Showing papers on "Laser Doppler vibrometer published in 2016"
TL;DR: It is confirmed that using the ACT/LDV system and implementing simple Snell's law method is highly sensitive and effective in characterizing the dispersion curves of Lamb waves in composite structures as well as its angular dependency.
64 citations
TL;DR: In this paper, a hybrid non-contact inspection system was proposed to image damage in an aluminum plate using a piezoelectric linear array for actuation and a laser Doppler vibrometer line-scan perpendicular to the actuator array for sensing.
Abstract: A Lamb wave-based, subwavelength imaging algorithm is developed for damage imaging in a metallic plate based on a decomposition of the time-reversal operator method together with a multiple signal classification imaging condition in the space-frequency domain. In this study, a hybrid non-contact inspection system was proposed to image damage in an aluminum plate using a piezoelectric linear array for actuation and a laser Doppler vibrometer line-scan perpendicular to the piezoelectric array for sensing. The physics of incident waves, reflection, and reflected waves that underlie the transfer matrix in the decomposition of the time-reversal operator method is mathematically formulated in the context of guided waves based on the first-order Born approximation. Singular value decomposition is then employed to decompose the experimentally measured transfer matrix into three matrices, detailing the incident wave propagation from the linear actuator array, reflection from the damage, and followed by reflected w...
62 citations
TL;DR: Theoretical and experimental non-linear vibrations of thin rectangular plates and curved panels subjected to out-of-plane harmonic excitation are investigated in this article, where a unified energy approach has been utilized to obtain the discretized nonlinear equations of motion by using the linear natural modes of vibration.
Abstract: Theoretical and experimental non-linear vibrations of thin rectangular plates and curved panels subjected to out-of-plane harmonic excitation are investigated. Experiments have been performed on isotropic and laminated sandwich plates and panels with supported and free boundary conditions. A sophisticated measuring technique has been developed to characterize the non-linear behavior experimentally by using a Laser Doppler Vibrometer and a stepped-sine testing procedure. The theoretical approach is based on Donnell's non-linear shell theory (since the tested plates are very thin) but retaining in-plane inertia, taking into account the effect of geometric imperfections. A unified energy approach has been utilized to obtain the discretized non-linear equations of motion by using the linear natural modes of vibration. Moreover, a pseudo arc-length continuation and collocation scheme has been used to obtain the periodic solutions and perform bifurcation analysis. Comparisons between numerical simulations and the experiments show good qualitative and quantitative agreement. It is found that, in order to simulate large-amplitude vibrations, a damping value much larger than the linear modal damping should be considered. This indicates a very large and non-linear increase of damping with the increase of the excitation and vibration amplitude for plates and curved panels with different shape, boundary conditions and materials.
62 citations
TL;DR: In this article, a rapid guided ultrasonic wave inspection approach through global inspection by phased array beamforming and local damage evaluation via wavenumber analysis was presented, which reduced the total composite inspection (damage detection and characterization) time by ~97% compared to using a full scan approach.
Abstract: This paper presents a rapid guided ultrasonic wave inspection approach through global inspection by phased array beamforming and local damage evaluation via wavenumber analysis. The global-local approach uses a hybrid system consisting of a PZT wafer and a non-contact laser vibrometer. The overall inspection is performed in two steps. First, a phased array configured by a small number of measurements performs beamforming and beamsteering over the entire plate in order to detect and locate the presence of the damage. A local area is identified as target damage area for the second step. Then a high density wavefield measurement is taken over the target damage area and a spatial wavenumber imaging is performed to quantitatively evaluate the damage. The two-step inspection has been applied to locate and quantify impact-induced delamination damage in a carbon fiber reinforced polymer composite plate. The detected delamination location, size and shape agree well with those of an ultrasonic C-scan. For the test case studied in this work the global-local approach reduced the total composite inspection (damage detection and characterization) time by ~97% compared to using a full scan approach.
57 citations
TL;DR: In this paper, a coherent interferometric dual frequency laser radar that merges the concept of laser and radio detection and ranging (ladar and radar, respectively), for both range and velocity measurement, is presented and experimentally demonstrated.
Abstract: A novel coherent interferometric dual frequency laser radar that merges the concept of laser and radio detection and ranging (ladar and radar, respectively), for both range and velocity measurement, is presented and experimentally demonstrated. The innovative architecture combines the broadband tunability of dual-wavelength optical sources, enabling a dynamic trade-off between precision and robustness in Doppler estimation, with the high stability of low frequency RF sources for the interferometric measure of the target range with extreme accuracy. The possibility to easily reconfigure the employed frequencies, allows to change the Doppler resolution, as well as the range ambiguity and precision, to dynamically adapt the system to reliably operate in different environments. Moreover, the coherent detection allows to enhance the signal to noise ratio reaching excellent performances also with low level of received power. The laboratory characterization provides an estimation of the system performances, in terms of resolution and sensitivity, as well as the indoor demonstration with targets of opportunity proves the effectiveness of the proposed architecture to operate in real scenarios.
