Acoustic characterization method

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. 

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... 

Most of the studies about the use of acoustic waves for fouling characterization gave qualitative information about the cake layer (relative amplitude variations) and concerned flat-sheet membranes. The originality of the method presented here [9] is to give the possibility of extracting qualitative information by using another characterization method in parallel. 

The goal of the study was to obtain several kinds of information (thickness, porosity) about a deposit. Therefore, two characterization methods were developed. First, the acoustic method gives time variations from a complex signal, which are qualitative variations. Second, the optical method gives thickness measurements, which are quantitative variations. Adaptation of the two methods on the same apparatus, a confined channel, enables a complete deposit characterization to be obtained. 

Nestleroth et al. [15], Segal et al. [16] considered some established novel signal processing schemes to assist in adhesive bond inspection. Sinclair et al. [17] and Filimonov [18] employed acoustic resonance methods for dynamic elastic modulus measurements in adhesively bonded structures. Yost and Cantrell [19], Achenbach and Parikh [20] and Nagy et al. [21] considered a nonlinear response of bonded structures to estimate material characteristics. In Achenbach and Parikh [20], failure was preceded by nonlinear behavior of thin boundary layers at the interfaces. Billson and Hutchins [22] considered lasers and EMATS in bond investigations. It was shown that this non-contact technique was reasonable when compared to that obtained by conventional piezoelectric transducers. Ince et al. [23] also characterized bonds with laser-generated ultrasound and through-transmission measurements. 

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]. 

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. 

Yasui et al. [29] have used solution of wave equation based on finite element method for characterization of the acoustic field distribution. A unique feature of the work is that it also considers contribution of the vibrations occurring due to the reactor wall and have evaluated the effect of different types of the reactor walls or in other words the effect of material of construction of the sonochemical reactor. The work has also contributed to the understanding of the dependence of the attenuation coefficient due to the liquid medium on the contribution of the vibrations from the wall. It has been shown that as the attenuation coefficient increases, the influence of the acoustic emission from the vibrating wall becomes smaller and for very low values of the attenuation coefficient, the acoustic field in the reactor is very complex due to the strong acoustic emission from the wall. 

The method delineated in the preceding sections can readily be extended to the case of two atoms in the chain. An illustration of the diatomic chain model is given in Figure 8.8. The two atoms are characterized by having different masses m and m2. The two equations of motion obtained (one for each type of atom) must be solved simultaneously, giving two solutions for the angular frequency known as the acoustic and optic branches... 

Acoustic emission (AE) technique, in nondestructive evaluation, 17 425 Acoustic fields, filtration and, 11 324 Acoustic methods, of emulsion characterization, 10 128 Acoustic microscope, 16 505... 

FFT spectra contain an abundance of potential information (as a function of frequency) related to the process/products characterized by the acoustic sensors. FFT spectra constitute fit for purpose input to any chemometric data analytical method deemed beneficial for making the final model relating the acoustic emissions (vibrations), X, to the salient functional properties (quality, quantity) of the products or process... 

A number of methods are available for the characterization and examination of SAMs as well as for the observation of the reactions with the immobilized biomolecules. Only some of these methods are mentioned briefly here. These include surface plasmon resonance (SPR) [46], quartz crystal microbalance (QCM) [47,48], ellipsometry [12,49], contact angle measurement [50], infrared spectroscopy (FT-IR) [51,52], Raman spectroscopy [53], scanning tunneling microscopy (STM) [54], atomic force microscopy (AFM) [55,56], sum frequency spectroscopy. X-ray photoelectron spectroscopy (XPS) [57, 58], surface acoustic wave and acoustic plate mode devices, confocal imaging and optical microscopy, low-angle X-ray reflectometry, electrochemical methods [59] and Raster electron microscopy [60]. 

There are considerable difficulties in comparing theory and experiment even in such model experiments. The theoretical calculations are subject to the approximations inherent in the method, and also to uncertainties in the pupil function used to characterize the lens and in the two parameters used to characterize the crack. The experiments are subject to the difficulties of making a crack that is straight and flat to a fraction of the acoustic wavelength used, over the length measured by the line-focus-beam lens, and to the sensitivity of the results in some cases to small changes in x or z. Nevertheless, when all these considerations are taken into account it does seem... 

This brought a bout a keen interest in other methods of intensification in processing. Lately, the directed effect of physical (mechanical) fields on molten polymers has become one such area. These effects, as demonstrated in many works published in the 1970s and in the 1980s, (see for examples [6-9]) result in altered parameters of micro- and macrostress of the system. Molding under conditions of directed physical fields, in particular, in the case of mechanical and acoustic vibration effects upon melts, is performed so that an additional stress superimposed on the polymer s main shear flow and the state of material is characterized by combined stress. 

Applications The physical principle of measurement is similar to the scanning acoustic microscopy discussed in the Section 14.23, but applications and the method of data processing are essentially different. Sonic methods were used in the following applications to filled materials the effect of particle size and surface treatment on acoustic emission of filled epoxy, longitudinal velocity measurement of tungsten filled epoxy, and in-line ultrasonic measurement of fillers during extrusion. Numerous parameters related to fillers can be characterized by this non-destructive method. 

An important advantage of the ultrasonic method of particle size analysis over other methods is its applicability to systems that are concentrated, electrically non-conductive and optically opaque. Equations (V.46 - V.49) indicate that attenuations due to different mechanisms of acoustic losses are proportional to the volume fraction of the dispersed phase. This dependance becomes critical for the evaluation of particle size in concentrated dispersions. A number of studies (see [26,27], and references therein) have showed that such proportionality does not hold over the entire range of volume fractions, which indicates that eqs. (V.46) - (V.49) are not suitable for the characterization of concentrated disperse systems. 

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