- 标题
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Environmentally friendly methodology for fouling removal in pipeline based on leaky guided wave generated by quasi-axisymmetric excitation mode
摘要： In this paper, an environmental and innovative clean technique for pipeline fouling is proposed, which is based on leaky ultrasonic guided waves (LUGWs) generated by quasi-axisymmetric excitation mode. The cavitation, which induced by the LUGWs in liquid medium, is employed for removing fouling inside a pipe. Cavitation corrosion and high-speed jet generated by the collapse of cavitation bubbles destroy fouling layer, and no by-products are formed during the removal process, which means that fouling removal in this way is friendly to the environment. The working frequency is determined by finite element method models and experiment. The effect of removal and its uniformity are measured by mass analysis, scanning electron microscope and energy-dispersive spectroscopy from macro to micro. The descaling experiment results show that the proposed method is able to remove the fouling inside a pipe uniformly.
关键词： Finite element method,Fouling removal,Quasi-axisymmetric,Leaky ultrasonic guided waves
更新于2025-09-23 15:23:52
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A transformation elasticity based device for wavefront manipulation
摘要： The authors propose a metamaterial plate made of gradient refractive index phononic crystals for manipulation of the wavefront of propagating waves. A square unit cell with through holes is considered. Guidance on the design of the hole pattern and the choice of materials is obtained with the aid of transformation elasticity principles. Manipulation of a plane wavefront into a cylindrical wavefront is first observed through Finite Element simulations at low frequency (100 kHz), and then practically demonstrated through experiments. Wave propagation with and without the holey region is compared and possible applications at higher frequencies are discussed.
关键词： Metamaterial Plate,Transformation Elasticity,GRIN PC,Wave Manipulation,Guided Waves
更新于2025-09-23 15:22:29
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Guided wave inspection of dissimilar material joints using time reversal techniques
摘要： Dissimilar material bonding has recently gained a lot of attention in automotive, marine and defense applications. Nevertheless, a major hurdle limiting the full acceptance of such structural components is the lack of non-destructive evaluation (NDE) technique to evaluate their strength, which depends on the integrity of the bonding layer. In this work, guided wave (GW) inspection with surface-mounted piezoelectric sensors (PZT) was employed along with time reversal for Structural Health Monitoring (SHM) of dissimilar material lap-joints. Baseline-free probability imaging was used to identify the location of artificial disbond. The results of GW inspection were further validated with ultrasonic C-scan. Overall, the technique shows great potential in detection of defects in bonded joints.
关键词： guided waves,time reversal,diagnostic imaging,SHM,Dissimilar material joints
更新于2025-09-23 15:22:29
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A Novel Fabry-P??rot Optical Sensor for Guided Wave Signal Acquisition
摘要： In this paper, a novel hybrid damage detection system is proposed, which utilizes piezoelectric actuators for guided wave excitation and a new ?bre optic (FO) sensor based on Fabry-Perot (FP) and Fiber Bragg Grating (FBG). By replacing the FBG sensors with FBG-based FP sensors in the hybrid damage detection system, a higher strain resolution is achieved, which results in higher damage sensitivity and higher reliability in diagnosis. To develop the novel sensor, optimum parameters such as re?ectivity, a wavelength spectrum, and a sensor length were chosen carefully through an analytical model of the sensor, which has been validated with experiments. The sensitivity of the new FBG-based FP sensors was compared to FBG sensors to emphasize the superiority of the new sensors in measuring micro-strains. Lastly, the new FBG-based FP sensor was utilized for recording guided waves in a hybrid setup and compared to the conventional FBG hybrid sensor network to demonstrate their improved performance for a structural health monitoring (SHM) application.
关键词： ?ber optic sensors,guided waves,structural,health monitoring,hybrid PZT-FBG,Fabry-Perot
更新于2025-09-23 15:19:57
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Analysis of Guided Waves Dispersion and Acoustoelastic Effect in Stressed Waveguides by Eigenfrequency Method and Experimental Study
摘要： On the basis of the effect of initial stress and acoustoelastic coefficients on the dispersion behavior of guided waves in stressed waveguides. a finite element method is presented to analyze the wave propagation in prestressed waveguides. The approach was based on the acoustoelastic theory to solve the eigenfrequency of prestressed waveguides, where wavenumbers and modes are distinguished by modal shape, and the solutions of the phase velocity and the group velocity were determined. The algorithm was applied to analyze the dispersion and acoustoelastic coefficients of a prestressed plate and an axisymmetric bar model. Obtained results were consistent with previous research, proving that the approach is useful for the analysis of dispersion and acoustoelastic effect in prestressed waveguides. The acoustoelastic effect of the longitudinal mode guided wave in the rod was experimentally studied according to on the method of eigenfrequency analysis. The results show that the trend of the experimental results is in good agreement with that of the eigenfrequency method. The detection frequency of L(0.1) mode is around 72 kHz, the error of L(0.2) mode is small in the range of 240–280 kHz, which is more suitable for acoustoelastic stress detection.
