Sound velocity, ultrasonic

We used the concept of sound velocity dispersion for explanation of the shift of pulse energy spectrum maximum, transmitted through the medium, and correlation of the shift value with function of medium heterogeneity. This approach gives the possibility of mathematical simulation of the influence of both medium parameters and ultrasonic field parameters on the nature of acoustic waves propagation in a given medium. 

In general a thickness measurement using ultrasound is done by measuring the time of flight of the ultrasonic pulse and calculating the thickness of the objeet multiplying the time and the known constant sound velocity in the material. 

This paper presents solutions of two different NDT problems which could not be solved using standard ultrasonic systems and methods. The first problem eoncems the eraek detection in the root of turbine blades in a specified critical zone. The second problem concerns an ultrasonie thiekness measurement for a case when the sound velocity varies along the object surface, thus not allowing to take a predetermined eonstant velocity into account. 

Pandey et al. have used ultrasonic velocity measurement to study compatibility of EPDM and acrylonitrile-butadiene rubber (NBR) blends at various blend ratios and in the presence of compa-tibilizers, namely chloro-sulfonated polyethylene (CSM) and chlorinated polyethylene (CM) [22]. They used an ultrasonic interferometer to measure sound velocity in solutions of the mbbers and then-blends. A plot of ultrasonic velocity versus composition of the blends is given in Eigure 11.1. Whereas the solution of the neat blends exhibits a wavy curve (with rise and fall), the curves for blends with compatibihzers (CSM and CM) are hnear. They resemble the curves for free energy change versus composition, where sinusoidal curves in the middle represent immiscibility and upper and lower curves stand for miscibihty. Similar curves are obtained for solutions containing 2 and 5 wt% of the blends. These results were confirmed by measurements with atomic force microscopy (AEM) and dynamic mechanical analysis as shown in Eigures 11.2 and 11.3. Substantial earher work on binary and ternary blends, particularly using EPDM and nitrile mbber, has been reported. 

Here p is the solution density, v the sound velocity, ctp the coefficient of thermal expansion, Cp the specific heat, and F the concentration dependence of the equilibrium, r = [LS] -f- [HS] . The measurement of ultrasonic relaxation thus enables the determination of both the relaxation time x and the... 

An acoustic wave (sound) is a propagation of pressure oscillation in medium such as air or liquid water with the sound velocity [1]. Ultrasound is inaudible sound and its frequency of pressure oscillation is above 20 kHz (20,000 oscillations per second) [2]. For convenience, an acoustic wave above 10 kHz in frequency is sometimes called an ultrasonic wave. 

As ultrasonic frequency increases, the acoustic field is more restricted above an ultrasonic transducer. Roughly speaking, when the wavelength of ultrasound (2 = c/f, where c is the sound velocity in the liquid and/is the ultrasonic frequency) is much smaller than the radius of the transducer, the acoustic field is restricted above the transducer. It should be noted that the sound velocity in a bubbly liquid is smaller or occasionally larger than that in liquid without bubbles [87, 88]. 

In principle any physical constant may be useful for structural analysis of mixtures. For practical reasons those constants should be applied that can be easily determined. High demands should be made upon the accuracy of the determinations. For example the physical constants density, refractive index, kinematic viscosity, ultrasonic sound velocity and surface tension may be chosen. Combination of constants, e.g. in certain additive functions, is useful only when the constants in question have been determined with comparable accuracy. In this respect density and refractive index may be combined, whereas molecular weight, the determination of which is not so precise, cannot always be combined with refractive index and density. 

For practical purposes it is necessary to represent the connection between the ultrasonic sound velocity u (m/sec) and v, n and d by means of cross-sections for constant log v values of the log v -n-d space model. The sections contain the intersecting lines with the surfaces of equal u values, Figs. 30, 31, 32, 33 and 34. 

The intersecting lines of equal u values are straight and mutually parallel. In order to determine the ultrasonic sound velocity at 20°C from log vf0, ti and d °, use has in general to be made of two cross-sections for the log vf0 values adjacent to the actual log vfQ value of the oil fraction in question. This will be made clear in the following example. 

It appears that the lines of equal values of the ultrasonic sound velocity in the graph are straight. The slope of the lines changes steadily from one line to the next. 

