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Arnab Gupta, John C Duke
In health monitoring applications of composite materials, the health state of specimens is often evaluated using naturally occurring and simulated Acoustic Emission stress waves. For such applications, identifying the arrival times of the extensional and flexural wave modes from acquired signals is a crucial step, and must be performed reliably and potentially on large sets of signals. This article proposes using the wavelet decomposition of a signal to develop a fast, algorithmic and automated approach to estimate the arrival times of the extensional and flexural wave modes...
September 9, 2017: Ultrasonics
Jiu-Jiu Chen, Jian-Cheng Zhang, Shao-Yong Huo
Asymmetric acoustic wave propagation is important for control and manipulation of the acoustic wave signals in various devices. However, previous approach to find optimal asymmetric acoustic transmission (AAT) is through repeatedly adjusting the geometrical parameters, thus causing time-consuming. Here we propose a study on the multi-objective optimization of the AAT, aiming to achieve the widest working frequency range (fr) and the highest transmittance peak (η) with regard to the design variables. For this purpose, the Radial Basis Function (RBF) neural work and finite element (FE) method are applied to obtain the valuable data in the procedure...
September 8, 2017: Ultrasonics
Krisztián Füzesi, Natalia Ilyina, Erik Verboven, Koen Van Den Abeele, Miklós Gyöngy, Jan D'hooge
The temperature dependence of soft tissue acoustic properties is relevant for monitoring tissue hyperthermia. In the current work, the propagation speed and attenuation of healthy porcine left ventricular myocardium (N=5) was investigated in a frequency range relevant for clinical diagnostic imaging, i.e. 2.5-13.0MHz. Each tissue sample was held in a water bath at a temperature T=25°C, heated to 45°C, and allowed to cool back down to 25°C. Due to initial tissue swelling, the data for decreasing temperatures was considered more reliable...
September 6, 2017: Ultrasonics
H Reed, Cara A C Leckey, A Dick, G Harvey, J Dobson
Ultrasonic damage detection and characterization is commonly used in nondestructive evaluation (NDE) of aerospace composite components. In recent years there has been an increased development of guided wave based methods. In real materials and structures, these dispersive waves result in complicated behavior in the presence of complex damage scenarios. Model-based characterization methods utilize accurate three dimensional finite element models (FEMs) of guided wave interaction with realistic damage scenarios to aid in defect identification and classification...
September 5, 2017: Ultrasonics
S Boccardi, D B Callá, F Ciampa, M Meo
Nonlinear ultrasonic techniques rely on the measurement of nonlinear elastic effects caused by the interaction of ultrasonic waves with the material damage, and have shown high sensitivity to detect micro-cracks and defects in the early stages. This paper presents a nonlinear ultrasonic technique, here named nonlinear elastic multi-path reciprocal method, for the identification and localisation of micro-damage in composite laminates. In the proposed methodology, a sparse array of surface bonded ultrasonic transducers is used to measure the second harmonic elastic response associated with the material flaw...
September 5, 2017: Ultrasonics
Boris Sveshnikov, Aleksey Koigerov, Sergey Yankin
The spatial three dimensional variation of the polarization ellipse characterizing an elastic movement of the solid particles in the harmonically oscillating ultrasonic fields is studied. Such a variation comes into sight because of the interference of various elastic modes generated during the excitation and/or scattering of acoustic waves by the inhomogeneities located on the solid surface. In order to confirm this effect, an innovative method based on finite element approach is used showing a rule to find the form and orientation of the elastic polarization ellipse in general case...
September 1, 2017: Ultrasonics
Jiangyu Wu, Meimei Feng, Bangyong Yu, Guansheng Han
It is important to study the mechanical properties of cracked rock to understand the engineering behavior of cracked rock mass. Consequently, the influence of the length of pre-existing fissures on the strength, deformation, acoustic emission (AE) and failure characteristics of cracked rock specimen was analyzed, and the optimal selection of strength parameter in engineering design was discussed. The results show that the strength parameters (stress of dilatancy onset and uniaxial compressive strength) and deformation parameters (axial strain and circumferential strain at dilatancy onset and peak point) of cracked rock specimen decrease with the increase of the number of pre-existing fissures, and the relations which can use the negative exponential function to fit...
