Articles de revues : « 3D vibrometry »

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Breaban, Florin, Roger Debuchy et Didier Defer. « Laser Scanning Vibrometry and Holographic Interferometry Applied to Vibration Study ». Applied Mechanics and Materials 801 (octobre 2015) : 303–11. http://dx.doi.org/10.4028/www.scientific.net/amm.801.303.

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The applications of high performance materials in the aerospace and in the automotive technology in the next years need to develop new vibration study, nondestructive testing, predictive maintenance and industrial control methods.The Laser Scanning Vibrometry and Holographic Interferometry methods of vibration study and nondestructive testing by modal analysis are described. The Laser Scanning Vibrometer PSV 400 is made by Polytec GmbH and the PSV software reconstructs the 3D model of the measured micro-deformation of the object. The holographic laser system HLS-3 from Lumonics Inc. has 100 MW ruby laser peak power and 30 ns pulse width.Using mechanical excitation to induce a measurable vibration, the Laser Scanning Vibrometry and Holographic Interferometry modal analysis measurements show up the vibrational signatures and the damaged areas of the objects made by high performance materials - polymers, composites.

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Orta, Adil Han, Mathias Kersemans et Koen Van Den Abeele. « On the Identification of Orthotropic Elastic Stiffness Using 3D Guided Wavefield Data ». Sensors 22, n^o 14 (15 juillet 2022) : 5314. http://dx.doi.org/10.3390/s22145314.

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Scanning laser Doppler vibrometry is a widely adopted method to measure the full-field out-of-plane vibrational response of materials in view of detecting defects or estimating stiffness parameters. Recent technological developments have led to performant 3D scanning laser Doppler vibrometers, which give access to both out-of-plane and in-plane vibrational velocity components. In the present study, the effect of using (i) the in-plane component; (ii) the out-of-plane component; and (iii) both the in-plane and out-of-plane components of the recorded vibration velocity on the inverse determination of the stiffness parameters is studied. Input data were gathered from a series of numerical simulations using a finite element model (COMSOL), as well as from broadband experimental measurements by means of a 3D infrared scanning laser Doppler vibrometer. Various materials were studied, including carbon epoxy composite and wood materials. The full-field vibrational velocity response is converted to the frequency-wavenumber domain by means of Fourier transform, from which complex wavenumbers are extracted using the matrix pencil decomposition method. To infer the orthotropic elastic stiffness tensor, an inversion procedure is developed by coupling the semi-analytical finite element (SAFE) as a forward method to the particle swarm optimizer. It is shown that accounting for the in-plane velocity component leads to a more accurate and robust determination of the orthotropic elastic stiffness parameters.

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Parikesit, Gea O. F., et Indraswari Kusumaningtyas. « How to use 3D shadows for simple microscopy and vibrometry ». Physics Education 52, n^o 4 (13 juin 2017) : 045026. http://dx.doi.org/10.1088/1361-6552/aa74aa.

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Grigg, S., M. Pearson, R. Marks, C. Featherston et R. Pullin. « Assessment of Damage Detection in Composite Structures Using 3D Vibrometry ». Journal of Physics : Conference Series 628 (9 juillet 2015) : 012101. http://dx.doi.org/10.1088/1742-6596/628/1/012101.

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Weekes, Ben, et David Ewins. « Multi-frequency, 3D ODS measurement by continuous scan laser Doppler vibrometry ». Mechanical Systems and Signal Processing 58-59 (juin 2015) : 325–39. http://dx.doi.org/10.1016/j.ymssp.2014.12.022.

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Marks, Ryan, Clare Gillam, Alastair Clarke, Joe Armstrong et Rhys Pullin. « Damage detection in a composite wind turbine blade using 3D scanning laser vibrometry ». Proceedings of the Institution of Mechanical Engineers, Part C : Journal of Mechanical Engineering Science 231, n^o 16 (6 décembre 2016) : 3024–41. http://dx.doi.org/10.1177/0954406216679612.

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As worldwide wind energy generation capacity grows, there is an increasing demand to ensure structural integrity of the turbine blades to maintain efficient and safe energy generation. Currently, traditional non-destructive testing methods and visual inspections are employed which require the turbine to be out-of-operation during the inspection periods, resulting in costly and lengthy downtime. This study experimentally investigates the potential for using Lamb waves to monitor the structural integrity of a composite wind turbine blade that has been subject to an impact representative of damage which occurs in service. 3D scanning laser vibrometry was used to measure Lamb waves excited at three different frequencies both prior to, and after, impact to identify settings for an optimal system. Signal processing techniques were applied to the datasets to successfully locate the damage and highlight regions on the structure where the Lamb wave was significantly influenced by the presence of the impact damage. Damage size resulting from the impact was found to correlate well with the laser vibrometry results. The study concluded that acousto-ultrasonic-based structural health monitoring systems have great potential for monitoring the structural integrity of wind turbine blades.

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Sokołowski, Jacek, Adam Orłowski, Robert Bartoszewicz, Magdalena Lachowska, Alicja Gosiewska, Przemyslaw Biecek et Kazimierz Niemczyk. « Quantitative analysis of 3D-printed custom ossicular prostheses motion using laser Doppler vibrometry ». Otolaryngologia Polska 77, n^o 6 (29 février 2024) : 23–30. http://dx.doi.org/10.5604/01.3001.0053.9038.

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Introduction: In chronic otitis media, the reconstruction of the middle ear's sound conducting system involves repairing the tympanic membrane and filling the space between ossicular chain remnants. The final shape of the prosthesis is usually determined intraoperatively. However, the ossicular chain may be preoperatively measured using computed tomography (CT) scans, and an individualized prosthesis can be designed. Custom 3D printing seems to be an attractive solution for optimal adjustment. Aim: Our study aimed to assess the 3D-printed custom prosthesis movability and compare it to the original ossicular chain. Material and methods: Five fresh-frozen temporal bone specimens were used. Using Cone-Beam CT scans, the incus model was designed individually and 3D-printed. The ossicular chain was reconstructed inside the cadaveric temporal bone. Acoustic stimuli were applied to the external ear canal one frequency at a time. The laser Doppler vibrometer (LDV) measured the intact and 3D-printed prosthesis reconstructed ossicular chain vibrations. Results: At all stimulation frequencies, there was no significant difference in velocity values between the intact and reconstructed ossicular chain at the intensity of 80 dB SPL. The obtained values of the velocity gain were: −7.9 (SD-19) dB, −6.8 (SD8.12) dB, −10,9 (SD-5.3) dB, −7.4 (SD-8.16) dB for 500 Hz, 1000 Hz, 2000 Hz, 4000 Hz, respectively. The vibration threshold shift values ranged between –0.57 dB at 500 Hz and 3.81 dB at 2000 Hz. Conclusions: This study analyzed the movability of individualized 3D-printed custom ossicular prostheses using LDV. Compared to the intact ossicular chain, the reconstructed ossicular chain movability was characterized by statistically insignificant reduced movability at all tested frequencies. Because the prosthesis's new design conception as custom 3D individualized printing allows for patient-specific ossiculoplasty, it represents a promising new direction for ossicular chain reconstruction. It seems to be an attractive solution for prosthesis optimal adjustment and, hopefully, better hearing results.

