Ultrasonic transducers

Some of the problems often encountered during ultrasonic inspection of plane specimens are also found on cylindrical specimens. For example, problems associated with the directional characteristic of the ultrasonic transducer. Furthermore, the discontinuity influences the shape and propagation direction of a reflected pulse, causing wave mode transformation. In addition, the specimen influences the shape and amplitude of the reflected pulse by sound absorption. 

Accurate modelling of the field radiated by ultrasonic transducers is an essential step forward considering the final goal of the complete simulation of pulse echo experiments. 

W.A. Grandia, C.M. Fortunko NDE Applications of Air-Coupled Ultrasonic Transducers, IEEE Int. Ultrasonics Symposium, November 7-10, 1995, Seattle, Washington. 

Castaings, M. and Cawley, P. The generation, propagation, and detection of Lamb waves in plates using air-coupled ultrasonic transducers... 

In UltraSIM/UlSim the ultrasonic sound propagation from a virtual ultrasonic transducer can be simulated in ray tracing mode in any isotropic and homogeneous 3D geometry, including possible mode conversions phenomenons, etc. The CAD geometry for the simulation is a 3D NURBS surface model of the test object. It can be created in ROBCAD or imported from another 3D CAD system. 

The dependencies described are sufficient for designing the different types of ultrasonic transducers for testing by surface waves. The constant transmission of acoustic energy is provided. 

Structure of installation enter the source-receiver of acoustic oscillations, block of ultrasonic transducers, system of scanning, control system engines, block of the analysis and registration. 

The development of active ceramic-polymer composites was undertaken for underwater hydrophones having hydrostatic piezoelectric coefficients larger than those of the commonly used lead zirconate titanate (PZT) ceramics (60—70). It has been demonstrated that certain composite hydrophone materials are two to three orders of magnitude more sensitive than PZT ceramics while satisfying such other requirements as pressure dependency of sensitivity. The idea of composite ferroelectrics has been extended to other appHcations such as ultrasonic transducers for acoustic imaging, thermistors having both negative and positive temperature coefficients of resistance, and active sound absorbers. 

Another important class of titanates that can be produced by hydrothermal synthesis processes are those in the lead zirconate—lead titanate (PZT) family. These piezoelectric materials are widely used in manufacture of ultrasonic transducers, sensors, and minia ture actuators. The electrical properties of these materials are derived from the formation of a homogeneous soHd solution of the oxide end members. The process consists of preparing a coprecipitated titanium—zirconium hydroxide gel. The gel reacts with lead oxide in water to form crystalline PZT particles having an average size of about 1 ]lni (Eig. 3b). A process has been developed at BatteUe (Columbus, Ohio) to the pilot-scale level (5-kg/h). 

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... 

Fothergill, J. R., Willis, P. and Waywells, S. Development of High Temperature Ultrasonic Transducers for under Sodium Viewing Applications , Brit. J. of NOT, 31, 5, 259-264, May (1989)... 

With nondestructive ultrasonic test back and forth scanning of a specimen is accomplished with ultrasonics. This NDT can be used to find voids, delaminations, defects in fiber distribution, etc. In ultrasonic testing the sound waves from a high frequency ultrasonic transducer are beamed into a material. Discontinuities in the material interrupt the sound beam and reflect the energy back to the transducer, providing data that can be used to detect and characterize flaws. It can locate internal flaws or structural discontinuities by the use of high frequency reflection or attenuation (ultrasonic beam). 

A commercially available ultrasonic cleaner was used for the prqjaration of nickel powders from nickel salt in aqueous solution. This cleaner, Model 3210 (Branson Ultrasonic Corp., CT), is normally used as a cleaning apparatus, working at a frequency of 47 kHz with e power of 130 W that consists of a stainless-steel bath of 5.17 1 capacity and has an ultrasonic transducer attached to the bottom of the bath. A liquid solution temperature in the bath can be varied from room temperature to maximum of 80 °C. 

An ultrasonic transducer is installed on the pH probe mount in the acid-alkali treatment module [T-31], This prevents fouling of the electrodes and provides a more closely controlled pH in the effluent discharged to the precipitator. 

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]. 

Lamminen MO, Walker HW, Weavers LK (2006) Cleaning of particle-fouled membranes during cross-flow filtration using an embedded ultrasonic transducer system. J Membrane Sci 283 225-232... 

Gallego-Juarez JA, Rodriguez Corral G, Riera E et al. (2001) Development of industrial models of high power stepped-plate sonic and ultrasonic transducer for use in fluids. IEEE Ultrasonic Sypoos. Proceedings, pp 571-578... 

The ultrasonic levitation technique was introduced in the 1930s and does not rely on any specific properties of the sample except size and mass, and has been used in bioanalytical and analytical chemistry applications6-10. The acoustic levitator consists of an ultrasonic transducer and a solid reflector supporting standing waves (see Fig. 17.5). 

Ultrasonic insertion an ultrasonic transducer (horn) vibrates the insert, which heats by vibrating against the plastic. The advantages and drawbacks of this process are ... 

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