August 30, 2017: Ultrasonics
Seyed Kamran Pedram, Sina Fateri, Lu Gan, Alex Haig, Keith Thornicroft
Ultrasonic guided wave (UGW) systems are broadly used in several branches of industry where the structural integrity is of concern. In those systems, signal interpretation can often be challenging due to the multi-modal and dispersive propagation of UGWs. This results in degradation of the signals in terms of signal-to-noise ratio (SNR) and spatial resolution. This paper employs the split-spectrum processing (SSP) technique in order to enhance the SNR and spatial resolution of UGW signals using the optimized filter bank parameters in real time scenario for pipe inspection...
August 24, 2017: Ultrasonics
Fengyu Jiao, Peijun Wei, Yueqiu Li
Reflection and transmission of plane waves through a flexoelectric piezoelectric slab sandwiched by two piezoelectric half-spaces are studied in this paper. The secular equations in the flexoelectric piezoelectric material are first derived from the general governing equation. Different from the classical piezoelectric medium, there are five kinds of coupled elastic waves in the piezoelectric material with the microstructure effects taken into consideration. The state vectors are obtained by the summation of contributions from all possible partial waves...
August 24, 2017: Ultrasonics
Khaled Metwally, Emma Lubeigt, Sandrine Rakotonarivo, Jean-François Chaix, François Baqué, Gilles Gobillot, Serge Mensah
This paper reports a methodology for the non-destructive ultrasonic evaluation of welds, based on probing, residue back-focusing and topological energy calculation using an enhanced (focused) adjoint method. The proposed method combines the advantages of time reversal to compensate for the cumulative distorsions experienced by a wave propagating in a heterogeneous medium, and topological imaging to highlight the defect location. The synergistic effect of this combined approach makes it possible to detect anomalies in the most efficient way...
August 24, 2017: Ultrasonics
Abdelkader Elhanaoui, Elhoucein Aassif, Gérard Maze, Dominique Décultot
In this paper, recent studies of backscattered acoustic signals in thinner steel-polymer tubing structures have been presented. Reassigned smoothed pseudo Wigner-Ville (rspWV) analysis has been adopted in order to diminish the cross-term effect, and achieve high resolution spectral. Vibration modes, which are associated to the resonances of circumferential waves, have been determined by using the modal isolation plan representation. At normalized frequencies below 140, an appreciable influence from the polymer coating thickness on the A0(+) and S0 modes has been noticed...
August 19, 2017: Ultrasonics
Haesang Yang, Woojae Seong, Keunhwa Lee
Several acoustic models, such as the poro-elastic model, visco-elastic model, and multiple scattering model, have been used for describing the dispersion relation in a porous granular medium. However, these models are based on continuum or scattering theory, and therefore cannot explain the broadband measurements in cases where scattering and non-scattering losses co-exist. Additionally, since the models assume that the porous granular medium consists of grains of identical size (unimodal size distribution), the models does not account for the behavior of wave dispersion in a medium that has a distribution of differing grain sizes...
August 19, 2017: Ultrasonics
Mingliang Li, Mingxi Deng, Guangjian Gao, Yanxun Xiang
The appropriate mode pairs of primary and double-frequency circumferential guided waves (CGWs) have been investigated and selected for generation of the cumulative second harmonics, which are applicable for quantitative assessment of damage/degradation in a circular tube. The selection criteria follow the requirements: the higher efficiency of cumulative second-harmonic generation (SHG) of primary CGW propagation, and the larger response sensitivity of cumulative SHG to material damage/degradation [characterized by variation in the third-order elastic (TOE) constants]...
