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Article

Investigation of a Magnetic Tunnel Junction Based Sensor for the Detection of Defects in Reinforced Concrete at High Lift-Off

1
Department of Applied Physics, Tohoku University, Sendai 980-8579, Japan
2
Graduate Program in Spintronics, Tohoku University, Sendai 980-8578, Japan
3
Center for Science and Innovation in Spintronics (Core Research Cluster), Organization for Advanced Studies, Tohoku University, Sendai 980-8577, Japan
4
Center for Spintronics Research Network, Tohoku University, Sendai 980-8577, Japan
*
Author to whom correspondence should be addressed.
Received: 7 October 2019 / Revised: 25 October 2019 / Accepted: 28 October 2019 / Published: 30 October 2019
(This article belongs to the Special Issue Sensors Fusion in Non-Destructive Testing Applications)
Magnetic flux leakage (MFL) testing is a method of non-destructive testing (NDT), whereby the material is magnetized, and when a defect is present, the magnetic flux lines break out of the material. The magnitude of the leaked magnetic flux decreases as the lift-off (distance from the material) increases. Therefore, for detection at high lift-off, a sensitive magnetic sensor is required. To increase the output sensitivity, this paper proposes the application of magnetic tunnel junction (MTJ) sensors in a bridge circuit for the NDT of reinforced concrete at high lift-off. MTJ sensors were connected to a full-bridge circuit, where one side of the arm has two MTJ sensors connected in series, and the other contains a resistor and a variable resistor. Their responses towards a bias magnetic field were measured, and, based on the results, the sensor circuit sensitivity was 0.135 mV/mT. Finally, a reinforced concrete specimen with a 1 cm gap in the center was detected. The sensor module (with an amplifier and low pass filter circuits) could determine the gap even at 50 cm, suggesting that MTJ sensors have the potential to detect defects at high lift-off values and have a promising future in the field of NDT. View Full-Text
Keywords: non-destructive testing; reinforced concrete; lift-off; magnetic tunnel junction sensors non-destructive testing; reinforced concrete; lift-off; magnetic tunnel junction sensors
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MDPI and ACS Style

Mohd Noor Sam, M.A.I.; Jin, Z.; Oogane, M.; Ando, Y. Investigation of a Magnetic Tunnel Junction Based Sensor for the Detection of Defects in Reinforced Concrete at High Lift-Off. Sensors 2019, 19, 4718. https://0-doi-org.brum.beds.ac.uk/10.3390/s19214718

AMA Style

Mohd Noor Sam MAI, Jin Z, Oogane M, Ando Y. Investigation of a Magnetic Tunnel Junction Based Sensor for the Detection of Defects in Reinforced Concrete at High Lift-Off. Sensors. 2019; 19(21):4718. https://0-doi-org.brum.beds.ac.uk/10.3390/s19214718

Chicago/Turabian Style

Mohd Noor Sam, Muhamad A.I., Zhenhu Jin, Mikihiko Oogane, and Yasuo Ando. 2019. "Investigation of a Magnetic Tunnel Junction Based Sensor for the Detection of Defects in Reinforced Concrete at High Lift-Off" Sensors 19, no. 21: 4718. https://0-doi-org.brum.beds.ac.uk/10.3390/s19214718

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