Acoustic characterization

Insofar as Ultrasonic Array probes have come onto the market from several years and are now moving from prototype stages into industrial tools for on-site inspections, methods and tools for acoustic characterization is becoming a real concern. Furthermore, the lack of standards, either national or European, enhances the needs for guidelines proposal. 

A new Pt(II) polyyne polymer, P15, prepared from the reaction of cfs-[Pt(PPh3)2Cl2] with l,4-diethynyl-2,5-dihexadecyloxybenzene using the extended one pot polymerization route, was tested for its sensing properties and showed fast and reproducible response to relative humidity variations and methanol vapor in surface acoustic-wave (SAW) sensors.46 A SAW sensor was fabricated from polymer P15 as a sensitive membrane, and the polymer was deposited as thin film on the surface of SAW delay lines implemented on three different piezoelectric substrates. High sensitivity and reproducibility were recorded for such devices. The acoustic characterization of the polymer film was also studied with the aid of theoretical results obtained by the perturbation theory. 

Holl, L. Acoustic Characterization ol Contrast Agents for Medical Ultrasound Imaging, Kluwer Academic Publishers Dordrecht, 2001. 

Alvarez FX, Jou D, Sellitto A (2010) Pore-size dependence of the thermal conductivity of porous silicon A phonon hydrodynamic approach. Appl Phys Lett 97 033103 Amato G, Angelucci R, Benedetto G, Boarino L, Dori L, Maccagnani P, Rossi AM, Spagnolo R (2000) Thermal Characterisation of Porous Silicon Membranes. J Porous Mater 7 183 Benedetto G, Boarino L, Spagnolo R (1997) Evaluation of thermal conductivity of porous silicon layers by a photoacoustic method. Appl Phys A 64 155 Bernini U, Maddalena P, Massena E, Ramaglia A (1999) Photo-acoustic characterization of porous silicon samples. J Opt A Pure Appl Opt 1 210... 

Bernini U, Maddalena P, Massera E, Ramaglia A (1999) Photo-acoustic characterization of porous silicon samples. J Appl Opt A Pure Appl Opt 168 210-213... 

A. K. Hipp, G. Storti, M. Morbidelli, Acoustic characterizations of concentrated suspensions and emulsions. 1. Model Analysis , Langmuir, 2002, 18, 391. 

Attenborough K. Acoustical characterization of rigid fibrous absorbents and granular media. J. Acoust. Soc. 

The last part, following the method to analyse radioscopy and acoustic emission values, will be to correlate the characteristic values of the radioscopic detection of casting defects with extracted characteristic values of the acoustic emission analysis. The correlation between the time based characteristic values of acoustic emission analysis and the defect characterizing radioscopy values did not come to very satisfactory results referring the low frequency measurements. The reason can be found in the... 

There have been numerous efforts to inspect specimens by ultrasonic reflectivity (or pulse-echo) measurements. In these inspections ultrasonic reflectivity is often used to observe changes in the acoustical impedance, and from this observation to localize defects in the specimen. However, the term defect is related to any discontinuity within the specimen and, consequently, more information is needed than only ultrasonic reflectivity to define the discontinuity as a defect. This information may be provided by three-dimensional ultrasonic reflection tomography and a priori knowledge about the specimen (e.g., the specimen fabrication process, its design, the intended purpose and the material). A more comprehensive review of defect characterization and related nondestructive evaluation (NDE) methods is provided elsewhere [1]. 

Briggs A., Kolosov O. Acoustic Microscopy for Imaging and Characterization // Materials Research Society Bulletin - 1996. - 21, 10. - P. 30-35. 

This paper intends to give, through different examples, guide-lines for characterization of array probes. We discuss, particularly, beam pattern measurement methods and raise the question whether it is useful to achieve a full characterization of all beams steered by the probe or to limit the characterization to a minimum set of acoustic configurations. An automatic bench for full characterization of tube inspection probes is described. 

For conventional probes, acoustic verification aims at characterizing the beam pattern, beam crossing, beam angle, sensitivity, etc., which are key characteristics in the acoustic interaction between acoustic beam and defect. For array transducers, obviously, it is also a meaning to check the acoustic capabilities of the probe. That is to valid a domain (angle beam, focus, etc.) in which the probe can operate satisfactorily. 

As any conventional probe, acoustic beam pattern of ultrasound array probes can be characterized either in water tank with reflector tip, hydrophone receiver, or using steel blocks with side-drilled holes or spherical holes, etc. Nevertheless, in case of longitudinal waves probes, we prefer acoustic beam evaluation in water tank because of the great versatility of equipment. Also, the use of an hydrophone receiver, when it is possible, yields a great sensitivity and a large signal to noise ratio. 

The required acoustic verifications depend on what the probe is made for. If the probe is used as an angular scamiing system with a fix set of elements, then we think it is only needed to characterize the array behavior with a few selected time delay laws to isolate the angular steering capability and the foeusing capability as explained before. 

However, if the probe is used as linear scanning system, the acoustic beam depends on the element characteristics which are liable to change from one element to an other. Therefore, the only two alternative proposals are to characterise the aeoustie behaviour of all active sub-set of elements or to proeeed to a statistical characterization. 

In the case of the Superphenix probes we were asked to provide a 100% characterization of the probes, that meant to verify all acoustics characteristics over the 160 groups of element multiplexed around the probe. This task has required the development of an automatic acquisition and analysis system which is described below. 

Figure 4 Acoustic beam characterization set-up for the immersion SW array probe a/ Angle beam characterization principle b/ General view of the automatic bench...

There have been a few other experimental set-ups developed for the IR characterization of surfaces. Photoacoustic (PAS), or, more generally, photothemial IR spectroscopy relies on temperature fluctuations caused by irradiating the sample with a modulated monocliromatic beam the acoustic pressure wave created in the gas layer adjacent to the solid by the adsorption of light is measured as a fiinction of photon wavelength... 

Nondestmctive evaluation, also termed nondestmctive testing or nondestmctive inspection, is extensively used in weld testing (14). Nondestmctive tests do no impair the serviceabiUty of the material or component under stress. The most widely used tests for evaluation of welds are Hquid penetrant, magnetic particle, ultrasonics, and radiography. Acoustic-emission tests are increasingly used. Nondestmctive tests detect and characterize, in terms of size, shape, and location, the various types of weld discontinuities that can occur. 

The acoustic microscopy s primary application to date has been for failure analysis in the multibillion-dollar microelectronics industry. The technique is especially sensitive to variations in the elastic properties of semiconductor materials, such as air gaps. SAM enables nondestructive internal inspection of plastic integrated-circuit (IC) packages, and, more recently, it has provided a tool for characterizing packaging processes such as die attachment and encapsulation. Even as ICs continue to shrink, their die size becomes larger because of added functionality in fact, devices measuring as much as 1 cm across are now common. And as die sizes increase, cracks and delaminations become more likely at the various interfaces. 

Vol. 144. Surface-Launched Acoustic Wave Sensors Chemical Sensing and Thin-Film Characterization. By Michael Thompson and David Stone... 

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