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Derusova, Daria A., Vladimir P. Vavilov, Nikolay V. Druzhinin, Victor Y. Shpil’noi et Alexey N. Pestryakov. « Detecting Defects in Composite Polymers by Using 3D Scanning Laser Doppler Vibrometry ». Materials 15, n^o 20 (14 octobre 2022) : 7176. http://dx.doi.org/10.3390/ma15207176.

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The technique of 3D scanning laser Doppler vibrometry has recently appeared as a promising tool of nondestructive evaluation of discontinuity-like defects in composite polymers. The use of the phenomenon of local defect resonance (LDR) allows intensifying vibrations in defect zones, which can reliably be detected by means of laser vibrometry. The resonance acoustic stimulation of structural defects in materials causes compression/tension deformations, which are essentially lower than the material tensile strength, thus proving a nondestructive character of the LDR technique. In this study, the propagation of elastic waves in composites and their interaction with structural inhomogeneities were analyzed by performing 3D scanning of vibrations in Fast Fourier Transform mode. At each scanning point, the in-plane (x, y) and out of plane (z) vibration components were analyzed. The acoustic stimulation was fulfilled by generating a frequency-modulated harmonic signal in the range from 50 Hz to 100 kHz. In the case of a reference plate with a flat bottom hole, the resonance frequencies for all (x, y, and z) components were identical. In the case of impact damage in a carbon fiber reinforced plastic sample, the predominant contribution into total vibrations was provided by compression/tension deformations (x, y vibration component) to compare with vibrations by the z coordinate. In general, inspection results were enhanced by analyzing total vibration patterns obtained by averaging results at some resonance frequencies.

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Marks, Ryan, Alastair Clarke, Carol Featherston, Christophe Paget et Rhys Pullin. « Lamb Wave Interaction with Adhesively Bonded Stiffeners and Disbonds Using 3D Vibrometry ». Applied Sciences 6, n^o 1 (7 janvier 2016) : 12. http://dx.doi.org/10.3390/app6010012.

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Crua, Cyril, et Morgan R. Heikal. « Time-resolved fuel injector flow characterisation based on 3D laser Doppler vibrometry ». Measurement Science and Technology 25, n^o 12 (29 octobre 2014) : 125301. http://dx.doi.org/10.1088/0957-0233/25/12/125301.

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Scislo, Lukasz. « Single-Point and Surface Quality Assessment Algorithm in Continuous Production with the Use of 3D Laser Doppler Scanning Vibrometry System ». Sensors 23, n^o 3 (22 janvier 2023) : 1263. http://dx.doi.org/10.3390/s23031263.

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In the current economic situation of many companies, the need to reduce production time is a critical element. However, this cannot usually be carried out with a decrease in the quality of the final product. This article presents a possible solution for reducing the time needed for quality management. With the use of modern solutions such as optical measurement systems, quality control can be performed without additional stoppage time. In the case of single-point measurement with the Laser Doppler Vibrometer, the measurement can be performed quickly in a matter of milliseconds for each product. This article presents an example of such quality assurance measurements, with the use of fully non-contact methods, together with a proposed evaluation criterion for quality assessment. The proposed quality assurance algorithm allows the comparison of each of the products’ modal responses with the ideal template and stores this information in the cloud, e.g., in the company’s supervisory system. This makes the presented 3D Laser Vibrometry System an advanced instrumentation and data acquisition system which is the perfect application in the case of a factory quality management system based on the Industry 4.0 concept.

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Staszewski, W. J., B. C. Lee et R. Traynor. « Fatigue crack detection in metallic structures with Lamb waves and 3D laser vibrometry ». Measurement Science and Technology 18, n^o 3 (24 janvier 2007) : 727–39. http://dx.doi.org/10.1088/0957-0233/18/3/024.

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Pedrini, G., S. Schedin et H. J. Tiziani. « Pulsed digital holography combined with laser vibrometry for 3D measurements of vibrating objects ». Optics and Lasers in Engineering 38, n^o 3-4 (septembre 2002) : 117–29. http://dx.doi.org/10.1016/s0143-8166(02)00005-2.

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Kim, Wihan, Derek Liu, Sangmin Kim, Kumara Ratnayake, Frank Macias-Escriva, Scott Mattison, John S. Oghalai et Brian E. Applegate. « Vector of motion measurements in the living cochlea using a 3D OCT vibrometry system ». Biomedical Optics Express 13, n^o 4 (30 mars 2022) : 2542. http://dx.doi.org/10.1364/boe.451537.

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Filippov, Andrey V., Vladimir A. Krasnoveikin, Nikolay V. Druzhinin et Valery E. Rubtsov. « The Use of Laser-Doppler Vibrometry for Modal Analysis of Carbon-Fiber Reinforced Composite ». Key Engineering Materials 712 (septembre 2016) : 313–18. http://dx.doi.org/10.4028/www.scientific.net/kem.712.313.

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Both modal analysis procedure and the results obtained on a three-component 3D-printed carbon-fiber reinforced composite (CFRC) are presented. Experimental modal analysis of on the composite has been carried out to obtain the dynamic behavior characteristics. As revealed, the different eigen-oscillations waveforms possess different sensitivity of its amplitude frequency response to structural defects of the composite. For the similar waveforms we observed the differences in eigen-oscuillation frequencies, vibration velocities and damping factors which can be caused by the presence of numerous defects homogeneously distributed in one of the samples.

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Medel, Francisco, Víctor Esteban et Javier Abad. « On the use of laser-scanning vibrometry for mechanical performance evaluation of 3D printed specimens ». Materials & ; Design 205 (juillet 2021) : 109719. http://dx.doi.org/10.1016/j.matdes.2021.109719.

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Candelaresi, D., A. Annessi, G. Allevi, M. Martarelli et P. Castellini. « A wavefront track approach to defect detection in composites by scanning laser Doppler vibrometry ». Journal of Physics : Conference Series 2698, n^o 1 (1 février 2024) : 012008. http://dx.doi.org/10.1088/1742-6596/2698/1/012008.

