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Nan Li, Christopher R Lowe, Adrian C Stevenson
A versatile system to construct bulk polymeric phononic crystals by using acoustic waves is described. In order to fabricate this material, a customised cavity device fitted with a ∼2 MHz acoustic transducer and an acoustic reflector is employed for the acoustic standing wave creation in the device chamber. The polymer crystal is formed when the standing waves are created during the polymerisation process. The resulting crystals are reproduced into the shape of the tunable device cavity with a unique periodic feature...
July 7, 2018: Ultrasonics
Yuriy Tasinkevych, Katarzyna Falińska, Peter A Lewin, Jerzy Litniewski
The purpose of this work was to present a new approach that allows the influence of cortical bone on noninvasive measurement of broadband ultrasound attenuation (BUA) to be corrected. The method, implemented here at 1 MHz makes use of backscattered signal and once refined and clinically confirmed, it would offer an alternative to ionizing radiation based methods, such as DEXA (Dual-energy X-ray absorptiometry), quantitative computed tomography (QCT), radiographic absorptiometry (RA) or single X-ray absorptiometry (SXA), which are clinically approved for assessment of progress of osteoporosis...
July 2, 2018: Ultrasonics
Kai-Alexander Saalbach, Jens Twiefel, Jörg Wallaschek
The generation of cavitation by ultrasound is used in a large number of processes in different scientific and industrial applications. Chemical reactions are made possible or accelerated by locally occurring high temperatures and pressures generated by the collapse of cavitation bubbles. Mixing or separating substances, emulsification, ultrasonic cleaning, degassing, and microbiological treatment of fluids are some more applications for ultrasonic generated cavitation. In most of these applications, an optical examination of the events within the cavitating medium is not possible...
June 28, 2018: Ultrasonics
Luan T Nguyen, Georg K Kocur, Erik H Saenger
This work presents a reverse-time imaging technique by cross-correlating the forward wavefield with the reverse wavefield for the detection, localization, and sizing of defects in pipelines. The presented technique allows to capture the wavefield reflectivity at the places of ultrasonic wave scattering and reflections. Thus, the method is suitable for detecting pipe defects of either point-like or finite-size types using data from a pulse-echo setup. By using synthetic data generated by 3D spectral element pipe models, we show that the 3D wavefield cross-correlation imaging is capable in the case of cylindrical guided ultrasonic waves...
June 25, 2018: Ultrasonics
Lucas Lobianco De Matheo, Juliana Geremia, Maria Júlia Gregorio Calas, José Francisco Silva Costa-Júnior, Flavia Fernandes Ferreira da Silva, Marco Antônio von Krüger, Wagner Coelho de Albuquerque Pereira
The purpose of this work was to obtain an anthropomorphic phantom with acoustic properties similar to those of breast tissue, possessing lactiferous duct-like structures, which would be a first for this type of phantom. Breast lesions usually grow in glandular tissues or lactiferous ducts. Shape variations in these structures are detectable by using ultrasound imaging. To increase early diagnosis, it is important to develop computer-aided diagnosis (CAD) systems and improve medical training. Using tissue-like materials that mimic known internal structures can help achieve both of these goals...
June 23, 2018: Ultrasonics
Pabitro Ray, Balaji Srinivasan, Krishnan Balasubramaniam, Prabhu Rajagopal
Recent literature shows that low-frequency ultrasonic guided waves experience mode confinement and loss of axi-symmetry in pipes with axially uniform features such as eccentricity. Considering extended wall loss as a case of uniform eccentricity, this paper proposes to monitor pipe integrity by measuring changes to the modal structure of low-frequency axisymmetric L(0,2) longitudinal guided waves. Fiber Bragg gratings are shown to be effective in detecting changes to L(0,2) modal characteristics, providing a novel route to health monitoring of pipe assets...
