Ultrasonic zones

Undatim Ultrasonics, Zoning Industriel, Rue de I lndustrie 3, B 1400 Nivelles, Belgium. 

FIGURE 15.11 Photographs of GRT powder, and devulcanized and revulcanized rubbers. Devulcanization conditions in ultrasonic twin-screw extruder are feed rate of 0.19 g/s, ultrasonic amplitude of 13 Jim, frequency of 40 kHz, ultrasonic zone gap of 2.5 mm temperature at various zones are from the feeding section to die 100/180/180/180/160/150°C. 

The ultrasonic treatment of PET/LCP blends leads to improvements in the mechanical properties of the homopolymers and some blends. The increase in the viscosity and mechanical properties of neat PET and LCP, as well as some of their blends at certain amplitudes, points toward homo- and copolymerization. The increase in viscosity of PET after ultrasonic treatment is attributed to possible esterification reaction. The presence of hairy structures on the surface of LCP droplets in the core region of 90/10 PET/LCP blends after ultrasonic treatment at an amplitude of 7.5 otm illustrates the improved adhesion between the PET and LCP phases, and possible copolymer formation under the action of ultrasound. Low residence times in the ultrasonic zone and energy saving due to reduced pressure render ultrasonic extrusion a viable method for the compatibilization of thermoplastic polymer/thermotropic LCP blends. Further refinement of processing conditions could allow one to achieve greater enhancements in the performance of LCP, and its blends with PET. 

Insurance in pressure boundary integrity of NPP unit is strongly influenced by technical capabilities and efficiency of metal examination system. Ordinary ultrasonic examination tools and procedures have limitations in flaw sizing and positioning. The problems arise for welds and repair zones of welds made by filler materials of austenitic type. 

The main purpose of AUGUR4.2 expert ISI is the application to zones where some flaws (indications) had been revealed by scheduled manual ultrasonic inspections. Information provided by AUGUR 4.2 is used for decision-making further surveillance of these zones or corrective measures. The procedure of AUGUR 4.2 examination is included into the approved general scheme of ISI [1]... 

Representative set of weldments was examined site welds (with pearlitic type weld metal) and two types of site weld repair zones with different welding technologies using Cr-Ni filler metals and Ni-based alloy. Results of AUGUR 4.2 inspection were compared with manual ultrasonic inspection ones in terms of defect detection, characterization, positioning and sizing in order to estimate correlation between these data. 

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. 

A Technique of Ultrasonic Testing without Dead Zone for Coarse-Grained TC4 Extrusion Pipe. - The Development of Single Crystal Creeping Wave Prohe. 

In this paper, the following aspects have been studied (A) Flaw detection can be made directly on the surface of the pipes, (B) The defects within the range of wall thickness can be tested out, that is to say, the ultrasonic testing without dead zone for the pipe wall can be realized and (C) Testing the defects of FBH as our testing. Objects, we may make the testing... 

The use of the surface ultrasonic waves seems to be convenient for these purposes. However, this method has not found wide practical application. Peculiarities of excitation, propagation and registration of surface waves created before these time great difficulties for their application in automatic systems of duality testing. It is connected with the fact that the surface waves are weakened by soil on the surface itself In addition, the methods of testing by the surface waves do not yield to automation due to the difficulties of creation of the acoustic contact. In particular, a flow of contact liquid out of the zone of an acoustic line, presence of immersion liquid, availability of chink interval leads to the adsorption and reflection of waves on tlie front meniscus of a contact layer. The liquid for the acoustic contact must be located only in the places of contact, otherwise the influence on the amplitude will be uncontrolled. This phenomenon distorts the results of testing procedure. 

The choice of the solvent also has a profound influence on the observed sonochemistry. The effect of vapor pressure has already been mentioned. Other Hquid properties, such as surface tension and viscosity, wiU alter the threshold of cavitation, but this is generaUy a minor concern. The chemical reactivity of the solvent is often much more important. No solvent is inert under the high temperature conditions of cavitation (50). One may minimize this problem, however, by using robust solvents that have low vapor pressures so as to minimize their concentration in the vapor phase of the cavitation event. Alternatively, one may wish to take advantage of such secondary reactions, for example, by using halocarbons for sonochemical halogenations. With ultrasonic irradiations in water, the observed aqueous sonochemistry is dominated by secondary reactions of OH- and H- formed from the sonolysis of water vapor in the cavitation zone (51—53). 

Doppler Flow Meters. Doppler flow meters sense the shift in apparent frequency of an ultrasonic beam as it is reflected from air bubbles or other acoustically reflective particles that ate moving in a Hquid flow. It is essential for operation that at least some particles ate present, but the concentration can be low and the particles as small as ca 40 p.m. CaUbration tends to be influenced by particle concentration because higher concentrations result in mote reflections taking place neat the wall, in the low velocity portion of the flow profile. One method used to minimize this effect is to have separate transmitting and receiving transducers focused to receive reflections from an intercept zone neat the center of the pipe. 

On the other hand stable cavitation (bubbles that oscillate in a regular fashion for many acoustic cycles) induce microstreaming in the surrounding liquid which can also induce stress in any microbiological species present [5]. This type of cavitation may well be important in a range of applications of ultrasound to biotechnology [6]. An important consequence of the fluid micro-convection induced by bubble collapse is a sharp increase in the mass transfer at liquid-solid interfaces. In microbiology there are two zones where this ultrasonic enhancement of mass transfer will be important. The first is at the membrane and/or cellular wall and the second is in the cytosol i. e. the liquid present inside the cell. 

Diffusion through pores to the reaction zone will be enhanced by the ultrasonic capillary effect. 

DNB is more resistant to sonolysis than NB. Because the production of byproducts does not track the disappearance of DNB, volatility is the primary mode of DNB loss. The poor solvation of DNB by water as well as the large solution surface area allows rapid volatility. Because NB is more soluble in water, it remains available for sonolysis longer and produces a wider variety of by-products than sonolysis of DNB therefore, organic compounds that are less soluble in water will be more difficult to effectively treat by sonolysis unless steps are taken to increase the presence of the contaminant in the irradiation zone. It is also noted that a higher irradiation frequency is more efficient for sonolysis. More intermediates are observed at shorter irradiation time than with a lower ultrasonic frequency. In addition, a different subset of intermediates was detected, indicating alternate sonolytic pathways are followed. 

Upon ultrasonic action, turbulence occurred, moving material throughout the whole mixing chamber [22], After termination of ultrasonic mixing, the initial pattern rapidly developed, the two zones being separated by a straight interface. 

A simultaneous ultrasonic treatment of the reaction phase (with ultrasonic cleaner Bransonic 12 was carried out in all experiments using a weak source of ultrasound in order to eliminate formed products from the metal surface and thus stabilize the current in the process. Stronger sources of ultrasound have not been used to avoid turbulent processes and the uncontrolled superheating of the reaction zone. 

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