Ultrasonic transmissibility

Some of the ultrasonic systems include ultrasonic transmitters that can be placed inside plant piping or vessels. In this mode, ultrasonic monitors can be used to detect areas of sonic penetration along the container s surface. This ultrasonic transmission method is useful in quick checks of tank seams, hatches, seals, caulking, gaskets or building wall joints. 

Interfacial area measurement. Knowledge of the interfacial area is indispensable in modeling two-phase flow (Dejesus and Kawaji, 1990), which determines the interphase transfer of mass, momentum, and energy in steady and transient flow. Ultrasonic techniques are used for such measurements. Since there is no direct relationship between the measurement of ultrasonic transmission and the volumetric interfacial area in bubbly flow, some estimate of the average bubble size is necessary to permit access to the volumetric interfacial area (Delhaye, 1986). In bubbly flows with bubbles several millimeters in diameter and with high void fractions, Stravs and von Stocker (1985) were apparently the first, in 1981, to propose the use of pulsed, 1- to 10-MHz ultrasound for measuring interfacial area. Independently, Amblard et al. (1983) used the same technique but at frequencies lower than 1 MHz. The volumetric interfacial area, T, is defined by (Delhaye, 1986)... 

Thompson, R. B., Fiedler, C. J., and Buck, O. (1984). Inference of fatigue crack closure stresses from ultrasonic transmission measurements. In Nondestructive methods for materials property determination (ed. C. O. Ruud and R. B. Thompson), pp. 161-70. Plenum Press, New York. [278]... 

Acoustic and elastic properties are directly concerned with seismic wave propagation in marine sediments. They encompass P- and S-wave velocity and attenuation and elastic moduli of the sediment frame and wet sediment. The most important parameter which controls size and resolution of sedimentary structures by seismic studies is the frequency content of the source signal. If the dominant frequency and bandwidth are high, fine-scale structures associated with pore space and grain size distribution affect the elastic wave propagation. This is subject of ultrasonic transmission measurements on sediment cores (Sects. 2.4 and 2.5). At lower frequencies larger scale features like interfaces with different physical properties above and below and bed-forms like mud waves, erosion zones and ehatmel levee systems are the dominant structures imaged... 

Fig. 2.16 Comparison of P-wave attenuation and velocity dispersion data derived from ultrasonic transmission seismograms with theoretical curves based on Biot-Stoll s model for six traces of the turbidite layer of gravity core GeoB1510-2. Permeabilities vary in the model curves according to constant ratios K/a = 0.030, 0.010, 0.003 (K = permeability, a = pore size parameter). The resulting permeabilities are given in each diagram. Modified after Breitzke et al. (1996).

Breitzke M., Grobe H., Kuhn G, Muller R, 1996. Full waveform ultrasonic transmission seismograms - a fast new method for the determination of physical and sedimentological parameters in marine sediment cores. Journal of Geophysical Research 101 22123-22141... 

I 25 Calibration and Evaluation of Nonlinear Ultrasonic Transmission Measurements... 

Fig. 25.1 Ultrasonic transmission data for a sample of two aluminum plates 4 mm thick bonded together by an adhesive epoxy layer of 30 p,m thickness showing the measure of the interface strain amplitude Bi = 2- /e — versus the input strain amplitude i and the linear fit of the first 12 measuring points.

In order to allow both ultrasonic transmission experiments and tensile loading, the ultrasonic set-up was integrated into a small laboratory-scale tensile test stage (Fig. 25.9). The incentive for these experiments originated from the results of combined ultrasonic transmission and dynamic and quasi-static tensile tests of bonded steel tubes [14] and the data shown above. We wanted to test whether there is a correlation of any of the following parameters the second-order nonlinearity parameter y 2, the third-order nonlinearity parameter / 3, the distortion factor K, or the interaction force Fip to the destractively determined tensile strengths. 

Before the tensile test the samples were investigated by ultrasonic transmission measurements as described in Section 25.2. The peak power of the RF-car-rier pulse (again 10-30 cycles, center frequency 2.25 MHz) was swept from 0 up to 3.6 kW and back to zero. The transmitted ultrasonic signal was detected by a broadband receiver probe, recorded, and Fourier-transformed. The dependence of the resulting amplitude and phase spectra on the transmitting pulse power was recorded. Figs. 25.11 and 25.12 show the results obtained for two of the specimens, one with a weak and one with a strong bond of 5.5 and... 

After the ultrasonic measurements the specimens were loaded until fracture to obtain the tensile strength. During the loading procedure nonlinear ultrasonic transmission measurements with an excitation peak power of 1.86 kW were carried out Figs. 25.13 and 25.14 show the results. The amplitudes of the transmitted waves of fundamental frequency (Fig. 25.13) and of the second and the third harmonic (Fig. 25.14) are plotted in arbitrary units as recorded by the receiver probe. The horizontal axis represents the number of measuring points... 

Fig. 25.13 Ultrasonic transmission measurement results (excitation RF peak power 1.85 kW) carried out on samples of two aluminum plates 5 mm thick bonded together by an adhesive epoxy layer of 30-50 pm thickness during quasi-static tension loading (displacement rate 0.5 pm s ) until fracture. The amplitudes of the fundamental frequency transmitted through (a) a weak...

Fig. 25.17 Calculated phase of the transmitted wave of fundamental frequency as a function of the ultrasonic transmission coefficient of the interface in the range from 0 (complete delamination) to 1 (perfect bond, i.e., complete transfer of ultrasound) ...

The oldest techmque for obtaining the ultrasonic transmission characteristic of a material as a function of the frequency is manual tuning of a conventional pulse echo measuring instrument. Of course, tunable and wide-band transmitter and receiver are required to carry out this technique. However, a narrow-band transducer had to be selected according to the test frequency and consequently this techmque is clumsy and rarely used outside the laboratory. 

Frohn A, Dick HB, Fritzen CP, Breitenbach M, Thiel HJ. Ultrasonic transmission in viscoelastic substances. J Cataract Refract Surg 2000 26 282-286... 

The ultrasonic method can also be used to measure molecular adhesion. According to Hertz, the contact stiffness is zero at zero load and so the ultrasonic transmission should be zero. But experiments show that ultrasonic waves are transmitted through contacts at zero load. This proves that adhesive molecular... 

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