June 19, 2018: Ultrasonics
M Alami, E H El Boudouti, B Djafari-Rouhani, Y El Hassouani, A Talbi
We study the propagation of transverse acoustic waves associated with the surface of a semi-infinite superlattice (SL) composed of piezoelectric-metallic layers and capped with a piezoelectric layer. We present closed-form expressions for localized surface waves, the so-called Bleustein-Gulyaev (BG) waves depending on whether the cap layer is open-circuited or short-circuited. These expressions are obtained by means of the Green's function method which enables to deduce also the densities of states. These theoretical results are illustrated by a few numerical applications to SLs made of piezoelectric layers of hexagonal symmetry belonging to the 6 mm class such as PZT4 and ZnO in contact with metallic layers such as Fe, Al, Au, Cu and boron-doped-diamond...
June 18, 2018: Ultrasonics
Piotr Szłapa, Wojciech Marczak
Acoustic spectra of sound emitted by metal active gas welding in series of thirty experiments with different technological parameters evidenced that about 50% of the acoustic energy generated during welding was transmitted by the waves belonging to the octave band with center frequency of 31.5 kHz. Since the time series of the sound pressure levels in this frequency band resembled that of the respective total sound pressure levels, empirical correlation equations of the two quantities and the welding current were fitted...
June 18, 2018: Ultrasonics
Gian Piero Malfense Fierro, Michele Meo
Linear and nonlinear ultrasound imaging methods highlight different damage features: the linear method detects large stiffness changes, while the nonlinear technique identifies small impedance mismatches, such as microcracks or closed delaminations. Typically, nonlinear ultrasound techniques detect damage/defects in materials by measuring higher order harmonics. These harmonics can be difficult to measure due to low magnitude and signal to noise ratios (SNR): hence large excitation amplitudes are needed, which can further complicate the reliability of these methods as equipment nonlinearities can be generated...
June 15, 2018: Ultrasonics
Marek Rjelka, Bernd Köhler, Andreas Mayer
For an elastic medium containing a homogeneous distribution of micro-cracks, an effective one-dimensional stress-strain relation has been determined with finite element simulations. In addition to flat micro-cracks, voids were considered that contain a Hertzian contact, which represents an example for micro-cracks with internal structure. The orientation of both types of micro-cracks was fully aligned or, for flat micro-cracks, totally random. For micro-cracks with Hertzian contacts, the case of random orientation was treated in an approximate way...
June 15, 2018: Ultrasonics
Saurabh Gupta, Prabhu Rajagopal
This paper studies the interaction of the fundamental symmetric Lamb wave mode S0 with delaminations in 8-layered glass fibre reinforced polymer (GFRP) laminated composites, using numerical models validated against experiments. The validation is performed using experiments on the eight layer quasi-isotropic GFRP composite laminate [0/90/45/-45]S . Further numerical studies were performed on the laminates [0/45/-45/90]S, [0/45/90/-45]S, [90/45/-45/0]S, [90/-45/0/45]S, [45/-45/0/90]S, and [45/90/-45/0]S to study the effect of ply layups on the reflection of S0 Lamb waves...
June 15, 2018: Ultrasonics
Weijia Shi, Hui Zhao, Bo Zhao, Xue Qi, Weishan Chen, Jiubin Tan
This work presents a general optimum frequency tracking scheme for an ultrasonic motor, which no longer requires the amplitudes of the applied voltages to keep identical. The proposed scheme here greatly extends the application of the optimum frequency in comparison to the existing studies. The mechanical quality factor of an ultrasonic motor is initially derived to describe the loss, which further is also in proportion to the temperature rise. The optimum frequency from the loss reduction viewpoint is then obtained, at which frequency the ultrasonic motor maintains the minimum loss and subsequently the minimum temperature rise...
June 15, 2018: Ultrasonics
Yuanguo Wang, Chichao Zheng, Hu Peng, Qiang Chen
The beamforming performance has a large impact on image quality in ultrasound imaging. Previously, several adaptive weighting factors including coherence factor (CF) and generalized coherence factor (GCF) have been proposed to improved image resolution and contrast. In this paper, we propose a new adaptive weighting factor for ultrasound imaging, which is called signal mean-to-standard-deviation factor (SMSF). SMSF is defined as the mean-to-standard-deviation of the aperture data and is used to weight the output of delay-and-sum (DAS) beamformer before image formation...