August 18, 2017: Ultrasonics
S Wang, J Kang, X Zhang, Z Guo
The fragmentation of the dendrites of succinonitrile (SCN)-2-wt.% acetone organic transparent alloy caused by ultrasound-induced cavitation bubbles was studied by using ultra-high-speed digital camera with a rate of 40,000fps. Real-time imaging reveals that the vibrating cavitation bubbles can fragment not only secondary arms but also the primary ones under high ultrasound power. The secondary arms always broke at their roots as a result of stress concentration induced by oscillated cavitation bubble and then ripped off from their primary arms...
August 16, 2017: Ultrasonics
Shen Liu, Xiaobiao Shan, Kai Guo, Yuancai Yang, Tao Xie
Titanium and its alloys have been widely used in aerospace and biomedical industries, however, they are classified as difficult-to-machine materials. In this paper, ultrasonic vibration is imposed on the die to overcome the difficulties during conventional titanium wire drawing processes at the room temperature. Numerical simulations were performed to investigate the variation of axial stress within the contacting region and study the change of the drawing stress with several factors in terms of the longitudinal amplitude and frequency of the applied ultrasonic vibration, the diameter reduction ratio, and the drawing force...
August 12, 2017: Ultrasonics
Masahiro Kusano, Shota Takizawa, Tetsuya Sakai, Yoshihiko Arao, Masatoshi Kubouchi
Since thermosetting resins have excellent resistance to chemicals, fiber reinforced plastics composed of such resins and reinforcement fibers are widely used as construction materials for equipment in chemical plants. Such equipment is usually used for several decades under severe corrosive conditions so that failure due to degradation may result. One of the degradation behaviors in thermosetting resins under chemical solutions is "corrosion-layer-forming" degradation. In this type of degradation, surface resins in contact with a solution corrode, and some of them remain asa corrosion layer on the pristine part...
August 10, 2017: Ultrasonics
Chunying Wang, Zhaojiang Chen, Wenwu Cao
Ultrasonic wave tunneling through seriously mismatched media, such as steel and water, is possible only when the frequency matches the resonance of the steel plate. But it is nearly impossible to realize continuous wave tunneling if the low acoustic impedance media is air because the transducer frequency cannot be made so accurate. The issue might be resolved using tone-burst signals. Using finite element simulations, we found that for air media when the cycle number is 20, the -6dB bandwidth of energy transmission increased from 0...
August 2, 2017: Ultrasonics
Francisco Ruiz Botello, Miguel A S Quintanilla, Antonio Castellanos, Elena F Grekova, Vincent Tournat
We analyze experimentally and theoretically the sound propagation velocity of P-waves in granular media made of micrometer-size magnetite particles under an external magnetic field. The sound velocity is measured in a coherent (long-wavelength) regime of propagation after a controlled sample preparation consisting of a fluidization and the application of a magnetic field. Several different procedures are applied and result in different but reproducible particle arrangements and preferential contact orientations affecting the measured sound velocity...
August 1, 2017: Ultrasonics
Ji Li, Bogdan Piwakowski
This paper presents a time-domain model for the prediction of an acoustic field in an air-coupled, non-contact, ultrasonic setup, which includes an air-coupled Emitter, the Propagation space and an air-coupled Receiver (EPR). The model takes into account the finite size of the aperture receiver, attenuation in air, and the electric response of the emitter-receiver set he. The attenuation is characterized by a causal time-domain Green's function, allowing the wideband attenuation of a lossy medium obeying the power law α(ω)=α0ω(η),1⩽η⩽2 to be included...
August 1, 2017: Ultrasonics
Hauke Gravenkamp
This paper presents an approach to model transmission and reflection phenomena of elastic guided waves in plates. The formulation is applied to plate structures containing notches, inclined edges, delaminations or (adhesive) joints. For these cases, only the thickness direction of the structure needs to be discretized at several locations, while the direction of propagation is described analytically. Consequently, the number of degrees of freedom is very small. Semi-infinite domains can be modeled, in which case the radiation condition is fulfilled exactly...
August 1, 2017: Ultrasonics
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