关键词： stressed waveguides,dispersion,guided waves,eigenfrequency method,acoustoelastic effect
更新于2025-09-19 17:13:59
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A Waveguide Gate-Type Complex Detecting Mechanism on Micro-Channel Plate Substrate
摘要： The waveguide gate-type mechanism on micro-channel plate substrate was ?rstly put forward for the complex photo detection in Free space optical communication (FSO). Based on the losses of energy coupling between both Micro-channel plates (MCP), we further proposed waveguide gate-type complex detecting mechanism, which was veri?ed in electron optic system by vacuum testing. With the application of the complex detecting mechanism, the device performance has greatly improved, including higher space optical transfer and wider dynamic detecting range.
关键词： Detectors,Free-space optical communication,Guided waves
更新于2025-09-16 10:30:52
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Rigorous Eigenmode Derivations and Spectral Analysis for Step-Index Confocal Parabolic Optical Fibers
摘要： For quite some time, the geometry-dependence of electric fields confined in two-dimensional systems of propagation has been known. We explore a lesser known way in which one can confine light, parabolically. One can use this method to understand the different forms modes take in such fibers and the appropriate eigenfunction for spectral analysis. In this paper, a fiber with a parabolic core and a circular cladding for the preservation of coaxiality are proposed.
关键词： optical fiber,parabolic geometry,optical spectral analysis,geometry,guided waves
更新于2025-09-11 14:15:04
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Bolted joint integrity monitoring with second harmonic generated by guided waves
摘要： In this study, the second harmonic generation due to the contact nonlinearity caused by bolt loosening is studied experimentally and numerically using three-dimensional explicit finite element simulations. In particular, it is demonstrated that the magnitude of the second harmonic generation normally increases with the loosening of the bolted joint, and there is a reasonable agreement between the numerical simulations and experimental results. The finite element model, which was validated against the experimentally measured data, is further utilized to investigate an important practical situation when a loosened bolt is weakened by fatigue cracks located at the edge of the hole. The numerical case studies show that the contact nonlinearity and the change of the behaviour of the second harmonic generation with the tightening level are very different to the corresponding results with the fatigue cracks. This identified difference in the second harmonic generation behaviour can serve as an indicator of the bolted joint integrity and thus provide early warning for engineers to make decision on the necessity of carrying out further safety inspections. Overall, the findings of this study provide improved physical insights into second harmonic generation for bolt loosening, which can be used to further advance damage detection techniques using nonlinear guided waves.
关键词： Bolt loosening,bolted joint,second harmonic generation,fatigue crack,contact nonlinearity,torque loss,structural health monitoring,guided waves
更新于2025-09-10 09:29:36
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Electromagnetic Acoustic Transducers Applied to High Temperature Plates for Potential Use in the Solar Thermal Industry
摘要： Concentrated Solar Plants (CSPs) are used in solar thermal industry for collecting and converting sunlight into electricity. Parabolic trough CSPs are the most widely used type of CSP and an absorber tube is an essential part of them. The hostile operating environment of the absorber tubes, such as high temperatures (400–550 °C), from creep, contraction/expansion, and vibrations, may lead them to suffer thermo-mechanical fatigue, and hot corrosion. Hence, their condition monitoring is of crucial importance and a very challenging task as well. Electromagnetic Acoustic Transducers (EMATs) are a promising, non-contact technology of transducers that has the potential to be used for the inspection of large structures at high temperatures by exciting Guided Waves. In this paper, a study regarding the potential use of EMATs in this application and their performance at high temperature is presented. A Periodic Permanent Magnet (PPM) EMAT with a racetrack coil, designed to excite Shear Horizontal waves (SH0), has been theoretically and experimentally evaluated at both room and high temperatures.
关键词： non-destructive testing,high temperatures,Electromagnetic Acoustic Transducer (EMAT),solar thermal plants,guided waves
更新于2025-09-09 09:28:46
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[IEEE 2018 IEEE Research and Applications of Photonics In Defense Conference (RAPID) - Miramar Beach, FL, USA (2018.8.22-2018.8.24)] 2018 IEEE Research and Applications of Photonics In Defense Conference (RAPID) - Design of a High-Q Raman Amplifier with Guided-Mode Resonant Gratings
摘要： We propose a Raman amplifier with one dimensional guided-mode resonant gratings with silicon-on- quartz. We provide an initial design based on nanopatterned c-Si films. Raman spectrum separation will be presented by two resonant modes with proper spectral and angular tuning.
关键词： Scattering: Raman scattering,Optical amplifiers,Guided waves
更新于2025-09-09 09:28:46