scholarly journals Optimized Design of CMUT with Hexagonal Membranes

2019 ◽  
Vol 8 (10) ◽  
pp. 1805-1809
Keyword(s):  
Resonant Frequency ◽  
Ultrasonic Transducer ◽  
Ultrasonic Signal ◽  
Ultrasonic Waves ◽  
Capacitive Transducer ◽  
Optimized Design ◽  
Circular Membrane ◽  
Electrical Capacitance ◽  
Capacitance Change ◽  
Stationary Analysis

A Capacitive Micro-machined Ultrasonic Transducer (CMUT) with hexagonal membrane is constructed to work as a transmitter and compared to a CMUT with circular membrane. In this paper, three desirable combination of circular and hexagon are analyzed to select the dimensions for hexagonal shaped CMUT. Capacitive Micro-machined Ultrasonic Transducer (CMUT) is a micro constructed transducer used both as transmitter for generating ultrasonic waves and as receiver to modulate the electrical capacitance of the capacitive transducer. It can be fabricated with many geometries especially circular, square, rectangular, and hexagon. Circular CMUTs offers optimum performance in terms of deflection with DC, deflection of biased membrane with AC bias, resonant frequency, capacitance and deflection along frequency but for array formation the wafer area is wasted. A CMUT with hexagonal membrane gives an ultrasonic signal of constant amplitude with less deflection of membrane within the cavity and the outside environment. Stationary analysis is carried out with electro-mechanics for discussing the capacitance change of CMUT. The collapse or pull in voltage of hexagon CMUT is found to be high and increases the bandwidth of CMUT. The absolute percent difference of resonant frequency is observed to be 2.3 % with dimensions selected from the COH configuration of the CMUT

CREEPING SURFACE LONGITUDINAL ACOUSTIC WAVE: MAIN PROPERTIES AND APPLICATION POSSIBILITIES

2021 ◽  
pp. 4-12
Author(s):  
V. G. Shevaldykin
Keyword(s):  
Critical Angle ◽  
Flaw Detection ◽  
Ultrasonic Signal ◽  
Ultrasonic Waves ◽  
Concave Surface ◽  
Ultrasonic Tomography ◽  
Transverse Waves ◽  
Near Surface ◽  
The Third ◽  
Creeping Wave

Creeping ultrasonic waves have long been successfully used for flaw detection of near-surface and near-bottom zones of metal products. However, due to the fact that the creeping wave generates a lateral transverse wave directed into the metal volume at the third critical angle, it is also possible to test internal defects in principle. At known velocities of propagation of longitudinal and transverse waves in the metal, the third critical angle is easily calculated. Therefore, the time of propagation of the ultrasonic signal along any trajectory between points on the surface and in the volume of the metal can be calculated. Usually, creeping waves are used to test products of plane-parallel shape. There are no cases of their application on curved surfaces in the literature. It is possible that the creeping wave can also propagate over a concave surface. The aim of the article is to test experimentally new ways of using creeping waves. The propagation trajectories of the creeping and lateral transverse waves were studied on a steel plate. The time of passage of the ultrasonic signal along such trajectories of different lengths was measured, and the measurement results were compared with the calculated time values. The measured and calculated values coincided with accuracy sufficient for the coherent accumulation of echo signals that passed through the metal part of the path by the creeping wave and another part of the path by the lateral transverse wave.The propagation of the creeping wave over a concave surface was studied on a steel sample with cylindrical faces of different radii. As a result, it turned out that on a concave surface, the creeping wave propagates at the same speed of longitudinal waves as on a flat surface, but it decays much more strongly with distance. Studies have shown that creeping waves can be used in ultrasonic tomography, where a preliminary calculation of the propagation trajectories of ultrasonic signals is required. The propagation of creeping waves over concave surfaces extends the capabilities of the TOFD method to the area of intube testing

Theoretical Approach to Contrast Mechanism for U-AFM

2002 ◽  
Author(s):  
C. Miyasaka ◽  
B. R. Tittmann ◽  
T. Adachi ◽  
A. Yamaji
Keyword(s):  
Theoretical Analysis ◽  
Resonant Frequency ◽  
Atomic Force Microscope ◽  
Dynamic Theory ◽  
Beam Theory ◽  
Ultrasonic Waves ◽  
Two Dimensional ◽  
Atomic Force ◽  
Afm Imaging ◽  
Contrast Mechanism

