Investigation of an air-coupled transducer with a closed-cell material matching strategy and an optimization design considering the electrical input impedance

Wu, Qiao; Chen, Qiu-ying; Lian, Guo-xuan; Wang, Xiaomin; Song, Xiaochun; Zhang, Xu

doi:10.1016/j.ultras.2021.106477

Cited by 6 publications

(3 citation statements)

References 33 publications

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“…From the literature [ 8 , 11 , 13 , 17 ], the first matching layer is commonly fabricated by the mixture of hollow glass microspheres with epoxy, and the second matching layer is often made of microcellular foam polypropylene. Their acoustic impedances can be adjusted by changing the ratio between hollow glass microspheres and epoxy and the foaming rate, respectively.…”

Section: Fabrication Of Transducermentioning

confidence: 99%

“…Wang et al [ 16 ] used the superposition of two low impedance matching layers to improve the sensitivity of the designed transducer, which can detect microcracks. Wu et al [ 17 ] developed a single matched layer air-coupled ultrasonic transducer using a hollow polymer microspheres/epoxy resin system, increasing the transducer sensitivity by 20.9 dB. Song [ 18 ] introduced the periodic subwavelength apertures that employ coupled resonances to enhance the efficiency and bandwidth of the non-contact ultrasonic transducers.…”

Section: Introductionmentioning

confidence: 99%

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Fabrication and Modeling of Matching System for Air-Coupled Transducer

2022

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The tremendous acoustic impedance difference between the piezoelectric composite and air prevents the ultrasonic transition, resulting in low amplitude for the received signal for the composite defect detection using an air-coupled transducer. The matching system, which includes the matching layers and bonding layers attached to the piezoelectric composite, can reduce the acoustic impedance difference and benefit the acoustic transition. In this paper, the fabrication method and modeling for the matching layers are proposed to optimize the transducer performance. The effects of bonding layer material on the transducer performance are also discussed. Experiments were conducted for modeling validation. The proposed model can predict the matching layer acoustic properties with an error of less than 11%. The bonding layer using the same material as the first matching layer can help to increase the sensitivity by about 33% compared to the traditional epoxy bonding. The optimized air-coupled ultrasonic transducer, based on the results of this study, has a 1283 mV amplitude in the air, which is 56% higher than commercially available transducers, and can identify the defects in two typical non-metallic composite materials easily.

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Section: Fabrication Of Transducermentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Fabrication and Modeling of Matching System for Air-Coupled Transducer

2022

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“…Such transducers typically consist of a piezoelectric plate, a matching layer, and a backing layer, with both the piezoelectric plate and the matching layer being planar thin plates. The ideal thickness of the matching layer should be 1/4 wavelength corresponding to the central frequency designed to ensure the maximum transmittance of the acoustic wave [22]. When an acoustic concave lens is attached to a planar transducer, the inhomogeneous thickness of the lens disrupts the thickness conditions of the acoustic impedance matching.…”

Section: Introductionmentioning

confidence: 99%

Investigation of an Active Focusing Planar Piezoelectric Ultrasonic Transducer

Wu,

You,

Zhang

et al. 2024

Sensors

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Ultrasonic focusing transducers have broad prospects in advanced ultrasonic non-destructive testing fields. However, conventional focusing methods that use acoustic concave lenses can disrupt the acoustic impedance matching condition, thereby adversely affecting the sensitivity of the transducers. In this paper, an active focusing planar ultrasonic transducer is designed and presented to achieve a focusing effect with a higher sensitivity. An electrode pattern consisting of multiple concentric rings is designed, which is inspired by the structure of Fresnel Zone Plates (FZP). The structural parameters are optimized using finite element simulation methods. A prototype of the transducer is manufactured with electrode patterns made of conductive silver paste using silk screen-printing technology. Conventional focusing transducers using an acoustic lens and an FZP baffle are also manufactured, and their focusing performances are comparatively tested. The experimental results show that our novel transducer has a focal length of 16 mm and a center frequency of 1.16 MHz, and that the sensitivity is improved by 23.3% compared with the conventional focusing transducers. This research provides a new approach for the design of focusing transducers.

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