Ultrasonic systems

The advantage of this approach is that a stationary array of transducers can be made to scan a range of objects without the use of moving parts under sodium. 

The main objective of ISI R (In-Service Inspection and Repair) is to provide fast-neutron reactors with effective inspection and repur capabilities in order to (1) assist in 

Ultrasonic image of part of the PFR core seen from above 

Ultrasonic rays reflected from high-spots 

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Chan,R.W.Y., Hay,D.R., Matthews,J.R., MacDonald,H.A., (1988), Automated Ultrasonic System for Submarine Pressure Hull Inspection , Signal Processing and Pattern Recognition in Nondestructive Evaluation of Materials, C.H.Chen (ed). Springer-Verlag, pp. 175-187... 

Arzhaev A T, Kiselyov VA., Badalyan V.G., Vopilkin A.Kb., Strelkov B.R,Vanukov V.N., Aladinsky V. V, Makhanev V.O. Field application of Augur)> ultrasonic system during RBMK NPP Unit ISI and its impact on pressure boundary integrity. In Ageing of Materials and Methods for the Assessment of Lifetimes of Engineering Plant, R K. Penny (Ed.), 1997, pp. 97-104. 

This paper deals with the control of weld depth penetration for cylinders in gold-nickel alloy and tantalum. After introducing the experimental set-up and the samples description, the study and the optimization of the testing are presented for single-sided measurements either in a pulse-echo configuration or when the pump and the probe laser beams are shifted (influence of a thermal phenomenon), and for different kind of laser impact (a line or a circular spot). First, the ultrasonic system is used to detect and to size a flat bottom hole in an aluminium plate. Indeed, when the width of the hole is reduced, its shape is nearly similar to the one of a slot. Then, the optimization is accomplished for... 

Our solution for this inspection problem is a special ultrasonic system consisting of a special probe and a modified pulse-echo ultrasonic instrument. 

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. 

The P-scan System 4 can be configured in many ways, dependent on the application. Figure 1 shows a basic system configuration. The P-scan processor (PSP-4) controls the scanner and the water pump. Scarmer operation on site is performed from the remote control unit, as an alternative to the control from the computer. The PSP-4 also includes the ultrasonic system. 

In order to test a wide range of materials a series of ultrasonic pulser/receiver boards has been developed. In combination with an ADC-board (analogue-to-digital converter) a PC can be converted to a high performance ultrasonic system not only for manual testing but also for automatic testing and imaging systems. 

Fig.2 Portable PC used as ultrasonic system Fig-3 D- scan of an impacted RTM-panei...

The great advantage of installing an ultrasonic system in a PC is that both the hardware (processor, grafics, power supply,. .) aud the software (evaluation and documentation) are directly available for the inspections. 

MAPPscan is a manual ultrasonic testing system connected to an acoustic positioning system.. The system is developed as a consequence of the increased radiation doses in nuclear plants The system has the same flexibility as manual scanning with the same accuracy and the possibilties to collect, store and evaluate the UT data as with mechanised Ultrasonic systems The positioning system is based on spatial acoustic triangulation and have an accuracy of better than 1.0 mm within its recommended range. 

In addition to the controlling computer the system contains only a small control unit - PSP-4 (weight approx. 5 kg.) which among other system components includes a motor control system integrated closely with the PS-4 ultrasonic system. For communication between the PSP-4 control unit and the robot as well as robot power supply is used a single cable less than 10 mm. in diameter. 

The principal equipment for the ultrasonic examination is the P-scan system, PS-4, which is a computerised ultrasonic system, developed by FORCE Institute, for automatic, mechanical and manual ultrasonic examination of welds and materials. The system has documentation and storage facilities for all data related to each inspection operation, and includes visualisation of the inspection results in the form of images of the material volume examined. 

Two types of ultrasonic systems are available that can be used for predictive maintenance structural and airborne. Both provide fast, accurate diagnosis of abnormal operation and leaks. Airborne ultrasonic detectors can be used in either a scanning or contact mode. As scanners, they are most often used to detect gas pressure leaks. Because these instruments are sensitive only to ultrasound, they are not limited to specific gases as are most other gas leak detectors. In addition, they are often used to locate various forms of vacuum leaks. 

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. 