When the Ultrasonic-Atomic Force Microscope (U-AFM) is used to form an image of a surface of a specimen having discontinuities, contrast of the specimen in the image is usually stronger than that of an image formed by a conventional Atomic Force Microscope (AFM). In this article, the mechanism of the contrast of the image obtained by the U-AFM was explained by theoretical analysis. A ceramic and metal jointed bar (Steel/Cu/Si3N4) was selected as a specimen for this study. The specimen was located on the surface of a disc transducer generating ultrasonic waves up to 500 KHz, and was vibrated, wherein its first resonant frequency was 133.43 kHz. Both stress and displacement of the specimen were analyzed by classical beam theory and the two-dimensional elasto-dynamic theory. Experimental U-AFM imaging analyses were also carried out to compare the results.

scholarly journals Development of a High-Density Piezoelectric Micromachined Ultrasonic Transducer Array Based on Patterned Aluminum Nitride Thin Film

Micromachines ◽  
2020 ◽  
Vol 11 (6) ◽  
pp. 623 ◽  
Author(s):  
Eunjung Shin ◽  
Hong Goo Yeo ◽  
Ara Yeon ◽  
Changzhu Jin ◽  
Wonki Park ◽  
...  
Keyword(s):  
Thin Film ◽  
Aluminum Nitride ◽  
Resonant Frequency ◽  
Fill Factor ◽  
Ultrasonic Transducer ◽  
Peak Displacement ◽  
Biomedical Sensing ◽  
Potential Applications ◽  
Pressure Output

This study presents the fabrication and characterization of a piezoelectric micromachined ultrasonic transducer (pMUT; radius: 40 µm) using a patterned aluminum nitride (AlN) thin film as the active piezoelectric material. A 20 × 20 array of pMUTs using a 1 µm thick AlN thin film was designed and fabricated on a 2 × 2 mm2 footprint for a high fill factor. Based on the electrical impedance and phase of the pMUT array, the electromechanical coefficient was ~1.7% at the average resonant frequency of 2.82 MHz in air. Dynamic displacement of the pMUT surface was characterized by scanning laser Doppler vibrometry. The pressure output while immersed in water was 19.79 kPa when calculated based on the peak displacement at the resonant frequency. The proposed AlN pMUT array has potential applications in biomedical sensing for healthcare, medical imaging, and biometrics.

scholarly journals Piezoelectric Micromachined Ultrasonic Transducers with a Cost-Effective Bottom-Up Fabrication Scheme for Millimeter-Scale Range Finding

Sensors ◽  
2019 ◽  
Vol 19 (21) ◽  
pp. 4696 ◽  
Author(s):  
Guo-Hua Feng ◽  
Hua-Jin Liu
Keyword(s):  
Ultrasonic Transducer ◽  
Time Of Flight ◽  
Cost Effective ◽  
Ultrasonic Waves ◽  
Metal Foil ◽  
Large Area ◽  
Bottom Up ◽  
Processing Scheme ◽  
Range Finding ◽  
Mems Microphone

This study proposes a novel piezoelectric micromachined ultrasonic transducer (PMUT), fabricated on a metal foil. Using a bottom-up, cost-effective micromachining technique, the PMUTs made of electrodes, a piezoelectric film, or electrode-sandwiched structures with versatile patterns were implemented on a large-area foil thinner rather than regular paper. The proposed microfabrication facilitated the PMUT to be able to generate ultrasonic waves with fundamental and harmonic resonances. The fourth-order resonances of the fabricated PMUT functionally operated at an ultrasonic spectrum of approximately 30 kHz as an ultrasonic emitter. The developed PMUT was paired with a microelectromechanical system (MEMS) microphone module for range-finding applications in the range of several tens of millimeters. A signal-processing scheme was developed to extract the representative pattern from the acquired signals that were emitted and received. The pattern enabled finding the distance between the PMUT and the microphone using time-of-flight and strength-variation technology. The developed PMUT-microphone pair demonstrated its range-finding performance, displaying an error of less than 0.7% using the time-of-flight method.

