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Majid Rajabi, Alireza Mojahed
The interaction between harmonic plane progressive acoustic beams and a pulsating spherical radiator is studied. The acoustic radiation force function exerted on the spherical body is derived as a function of the incident wave pressure and the monopole vibration characteristics (i.e., amplitude and phase) of the body. Two distinct strategies are presented in order to alter the radiation force effects (i.e., pushing and pulling states) by changing its magnitude and direction. In the first strategy, an incident wave field with known amplitude and phase is considered...
June 13, 2017: Ultrasonics
Naoki Mori, Shiro Biwa
In order to gain basic insight into the interaction between ultrasonic guided waves and structural discontinuities with contacting surfaces, the transmission characteristics of Lamb waves at contacting edges of two plates are studied experimentally. The edges of two 2.5-mm thick aluminum alloy plates are mated together to constitute a contacting interface of plates and subjected to different levels of compressive loading. The transmission measurements of the lowest-order symmetric (S0) and antisymmetric (A0) Lamb modes across the contacting interface are performed in a frequency range below the cut-off frequencies of the higher-order modes...
June 13, 2017: Ultrasonics
F G Mitri
The prediction of the elastic scattering by voids (and cracks) in materials is an important process in structural health monitoring, phononic crystals, metamaterials and non-destructive evaluation/imaging to name a few examples. Earlier analytical theories and numerical computations considered the elastic scattering by voids in plane waves of infinite extent. However, current research suggesting the use of (limited-diffracting, accelerating and self-healing) Airy acoustical-sheet beams for non-destructive evaluation or imaging applications in elastic solids requires the development of an improved analytical formalism to predict the scattering efficiency used as a priori information in quantitative material characterization...
June 8, 2017: Ultrasonics
Boran Zhou, Arthur J Sit, Xiaoming Zhang
The objective of this study was to extend an ultrasound surface wave elastography (USWE) technique for noninvasive measurement of ocular tissue elastic properties. In particular, we aim to establish the relationship between the wave speed of cornea and the intraocular pressure (IOP). Normal ranges of IOP are between 12 and 22mmHg. Ex vivo porcine eye balls were used in this research. The porcine eye ball was supported by the gelatin phantom in a testing container. Some water was pour into the container for the ultrasound measurement...
June 7, 2017: Ultrasonics
David Torello, Nicholas Selby, Jin-Yeon Kim, Jianmin Qu, Laurence J Jacobs
Quantitative evaluation of the microstructural state of a specimen can be deduced from knowledge of the sample's absolute acoustic nonlinearity parameter, β, making the measurement of β a powerful tool in the NDE toolbox. However, the various methods used in the past to measure β each suffer from significant limitations. Piezoelectric contact transducers are sensitive to nonlinear signals, cheap, and simple to use, but they are hindered by the variability of the interfacial contact between transducer and specimen surface...
June 3, 2017: Ultrasonics
A J Balvantín, J A Diosdado-De-la-Peña, P A Limon-Leyva, E Hernández-Rodríguez
In this work, fundamental symmetric Lamb wave S0 mode is characterized in terms of its velocity variation as function of the interfacial conditions between solid bodies in contact. Imperfect contact conditions are numerically and experimentally determined by using ultrasonic Lamb wave propagation parameters. For the study, an experimental system was used, formed by two solid aluminum rods (25.4mm in diameter) axially loading a thin aluminum plate to control contact interfacial stiffness. The axially applied load on the aluminum plate was varied from 0MPa to 10MPa...
June 3, 2017: Ultrasonics
M Celmer, K J Opieliński, M Dopierała
One of the reasons of distortions in ultrasonic imaging are crosstalk effects. They can be divided into groups according to the way of their formation. One of them is constituted by mechanical crosstalk, which is propagated by a construction of a multi-element array of piezoelectric transducers. When an individual transducer is excited, mechanical vibrations are transferred to adjacent construction components, thereby stimulating neighboring transducers to an undesired operation. In order to explore ways of the propagation of such vibrations, the authors developed the FEM model of the array of piezoelectric transducers designed for calculations in COMSOL Multiphysics software...
