Passive focusing techniques for piezoelectric air-coupled ultrasonic transducers

Álvarez-Arenas, Tomás Gómez; Camacho, J.; Fritsch, C.

doi:10.1016/j.ultras.2016.01.001

Cited by 40 publications

(27 citation statements)

References 39 publications

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“…By shaping the pump ultrasound field launched with a focused air-coupled transducer, and also with acoustic masks, focusing mirrors, [9][10][11] and Fresnel plates [11][12][13] ), the radiation pattern (i.e., spatial distribution of I) can be manipulated at the air/medium interface. In addition, ultrasound arrays can electronically scan the pump field across the interface.…”

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confidence: 99%

Air-coupled acoustic radiation force for non-contact generation of broadband mechanical waves in soft media

Ambroziński

Pelivanov

Song

et al. 2016

Applied Physics Letters

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A non-contact method for efficient, non-invasive excitation of mechanical waves in soft media is proposed, in which we focus an ultrasound (US) signal through air onto the surface of a medium under study. The US wave reflected from the air/medium interface provides radiation force to the medium surface that launches a transient mechanical wave in the transverse (lateral) direction. The type of mechanical wave is determined by boundary conditions. To prove this concept, a homemade 1 MHz piezo-ceramic transducer with a matching layer to air sends a chirped US signal centered at 1 MHz to a 1.6 mm thick gelatin phantom mimicking soft biological tissue. A phasesensitive (PhS)-optical coherence tomography system is used to track/image the mechanical wave. The reconstructed transient displacement of the mechanical wave in space and time demonstrates highly efficient generation, thus offering great promise for non-contact, non-invasive characterization of soft media, in general, and for elasticity measurements in delicate soft tissues and organs in bio-medicine, in particular. Published by AIP Publishing. [http://dx.doi.org/10.1063/1.4959827] Acoustic radiation force (ARF) is commonly used in ultrasound (US)-based elastography to remotely generate shear waves deep within tissue. 1-3 Detection of shear waves can be performed with a conventional ultrasound (US) imaging probe or with another imaging method, e.g., optical coherence tomography (OCT). The combination of ARF with high frame rate OCT can produce quantitative crosssectional maps of the shear modulus in soft tissues. 4 For many clinical applications, however, a totally non-contact system for generation/detection of mechanical waves is desirable and, in some cases (for instance, the eye), is necessary. OCT is an ideal approach for these applications if an efficient and robust non-contact generation technology can be developed.Generation of mechanical waves with an air puff was used in Ref. 5 to produce very narrow bandwidth displacements in the cornea, which may not be able to characterize corneal elasticity at the spatial resolution required for clinical decision making. Our group has recently demonstrated non-contact generation using absorption of pulsed UV laser light. 6 Although UV generation can provide the bandwidth required for high spatial resolution maps of corneal elasticity, it is not clear at this point whether the required UV energy levels will meet the safety requirement for routine clinical use.Here we propose a fully non-contact and non-invasive US technique to create efficient localized wideband mechanical waves in soft tissue. The method utilizes US launched with an air-coupled transducer (i.e., through air) to the air/ medium interface. The US wave reflected from this interface provides radiation force to the medium surface, which induces a transient displacement at that surface, ultimately generating a propagating shear/guided/interface/Lamb wave (wave type determined by boundary conditions). We will call this the mechanical wave to maintain ge...

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confidence: 99%

Air-coupled acoustic radiation force for non-contact generation of broadband mechanical waves in soft media

Ambroziński

Pelivanov

Song

et al. 2016

Applied Physics Letters

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“…According to the manufacturing data, this test piece has a density of 0,966 g/cm 3 (high), which corresponds to an equivalent porosity of 64% and a thickness of 40mm. All configurations applied show similar results with respect to porosity distribution, but cone focused and sonojet show the best resolution while spherical focusing transducer did not improve the resolution compared to nonfocused one.…”

