
Year Published: 2017

Link to full text (if available)


Share on Social Media:                               Sign Up to like & get
recommendations!

Related content

More Information              News              Social Media              Video              Recommended



                Click one of the above tabs to view related content.