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Abstract Composite laminates are becoming increasingly popular in a large variety of applications due to their favourable mechanical properties. However, laminates production processes can lead to various defects in the final material. The most common type is related to thickness variations, e.g. delaminations between layers, which can compromise the mechanical strength of the structure. Therefore, there is a great interest in developing non-destructive and non-contact quality control techniques for composite material assessment to minimize process costs. An interesting approach is the use of laser Doppler vibrometry combined with signal analysis based on Lamb waves propagation. In this work, we used an impulsive force given by a piezoelectric disk to the specimen and a laser Doppler vibrometer acquiring the points velocity over time along a scanning grid on the surface. The specimen is a fiberglass reinforced flat panel with seven different orientated layers which presents a delamination of about 22 mm. The maximum thickness-frequency product achieved in this analysis has been 0.2 MHz∙mm. In contrast to state-of-the-art methods for identifying thickness variation based on local estimation of the principal wave number, the proposed algorithm makes use of a tracking filter of the wave front of the propagating A0 mode waves, returning a final image in polar coordinates. The final information given by the algorithm provides the position of the delamination and, hence, can be used as a pass/failure test. State-of-the-art methods are also able to identify the shape of the defect but pay the price of a higher computational cost by using at least 4D matrix processing unlike our method which only uses 3D matrices.

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Lee, Hee Yoon, Patrick D. Raphael, Jesung Park, Audrey K. Ellerbee, Brian E. Applegate et John S. Oghalai. « Noninvasive in vivo imaging reveals differences between tectorial membrane and basilar membrane traveling waves in the mouse cochlea ». Proceedings of the National Academy of Sciences 112, n^o 10 (3 mars 2015) : 3128–33. http://dx.doi.org/10.1073/pnas.1500038112.

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Sound is encoded within the auditory portion of the inner ear, the cochlea, after propagating down its length as a traveling wave. For over half a century, vibratory measurements to study cochlear traveling waves have been made using invasive approaches such as laser Doppler vibrometry. Although these studies have provided critical information regarding the nonlinear processes within the living cochlea that increase the amplitude of vibration and sharpen frequency tuning, the data have typically been limited to point measurements of basilar membrane vibration. In addition, opening the cochlea may alter its function and affect the findings. Here we describe volumetric optical coherence tomography vibrometry, a technique that overcomes these limitations by providing depth-resolved displacement measurements at 200 kHz inside a 3D volume of tissue with picometer sensitivity. We studied the mouse cochlea by imaging noninvasively through the surrounding bone to measure sound-induced vibrations of the sensory structures in vivo, and report, to our knowledge, the first measures of tectorial membrane vibration within the unopened cochlea. We found that the tectorial membrane sustains traveling wave propagation. Compared with basilar membrane traveling waves, tectorial membrane traveling waves have larger dynamic ranges, sharper frequency tuning, and apically shifted positions of peak vibration. These findings explain discrepancies between previously published basilar membrane vibration and auditory nerve single unit data. Because the tectorial membrane directly overlies the inner hair cell stereociliary bundles, these data provide the most accurate characterization of the stimulus shaping the afferent auditory response available to date.

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Zdziebko, Paweł, Mateusz Krzemiński, Maciej Okoń, Gabriela Loi, Francesco Aymerich, Łukasz Pieczonka et Andrzej Klepka. « An Approach to the Automated Characterization of Out-of-Plane and In-Plane Local Defect Resonances ». Materials 16, n^o 8 (13 avril 2023) : 3084. http://dx.doi.org/10.3390/ma16083084.

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The paper presents an approach to efficiently detect local defect resonances (LDRs) in solids with localized defects. The 3D scanning laser Doppler vibrometry (3D SLDV) technique is applied to acquire vibration responses on the surface of a test sample due to a broadband vibration excitation applied by a piezoceramic transducer and modal shaker. Based on the response signals and known excitation, the frequency characteristics for individual response points are determined. The proposed algorithm then processes these characteristics to extract both out-of-plane and in-plane LDRs. Identification is based on calculating the ratio between local vibration levels and the mean vibration level of the structure as a background. The proposed procedure is verified on simulated data obtained from finite element (FE) simulations and validated experimentally for an equivalent test scenario. The obtained results confirmed the effectiveness of the method in identifying in-plane and out-of-plane LDRs for both numerical and experimental data. The results of this study are important for damage detection techniques utilizing LDRs to enhance the efficiency of detection.

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Wang, Chia-Fu, Junghyun Wee et Kara Peters. « Amplifying Lamb Wave Detection for Fiber Bragg Grating with a Phononic Crystal GRIN Lens Waveguide ». Sensors 22, n^o 21 (2 novembre 2022) : 8426. http://dx.doi.org/10.3390/s22218426.

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This paper demonstrates that a graded-index (GRIN) phononic lens, combined with a channel waveguide, can focus anti-symmetric Lamb waves for extraction by a detector with strong directional sensitivity. Guided ultrasonic wave inspection is commonly applied for structural health monitoring applications; however, obtaining sufficient signal amplitude is a challenge. In addition, fiber Bragg grating (FBG) sensors have strong directional sensitivity. We fabricate the GRIN structure, followed by a channel waveguide starting at the focal point, using a commercial 3D printer and mount it on a thin aluminum plate. We characterize the focusing of the A0 mode Lamb wave in the plate, traveling across the GRIN lens using 3D laser Doppler vibrometry. We also measure the extraction of focused energy using an FBG sensor, examining the optimal sensor bond location and bond length in the channel of the waveguide for maximum signal extraction. The measured amplification of the ultrasound signal is compared to theoretical predictions. The results demonstrate that significant amplification of the waveform is achieved and that selecting the location of the FBG sensor in the channel is critical to optimizing the amplification.

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Aryan, P., A. Kotousov, C. T. Ng et B. S. Cazzolato. « A baseline-free and non-contact method for detection and imaging of structural damage using 3D laser vibrometry ». Structural Control and Health Monitoring 24, n^o 4 (10 juin 2016) : e1894. http://dx.doi.org/10.1002/stc.1894.

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Rittmeier, Liv, Thomas Roloff, Natalie Rauter, Andrey Mikhaylenko, Jan Niklas Haus, Rolf Lammering, Andreas Dietzel et Michael Sinapius. « Influence of a Flat Polyimide Inlay on the Propagation of Guided Ultrasonic Waves in a Narrow GFRP-Specimen ». Materials 15, n^o 19 (29 septembre 2022) : 6752. http://dx.doi.org/10.3390/ma15196752.

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Structural health monitoring systems for composite laminates using guided ultrasonic waves become more versatile with the structural integration of sensors. However, the data generated within these sensors have to be transmitted from the laminate to the outside, where polyimide-based printed circuit boards play a major role. This study investigates, to what extent integrated polyimide inlays with applied sensor bodies influence the guided ultrasonic wave propagation in glass fiber-reinforced polymer specimens. For reasons of resource efficiency, narrow specimens are used. Numerical simulations of a damping-free specimen indicate reflections of the S0-mode at the integrated inlay. This is validated experimentally with an air-coupled ultrasonic technique and a 3D laser Doppler vibrometry measurement. The experimental data are evaluated with a method including temporal and spatial continuous wavelet transformations to clearly identify periodically occurring wave packages as edge reflections and distinguish them from possible inlay reflections. However, even when separating in-plane and out-of-plane movements using the 3D measurement, no reflections at the inlays are detected. This leads to the conclusion that polyimide inlays are well suited as substrates for printed circuit boards integrated into fiber-reinforced polymer structures for structural health monitoring, since they do not significantly influence the wave propagation.