Ultrasonic head forming and welding is a fast assembly technique. It is a very rapid operation of about 2 seconds or less and lends itself to full automation. In this process high-frequency vibrations and pressure are applied to the products to be joined, heat is generated at the plastic causing it to flow, and, when the vibrations cease, the melt solidifies. The heart of the ultrasonic system is the horn, which is made of a metal that can be carefully tuned to the frequency of the system. The manufacture of the horn and its shape is normally developed by the manufacturer of the equipment. The results from this operation are not only economical, but also most satisfactory from a quality control standpoint. 

The mechanisms of delivery are either air-blast or air-jet and ultrasonic systems. The theory for each of these mechanisms has been elucidated to the same degree. 

The design of a system for working with short pulses follows the same principles as other pulsed ultrasonic systems such as ultrasonic flaw detectors, but in this case it is necessary to achieve very much greater stability and higher bandwidth. A schematic circuit is shown in Fig. 5.4 A very short impulse is generated by a step recovery diode. The pulse has a width of half the period of the centre frequency of the lens if it is shorter than that the energy in the pulse is reduced without any improvement in the signal bandwidth. Thus the lens acts as a sort of matched filter with poor time resolution but optimal... 

Figure 5 illustrates an ultrasonic system. The waves are transmitted and impinge on the material under examination, returning to a receiver variations in the shape of waves received indicate the defects. 

In addition, ultrasonic probes are more flexible as regards construction, so they can be easily designed for specific purposes. Some variables with a strong influence on US characteristics including the direction, amplitude and frequency of the vibrations at the point of application or the way the workpiece is clamped can be adjusted with a view to maximizing the effects on the process within the constraints of the ultrasonic system. 

It is therefore more cost effective to use a large ultrasonic system supplying 80 kW to process liquids at a flow-rate of 10 m /h than to use 5 ultrasonic processors with a power of 16 kW each or 40 processors with a power of 2 kW each. The robustness of the transducer enables its use under heavy-duty industrial conditions. Also, the processor can be designed to be explosion-proof. Like the transducer and the flow cell, the generator is housed in two connected compact stainless steel cabinets. This makes the device self-contained, robust and easy to install. The standard footprint of a 16-kW system is just 600 mm x 1200 mm. 

This section discusses various applications of discrete ultrasonic systems according to the organic or inorganic nature of the leached species, and to sample type. 

Use For manual and ultrasonic systems for glassware, metal, ceramic and other materials in laboratories. 

The stimulation of chemical reactions has been known for a many years [1-15] and it has been suggested that some of them might be used as standards for the measurement of the efficiency of ultrasonic systems. Unfortunately, as is the case in the use of sonoluminescence as a probe, there seems to be no theoretical correlation between chemical effects and ultrasonic power. Nevertheless it is an undeniable fact that when sonochemistry is reported in the literature it would be extremely useful if the response of the system used to a standard sonochemical reaction could be included. 

All of these parameters have to be carefully monitored in order to obtain reproducible results, and it is quite clear that calibration of a chemical effect can only be sustained for a fully described ultrasonic system and reactor. Any change in the nature of the device will most likely result in a change in the SY. Furthermore, the relation between ultrasonic power and chemical yield or reaction rate will not be linear within the whole range of ultrasonic power. An optimum in reaction yield is quite often observed. Numerous examples have been given during the past few years where optimum yields are obtained with other variable parameters such as bulk temperature, external pressure, and gas content. 

Three basic schemes for the ultrasonic cleaning of the melt can be proposed (1) in a liquid bath of an ingot (the melt surface is in a contact with a waveguide-radiating ultrasonic system) (2) in a mold (oscillations transmit to the melt through mold walls) and (3) in an intermediate vessel placed in the flow of melt from a holding furnace to a mold (oscillations transmits to the melt according to the first scheme). 

Ultrasonic systems using less harmful and corrosive materials have been successfully used as an alternative to vapor cleaning. For example, stainless steel, which used to be cleaned with distillate-spray wash and vapor rinse using 1,1,1 -trichlo-roethane, has been replaced by immersion in ultrasonic bath containing trichloro-trifluoroethane and methanol. Hence the beneficial substitution of one organic solvent by a more environmentally friendly cleaner is possible. 

DiScalia, F.L. Green, R.E. Jr. A hybrid non-contact ultrasonic system for sensing bond quality in tow-placed thermoplastic composites. J. Compos. Mater. 2000, 34 (21), 1860-1880. 

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