scholarly journals High Frequency Longitudinal Damped Vibrations of a Cylindrical Ultrasonic Transducer

2014 ◽  
Vol 2014 ◽  
pp. 1-8 ◽  
Author(s):  
Mihai Valentin Predoi ◽  
Cristian Cătălin Petre ◽  
Ovidiu Vasile ◽  
Mihail Boiangiu
Keyword(s):  
High Frequency ◽  
Ultrasonic Transducer ◽  
Classical Model ◽  
Longitudinal Mode ◽  
Piezoelectric Transducers ◽  
Normal Velocity ◽  
Longitudinal Vibrations ◽  
Elastic Rod ◽  
Damping Term ◽  
Beat Phenomenon

Ultrasonic piezoelectric transducers used in classical nondestructive testing are producing in general longitudinal vibrations in the MHz range. A simple mechanical model of these transducers would be very useful for wave propagation numerical simulations, avoiding the existing complicated models in which the real components of the transducer are modeled by finite elements. The classical model for longitudinal vibrations is not adequate because the generated longitudinal wave is not dispersive, the velocity being the same at any frequency. We have adopted the Rayleigh-Bishop model, which avoids these limitations, even if it is not converging to the first but to the second exact longitudinal mode in an elastic rod, as obtained from the complicated Pochhammer-Chree equations. Since real transducers have significant vibrations damping, we have introduced a damping term in the Rayleigh-Bishop model, increasing the imaginary part and keeping almost identical real part of the wavenumber. Common transducers produce amplitude modulated signals, completely attenuated after several periods. This can be modeled by two close frequencies, producing a “beat” phenomenon, superposed on the high damping. For this reason, we introduce a two-rod Rayleigh-Bishop model with damping. Agreement with measured normal velocity on the transducer free surface is encouraging for continuation of the research.

Modeling of a high frequency ultrasonic transducer using periodic structures

2007 ◽  
Author(s):  
P. Maréchal ◽  
L. Haumesser ◽  
G. Feuillard ◽  
L.P. Tran-Huu-Hue ◽  
J. Holc ◽  
...  
Keyword(s):  
High Frequency ◽  
Periodic Structures ◽  
Ultrasonic Transducer

Design and Experiment of Capacitive Micromachined Ultrasonic Transducer Array for High-Frequency Underwater Imaging

2020 ◽  
Vol 13 ◽  
Author(s):  
Yuanyu Yu ◽  
Jiujiang Wang ◽  
Xin Liu ◽  
Sio Hang Pun ◽  
Weibao Qiu ◽  
...  
Keyword(s):  
Ultrasound Imaging ◽  
High Frequency ◽  
Ultrasonic Transducer ◽  
Center Frequency ◽  
Design Parameters ◽  
Underwater Imaging ◽  
Release Process ◽  
Steel Wires ◽  
Capacitive Micromachined Ultrasonic Transducer ◽  
Frequency Ultrasound

Background:: Ultrasound is widely used in the applications of underwater imaging. Capacitive micromachined ultrasonic transducer (CMUT) is a promising candidate to the traditional piezoelectric ultrasonic transducer. In underwater ultrasound imaging, better resolutions can be achieved with a higher frequency ultrasound. Therefore, a CMUT array for high-frequency ultrasound imaging is proposed in this work. Methods:: Analytical methods are used to calculate the center frequency in water and the pull-in voltage for determining the operating point of CMUT. Finite element method model was developed to finalize the design parameters. The CMUT array was fabricated with a five-mask sacrificial release process. Results:: The CMUT array owned an immersed center frequency of 2.6 MHz with a 6 dB fractional bandwidth of 123 %. The pull-in voltage of the CMUT array was 85 V. An underwater imaging experiment was carried out with the target of three steel wires. Conclusion:: In this study, we have developed CMUT for high-frequency underwater imaging. The experiment showed that the CMUT can detect the steel wires with the diameter of 100 μm and the axial resolution was 0.582 mm, which is close to one wavelength of ultrasound in 2.6 MHz.

High-frequency PIN–PMN–PT single crystal ultrasonic transducer for imaging applications

2012 ◽  
Vol 108 (4) ◽  
pp. 987-991 ◽  
Author(s):  
Y. Chen ◽  
K. H. Lam ◽  
D. Zhou ◽  
W. F. Cheng ◽  
J. Y. Dai ◽  
...  
Keyword(s):  
Single Crystal ◽  
High Frequency ◽  
Ultrasonic Transducer

scholarly journals Novel Experimental Study of Fabric Drying Using Direct-Contact Ultrasonic Vibration

2018 ◽  
Vol 11 (2) ◽  
Author(s):  
Viral K. Patel ◽  
Frederick Kyle Reed ◽  
Roger Kisner ◽  
Chang Peng ◽  
Saeed Moghaddam ◽  
...  
Keyword(s):  
High Frequency ◽  
Direct Contact ◽  
First Generation ◽  
Scale Up ◽  
Enthalpy Of Vaporization ◽  
Piezoelectric Transducers ◽  
Scaling Analysis ◽  
Moisture Removal ◽  
Low Efficiency

Abstract Fabric drying is an energy-intensive process, which generally involves blowing hot dry air across tumbling wet fabric to facilitate evaporation and moisture removal. Most of the energy supplied is used to overcome the enthalpy of vaporization for water. Although this process tends to be inefficient, it is fairly simple and forms the basis for the majority of existing clothes dryer technology today. To address the relatively low efficiency, a new method of drying called “direct contact ultrasonic fabric drying” is proposed. The process involves using high-frequency vibration introduced by piezoelectric transducers, which are in contact with wet fabric. The vibration is used to extract water droplets from the fabric mechanically. In this study, a total of 24 individual transducers are used in a module to dry a 142 cm2 sized fabric. The performance characterization of this single module has enabled successful scale-up of the system to a midscale prototype dryer, which can be used to ultrasonically dry clothing-sized fabric (∼750 cm2). The first-generation ultrasonic fabric dryer fabricated uses as little as 17% of the energy needed by traditional evaporation-based drying techniques. In addition to experimental data, this paper presents the results of a kinetic and scaling analysis that provides some important insights into ultrasonic drying.

The Propagation of Compressional Waves in a Dispersive Elastic Rod: Part II—Experimental Results and Comparison With Theory

1957 ◽  
Vol 24 (2) ◽  
pp. 240-244
Author(s):  
Julius Miklowitz ◽  
C. R. Nisewanger
Keyword(s):  
Shock Tube ◽  
Longitudinal Mode ◽  
Long Waves ◽  
Experimental Results ◽  
Radial Mode ◽  
Approximate Representation ◽  
Elastic Rod ◽  
Compressional Waves ◽  
Short Waves

Abstract Experimental results, obtained by employing an aerodynamic shock tube for rod excitation, are presented. Comparison of these results with the theoretical information presented in Part I is made. It is shown that the Mindlin-Herrmann theory, through its upper mode (radial), offers a good approximate representation of the moderately short waves that predominate at the later times at a random station of the rod. The very short waves of this same radial mode, however, govern the early disturbance, thus precluding the possibility of representing this portion of the disturbance, which the experiment shows to be composed of relatively long waves, by the longitudinal mode of the theory.

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