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De Boi, Ivan, Bart Ribbens, Pieter Jorissen et Rudi Penne. « Feasibility of Kd-Trees in Gaussian Process Regression to Partition Test Points in High Resolution Input Space ». Algorithms 13, n^o 12 (5 décembre 2020) : 327. http://dx.doi.org/10.3390/a13120327.

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Bayesian inference using Gaussian processes on large datasets have been studied extensively over the past few years. However, little attention has been given on how to apply these on a high resolution input space. By approximating the set of test points (where we want to make predictions, not the set of training points in the dataset) by a kd-tree, a multi-resolution data structure arises that allows for considerable gains in performance and memory usage without a significant loss of accuracy. In this paper, we study the feasibility and efficiency of constructing and using such a kd-tree in Gaussian process regression. We propose a cut-off rule that is easy to interpret and to tune. We show our findings on generated toy data in a 3D point cloud and a simulated 2D vibrometry example. This survey is beneficial for researchers that are working on a high resolution input space. The kd-tree approximation outperforms the naïve Gaussian process implementation in all experiments.

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Marks, R., A. Clarke, C. Featherston, L. Kawashita, C. Paget et R. Pullin. « Using genetic algorithms to optimize an active sensor network on a stiffened aerospace panel with 3D scanning laser vibrometry data ». Journal of Physics : Conference Series 628 (9 juillet 2015) : 012116. http://dx.doi.org/10.1088/1742-6596/628/1/012116.

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Hedayatrasa, Saeid, et Mathias Kersemans. « 3D intra-cellular wave dynamics in a phononic plate with ultra-wide bandgap : attenuation, resonance and mode conversion ». Smart Materials and Structures 31, n^o 3 (2 février 2022) : 035010. http://dx.doi.org/10.1088/1361-665x/ac4d65.

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Abstract The intra-cellular wave dynamics of a water jetted phononic plate are experimentally investigated by means of high-resolution three-dimensional (3D) scanning laser Doppler vibrometry. The study is focused on the vibrational behavior around the ultra-wide bandgap of the plate (with a relative bandgap width of 0.89), as the critical frequency range of its phononic functionality. Broadband vibrational excitations are applied using a piezoelectric transducer and both in-plane and out-of-plane operational deflection shapes of the unit-cells are analyzed with respect to mode shapes calculated by finite element (FE) simulation. Attenuation and resonance of both symmetric and antisymmetric wave modes are validated, and it is shown that despite the absence of in-plane wave energy actuation, the symmetric modes are effectively excited in the phononic lattice, due to mode conversion from co-existing antisymmetric modes. Supported by FE modal analysis, this mode conversion observation is explained by the slight through-the-thickness asymmetry introduced during manufacturing of the phononic plate which leads to coupling of modes with different symmetry. The results confirm the potential of such detailed 3D inspection of phononic crystals (and in general acoustic metamaterials) in gaining full insight about their intracellular dynamics, which can also illuminate discrepancies with respect to idealized numerical models that might be due to manufacturing imperfections.

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Woodrow, Charlie, Ed Baker, Thorin Jonsson et Fernando Montealegre-Z. « Reviving the sound of a 150-year-old insect : The bioacoustics of Prophalangopsis obscura (Ensifera : Hagloidea) ». PLOS ONE 17, n^o 8 (10 août 2022) : e0270498. http://dx.doi.org/10.1371/journal.pone.0270498.

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Determining the acoustic ecology of extinct or rare species is challenging due to the inability to record their acoustic signals or hearing thresholds. Katydids and their relatives (Orthoptera: Ensifera) offer a model for inferring acoustic ecology of extinct and rare species, due to allometric parameters of their sound production organs. Here, the bioacoustics of the orthopteran Prophalangopsis obscura are investigated. This species is one of only eight remaining members of an ancient family with over 90 extinct species that dominated the acoustic landscape of the Jurassic. The species is known from only a single confirmed specimen–the 150-year-old holotype material housed at the London Natural History Museum. Using Laser-Doppler Vibrometry, 3D surface scanning microscopy, and known scaling relationships, it is shown that P. obscura produces a pure-tone song at a frequency of ~4.7 kHz. This frequency range is distinct but comparable to the calls of Jurassic relatives, suggesting a limitation of early acoustic signals in insects to sonic frequencies (<20 kHz). The acoustic ecology and importance of this species in understanding ensiferan evolution, is discussed.

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Sharma, Arun K., et Bishakh Bhattacharya. « Parameter estimation of butyl rubber aided with dynamic mechanical analysis for numerical modelling of an air-inflated torus and experimental validation using 3D-laser Doppler vibrometer ». Journal of Low Frequency Noise, Vibration and Active Control 38, n^o 2 (30 janvier 2019) : 296–311. http://dx.doi.org/10.1177/1461348419825685.

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Over the few decades, there has been an exponential growth in the application of inflated torus system in the field of space deployable antenna design, solar propulsion, and aerodynamic deceleration system. However, such a system is inherently susceptible to mechanical vibration and hence requires precise modal analysis to produce stable inflatable structures. This paper summarizes all the necessary steps to be followed for dynamic analysis of inflatable structures. With this objective, a butyl rubber-based inflated torus system with dynamic material properties has been considered in this work. On performing mechanical tests of the rubber sample, properties like Prony series parameters, complex modulus, and damping values were obtained. Using laser Doppler vibrometry, the modal behavior of a butyl rubber-based air-inflated torus with free–free boundary condition was studied. The results achieved from experimental modal analysis and simulation involving fluid–structure interaction were found to be in close proximity. It is envisaged that the test template integrated with numerical validation can lay the foundation for designing complex inflatable torus structures.

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Bouzzit, Aziz, Loïc Martinez, Andres Arciniegas, Stéphane Serfaty et Nicolas Wilkie-Chancellier. « Ellipsometry of surface acoustic waves using 3D vibrometry for viscoelastic material characterization by the estimation of complex Lamé coefficients versus the frequency ». Applied Acoustics 228 (janvier 2025) : 110312. http://dx.doi.org/10.1016/j.apacoust.2024.110312.

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Normandin, Benjamin, et Martin Veidt. « Single Transducer Pair Lamb Wave Time Reversal for Damage Detection in Composite Laminates ». Key Engineering Materials 558 (juin 2013) : 205–17. http://dx.doi.org/10.4028/www.scientific.net/kem.558.205.