June 3, 2017: Ultrasonics
Elif Eren Gültekin
The scope of the present study is to investigate the change of elastic modulus with the physical and mechanical properties of porcelain tiles. In the study, porcelain tiles were sintered at different temperatures and at different heating rates to obtain minimum water absorption (%). After this, the time of flight of longitudinal and shear ultrasonic waves was measured through the tile. The time of flight of ultrasonic waves was measured using contact ultrasonic transducers operating on a pulse-echo mode. Using the time of flight of the ultrasonic waves and the thickness of the tiles, the velocity of the waves was determined...
June 3, 2017: Ultrasonics
Medhat Awad El-Hadek
Ultrasonic stress waves, generated during the dynamic impact on structures, were studied. A benchmark for the finite element analysis (FEA) was made to define the optimum geometrical factors, which were represented as, mesh distribution, analysis time, ultrasonic wave properties, element type, and shape to capture the dynamic phenomena compared to the theoretical exact solution. Comparison of three different dimensional finite element models was performed depending on the applied impact forces, the element size, and the structural geometry...
June 3, 2017: Ultrasonics
Shoubing Liu, Wenke Lu, Changchun Zhu
The goal of this research is to study two-port network of wavelet transform processor (WTP) using surface acoustic wave (SAW) devices and its application. The motive was prompted by the inconvenience of the long research and design cycle and the huge research funding involved with traditional method in this field, which were caused by the lack of the simulation and emulation method of WTP using SAW devices. For this reason, we introduce the two-port network analysis tool, which has been widely used in the design and analysis of SAW devices with uniform interdigital transducers (IDTs)...
May 29, 2017: Ultrasonics
Parisa Shokouhi, Jacques Rivière, Colton R Lake, Pierre-Yves Le Bas, T J Ulrich
The use of nonlinear acoustic techniques in solids consists in measuring wave distortion arising from compliant features such as cracks, soft intergrain bonds and dislocations. As such, they provide very powerful nondestructive tools to monitor the onset of damage within materials. In particular, a recent technique called dynamic acousto-elasticity testing (DAET) gives unprecedented details on the nonlinear elastic response of materials (classical and non-classical nonlinear features including hysteresis, transient elastic softening and slow relaxation)...
May 27, 2017: Ultrasonics
Jae-Wan Lee, Won-Suk Ohm, Yong-Tae Kim
A method for fabricating disposable membrane hydrophones is presented. The disposable hydrophones are intended for onetime use in such damaging environments as chemically contaminating fluids and high-amplitude (peak amplitude ∼100MPa) shock wave fields, where the use of commercial membrane hydrophones is not recommended. Fabrication of a hydrophone is done using only off-the-shelf components and hand tools, which translates into ease of fabrication and orders-of-magnitude reduction in unit cost. In particular, poling and sputtering, the two processes that are chiefly responsible for the cost and difficulty associated with the conventional fabrication method, are replaced with the use of pre-poled polyvinylidene fluoride (PVDF) films and polyethylene terephthalate (PET)-coated aluminum foils, respectively...
May 25, 2017: Ultrasonics
Qibao Lv, Zhiyuan Yao, Xiang Li
The effects of surface roughness are not considered in the traditional motor model which fails to reflect the actual contact mechanism between the stator and slider. An analytical model for calculating the tangential force of linear ultrasonic motor is proposed in this article. The presented model differs from the previous spring contact model, the asperities in contact between stator and slider are considered. The influences of preload and exciting voltage on tangential force in moving direction are analyzed...
May 25, 2017: Ultrasonics
Shen Wang, Songling Huang, Alexander Velichko, Paul Wilcox, Wei Zhao
In this paper an axisymmetric model of an omnidirectional electromagnetic acoustic transducer (EMAT) used to generate Lamb waves in conductive plates is introduced. Based on the EMAT model, the structural parameters of the permanent magnet were used as the design variables while other parameters were fixed. The goal of the optimization was to strengthen the generation of the A0 mode and suppress the generation of the S0 mode. The amplitudes of the displacement components at the observation point of the plate were used for calculation of the objective functions...