As has been stated above the lines for equal values of the ultrasonic sound velocity of mineral oil fractions in the log v -(n — d) graph are straight. Therefore it is possible to construct a nomogram with the parallel coordinates log v% and (n — 0.181 d), the value of 0.181 in the function (n — 0.181 d) being somewhat more accurate than in the function (n — d). 

A third example of the correlation of physical constants of mineral oil fractions is the determination of the surface tension from the ultrasonic sound velocity u and the density 22. 

This determination can be carried out by using a graph with the ultrasonic sound velocity u and the density d as coordinates, as shown in Fig. 44. 

Fig. 45. Log v-n diagram for the determination of the ultrasonic sound velocity and the surface tension of saturated mineral oil fractions from their viscosity and refractive index.

It was found by Cornelissen, Harva and Waterman23 that a log v-n diagram can be constructed for the determination of both the ultrasonic sound velocity and the surface tension of saturated mineral oil fractions. This was possible by constructing lines of equal values of the ultrasonic sound velocity and the surface tension, respectively, as shown in Fig. 45. 

It is also possible to determine the surface tension of hydrogenated fractions from the ultrasonic sound velocity and the density22. This can be done by means of a u-d diagram in which lines of equal values of the surface tension have been constructed. This diagram is shown in Fig. 46. 

Measurements of sound velocity at ultrasonic frequencies are usually made by an acoustic interferometer. An example of this apparatus11 is shown in Fig. 2. An optically flat piezo-quartz crystal is set into oscillation by an appropriate electrical circuit, which is coupled to an accurate means of measuring electrical power consumption. A reflector, consisting of a bronze piston with an optically flat head parallel to the oscillating face of the quartz, is moved slowly towards or away from the quartz by a micrometer screw. The electrical power consumption shows successive fluctuations as the distance between quartz and reflector varies between positions of resonance and non-resonance of the gas column. Measurement of the distance between resonance positions gives a value for A/2, and if /... 

The entire thickness of the polyurethane over the reinforcing can be measured using an ultrasonic gauge. The correct head and sound velocity will have to be used, as polyurethanes require different conditions than metals. 

The transmitting frequency / of the UVP-DUO systems is 4 MHz in all tests. The ultrasound wavelength X is 370 pm and the sound velocity in water c is 1,480 m/s. 100 mm ion exchange (Diaion) particles are added to the flow as flow tracers their ability to follow the liquid flow has been assessed using Basset s analysis (Melling, 1997). Owing to theoretical considerations, the size of the flow tracers must be larger than one quarter of the emitted ultrasonic burst (Met-Flow, 2002). 

The agreement between fee bulk modulus deduced from Brillouin scattering measurements and fee ADX results is very good. The determination of fee elastic moduli by ultrasonics was made by fee measurement of surface acoustic wave velocities on thin films [22], The second ultrasonics experiment was made on sintered powder, by measuring fee longitudinal and transverse sound velocity at ambient and under uniaxial compression. From feat, fee bulk modulus and its pressure derivative were deduced, but this result seems to be quite imprecise. The ultrasonics experiment on thin films gives rise to a very small difference in fee bulk modulus (5%), but fee ADX or Brillouin determination should be utilised for preference. 

Saito 7) measured the sound velocity in well-characterized CA solutions with a Pierce type ultrasonic interferometer with high accuracy and determined s. Figure 26 shows the relation between s,, of CA whole polymer solutions and e of the solvent at 25 °C 7). While the dependence of Sq on e differs depending on < F>, s, , except for C A(2.46)-acetone increases with increasing polarity of the solvent in a similar manner as the chemical shifts of the O-acetyl and hydroxyl groups. In Fig. 27, the effects of on Sq for CA-DMAc and CA-dimethylsulfoxide (DMSO) solutions at 25 °C are shown. In both systems, Sq has a maximum at F 2.5 7). 

Ultrasonic sensors Attach to die Sound velocity, attenuation Low No... 

The most accurate method of measuring elastic constants is based on the use of ultrasonic sound velocity measurements. This is a dynamical... 

Ultrasonic sound velocity measurements provide an easy method of determination of the elastic properties as a function of temperature by using a suitable variable temperature cell. 

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