June 12, 2018: Ultrasonics
Kuanshuang Zhang, Shicheng Li, Zhenggan Zhou
The laser ultrasonic technique with a pulse-echo mode has been investigated to detect disbonds in a multi-layer bonded structure and a quantitative method has been proposed to evaluate the defect sizes. The simulations were carried out to analyze influences of spot sizes on the characteristics of laser ultrasonic reflected waves, the interaction of laser ultrasonic reflected waves with disbonds, and quantitative characterization on disbonds. A noncontact laser ultrasonic inspection system has been established to perform a series of experiments to verify the theoretical results...
June 6, 2018: Ultrasonics
I A Renteria-Marquez, A Renteria-Marquez, B T L Tseng
The operating principle of the piezoelectric traveling wave rotary ultrasonic motor is based on two energy conversion processes: the generation of the stator traveling wave and the rectification of the stator movement through the stator-rotor contact mechanism. This paper presents a methodology to model in detail the stator-rotor contact interface of these motors. A contact algorithm that couples a model of the stator which is discretized with the finite volume method and an analytical model of the rotor is presented...
June 6, 2018: Ultrasonics
Wujun Zhu, Yanxun Xiang, Chang-Jun Liu, Mingxi Deng, Fu-Zhen Xuan
The feasibility of fatigue damage evaluation has been investigated using nonlinear Lamb waves with group-velocity mismatching. To choose an efficient mode pair, a parameter is proposed to quantify the efficiency of cumulative second-harmonic generation (SHG) of Lamb waves based on the normal modal analysis. Experiments and simulations are performed to verify the proposed parameter, which demonstrates that whether the matching condition of group velocity is satisfied or not, the efficiency of cumulative SHG increases with the order of Lamb mode for the five low-order Lamb waves investigated...
June 5, 2018: Ultrasonics
Maryam Odabaee, Mostafa Odabaee, Matthew Pelekanos, Gerhard Leinenga, Jürgen Götz
Ultrasound is increasingly being recognized as a neuromodulatory and therapeutic tool, inducing a broad range of bio-effects in the tissue of experimental animals and humans. To achieve these effects in a predictable manner in the human brain, the thick cancellous skull presents a problem, causing attenuation. In order to overcome this challenge, as a first step, the acoustic properties of a set of simple bone-modeling resin samples that displayed an increasing geometrical complexity (increasing step sizes) were analyzed...
June 1, 2018: Ultrasonics
J Michael Brown
Methods are evaluated in solution of the inverse problem associated with determination of elastic moduli for crystals of arbitrary symmetry from elastic wave velocities measured in many crystallographic directions. A package of MATLAB functions provides a robust and flexible environment for analysis of ultrasonic, Brillouin, or Impulsive Stimulated Light Scattering datasets. Three inverse algorithms are considered: the gradient-based methods of Levenberg-Marquardt and Backus-Gilbert, and a non-gradient-based (Nelder-Mead) simplex approach...
June 1, 2018: Ultrasonics
Ying-Xin Gao, Ran Ding, Xing Chen, Zhao-Bo Gong, Yu Zhang, Min Yang
Ultrasonic technology is a promising tool for washing oily sludge to remove oil, however, little information has been provided on the pilot scale application of ultrasonic washing. In this study, the ultrasonic conditions were optimized based on the pilot trial of the effects of ultrasonic properties on oil removal from oily sludge. An ultrasonic power of 0.24 w/cm2 was necessary to overcome the energy threshold for oil washing at the frequency of 25 kHz. The removal rate was changed from 46.0% to 60.7% with oily sludge content from 25...
May 31, 2018: Ultrasonics
Yafeng Chen, Di Guo, Yang Fan Li, Guangyao Li, Xiaodong Huang
The viscoelasticity of constituent materials has a significant effect on the dispersion relation of waves in viscoelastic phononic crystals (PCs). This paper extends the bi-directional evolutionary structure optimization (BESO) method to the design of viscoelastic PCs with the maximum attenuation and stiffness. The attenuation factor is calculated by the k(ω)-method, and the effective elasticity matrix of composite PCs is extracted by the homogenization theory. The inverse design of viscoelastic PCs is formulated with a topology optimization problem, which is then solved by the proposed BESO method...
May 17, 2018: Ultrasonics
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