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This paper investigates the potential of single transducer pair guided waves time reversal to detect damage in composite laminates. According to dynamic reciprocity of Lamb waves propagation in linear media, the time reversal process should reconstruct the original signal. The similarity of original and reconstructed time signals is calculated for different damage types using numerical and experimental studies with the aim to investigate, if the interaction of the wave pulse with inhomogeneities introduces any nonlinearity that time reversibility breaks down and single transducer pair time reversal could be used as damage diagnostics tool. 3D explicit finite element analysis is used for the numerical simulation and laser Doppler vibrometry is used to capture out-of-plane displacement time histories excited by an adhesively bonded piezoceramic transducer disc in the experimental time reversal process. In the case of an undamaged composite laminate the similarity index used to quantify the similarity of the original and reconstructed wave pulses is better than 95%. The similarity index is smaller for laminates with artificial damages including embedded fluoro polymer films to simulate delamination damage, through holes and bonded mass inhomogeneities. Although numerical and experimental similarity indices are smaller at higher frequencies, there is no clear evidence that single transducer pair time reversibility breaks down and represents a reliable damage diagnostics tool.

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Díaz-García, Lara, Andrew Reid, Joseph Jackson-Camargo et James Windmill. « Directional passive acoustic structures inspired by the ear of Achroia grisella ». Journal of the Acoustical Society of America 152, n^o 4 (octobre 2022) : A92. http://dx.doi.org/10.1121/10.0015652.

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The need for small directional microphones is patent in the current market. From smartphones to hearing aids, a small microphone capable of rejecting ambient noise is highly desirable. Most MEMS microphones are omnidirectional and have to resort to arrays to achieve directionality, effectively counteracting the reduced size that they offer in the first place. For this reason, we use bio-inspiration and turn to nature to find examples of solutions to this problem. The female specimens of the moth Achroia grisella are capable of monoaural directional hearing, which they use to track the males’ mating calls. It is believed that they achieve directionality solely due to the morphology of their tympana. To test it, we first produce a multiphysics simulation of the structure that serves as a starting point. For experimental measurements, additive manufacturing is chosen for its ease and cost-efficiency. 3D-printed samples of the same model are examined through micro-CT scanning and then measured using laser-Doppler vibrometry to determine their frequency and directivity responses. The results of both approaches are compared, and it is found that the structure does indeed show directionality with the second eigenfrequency showing a hypercardioid-like pattern towards the front of the moth.

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Wojtczak, E., M. Rucka et A. Andrzejewska. « Damage detection in 3D printed plates using ultrasonic wave propagation supported with weighted root mean square calculation and wavefield curvature imaging ». Journal of Physics : Conference Series 2647, n^o 18 (1 juin 2024) : 182003. http://dx.doi.org/10.1088/1742-6596/2647/18/182003.

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Abstract 3D printing (additive manufacturing, AM) is a promising approach to producing light and strong structures with many successful applications, e.g., in dentistry and orthopaedics. Many types of filaments differing in mechanical properties can be used to produce 3D printed structures, including polymers, metals or ceramics. Due to the simplicity of the manufacturing process, biodegradable polymers are widely used, e.g., polylactide (polylactide – PLA) with a practical application for manufacturing complex-shaped elements. The current work dealt with the application of ultrasonic guided waves for non-destructive damage detection and imaging in AM plates. Two specimens with defects were manufactured from PLA filament. Different sizes of damage areas were considered. The specimens were tested using the guided wave propagation technique. The waves were excited using a PZT actuator and recorded contactless with the scanning laser Doppler vibrometry (SLDV) in a set of points located at one surface of the sample. The collected signals were processed with two methods. The first was the weighted root mean square (WRMS) algorithm. Different values of the calculation parameters, namely, averaging time and weighting factor were considered. The WRMS damage maps for both samples were prepared to differentiate between intact and damaged areas. The second approach was wavefield curvature imaging (WCI) which allowed the determination of damage maps based on the curvature of the wavefront. The compensation of wave signals was performed to enhance the quality of results. It was observed that the size of the defect strongly influenced the efficiency of imaging with both methods. The limitations of the proposed approaches were characterized. The presented results confirmed that guided waves are promising for non-destructive damage imaging in AM elements.

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Heinz, Stefan, Frank Balle, Guntram Wagner et Dietmar Eifler. « Analysis of fatigue properties and failure mechanisms of Ti6Al4V in the very high cycle fatigue regime using ultrasonic technology and 3D laser scanning vibrometry ». Ultrasonics 53, n^o 8 (décembre 2013) : 1433–40. http://dx.doi.org/10.1016/j.ultras.2013.03.002.

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Reid, Andrew, Thibaut Marin-Cudraz, James F. C. Windmill et Michael D. Greenfield. « Evolution of directional hearing in moths via conversion of bat detection devices to asymmetric pressure gradient receivers ». Proceedings of the National Academy of Sciences 113, n^o 48 (14 novembre 2016) : E7740—E7748. http://dx.doi.org/10.1073/pnas.1615691113.

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Small animals typically localize sound sources by means of complex internal connections and baffles that effectively increase time or intensity differences between the two ears. However, some miniature acoustic species achieve directional hearing without such devices, indicating that other mechanisms have evolved. Using 3D laser vibrometry to measure tympanum deflection, we show that female lesser waxmoths (Achroia grisella) can orient toward the 100-kHz male song, because each ear functions independently as an asymmetric pressure gradient receiver that responds sharply to high-frequency sound arriving from an azimuth angle 30° contralateral to the animal's midline. We found that females presented with a song stimulus while running on a locomotion compensation sphere follow a trajectory 20°–40° to the left or right of the stimulus heading but not directly toward it, movement consistent with the tympanum deflections and suggestive of a monaural mechanism of auditory tracking. Moreover, females losing their track typically regain it by auditory scanning—sudden, wide deviations in their heading—and females initially facing away from the stimulus quickly change their general heading toward it, orientation indicating superior ability to resolve the front–rear ambiguity in source location. X-ray computer-aided tomography (CT) scans of the moths did not reveal any internal coupling between the two ears, confirming that an acoustic insect can localize a sound source based solely on the distinct features of each ear.

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Shen, Zhiyuan, Thomas R. Neil, Daniel Robert, Bruce W. Drinkwater et Marc W. Holderied. « Biomechanics of a moth scale at ultrasonic frequencies ». Proceedings of the National Academy of Sciences 115, n^o 48 (12 novembre 2018) : 12200–12205. http://dx.doi.org/10.1073/pnas.1810025115.