May 25, 2017: Ultrasonics
N Vyas, H Dehghani, R L Sammons, Q X Wang, D M Leppinen, A D Walmsley
Cavitation is a potentially effective and less damaging method of removing biofilm from biomaterial surfaces. The aim of this study is to characterise individual microbubbles around ultrasonic scaler tips using high speed imaging and image processing. This information will provide improved understanding on the disruption of dental biofilm and give insights into how the instruments can be optimised for ultrasonic cleaning. Individual cavitation microbubbles around ultrasonic scalers were analysed using high speed recordings up to a million frames per second with image processing of the bubble movement...
May 24, 2017: Ultrasonics
Hacene Lazri, Erick Ogam, Boudour Amar, Z E A Fellah, Andrew O Oduor, Paul Baki
A method for the identification of the mechanical moduli and density of flexible, supple thermoplastic thin films placed on elastic substrates using ultrasonic waves has been developed. The composite medium immersed in a fluid host medium (water) was excited using a 50MHz transducer operating at normal incidence in reflection mode. Inverse problems involving experimental data pertaining to elastic wave propagation in the thin films on their substrates and theoretical fluid-solid interaction models for stratified media using elasticity theory were solved...
May 23, 2017: Ultrasonics
Elisa Minnetti, Giuseppe Pandarese, Piersavio Evangelisti, Francisco Rodriguez Verdugo, Carmine Ungaro, Alessandro Bastari, Nicola Paone
The paper presents a technique to measure the speed of sound in fuels based on pulse-echo ultrasound. The method is applied inside the test chamber of a Zeuch-type instrument used for indirect measurement of the injection rate (Mexus). The paper outlines the pulse-echo method, considering probe installation, ultrasound beam propagation inside the test chamber, typical signals obtained, as well as different processing algorithms. The method is validated in static conditions by comparing the experimental results to the NIST database both for water and n-Heptane...
May 22, 2017: Ultrasonics
Qingbang Han, Lihua Qi, Minglei Shan, Cheng Yin, Xueping Jiang, Changping Zhu
Based on the modified Biot theory of Johnson, the propagation characteristics of the various interface waves at an interface between a semi-infinite fluid and a porous medium were studied. First, based on the characteristic equations of open-pore and sealed-pore, which were derived from the wave equations, time-domain waveforms at the interface were obtained by inverse Fourier transform. The effects of the longitudinal frame modulus on the interface waves were investigated. For open-pore and sealed-pore, the effect of porosity on the propagation of the interface waves was studied; the porosity was found to strongly influence the true surface wave...
May 19, 2017: Ultrasonics
Koussila Kassou, Youcef Remram, Pascal Laugier, Jean-Gabriel Minonzio
Guided waves-based techniques are currently under development for quantitative cortical bone assessment. However, the signal interpretation is challenging due to multiple mode overlapping. To overcome this limitation, dry point-contact transducers have been used at low frequencies for a selective excitation of the zeroth order anti-symmetric Lamb A0 mode, a mode whose dispersion characteristics can be used to infer the thickness of the waveguide. In this paper, our purpose was to extend the technique by combining a dry point-contact transducers approach to the SVD-enhanced 2-D Fourier transform in order to measure the dispersion characteristics of the flexural mode...
May 18, 2017: Ultrasonics
Konstantinos Diamantis, Alan Greenaway, Tom Anderson, Jørgen Arendt Jensen, Vassilis Sboros
Recent progress in adaptive beamforming techniques for medical ultrasound has shown that current resolution limits can be surpassed. One method of obtaining improved lateral resolution is the Minimum Variance (MV) beamformer. The frequency domain implementation of this method effectively divides the broadband ultrasound signals into sub-bands (MVS) to conform with the narrow-band assumption of the original MV theory. This approach is investigated here using experimental Synthetic Aperture (SA) data from wire and cyst phantoms...
April 21, 2017: Ultrasonics
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