Numerical Investigation of Propagation of Ultrasonic Waves in the Waveguides with Mode Conversion

2013 ◽  
Vol 543 ◽  
pp. 219-222
Author(s):  
Elena Jasiūnienė ◽  
Egidijus Žukauskas ◽  
Rymantas Kažys
Keyword(s):  
Numerical Investigation ◽  
Longitudinal Wave ◽  
Mode Conversion ◽  
Incidence Angle ◽  
Ultrasonic Transducer ◽  
Shear Waves ◽  
Ultrasonic Waves ◽  
Ultrasonic Transducers ◽  
Special Cases ◽  
Longitudinal And Shear Waves

Ultrasonic investigation techniques are widely used in materials characterisation and non-destructive testing applications. In special cases of applications, such as investigation of properties of melted polymers, metals and hot liquids, measurements must be performed in a wide temperature range. However conventional piezoelectric transducers cannot withstand higher temperatures than the Curie temperature. Therefore in order to protect conventional ultrasonic transducers from influence of a high temperature and to avoid depolarization, measurements must be performed using special waveguides with a low thermal conductivity between the object under investigation and the ultrasonic transducer. For measurements of the material properties, such as viscoelastic properties of materials, additional shear wave transducers must be used. In this work approach how to excite both, longitudinal and shear waves using special waveguides with mode conversion, using pair of conventional ultrasonic longitudinal wave transducers is presented. In this work numerical investigation of propagation of longitudinal and shear ultrasonic waves in the waveguides with mode conversion using finite element method and CIVA software was carried out. Modelling of propagation of simultaneously generated longitudinal and shear waves using pair of longitudinal ultrasonic transducers was performed. Influence of temperature gradient to the required incidence angle of the longitudinal wave was evaluated.

A Comparison Between Computational Simulation and Measurement of Acoustically Enhanced Heat Transfer

2005 ◽  
Author(s):  
Yool-Kwon Oh ◽  
Ho-Dong Yang
Keyword(s):  
Heat Transfer ◽  
Acoustic Field ◽  
Ultrasonic Transducer ◽  
Computational Simulation ◽  
Acoustic Streaming ◽  
Ultrasonic Waves ◽  
Structural Vibration ◽  
Computational Simulations ◽  
Enhancement Of Heat Transfer ◽  
Fortran Language

The strong upward flow called as “acoustic streaming”, when ultrasonic waves were applied in a medium, occurred near to ultrasonic transducer and enhanced the heat transfer. That is, applying ultrasonic waves in a medium may cause the flow velocity of the medium to increase: an effect known as acoustic streaming promotes heat transfer through convection and affects the thermal boundary layer. So, this study was compared with the pressure variations and enhancement of heat transfer by computational simulations and experiments in acoustic field. For the computational simulations, structural vibration simulator (SVS) programmed with a fortran language and based on a coupled finite element-boundary element method (coupled FE-BEM) was used. The results of this study reveal that the acoustic pressure is higher near two ultrasonic transducers than other points where no ultrasonic transducer was installed. The enhancement trend of heat transfer is similar with the profile of the pressure variations. It is concluded that the pressure variations are related to the enhancement of heat transfer in acoustic field.

Microstructure and Defects Evaluation of Varistors by Ultrasonic Waves in Low Frequency Range

2013 ◽  
Vol 592-593 ◽  
pp. 688-691
Author(s):  
Pavel Tofel ◽  
Pavel Škarvada ◽  
Josef Sikula ◽  
Gabriel Cséfalvay
Keyword(s):  
Mechanical Properties ◽  
Mass Density ◽  
Low Frequency ◽  
Sample Volume ◽  
Ultrasonic Signal ◽  
Ultrasonic Waves ◽  
Ultrasonic Vibrations ◽  
Ultrasonic Spectroscopy ◽  
Resistance Change ◽  
Acoustic Effect

Each material contains defects and in-homogeneities in a structure volume. It has influence on the properties of material (conductivity, mass density, mechanical properties). Interaction of the ultrasonic waves with defects or in-homogeneities in the solid state is not clear. Electro-ultrasonic spectroscopy can help to clarify this phenomenon. The electro-ultrasonic spectroscopy describes defects and un-homogeneities inside the sample structure. This method is quite different from electro-acoustic effect. Ultrasonic signal is in range from 20 kHz to 150 kHz. Ultrasonic signal changes geometry of the sample in elastic range only. The sizes of cracks are changing also in the sample volume. Conductivity near the area of cracks is strongly changing due to ultrasonic vibrations. It has influence on resistance of the sample which is changing along with a frequency of ultrasonic vibrations. The amplitude of the resistance change depends on the material, number of cracks, size of cracks and Eigen frequencies of the sample excited by ultrasonic wave. We applied the electro-ultrasonic spectroscopy on two types of varistors. It can be useful for understanding the relation between microstructure and mechanical properties of these types of varistors.

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