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Characterization of air-coupled transducers
IEEE Transactions on Ultrasonics, Ferroelectrics and Frequency Control, 1996This paper describes a theoretical and experimental study for determination of the through-air system impulse response and insertion loss with different air-coupled ultrasonic transducers. Wide-band piezopolymer transducers (PVDF) are employed in both transmission and reception modes and their behavior assessed by means of mathematical modeling and ...
Gachagan, Anthony +3 more
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Wideband characterisation of air coupled transducers
Proceedings of IEEE Ultrasonics Symposium ULTSYM-94, 1994This paper describes a theoretical and experimental study on the use of wideband piezopolymer transducers (PVDF) for the determination of the through-air system impulse response, in both transmission and reception. A linear systems model was used to design a PVDF transmitter/receiver possessing a unipolar, planar and wideband impulse response for ...
Gachagan, Anthony +2 more
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Air-coupled Lamb wave tomography
IEEE Transactions on Ultrasonics, Ferroelectrics and Frequency Control, 1997An entirely air-coupled inspection system using a pair of micromachined silicon capacitance transducers has been used to image defects in thin plates of different materials (0.7 mm to 2.22 mm thick) using air-coupled Lamb wave tomography. A filtered back projection algorithm was used in a form of difference tomography to reconstruct images of defects ...
W, Wright +3 more
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Progress in air-coupled ultrasound
SPIE Proceedings, 2007A variety of industrial and everyday non-destructive inspection applications exist where the target material/product is inaccessible or, contact with the material is prohibited. In such cases, air-coupled ultrasonic techniques play a major role but commonly significant transmission loss is known to occur.
Subash Jayaraman +4 more
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Gas jet as a waveguide for air-coupled ultrasound
Ultrasonics, 2002The directional characteristics of an ultrasonic signal have been studied during propagation within an axial gas jet. The effects of nozzle shape, nozzle diameter, and variations in jet velocity, temperature and gas composition have been investigated. At high flow velocities of an air jet, divergence of the ultrasonic beam was observed.
D W, Choi +3 more
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2011
Ultrasonic material characterization or inspection for defects is conventionally performed using either liquid coupling (water, usually) or some type of gel or oil in contact-mode coupling. Mechanical waves can be transmitted only through some sound-supporting medium from their source (a transducer) to the object under study, and back again.
Dale Chimenti +2 more
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Ultrasonic material characterization or inspection for defects is conventionally performed using either liquid coupling (water, usually) or some type of gel or oil in contact-mode coupling. Mechanical waves can be transmitted only through some sound-supporting medium from their source (a transducer) to the object under study, and back again.
Dale Chimenti +2 more
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Advances in Air‐Coupled Lamb Wave Scanning
Symposium on the Application of Geophysics to Engineering and Environmental Problems 2007, 2007Impact-echo is an effective method for the nondestructive evaluation of in-situ concrete members and has progressively developed over the past 20 years. This study outlines recent advances in the adoption of microphone-based signal acquisition in order to perform rapid non-contact impact echo scanning, in the context of the recently proposed Lamb wave ...
Alex Gibson +2 more
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Air-coupled ultrasound inspection of various materials
Ultrasonics, 2002Conventional ultrasound inspection, a standard non-destructive testing method, uses a coupling medium (e.g. water) because of impedance mismatch. This liquid contact is a drawback because it prevents inspection of many materials. There is a need, then, for air-coupled ultrasound testing, which is now feasible because of low impedance focused narrow ...
R, Stoessel +3 more
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Air-coupled ultrasonic evaluation of food materials
Ultrasonics, 2007This research was performed with the aim of detecting foreign bodies and additives within food products, and to measure selected acoustic properties, without contact to the sample. This would allow use in manufacturing plants on production lines, where contacting the product for ultrasonic inspection would not be feasible.
P, Pallav, D A, Hutchins, T H, Gan
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The use of air-coupled ultrasound to test paper
IEEE Transactions on Ultrasonics, Ferroelectrics and Frequency Control, 2001Capacitance transducers containing a thin polymer membrane have been used to transmit ultrasonic signals with frequencies in excess of 1 MHz through various paper products such as paper and cardboard. At normal incidence, a resonance was visible in thicker samples, the frequency of which could be correlated to parameters such as the thickness of the ...
C S, McIntyre +3 more
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