Results 211 to 220 of about 20,357 (252)

Progress in air-coupled ultrasound

SPIE Proceedings, 2007
A 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, Dominik Pellkofer, Ian Lucas, Michal Bezdek, Bernhard Tittmann   +4 more
openaire   +1 more source

The use of air-coupled ultrasound to test paper

IEEE Transactions on Ultrasonics, Ferroelectrics and Frequency Control, 2001
Capacitance 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, D A, Hutchins, D R, Billson, J, Stor-Pellinen   +3 more
openaire   +2 more sources

Gas jet as a waveguide for air-coupled ultrasound

Ultrasonics, 2002
The 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, C, McIntyre, D A, Hutchins, D R, Billson   +3 more
openaire   +2 more sources

Air-coupled piezoelectric detection of laser-generated ultrasound

IEEE Transactions on Ultrasonics, Ferroelectrics and Frequency Control, 1993
A pulsed laser has been used to generate ultrasonic transients in samples of metal and fiber-reinforced polymer composite material. These have been detected using an air-coupled piezoelectric transducer. It is demonstrated that such a transduction system can be used for longitudinal waves in bulk material, Rayleigh waves at solid surfaces and Lamb ...
Hutchins, D.A., Wright, WMD, Hayward, Gordon, Gachagan, Anthony   +3 more
openaire   +4 more sources

CMUTs for air coupled ultrasound with improved bandwidth

2011 IEEE International Ultrasonics Symposium, 2011
We present the design, fabrication and characterization of a multi-purpose capacitive micromachined ultrasonic transducer (CMUT) for air coupled ultrasound (∼300−500 kHz), with a focus on improved bandwidth. The focus of this work is to investigate whether and how waferbonded CMUTs can be improved in terms of bandwidth for airborne ultrasound by ...
Mario Kupnik, null Min-Chieh Ho, Srikant Vaithilingam, Butrus T. Khuri-Yakub   +3 more
openaire   +1 more source

Air-Coupled Ultrasound: A New Paradigm in NDE

Volume 13: Processing and Engineering Applications of Novel Materials, 2007
In any ultrasonic investigation, the contact between the transducer and the object has always been a source of problem. With the introduction of the air-coupled ultrasonic probes the couplant is totally eliminated. The limitation of these probes is that they are of very low frequency and as a result they bring their set of restrictions. We present here
Vinay Dayal, David K. Hsu, Adam H. Kite
openaire   +1 more source

Experiments in solids using air-coupled ultrasound

The Journal of the Acoustical Society of America, 1999
Electrostatic (capacitance) transducers have been designed and constructed for the imaging of solids in air, at frequencies of up to 1 MHz. The devices use a micromachined silicon backplate and a flexible membrane. The sensitivity and bandwidth of the resultant devices is such that signals can be propagated through solid samples in air.
D. A. Hutchins, D. R. Billson, C. S. McIntyre   +2 more
openaire   +1 more source

Focusing of ferroelectret air-coupled ultrasound transducers

AIP Conference Proceedings, 2016
Air-coupled ultrasound has been applied increasingly as a non-destructive testing method for lightweight construction in recent years. It is particularly appropriate for composite materials being used in automotive and aviation industry. Air-coupled ultrasound transducers mostly consist of piezoelectric materials and matching layers.
Mate Gaal, Jürgen Bartusch, Elmar Dohse, Florian Schadow, Enrico Köppe   +4 more
openaire   +1 more source

Air-coupled generation and detection of ultrasound in concrete

AIP Conference Proceedings, 2014
It is well known that liquid coupling agents used to couple an ultrasonic transducer to a solid specimen cause a number of problems including inconsistency in results and slowness of the inspection. Especially when the specimen surface is rough such as those in-field concrete structures, the long surface preparation time that it takes to polish every ...
Fabian Schempp, Jin-Yeon Kim, Laurence J. Jacobs   +2 more
openaire   +1 more source

Air-Coupled Ultrasound: A Novel Technique for Monitoring the Curing of Thermosetting Matrices

IEEE Transactions on Ultrasonics, Ferroelectrics, and Frequency Control, 2007
A custom-made, air-coupled ultrasonic device was applied to cure monitoring of thick samples (7-10 mm) of unsaturated polyester resin at room temperature. A key point was the optimization of the experimental setup in order to propagate compression waves during the overall curing reaction by suitable placement of the noncontact transducers, placed on ...
LIONETTO, Francesca, A. TARZIA, MAFFEZZOLI, Alfonso   +2 more
openaire   +2 more sources