TY - JOUR
T1 - Small electromagnetic acoustic transducer with an enhanced unique magnet configuration
AU - Sun, Hongjun
AU - Urayama, Ryoichi
AU - Uchimoto, Tetsuya
AU - Takagi, Toshiyuki
AU - Hashimoto, Mitsuo
N1 - Funding Information:
This work was partly supported by the Grant-in-Aid for JSPS Research Fellow Grant No. JP 18J11863 . A part of this study is the result of “ Piping System, Risk Management based on Wall Thinning Monitoring and Prediction ” performed under the Center of World Intelligence Project for Nuclear S&T and Human Resource Development by the Ministry of Education, Culture, Sports, Science and Technology of Japan, and ANR of France .
Publisher Copyright:
© 2019
PY - 2020/3
Y1 - 2020/3
N2 - We describe a small electromagnetic acoustic transducer (EMAT) that is different from traditional large EMATs. The maximum vertical magnetic flux density decreases quickly, and its distribution becomes very uneven with increasing lift-off distance of the permanent magnet. To increase the magnetic field strength of a small magnet without increasing the thickness of the magnet configuration, we propose a different permanent magnet configuration. With the same lift-off distance of the magnet, the increase in the maximum vertical magnetic flux density is about 20% when using this configuration. When this lift-off distance is 1.5 mm, the configuration increases the amplitude of the received signal by 71.4% for an aluminium specimen; in contrast, only a 29.0% increase is achieved with a low-carbon steel specimen. This is because, in the latter, the vertical magnetic flux density is less than 0.66 T. The interplay between the Lorentz force and magnetostrictive force leads to a decrease in the efficiency of both forces in generating ultrasonic waves.
AB - We describe a small electromagnetic acoustic transducer (EMAT) that is different from traditional large EMATs. The maximum vertical magnetic flux density decreases quickly, and its distribution becomes very uneven with increasing lift-off distance of the permanent magnet. To increase the magnetic field strength of a small magnet without increasing the thickness of the magnet configuration, we propose a different permanent magnet configuration. With the same lift-off distance of the magnet, the increase in the maximum vertical magnetic flux density is about 20% when using this configuration. When this lift-off distance is 1.5 mm, the configuration increases the amplitude of the received signal by 71.4% for an aluminium specimen; in contrast, only a 29.0% increase is achieved with a low-carbon steel specimen. This is because, in the latter, the vertical magnetic flux density is less than 0.66 T. The interplay between the Lorentz force and magnetostrictive force leads to a decrease in the efficiency of both forces in generating ultrasonic waves.
KW - Lift-off distance
KW - Permanent magnet configuration
KW - Small electromagnetic acoustic transducer
KW - Vertical magnetic flux density
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U2 - 10.1016/j.ndteint.2019.102205
DO - 10.1016/j.ndteint.2019.102205
M3 - Article
AN - SCOPUS:85075795746
SN - 0963-8695
VL - 110
JO - NDT and E International
JF - NDT and E International
M1 - 102205
ER -