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The wings of moths and butterflies are densely covered in scales that exhibit intricate shapes and sculptured nanostructures. While certain butterfly scales create nanoscale photonic effects, moth scales show different nanostructures suggesting different functionality. Here we investigate moth-scale vibrodynamics to understand their role in creating acoustic camouflage against bat echolocation, where scales on wings provide ultrasound absorber functionality. For this, individual scales can be considered as building blocks with adapted biomechanical properties at ultrasonic frequencies. The 3D nanostructure of a full Bunaea alcinoe moth forewing scale was characterized using confocal microscopy. Structurally, this scale is double layered and endowed with different perforation rates on the upper and lower laminae, which are interconnected by trabeculae pillars. From these observations a parameterized model of the scale’s nanostructure was formed and its effective elastic stiffness matrix extracted. Macroscale numerical modeling of scale vibrodynamics showed close qualitative and quantitative agreement with scanning laser Doppler vibrometry measurement of this scale’s oscillations, suggesting that the governing biomechanics have been captured accurately. Importantly, this scale of B. alcinoe exhibits its first three resonances in the typical echolocation frequency range of bats, suggesting it has evolved as a resonant absorber. Damping coefficients of the moth-scale resonator and ultrasonic absorption of a scaled wing were estimated using numerical modeling. The calculated absorption coefficient of 0.50 agrees with the published maximum acoustic effect of wing scaling. Understanding scale vibroacoustic behavior helps create macroscopic structures with the capacity for broadband acoustic camouflage.

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Ruiz-Díez, Víctor, Jorge Hernando-García, Javier Toledo, Abdallah Ababneh, Helmut Seidel et José Luis Sánchez-Rojas. « Bidirectional Linear Motion by Travelling Waves on Legged Piezoelectric Microfabricated Plates ». Micromachines 11, n^o 5 (20 mai 2020) : 517. http://dx.doi.org/10.3390/mi11050517.

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This paper reports the design, fabrication and performance of MEMS-based piezoelectric bidirectional conveyors featuring 3D printed legs, driven by linear travelling waves (TW). The structures consisted of an aluminium–nitride (AlN) piezoelectric film on top of millimetre-sized rectangular thin silicon bridges and two electrode patches. The position and size of the patches were analytically optimised for TW generation in three frequency ranges: 19, 112 and 420 kHz, by the proper combination of two contiguous flexural modes. After fabrication, the generated TW were characterized by means of Laser–Doppler vibrometry to obtain the relevant tables of merit, such as the standing wave ratio and the average amplitude. The experimental results agreed with the simulation, showing the generation of a TW with an amplitude as high as 6 nm/V and a standing wave ratio as low as 1.46 for a device working at 19.3 kHz. The applicability of the fabricated linear actuator device as a conveyor was investigated. Its kinetic performance was studied with sliders of different mass, being able to carry a 35 mg silicon slider, 18 times its weight, with 6 V of continuous sinusoidal excitation and a speed of 0.65 mm/s. A lighter slider, weighting only 3 mg, reached a mean speed of 1.7 mm/s at 6 V. In addition, by applying a burst sinusoidal excitation comprising 10 cycles, the TW generated in the bridge surface was able to move a 23 mg slider in discrete steps of 70 nm, in both directions, which is a promising result for a TW piezoelectric actuator of this size.

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Li, Jia, Liujie Ren, Tongge Wu, Dongming Yin, Peidong Dai, Lifen Chen et Tianyu Zhang. « Experimental and Numerical Studies on Vibration Modes and Transcranial Attenuation Characteristics in Unilateral Bone Conduction Hearing ». Shock and Vibration 2020 (1 juin 2020) : 1–17. http://dx.doi.org/10.1155/2020/4962098.

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Bone conduction (BC) hearing devices have been used to improve hearing in patients with unilateral conductive hearing loss; however, the clinical results of improvement in the sound localization ability are still controversial. Transcranial transmission in BC may be an important factor affecting sound localization abilities. Transcranial or interaural attenuation, derived from energy attenuation during the BC process, is determined by the different transfer functions of multiple pathways and affected by the whole-head vibration modes. The purpose of this study is to analyze the frequency dependence of BC vibration modes of the whole head, the contribution of middle and inner ear pathways to BC hearing, and the relationship between transcranial attenuation results by dynamics measurement and hearing thresholds. Experimental studies of vibration modes and transcranial attenuation characteristics in BC are performed using scanning laser Doppler vibrometry (LDV) measurements on human cadaver heads. Differences in vibration modes between the excitation and contralateral sides are observed. Additionally, a multiscale human whole-head FE model, including the skull, bony outer ear, ossicular chains, and bony inner ear structures, is proposed to study the mechanism of BC in the human hearing system. After verifying the rationality of the FE model using mechanical impedance and frequency response data, the transcranial attenuation on the temporal bone surfaces and the middle ear structure is calculated in the FE model. Moreover, the vibration characteristics of bilateral ossicular chains and the cochlear bony wall are observed in the whole-head FM model to study their contributions to BC hearing. By analyzing the experimental and numerical results of the vibration modes and the frequency response of the whole head incorporating the ossicular chain and cochlear bony wall, the intrinsic relationship between the results of transcranial attenuation by 1D LDV, 3D LDV, and hearing threshold measurements is further investigated.

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Holmes, Lewis B., Charlie Woodrow, Fabio A. Sarria-S, Emine Celiker et Fernando Montealegre-Z. « Wing mechanics and acoustic communication of a new genus of sylvan katydid (Orthoptera : Tettigoniidae : Pseudophyllinae) from the Central Cordillera cloud forest of Colombia ». PeerJ 12 (28 juin 2024) : e17501. http://dx.doi.org/10.7717/peerj.17501.

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Stridulation is used by male katydids to produce sound via the rubbing together of their specialised forewings, either by sustained or interrupted sweeps of the file producing different tones and call structures. There are many species of Orthoptera that remain undescribed and their acoustic signals are unknown. This study aims to measure and quantify the mechanics of wing vibration, sound production and acoustic properties of the hearing system in a new genus of Pseudophyllinae with taxonomic descriptions of two new species. The calling behaviour and wing mechanics of males were measured using micro-scanning laser Doppler vibrometry, microscopy, and ultrasound sensitive equipment. The resonant properties of the acoustic pinnae of the ears were obtained via μ-CT scanning and 3D printed experimentation, and numerical modelling was used to validate the results. Analysis of sound recordings and wing vibrations revealed that the stridulatory areas of the right tegmen exhibit relatively narrow frequency responses and produce narrowband calls between 12 and 20 kHz. As in most Pseudophyllinae, only the right mirror is activated for sound production. The acoustic pinnae of all species were found to provide a broadband increased acoustic gain from ~40–120 kHz by up to 25 dB, peaking at almost 90 kHz which coincides with the echolocation frequency of sympatric bats. The new genus, named Satizabalus n. gen., is here derived as a new polytypic genus from the existing genus Gnathoclita, based on morphological and acoustic evidence from one described (S. sodalis n. comb.) and two new species (S. jorgevargasi n. sp. and S. hauca n. sp.). Unlike most Tettigoniidae, Satizabalus exhibits a particular form of sexual dimorphism whereby the heads and mandibles of the males are greatly enlarged compared to the females. We suggest that Satizabalus is related to the genus Trichotettix, also found in cloud forests in Colombia, and not to Gnathoclita.

