TY - JOUR
T1 - Development of low‐frequency phased array for imaging defects in concrete structures
AU - Ohara, Yoshikazu
AU - Kikuchi, Kosuke
AU - Tsuji, Toshihiro
AU - Mihara, Tsuyoshi
N1 - Funding Information:
Funding: A part of this research was funded by JSPS KAKENHI, grant numbers 21H04592 and 19K21910.
Funding Information:
Acknowledgments: This paper includes a part of the results of “Advancement of Processing and Disposal Technique for the Geological disposal of TRU Waste (FY2013 and FY2014)” under a grant from the Agency for Natural Resources and Energy (ANRE) in the Ministry of Economy, Trade, and Industry (METI) of Japan.
Publisher Copyright:
© 2021 by the authors. Licensee MDPI, Basel, Switzerland.
PY - 2021/11/1
Y1 - 2021/11/1
N2 - The nondestructive inspection of concrete structures is indispensable for ensuring the safety and reliability of aging infrastructures. Ultrasonic waves having a frequency of tens of kHz are frequently used to reduce the scattering attenuation due to coarse aggregates. Such low frequen-cies enable the measurement of the thickness of concrete structures and detection of layer‐type de-fects, such as delamination, whereas it causes a lack of sensitivity to crack‐type defects. In this paper, to realize the ultrasonic phased array (PA) imaging of crack‐type defects, we fabricated a low‐fre-quency (LF) array transducer with a center frequency of hundreds of kHz. To avoid the crosstalk between piezoelectric elements and dampen the vibration of each element, we adopted soft lead zirconate titanate (soft PZT) with a low mechanical quality factor. Subsequently, we optimized the geometry of each piezoelectric element using a finite element method to generate a short pulse. After validating the design in a fundamental experiment using a single‐element transducer, we fabricated a 32‐element array transducer with a center frequency of 350 kHz. To show the imaging capability of the LF array transducer, we applied it to a concrete specimen with a delamination. As a result, the PA with the LF array transducer clearly visualized the delamination, which could not be visualized using the PA with a 2.5 MHz array transducer. Furthermore, we applied it to a more chal-lenging defect, a slit, which is sometimes used to simulate crack‐type defects. As a result, the PA with the LF array transducer clearly visualized a slit of 1 mm width and 40 mm height in a concrete specimen. Thus, we demonstrated the usefulness of the LF array transducer for inspecting crack-type defects.
AB - The nondestructive inspection of concrete structures is indispensable for ensuring the safety and reliability of aging infrastructures. Ultrasonic waves having a frequency of tens of kHz are frequently used to reduce the scattering attenuation due to coarse aggregates. Such low frequen-cies enable the measurement of the thickness of concrete structures and detection of layer‐type de-fects, such as delamination, whereas it causes a lack of sensitivity to crack‐type defects. In this paper, to realize the ultrasonic phased array (PA) imaging of crack‐type defects, we fabricated a low‐fre-quency (LF) array transducer with a center frequency of hundreds of kHz. To avoid the crosstalk between piezoelectric elements and dampen the vibration of each element, we adopted soft lead zirconate titanate (soft PZT) with a low mechanical quality factor. Subsequently, we optimized the geometry of each piezoelectric element using a finite element method to generate a short pulse. After validating the design in a fundamental experiment using a single‐element transducer, we fabricated a 32‐element array transducer with a center frequency of 350 kHz. To show the imaging capability of the LF array transducer, we applied it to a concrete specimen with a delamination. As a result, the PA with the LF array transducer clearly visualized the delamination, which could not be visualized using the PA with a 2.5 MHz array transducer. Furthermore, we applied it to a more chal-lenging defect, a slit, which is sometimes used to simulate crack‐type defects. As a result, the PA with the LF array transducer clearly visualized a slit of 1 mm width and 40 mm height in a concrete specimen. Thus, we demonstrated the usefulness of the LF array transducer for inspecting crack-type defects.
KW - Concrete
KW - Crack‐type defect
KW - Delamination
KW - Low‐frequency phased array
KW - Ultrasonic imaging
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U2 - 10.3390/s21217012
DO - 10.3390/s21217012
M3 - Article
C2 - 34770316
AN - SCOPUS:85117405189
VL - 21
JO - Sensors (Switzerland)
JF - Sensors (Switzerland)
SN - 1424-8220
IS - 21
M1 - 7012
ER -