Development of Low-Frequency Phased Array for Imaging Defects in Concrete Structures
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 frequencies enable th...
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MDPI AG
2021-10-01
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| Series: | Sensors |
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| Online Access: | https://www.mdpi.com/1424-8220/21/21/7012 |
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| author | Yoshikazu Ohara Kosuke Kikuchi Toshihiro Tsuji Tsuyoshi Mihara |
| author_facet | Yoshikazu Ohara Kosuke Kikuchi Toshihiro Tsuji Tsuyoshi Mihara |
| author_sort | Yoshikazu Ohara |
| collection | DOAJ |
| description | 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 frequencies enable the measurement of the thickness of concrete structures and detection of layer-type defects, 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-frequency (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 challenging 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. |
| first_indexed | 2024-03-10T05:53:19Z |
| format | Article |
| id | doaj.art-d7547f03724b4511bfa5a8b87f1c1dc1 |
| institution | Directory Open Access Journal |
| issn | 1424-8220 |
| language | English |
| last_indexed | 2024-03-10T05:53:19Z |
| publishDate | 2021-10-01 |
| publisher | MDPI AG |
| record_format | Article |
| series | Sensors |
| spelling | doaj.art-d7547f03724b4511bfa5a8b87f1c1dc12023-11-22T21:35:14ZengMDPI AGSensors1424-82202021-10-012121701210.3390/s21217012Development of Low-Frequency Phased Array for Imaging Defects in Concrete StructuresYoshikazu Ohara0Kosuke Kikuchi1Toshihiro Tsuji2Tsuyoshi Mihara3Department of Materials Processing, Tohoku University, Aoba 6-6-02, Aoba-ku, Sendai 980-8579, JapanDepartment of Materials Processing, Tohoku University, Aoba 6-6-02, Aoba-ku, Sendai 980-8579, JapanDepartment of Materials Processing, Tohoku University, Aoba 6-6-02, Aoba-ku, Sendai 980-8579, JapanDepartment of Materials Processing, Tohoku University, Aoba 6-6-02, Aoba-ku, Sendai 980-8579, JapanThe 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 frequencies enable the measurement of the thickness of concrete structures and detection of layer-type defects, 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-frequency (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 challenging 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.https://www.mdpi.com/1424-8220/21/21/7012low-frequency phased arrayultrasonic imagingconcretecrack-type defectdelamination |
| spellingShingle | Yoshikazu Ohara Kosuke Kikuchi Toshihiro Tsuji Tsuyoshi Mihara Development of Low-Frequency Phased Array for Imaging Defects in Concrete Structures Sensors low-frequency phased array ultrasonic imaging concrete crack-type defect delamination |
| title | Development of Low-Frequency Phased Array for Imaging Defects in Concrete Structures |
| title_full | Development of Low-Frequency Phased Array for Imaging Defects in Concrete Structures |
| title_fullStr | Development of Low-Frequency Phased Array for Imaging Defects in Concrete Structures |
| title_full_unstemmed | Development of Low-Frequency Phased Array for Imaging Defects in Concrete Structures |
| title_short | Development of Low-Frequency Phased Array for Imaging Defects in Concrete Structures |
| title_sort | development of low frequency phased array for imaging defects in concrete structures |
| topic | low-frequency phased array ultrasonic imaging concrete crack-type defect delamination |
| url | https://www.mdpi.com/1424-8220/21/21/7012 |
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