Read by QxMD icon Read


A Shakeri, S Darbari, M K Moravvej-Farshi
Reconfigurable phononic crystals (PnCs) and related devices are highly attractive because of their flexibility for different applications. We present the design procedure for a tunable acoustic resonator based on a 2D PnC, consisting of a periodic array of piezoelectric rods of radii 175 μm as inclusions arranged in air background. A single point defect devised by a rod of radius 161 μm, replacing one of the inclusions, plays the role of the acoustic resonator, leading to a defect frequency in the phononic band gap (fd  ≈ 432 kHz)...
September 5, 2018: Ultrasonics
Christopher Hakoda, Cliff J Lissenden
The Partial Wave Method is unique in that it establishes a foundation on which various elastodynamic guided waves can be compared. In this paper, the method is used to compare quasi-Rayleigh waves and Rayleigh waves, and investigate the eccentricities of the Partial Wave Method at phase velocities equal to the Rayleigh wave speed. The comparison results in the definition of two types of quasi-Rayleigh waves and an explanation for quasi-Rayleigh wave behavior reported in the literature at frequencies that do not satisfy Viktorov's quasi-Rayleigh wave condition...
September 1, 2018: Ultrasonics
Yeasin Bhuiyan, Bin Lin, Victor Giurgiutiu
In this article, a new avenue of using the piezoelectric wafer active sensor (PWAS) for detecting the fatigue crack generated acoustic emission (AE) signals is presented. In-situ AE-fatigue experiments were conducted using PWAS along with two commercially available AE sensors. It has been shown that the PWAS and existing AE sensors successfully captured the AE signals from the fatigue crack growth in a thin aerospace specimen. Two experiments were conducted using the PWAS with each of the commercial AE sensors...
September 1, 2018: Ultrasonics
Pilar Candelas, José Miguel Fuster, Sergio Pérez-López, Antonio Uris, Constanza Rubio
The Talbot effect using ultrasonic waves transmitted through a periodic perforated plate is presented. The ultrasonic wave-field at the exit of the perforated plate replicates the perforated pattern at the Talbot distance. Experimental results are validated by an analytical model. The measured propagating wave-field is consistent with the analytical results. The influence of the grating size and the filling fraction on the Talbot effect are also studied, and it is found that both parameters affect the formation of Talbot images...
August 30, 2018: Ultrasonics
Jiaze He, Cara A C Leckey, Patrick E Leser, William P Leser
The sensitivity of Lamb wave modes to a particular defect or instance of damage is dependent on various factors (e.g., the local strain energy density due to that wave mode). As a result, different modes will be more useful than others for damage detection and quantification, dependent on damage type and location. For example, prior work in the field has shown that out-of-plane modes may have a higher sensitivity than in-plane modes to surface defects in plates. The excitability of a certain data acquisition system and the corresponding resolution for damage imaging also varies with frequency...
August 24, 2018: Ultrasonics
C Kollmann, D Dubravský, B Kraus
A new generation of speed of sound (SOS) test object is presented that is fully constructed using additive manufacturing processes with a 3D-printer. The object contains 2 compartments with thin filaments and tubes that can be filled with fluid substances. The filaments are located at equal distances to each other; the tubes have fixed diameters. Depending on the chosen fluids (e.g. water, glycerol-water, corn oil, salt water) and room temperature, the mismatch in distance or diameter depending on the SOS error has been measured using ultrasound imaging equipment...
August 23, 2018: Ultrasonics
Xiaoran Wang, Xiandong Liu, Junfei Tai, Tian He, Yingchun Shan
Due to the difference between the characteristic impedance of air and plate structure, the acoustic emission (AE) wave propagating in a plate structure is reflected when reaching the boundary. It leads to the fact that the obtained signal contains not only direct AE components but also reflected components. The existence of the reflected AE wave brings error and difficulty to accurate AE source analysis. This paper attempts to introduce the acoustic black hole (ABH) into an experimental plate structure (a disc structure in this paper) to attenuate the reflected AE wave from the structure boundary and obtain the high Signal-Noise Ratio (SNR) direct AE wave...
August 18, 2018: Ultrasonics
V I Anisimkin, E Verona, A S Kuznetsova
Using Bi12 GeO20 plate coated by AlN film, the main characteristics of the A0 , S0 , A1 , and S1 Lamb waves are numerically calculated and compared with those of SAW in the same structure. It is shown that (i) there exist only one SAW mode for this material combination, (ii) the mode exist in a narrow range of AlN thickness, (iii) it can be excited using four different transducer configurations, (iv) the velocity and coupling constants of the mode are, respectively, higher and lower as compared with the values for the uncoated Bi12 GeO20 substrate...
August 17, 2018: Ultrasonics
S Habib Alavi, Sandip P Harimkar
Recently, the applications of ultrasonic vibration assistance to laser-based manufacturing processes are rapidly proliferating. Ultrasonic vibration-assisted laser drilling (UVLD) process involves simultaneous application of high frequency vertical vibrations to the workpiece while being irradiated with a continuous wave laser beam. In UVLD, the ultrasonic vibration assistance causes expulsion of droplets from the laser melted surface, resulting in the formation of deep holes. In this paper, systematic analysis of the effects of ultrasonic vibration frequency (20-40 kHz) and displacement (16-32 µm) on melt expulsion characteristics in early stages of drilling and geometric/quality features of the holes for UVLD of AISI 316 is presented...