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Ding, Chengqiao, Dachen Wang, Zhe Feng et Di Cui. « Extracting and Modifying the Vibration Characteristic Parameters of Watermelon Based on Experimental Modal Measurement and Finite Element Analysis for Hollow Heart Defect Detection ». Journal of the ASABE 65, n^o 1 (2022) : 151–67. http://dx.doi.org/10.13031/ja.14871.

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HighlightsAn impulse vibration method is proposed to excite watermelon for hollow heart defect detection.Experimental models of watermelon were acquired with 3D scanning laser vibrometry.The relationship between hollow heart defect and vibration characteristic parameters was investigated with finite element analysis.Better prediction of hollow heart defect in watermelon was achieved with the wavelet transform method.Abstract. Hollow heart defect seriously influences the taste and storability of watermelon. In this study, a non-destructive detection system based on an impulse vibration method was developed to detect hollow watermelon. First, acceptable agreement between the theoretical and experimental models of watermelon proved the suitability of investigating the relationship between hollow heart defect and vibration characteristic parameters by finite element analysis (FEA). Through modal analysis, the optimum location for the detection sensor was determined at the opposite location or 90° from the excitation point. The normalized second to fourth resonance frequencies (f2n, f3n, and f4n) and the peak value at the second frequency (A2) were extracted as latent variables for prediction of hollow watermelon. The technical parameters of the pressurized-air excitation device were then modified in orthogonal tests, and the best combination of technical parameters was as follows: air pressure of 275 kPa, excitation distance of 9 cm, and pulse width of 200 ms. In the qualitative discrimination of hollow watermelon, the results showed that a back-propagation neural network (BPNN) using 13 vibration characteristic parameters had the best classification performance, with accuracies of 91.7% and 88.9% for the calibration and prediction sets. In the quantitative analysis of hollow rate, the best prediction result was achieved with the BPNN (rp = 0.829, RMSEP = 0.016), which selected ten vibration characteristic parameters as input variables. Therefore, it is feasible to detect hollow watermelon by impulse vibration, and this method has potential to be applied in on-line defect detection. Keywords: Doppler vibrometry, Finite element analysis, Hollow heart defect, Laser modal analysis, Watermelon.

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Weisbecker, H., B. Cazzolato, S. Wildy, S. Marburg, J. Codrington et A. Kotousov. « Surface Strain Measurements Using a 3D Scanning Laser Vibrometer ». Experimental Mechanics 52, n^o 7 (6 octobre 2011) : 805–15. http://dx.doi.org/10.1007/s11340-011-9545-5.

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Matczak, Joanna, et Kamil Matczak. « Research position for testing the natural frequency of rotor blades using a PSV-500-3D vibrometer ». AUTOBUSY – Technika, Eksploatacja, Systemy Transportowe 19, n^o 12 (31 décembre 2018) : 566–69. http://dx.doi.org/10.24136/atest.2018.453.

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The article presents the possibilities of using a laser vibrometer to perform non-contact vibration measurements, allowing it to be used as a tool for many measuring applications. The authors pointed to the possibilities of effective use of a laser vibrometer in the aviation industry for the purpose of designing the optimal geometry of the rotor blades, studying the impact of vibrations on the work of the blades and, as a consequence, increasing the efficiency and reliability of their work.

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Sels, Seppe, Bart Ribbens, Boris Bogaerts, Jeroen Peeters et Steve Vanlanduit. « 3D model assisted fully automated scanning laser Doppler vibrometer measurements ». Optics and Lasers in Engineering 99 (décembre 2017) : 23–30. http://dx.doi.org/10.1016/j.optlaseng.2016.09.007.

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Píštěk, Václav, Pavel Kučera, Oleksij Fomin, Alyona Lovska et Aleš Prokop. « Acoustic Identification of Turbocharger Impeller Mistuning—A New Tool for Low Emission Engine Development ». Applied Sciences 10, n^o 18 (14 septembre 2020) : 6394. http://dx.doi.org/10.3390/app10186394.

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At present, exhaust gas turbochargers not only form the basis for the economical operation of petrol, diesel or gas engines of all power categories, but also have an irreplaceable role on reducing their emissions. In order to reduce emissions from internal combustion engines, various systems are being developed, all of which have a turbocharger as an important component. Demands on turbocharger system durability and reliability keep growing, which requires the application of increasingly advanced computational and experimental methods at the development beginning of these systems. The design of turbochargers starts with a mathematical description of their rotationally cyclic impellers. However, mistuning, i.e., a slight individual blade property deviation from the intended design parameters, leads to a disturbance of the rotational cyclic symmetry. This article deals with the effects of manufacturing-related deviations on the structural dynamic behaviour of real turbine rotors. As opposed to methods exploiting expensive scanning vibrometers for experimental modal analysis or time-consuming accurate measurement of the geometry of individual blades using 3D optical scanners. A suitable microphone and a finite element rotor wheel model are the basis of this new method. After comparing the described acoustic approach with the laser vibrometer procedure, the results seemed to be practically identical. In comparison with the laser technique the unquestionable added value of this new method is the fact that it brings a significant reduction in the financial requirements for laboratory equipment. Another important benefit is that the measuring process of bladed wheel mistuning is significantly less time-consuming.

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Ren, Zesheng, Yuyong Xiong, Zhike Peng et Guang Meng. « 3D microwave vibrometer : Contactless three-dimensional vibration measurements using microwave radars ». Mechanical Systems and Signal Processing 183 (janvier 2023) : 109622. http://dx.doi.org/10.1016/j.ymssp.2022.109622.

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Ohara, Yoshikazu, Marcel C. Remillieux, T. J. Ulrich, Serina Ozawa, Kosuke Tsunoda, Toshihiro Tsuji et Tsuyoshi Mihara. « High-resolution 3D phased-array imaging of fatigue cracks using piezoelectric and laser ultrasonic system (PLUS) ». Japanese Journal of Applied Physics 61, SG (19 mai 2022) : SG1043. http://dx.doi.org/10.35848/1347-4065/ac48cd.

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Abstract This paper reports the effectiveness of a novel imaging system, piezoelectric and laser ultrasonic system (PLUS), for the three-dimensional (3D) imaging of fatigue cracks with a high-resolution. The PLUS combines a piezoelectric transmitter and the two-dimensional (2D) mechanical scanning of a laser Doppler vibrometer, enabling the 2D matrix array with an ultra-multiple number of receiving points for 3D phased array imaging. After describing the principle and 3D imaging algorithm of PLUS, we show the fundamental 3D imaging capability of the PLUS in a flat-bottom-hole specimen with varying the number of receiving points under a fixed large receiving aperture. We then demonstrate that the PLUS with 4275 receiving points (i.e. 75 × 57) achieves high-resolution 3D imaging of a fatigue crack with a high signal-to-noise ratio, providing the outline of the fatigue crack geometry. We also discuss the effectiveness of the ultra-multiple receiving points for suppressing grating lobes and random noise.

