Development of low‐frequency phased array for imaging defects in concrete structures

Research output: Contribution to journalArticlepeer-review

Abstract

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.

Original languageEnglish
Article number7012
JournalSensors
Volume21
Issue number21
DOIs
Publication statusPublished - 2021 Nov 1

Keywords

  • Concrete
  • Crack‐type defect
  • Delamination
  • Low‐frequency phased array
  • Ultrasonic imaging

ASJC Scopus subject areas

  • Analytical Chemistry
  • Information Systems
  • Atomic and Molecular Physics, and Optics
  • Biochemistry
  • Instrumentation
  • Electrical and Electronic Engineering

Fingerprint

Dive into the research topics of 'Development of low‐frequency phased array for imaging defects in concrete structures'. Together they form a unique fingerprint.

Cite this