August 17, 2018: Ultrasonics
O F Manfredi, R S Mills, M M Schirru, R S Dwyer-Joyce
The ability to monitor the viscosity of lubricating oils within metallic products is of interest to many industries, these being the automotive, aerospace and food industries to name a few. Acoustic mismatch at the metallic-liquid interface restricts ultrasonic signal transmission and so limits applicability and sensitivity of the technique. In this work, we propose the use of a continuously repeated chirp (CRC) shear wave to amplify the measurable acoustic response to liquid viscosity. The technique enables multiple reflections to superimpose inside the component and form a quasi-static standing wave whose amplitude spectrum depends on the condition at the solid-liquid boundary...
August 7, 2018: Ultrasonics
Ting Yu, Jean-François Chaix, Lorenzo Audibert, Dimitri Komatitsch, Vincent Garnier, Jean-Marie Hénault
Several non-destructive evaluation techniques to characterize concrete structures are based on ultrasonic wave propagation. The interpretation of the results is often limited by the scattering phenomena between the ultrasonic wave and the high concentration aggregates contained in the cement matrix. Numerical simulations allow for further insights. This study aims to build a two-dimensional numerical model in order to reproduce and interpret ultrasonic wave propagations in concrete. The model is built in a spectral-element software package called SPECFEM2D...
August 2, 2018: Ultrasonics
Victor V Sokolov
I have shown that authors (Prakash et al., 2015) to obtained unreasonably good agreement between the calculated by using wrong theory and the wrong experimental data.
July 25, 2018: Ultrasonics
Qiang Huan, Mingtong Chen, Faxin Li
Structural health monitoring (SHM) has become more and more important in modern industries as it can monitor the safety of structures during the full service life and prevent possible losses of life and economics. Shear horizontal wave in plate-like structures is very useful for long distance inspection since its fundamental mode (SH0 ) is totally non-dispersive. However, all the currently available SH wave transducers are not suitable for practical SHM because of their complicated structures. In this work, we firstly investigated via finite element (FEM) simulations the performances of thickness-poled d15 PZT ring based omni-directional SH wave piezoelectric transducers (OSH-PT) consisting of different number of elements...
July 19, 2018: Ultrasonics
Girish Chandra Verma, Pulak Mohan Pandey
Ultrasonic assisted milling (UAM) is one of the advancements in the area of conventional milling process. Literature suggests that superpositioning of ultrasonic vibration with milling process improves its efficacy by reducing forces and improving surface finish. In the present study experimental investigations were carried out to evaluate the effect of process parameters (power of ultrasonic vibration (UP), rotational speed, axial depth of cut (DOC) and feed rate) on the cutting responses (average cutting force and the standard deviation in cutting forces)...
July 17, 2018: Ultrasonics
M Schirru, X Li, M Cadeddu, R S Dwyer-Joyce
In-situ measurement of viscosity advances the field of rheology, and aides the development of sensing systems for condition and performance monitoring of lubricated mechanisms. Many lubricated mechanisms, such as journal bearings or seals, are characterised by three-layer interfaces; an oil separating two solid (usually metallic) bodies. The viscoelastic study of the lubricating oil in layered systems is possible in-situ by means of ultrasonic reflection (Schirru et al. (2015)). General solutions exist for the reflection of longitudinal plane waves from multi-layered solid-fluid systems...
July 7, 2018: Ultrasonics
Swetha S George, Michael C Huang, Zeljko Ignjatovic
This paper discusses an ultrasound technique where the echo signals from the array of transducer elements are compressed to as few as two RF channels while still in analog domain, with a much simplified front-end electronics. The method can achieve resolutions well beyond the diffraction limit, which is set by the excitation signal wavelength and numerical aperture of the imaging system. The fundamental principle that underlies this model based imaging technique is the preservation of the spatial frequency information content of the recorded echo signals with the help of pseudo-random apodization function followed by summation...
July 7, 2018: Ultrasonics
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
Xiaokai Wang, Shanyue Guan, Lin Hua, Bin Wang, Ximing He
Resistance spot welding (RSW) ultrasonic testing signal contains nugget size and internal defect information which can reflect the mechanical property of spot-welded joint. The mechanical property of spot-welded joint is the most direct indicator for evaluation of spot welding quality. In this paper, 100 samples of different quality spot-welded joints are detected by ultrasonic detection technology, then ultrasonic signals are processed by fast Fourier transform (FFT) and wavelet packet transform (WPT). After that, mathematical statistical methods are used to feature extraction for ultrasonic detection signals in time domain, frequency domain, and wavelet domain based on WPT...
January 2019: Ultrasonics
Fetch more papers »
Fetching more papers... Fetching...
Read by QxMD. Sign in or create an account to discover new knowledge that matter to you.
Remove bar
Read by QxMD icon Read

Search Tips

Use Boolean operators: AND/OR

diabetic AND foot
diabetes OR diabetic

Exclude a word using the 'minus' sign

Virchow -triad

Use Parentheses

water AND (cup OR glass)

Add an asterisk (*) at end of a word to include word stems

Neuro* will search for Neurology, Neuroscientist, Neurological, and so on

Use quotes to search for an exact phrase

"primary prevention of cancer"
(heart or cardiac or cardio*) AND arrest -"American Heart Association"