NDE applications of air-coupled ultrasonic transducers

Grandia, Willem; Fortunko, C. M.

doi:10.1109/ultsym.1995.495667

Cited by 113 publications

(53 citation statements)

References 40 publications

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“…Con las estimaciones realizadas, el borde de grano en una cer ‡mica, representa un volumen, que en condiciones normales y considerando la posible porosidad de una cer ‡mica, nunca deber'a ser superior al 15 % de la masa total. Valores mas altos nos alejar ‡n del sistema que pretendemos estudiar, aunque en el ‡mbito tecnol-gico pueden presentar interŽs como ÒcompositesÓ de monocristales (12). Conseguir compactar muestras en estas condiciones es complicado, y para lograrlo, hemos trabajado con diferentes bases polimŽricas y pegamentos (acetatos de etilo, con diferentes modificadores, resinas ep-xicas de diferentes viscosidades, etc.)…”

Section: Procedimiento Experimentalunclassified

Estudio de efectos dimensionales en pseudocerámicas ferroeléctricas

Melcón¹,

Frutos²,

González³

et al. 1999

Bol. Soc. Esp. Ceram. Vidr.

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Con el objetivo de avanzar en el estudio de la influencia de los par ‡metros dimensionales en las propiedades de materiales electrocer ‡micos, hemos fabricado materiales a los que llamaremos pseudocer ‡micas que, b ‡sicamente son composites de monocristales molidos embutidos en bases de diferentes pol'meros. En estos materiales controlamos entre otros factores el tama-o de grano y el espesor de la matriz polimŽrica entre granos, disponiendo as' de una amplia gama de pseudocer ‡micas en las que medimos y estudiamos propiedades ferroÐpiroÐpiezoelŽctricas y las relacionamos con los aspectos dimensionales de las mismas. Se presentan los resultados correspondientes a la conformaci-n del material y su respuesta elŽctrica. Palabras claves: ferro-piro-piezoelectricidad, dimensionalidad, electrocer ‡micas, composites Study of dimensional effects in ferroelectric pseudoceramicsWith the objective to advance in the study of dimensional properties in ferroelectric materials, we have prepared a new kind of materials, which are going to be called ÒpseudoceramicÓ. These are, basically, composites that are constituted of milled single crystals packed tightly in different polymers. In these materials, we control, between other factors, grain-size and the thickness of polymeric matrix between grains. Therefore, we have a large range of pseudoceramics, over we study and measure ferroÐpiroÐpiezoelectric properties, and we related them with the dimensional aspects.

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Section: Procedimiento Experimentalunclassified

Estudio de efectos dimensionales en pseudocerámicas ferroeléctricas

Melcón¹,

Frutos²,

González³

et al. 1999

Bol. Soc. Esp. Ceram. Vidr.

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“…The ultrasonic frequencies used for NDT of concrete are usually below 100 kHz to avoid strong scattering by aggregates. However, most commercially available air-coupled ultrasonic systems employ focused, narrow-band, high frequency transducers (Grandia and Fortunko, 1995), with the limitation of operating only at a few pre-selected frequencies ranging from 50 kHz to 4 MHz.…”

Section: Introductionmentioning

confidence: 99%

A focused electric spark source for non-contact stress wave excitation in solids

Dai¹,

Zhu²

2013

The Journal of the Acoustical Society of America

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A focused electric spark is used as a non-contact acoustic source to excite stress waves in solids. The source consists of an electric spark source located at the near focus of an ellipsoidal reflector that focuses the acoustic disturbance generated by the spark source to the far focal point. Experimental studies using both contact and non-contact sensors indicate that the source has the capability to excite the Rayleigh surface wave and impact-echo mode (S1-zero-group-velocity Lamb mode) in a 250 mm thick concrete slab and to enable fully air-coupled testing of concrete specimens.

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“…Safaeinili et al 3 in 1995 introduced both synthetic aperture scanning, which factors out sidelobe interference, and model-based prediction to yield a precision measurement of the dispersion relation of a sample. By 1995, air-coupled ultrasound was established as a qualitative tool for defect imaging, with development culminating in the release of a commercial air-coupled ultrasonic system, 4 which made narrowband air-coupled ultrasonic measurement broadly accessible as a research tool. Schindel et al 5 developed in 1995 broadband micromachined capacitive aircoupled transducers, making truly broadband air-coupled measurements possible.…”

Section: Introductionmentioning

confidence: 99%

Air-coupled, focused ultrasonic dispersion spectrum reconstruction in plates

Holland

Teles

Chimenti

2004

The Journal of the Acoustical Society of America

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This paper presents and demonstrates a noncontact method for measuring the Lamb wave dispersion spectrum of a plate. Noncontact air-coupled source and receive transducers are used with line-focus mirrors and 50-700 kHz broadband apparatus for simultaneous measurement over a broad spectrum of refractive angles and multiple guided modes. Broadband, wide-angle wave forms are measured as a function of position. The Fourier transform of these wave forms from the t -x domain to the v -k domain gives an approximate spectrum of the dispersion relation. We measure the dispersion spectra of Lucite™, aluminum, balsa wood, and a carbon fiber epoxy laminate, and show that the measured spectra agree well with the dispersion relation calculated from Lamb wave theory. This paper presents and demonstrates a noncontact method for measuring the Lamb wave dispersion spectrum of a plate. Noncontact air-coupled source and receive transducers are used with line-focus mirrors and 50-700 kHz broadband apparatus for simultaneous measurement over a broad spectrum of refractive angles and multiple guided modes. Broadband, wide-angle wave forms are measured as a function of position. The Fourier transform of these wave forms from the t -x domain to the -k domain gives an approximate spectrum of the dispersion relation. We measure the dispersion spectra of Lucite™, aluminum, balsa wood, and a carbon fiber epoxy laminate, and show that the measured spectra agree well with the dispersion relation calculated from Lamb wave theory.

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NDE applications of air-coupled ultrasonic transducers

Cited by 113 publications

References 40 publications

Estudio de efectos dimensionales en pseudocerámicas ferroeléctricas

Estudio de efectos dimensionales en pseudocerámicas ferroeléctricas

A focused electric spark source for non-contact stress wave excitation in solids

Air-coupled, focused ultrasonic dispersion spectrum reconstruction in plates

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