Ultrasonic interpretation

The effectiveness of the approach is demonstrated on two rqjresentative NDT techniques intapretation of data acquired with an ultrasonic rail inspection system and interpretation of eddy-current data from heat exchangers in (petro-)chemical industry. The results show that it is possible to provide a high level of automation in combination with efficient operator support for highly variable NDT measurements where up to now use of automated interpretation was only limited. 

Hopgood, F.F., N. Woodcock, N.J. HaUam, and P.D. Picton, Interpreting ultrasonic images using rules, algorithms and neural networks , European Journal of NDT, Vol. 2, No. 4, April 1993, pp. 135-149. 

In service inspections of French nuclear Pressure Water Reactor (PWR) vessels are carried out automatically in complete immersion from the inside by means of ultrasonic focused probes working in the pulse echo mode. Concern has been expressed about the capabilities of performing non destructive evaluation of the Outer Surface Defects (OSD), i.e. defects located in the vicinity of the outer surface of the inspected components. OSD are insonified by both a "direct" field that passes through the inner surface (water/steel) of the component containing the defect and a "secondary" field reflected from the outer surface. Consequently, the Bscan images, containing the signatures of such defects, are complicated and their interpretation is a difficult task. 

It is to be taken into account that there is a difference between ultrasonic and radiography defect imaging, so the ultrasonic image recognition knowledge required for the person interpreting the inspection results. The ISONIC postprocessing mode allows to ease sueh interpretation because it s maximally approached to inspection standards. 

Having set up the ultrasonic instrument (according to test specifications), the inspector scans the weld volume. Any indications subject to recording are interpreted and documented in a handwritten on-site report. The test report only describes the indications detected by the inspector, but not the completeness of the lest in the sense of a documented 100% volume testing as is the case with X-ray testing. 

Erequendy, a single ultrasonic transducer serves both as the sender of the ultrasonic pulse and as a receiver for the sound waves reflected from surfaces and interior discontinuities. The receiver transforms the stress pulse back into electrical oscillations. AH of the signals are displayed on an oscilloscope screen for interpretation. Eor a material of length E having a wave speed C, the anomaly shown in Eigure 4 would reflect a signal back to the... 

V. J. Pinfield, M. J.W. Povey, E. Dickinson 1996, (Interpretation of ultrasound velocity creaming profiles), Ultrasonics 34, 695. 

The ultrasonic absorption spectrum for a series of inorganic salts with /i-CD showed one relaxation process.166 No absorption was observed for solutions only containing /i-CD. The equilibrium constants determined from competitive binding isotherms were relatively low (2-30 M-1). The relaxation frequency (/, ) was related to the observed relaxation rate constant, which is equal to the sum of the association and dissociation processes. The association rate constants for all salts with the exception of perchlorate were similar and this result was interpreted to mean that... 

J.P. Lorimer, T.J. Mason, and K Fiddy, The enhancement of chemical reactivity by power ultrasound - an alternative interpretation of the hot-spot. Ultrasonics, 1991, 29, 338-343. 

Hersey and Robinson also foundthat many guest species that show kinetic behavior apparently explicable in terms of a single-step binding, give a discrepancy between the values of the equilibrium constant determined kinetically and those determined from equilibrium studies. It was found that the equilibrium constant, deterrmned spectrophotometrically, was usually greater than the ratio of the forward and backward rate-constants, determined kinetically. They therefore suggested that this discrepancy could be adequately explained if the two-step mechanism just described was used to interpret the results. A similar proposal has also been made by Hall and coworkers, who observed a large discrepancy between AV° values for the inclusion of 1-butanol and 1-pentanol by alpha cyclodextrin, calculated from equilibrium-density measurements and kinetic, ultrasonic-absorption data. 

These processes have previously been explored mainly in ultrasonic experiments or in shock waves 1. Both methods, however, may thermally populate many levels of the molecules under investigation, and the interpretation of relaxation times in mixtures... 

Measurement of an ultrasonic relaxation curve enables evaluation of both the relaxation time, t, and the relaxation amplitude, A. Interpretation of the relaxation time requires knowledge of the equilibrium constant. For a intramolecular isomerization such as a high-spin low-spin equilibrium, the forward and reverse rate constants, kl and respectively, can be evaluated from the relaxation time and the equilibrium constant from Eq. (8) (17). 

The objectives of this chapter are to introduce the basic concepts of ultrasonic propagation in materials, to describe some of the most important methods for measuring and interpreting ultrasonic measurements, and to outline existing and possible applications of the technique in the food industry. 

The greater the difference in acoustic impedance between the two materials the greater the fraction of ultrasound reflected. This has important consequences for the design and interpretation of ultrasonic experiments. For example, to optimize the transmission of ultrasound from one material to another it is necessary to chose two materials with similar acoustic impedance. To optimize the reflection coefficient materials with very different acoustic impedance should be used. The acoustic impedance of a material is often determined by measuring the fraction of ultrasound reflected from its surface. 

An ultrasonic experiment consists of two stages measurement of the ultrasonic properties of the material, e.g., velocity, attenuation or impedance interpretation of these measurements to provide information about the relevant properties of the material. These may either be fundamental physico-chemical properties (such as composition, microstructure or molecular interactions) or functional properties (such as stability, rheology or appearance). 

Relationships can either be established in an empirical fashion, or by using theories which describe ultrasonic propagation in materials (see section 4). To utilize the full potential of ultrasound for characterizing food materials it is important to choose the most suitable method of carrying out the measurements and to carefully analyze the data. Many applications have failed in the past because workers have used poorly designed experiments or have interpreted measurements in an inappropriate manner. 

Aqueous systems have been studied by a very large number of investigators. Economy, safety, convenience and quality of product have combined to make this the method of choice for commercial production of copolymers. The industrial importance of such end products as elastomers and acrylic fibers has been a special incentive to related fundamental studies. Furthermore, the relatively high solubility of acrylonitrile monomer in water coupled with insolubility of the polymer make it a convenient test monomer for studies of initiation by redox systems (6, 25, 102). Large numbers of homogeneous chemical initiators and some heterogeneous initiators have been studied as well as initiation by photochemical means, by ultrasonics and by ionizing radiation. It will not be possible here to review the enormous world literature. Several publications (/, 92, 117) refer in some detail to the older papers, and we shall restrict our comments to recent interpretations that have received support from several quarters. 

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