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Khalil, Hossam, Dongkyu Kim, Joonsik Nam et Kyihwan Park. « Accuracy and noise analyses of 3D vibration measurements using laser Doppler vibrometer ». Measurement 94 (décembre 2016) : 883–92. http://dx.doi.org/10.1016/j.measurement.2016.09.003.

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Bouzzit, A., A. Arciniegas, L. Martinez, S. Serfaty et N. Wilkie-Chancellier. « Material characterization by surface wave parameters extraction using 3D vibrometer and ellipsometry ». Journal of Physics : Conference Series 2768, n^o 1 (1 mai 2024) : 012001. http://dx.doi.org/10.1088/1742-6596/2768/1/012001.

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Abstract This work focuses on the monitoring of the 3D propagation of ultrasonic surface waves used in non-destructive testing and evaluation. The ellipticity of the movement related to the Rayleigh wave, specifically the H/V parameter, is studied analytically, numerically, and experimentally on an aluminum block. The study involves generating signals from the theoretical harmonic expression of particle displacement issued from Rayleigh wave, carrying out numerical simulations using a finite element method, and generating the Rayleigh wave using a shear contact transducer with a 1 MHz central frequency in the experimental study. The work also involves appropriate filtering of signals to extract components with specific polarization and suppress other modes with low polarization energy. The obtained results for aluminum show a good agreement between the analytical, numerical, and experimental studies of Rayleigh wave ellipticity. Moreover, these H/V ratios are consistent with the theoretical values described in the literature. As a proof of concept, this method is also applied to simulation data to study orthotropic materials (wood/bone), obtaining promising results.

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Dolev, Amit, et Selman Sakar. « The dynamics of partially encapsulated microbubbles subjected to ultrasound ». Journal of the Acoustical Society of America 153, n^o 3_supplement (1 mars 2023) : A52. http://dx.doi.org/10.1121/10.0018133.

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Acoustically excited microbubbles generate various nonlinear forces that can be leveraged in microscale systems for actuation and manipulation. To obtain optimal performances, bubbles should be characterized; however, so far, they were studied indirectly by measuring downstream phenomena. Here, we present a novel scheme to measure the vibrations of a bubble at the water-air interface using a laser vibrometer and the impinging pressure using a hydrophone. A custom-built optical setup couples the vibrometer to an inverted microscope. The microstructures encapsulating the bubbles are 3D nanoprinted on glass slides, which allows the realization of complex configurations with various polymers. The overall platform enables us to study the dynamics of bubbles with single or multiple interfaces, and their interactions. The measurements are also used to refine the analytical model of the multi-physics system and find optimal operating conditions. The conditions depend on the bubble geometry, boundaries, and excitation source. The measurements reveal that it is easier to excite certain vibration modes when the acoustic wavelength is much larger than the bubble. We demonstrate the controllable motion of 3D nanoprinted flexible structures by harnessing nonlinear forces that are produced by acoustically excited microbubbles. These structures will serve as building blocks for all-mechanical soft microrobots.

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He, Xiao Yuan, Fei Peng Zhu, Cheng Fei Wang et Ying Jun Xu. « Stroboscopic Fringe Projection Method for 3D Dynamic Displacement Measurement ». Applied Mechanics and Materials 70 (août 2011) : 255–60. http://dx.doi.org/10.4028/www.scientific.net/amm.70.255.

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The determination of dynamic characteristics of microelectromechanical system (MEMS) devices is of great importance. Currently, vibrometer techniques using a Laser-Doppler Vibrometer (LDV) are used for dynamic measurement of MEMS, utilizing an interferometer based on a stroboscope and high-speed cine photomicrography are used for MEMS. But, these methods can’t be used for 3D dynamic displacement measurement simultaneously because of their limitations. In this paper, an optical system for 3D dynamic displacement measurement of micro-components is presented using stroboscopic fringe projection and digital image correlation (DIC), which can measure both in-plane and out-of-plane motions simultaneously. In the system, stroboscopic fringe patterns are projected onto the surface of a vibrating specimen by a phase-shifting projector and stroboscopic illumination supplied with a pulsed laser diode. Synchronization between the stroboscopic laser and the driving signal for the specimen vibrating is achieved by the stroboscopic controller. For a certain vibration state, four deformed phase-shifting fringe patterns are captured by a high-resolution CMOS camera with a long working distance microscope. The images are processed by a phase-shifting technique to obtain the phase distribution. The surface pattern of the specimen without fringes could be obtained by certain phase-shifting algorithms. When stroboscopic pulses are delayed, the stroboscopic phase is changed and another vibrating status could be captured in the same way. Comparing the phase distributions of these two states, the out-of-plane displacement is achieved, which is the displacement of the specimen between these two states. The in-plane displacement could be obtained from the surface pattern without fringes by DIC. Adjusting the phase delay of illumination by stroboscopic controller, the motions of the specimen in the whole vibration period can be obtained.

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Vehovszky, Balázs, István Horváth, Karl Slenczka, Martin Schuster et Tamás Jakubík. « Vibration Damping Measurement on Car Windshields ». Periodica Polytechnica Mechanical Engineering 63, n^o 1 (13 novembre 2018) : 1–6. http://dx.doi.org/10.3311/ppme.11559.

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Knowledge of the damping properties of a windshield is a fundamental element of the acoustical characterization of a car. The measuring method of damping for a windshield is presented in the paper. The damping loss factor – as a basic measure of mechanical damping – was determined experimentally by two means: the reverberation time from impact hammer testing as well as the modal behavior from 3D laser scanning vibrometer measurements. The results proved that the modal shapes have a fundamental effect on the measured damping values.

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Rau, Mark, Julius O. Smith et Doug L. James. « Augmenting a single-point laser Doppler vibrometer to perform scanning measurements ». Journal of the Acoustical Society of America 151, n^o 4 (avril 2022) : A157. http://dx.doi.org/10.1121/10.0010962.

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Laser Doppler vibrometers (LDV) are used for non-contact vibration measurements of various structures and are frequently used for stringed instrument measurements. Single-point LDVs can be used with the roving hammer or LDV method for mode shape measurements, but this is time-consuming and requires constant attention. Scanning LDVs exist but are expensive and often out of reach of musical acoustics researchers. An inexpensive apparatus to modify a common single-point LDV such that it can perform automated scanning measurements is presented. The augmentation consists of a mirror galvanometer, impact hammer controller, and 3D printed mounting hardware. The scanning system is controlled by a microprocessor and can be easily automated. The total cost of the system, excluding the LDV and impact hammer, is under two hundred dollars. Measurements of guitars are presented to validate the scanning system and discuss any shortcomings.

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