Results 221 to 230 of about 18,925 (253)
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Experiments in solids using air-coupled ultrasound
The Journal of the Acoustical Society of America, 1999Electrostatic (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 +2 more
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Air-Coupled Ultrasound: A Novel Technique for Monitoring the Curing of Thermosetting Matrices
IEEE Transactions on Ultrasonics, Ferroelectrics, and Frequency Control, 2007A 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 +2 more
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Numerical Modeling of Air-Coupled Ultrasound with EFIT
1995In this paper the Elastodynamic Finite Integration Technique (EFIT) [1] is applied to an isotropic, inhomogeneous, three media acoustic-elastic problem. We consider three media: an acoustic medium, air, above an elastic layer of acrylic, and another layer of air below the elastic layer.
Rudolph, M. +3 more
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Graded piezocomposite for the construction of air-coupled ultrasound transducer
2014 IEEE International Ultrasonics Symposium, 2014In some cases of ultrasound nondestructive evaluation, the use of a coupling agent can damage the object being inspected, thus requiring the use of an air-coupled ultrasound transducer. This article presents a specific configuration of a graded piezocomposite of central frequency of 820 kHz to be used for constructing a transducer capable of emitting ...
D. J. Costa, F. Buiochi, L. Elvira
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Development of a Methodology for the Characterisation of Air-coupled Ultrasound Probes
AIP Conference Proceedings, 2010This study is aimed at developing a technique for the characterisation of air‐coupled ultrasound probes, starting from the analysis of the mechanical behaviour of the probe membrane. The vibratory behaviour of the emission membrane is studied using laser‐Doppler vibrometry techniques with high frequency demodulation system (20 MHz).
Paolo Pietroni +2 more
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Development of air-coupled ultrasound transducers for nondestructive evaluation
2008 IEEE 21st International Conference on Micro Electro Mechanical Systems, 2008We report the development of air-coupled ultrasound transducers for noncontact nondestructive evaluation applications. Air-coupled ultrasound is an attractive inspection technique for materials or structures that are not suitable for contact or immersion ultrasound inspections. However, due to large acoustic impedance mismatch between air and materials
Xuefeng Wang +6 more
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EVALUATION OF AIR COUPLED ULTRASOUND FOR COMPOSITE AEROSPACE STRUCTURE
AIP Conference Proceedings, 2009Non‐contact air coupled ultrasound suffers from the high acoustic impedance mismatch characteristics of air to solid interfaces. Advances in transducer technology, particularly MEMS, have improved the acoustic impedance match at the transmission stage and the signal to noise at the reception stage.
H. Tat +4 more
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Air-coupled ultrasound as a tool for new NDE applications
AIP Conference Proceedings, 2001Ultrasound testing is a standard non-destructive evaluation method that requires a coupling medium, e.g. water, which cannot be used for some materials. A new commercially available device uses improved transducers and sensitive electronics to enhance the signal-to-noise ratio so that air-coupled ultrasound testing is feasible.
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Air-coupled ultrasound for testing of batteries and components
The Journal of the Acoustical Society of AmericaThis work describes the use of an air-coupled and through transmission ultrasonic (0.2–1.5 MHz) technique, both at normal and oblique incidence, for the characterization and test of pouch-cell Li-ion (and similar types) batteries and components. Time domain measurements show that it is possible to measure ultrasonic velocity in the battery.
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Air-coupled ultrasound inspection of complex aluminium-CFRP components
2016 IEEE International Ultrasonics Symposium (IUS), 2016Composite Overwrapped Pressure Vessels (COPVs) are widely used to contain high-pressure fluids. COPVs consist of a thin metallic liner covered with a composite material based on structural fibres. The main function of the liner is to avoid direct contact between composite and chemical agents which can degrade the resin matrix.
Jose Brizuela +4 more
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