Section: Inspection Resultsmentioning

confidence: 99%

“…Test piece N° 170_26 has a density of 0,759 g/cm 3 (medium), which corresponds to an equivalent porosity of 72%. Test piece N° 170_28 has a density of 0,966 g/cm 3 (high), which corresponds to an equivalent porosity of 64%.…”

Section: _21mentioning

confidence: 99%

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Advanced nondestructive techniques applied for the detection of discontinuities in aluminum foams

Katchadjian

García

Brizuela

et al. 2018

AIP Conference Proceedings

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Abstract. Metal foams are finding an increasing range of applications by their lightweight structure and physical, chemical and mechanical properties. Foams can be used to fill closed moulds for manufacturing structural foam parts of complex shape [1]; foam filled structures are expected to provide good mechanical properties and energy absorption capabilities. The complexity of the foaming process and the number of parameters to simultaneously control, demand a preliminary and hugely wide experimental activity to manufacture foamed components with a good quality. That is why there are many efforts to improve the structure of foams, in order to obtain a product with good properties. The problem is that even for seemingly identical foaming conditions, the effective foaming can vary significantly from one foaming trial to another. The variation of the foams often is related by structural imperfections, joining region (foam-foam or foam-wall mold) or difficulties in achieving a complete filling of the mould. That is, in a closed mold, the result of the mold filling and its structure or defects are not known a priori and can eventually vary significantly. These defects can cause a drastic deterioration of the mechanical properties [2] and lead to a low performance in its application. This work proposes the use of advanced nondestructive techniques for evaluating the foam distribution after filling the mold to improve the manufacturing process. To achieved this purpose ultrasonic technique (UT) and cone beam computed tomography (CT) were applied on plate and structures of different thicknesses filled with foam of different porosity. UT was carried out on transmission mode with low frequency air-coupled transducers [3], in focused and unfocused configurations.

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“…Ultrasonic transmission techniques were carried out both, with low frequency air coupled transducers [4], and higher frequency transducers, focused and unfocused, by contact and immersion. To validate the results, the ultrasonic images obtained were compared whit radiographic images of the foam.…”

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confidence: 99%

Ultrasonic techniques for the detection of discontinuities in aluminum foams

Katchadjian¹,

García²,

Brizuela³

et al. 2017

AIP Conference Proceedings

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Metal foams are interesting materials with many potential applications [1,2,3]. They are characterized by a cellular structure, that is the metals or metal alloys foamed include gas voids in the material. Their particular lightweight structure and physical, chemical and mechanical properties make them suitable for a wide range of industrial applications in different sectors. For industrial applications, metal foams offer attractive combinations of low density, high stiffness to weight ratio, good energy absorption and vibration damping capacity that cannot be obtained with other materials.The control of the foaming process and the characterization of the metal foam are important issues in order to obtain a product with good properties and guarantee the quality of a mechanical component.The characterization and control of mechanical components and sandwich panels manufactured with metal foams require the assessment of the defects present in this material, like large pores or imperfections which are responsible of deteriorating the mechanical performance. Therefore, specific methods of non-destructive testing are required, both in the manufacturing process and during the life of the component.In this work, some ultrasonic transmission techniques developed for detection of defects associated with the manufacturing process of aluminum foams are proposed. These techniques were used on plates and structures of different thicknesses and geometries formed with this material.Ultrasonic transmission techniques were carried out both, with low frequency air coupled transducers [4], and higher frequency transducers, focused and unfocused, by contact and immersion. To validate the results, the ultrasonic images obtained were compared whit radiographic images of the foam.

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Passive focusing techniques for piezoelectric air-coupled ultrasonic transducers

Cited by 40 publications

References 39 publications

Air-coupled acoustic radiation force for non-contact generation of broadband mechanical waves in soft media

Air-coupled acoustic radiation force for non-contact generation of broadband mechanical waves in soft media

Advanced nondestructive techniques applied for the detection of discontinuities in aluminum foams

Ultrasonic techniques for the detection of discontinuities in aluminum foams

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