43 citations
TL;DR: In this article, the optimality and effect of machining parameters on machine performance monitoring in tangential and orthogonal turn-milling processes is studied using VibSoft analyzer for processing Acousto-optic emissions (AOE).
40 citations
TL;DR: In this article, an acoustic bubble-powered microswimmer is used for propulsion and 2D steering in a centimeter-scale pool with a single piezoelectric actuator.
Abstract: This paper describes bi-directional (linear and rotational) propelling and 2-D steering of acoustic bubble-powered microswimmers that are achieved in a centimeter-scale pool (beyond chip level scale). The core structure of a microswimmer is a microtube with one end open in which a gaseous bubble is trapped. The swimmer is propelled by microstreaming flows that are generated when the trapped bubble is oscillated by an external acoustic wave. The bubble oscillation and thus propelling force are highly dependent on the frequency of the acoustic wave and the bubble length. This dependence is experimentally studied by measuring the resonance behaviors of the testing pool and bubble using a laser Doppler vibrometer (LDV) and by evaluating the generated streaming flows. The key idea in the present 2-D steering is to utilize this dependence. Multiple bubbles with different lengths are mounted on a single microswimmer with a variety of arrangements. By controlling the frequency of the acoustic wave, only frequency-matched bubbles can strongly oscillate and generate strong propulsion. By arranging multiple bubbles of different lengths in parallel but with their openings opposite and switching the frequency of the acoustic wave, bi-directionally linear propelling motions are successfully achieved. The propelling forces are calculated by a CFD analysis using the Ansys Fluent® package. For bi-directional rotations, a similar method but with diagonal arrangement of bubbles on a rectangular swimmer is also applied. The rotation can be easily reversed when the frequency of the acoustic wave is switched. For 2-D steering, short bubbles are aligned perpendicular to long bubbles. It is successfully demonstrated that the microswimmer navigates through a T-junction channel under full control with and without carrying a payload. During the navigation, the frequency is the main control input to select and resonate targeted bubbles. All of these operations are achieved by a single piezoelectric actuator.
40 citations
TL;DR: In this article, a rapid imaging technique is proposed for imaging damage in metallic plates using a zero-lag cross-correlation imaging condition in the frequency domain, which is a fully non-contact, single-sensor approach.
Abstract: In this work, a rapid imaging technique is proposed for imaging damage in metallic plates using a zero-lag cross-correlation imaging condition in the frequency domain. A fully non-contact, single-s...
38 citations
TL;DR: In this paper, the performance of the surface response to excitation (SuRE) method was evaluated with the conventional piezoelectric elements and scanning laser vibrometer used as contact and non-contact sensors, respectively, for monitoring the presence of loads on the surface.
37 citations
TL;DR: In this article, state-of-the-art self-mixing interferometry is represented by the combination of high accuracy and contactless operation with compact, very low-cost and user-friendly setup.
36 citations
TL;DR: In this paper, a support vector machine (SVM) was used to find damage locations in aluminum beams using simulation data and experimental data, which can be used as a promising tool in the field of structural health monitoring (SHM).
Abstract: Summary
Support vector machine (SVM) has been established as a promising tool for classification and regression in many research fields recently. In the current research work, SVM is explored to find damage locations in aluminum beams using simulation data and experimental data. Displacement values corresponding to the first mode shape of the beam are used to predict the damage locations. Two boundary conditions namely fixed-free and fixed-fixed are considered for this study. Damages are introduced in the form of rectangular notches along the width of the beam at different locations. Numerical simulations using commercially available finite element (FE) package, Abaqus® are first carried out on beam and mode shape data is extracted to train and test SVM with and without noise in data. To validate the predictions of damage locations based on simulation data, actual experimentations are conducted on aluminum beams of identical dimensions and boundary conditions. In the experimental study, a Laser Doppler Vibrometer (LDV) is used to extract the mode shape data. It is shown that SVM is capable to predict damage locations with a good accuracy and can be used as a promising tool in the field of structural health monitoring (SHM). Copyright © 2015 John Wiley & Sons, Ltd.
TL;DR: In this paper, the authors investigate the within-the-bond guided wave propagation in a composite skin-stringer joint and find that the amplitude of the reflection, transmission coefficients and directivity patterns of scattered waves are affected by the presence of damage.
TL;DR: In this article, a modal analysis of a rotor with three active composite blades performed by different methods is presented, including a laser vibrometer and LMS analyzer with modal hammer.
TL;DR: In this article, the A-weighted noise of a three-phase transformer core can be less than that of an equivalent single-phase core when assembled from low magnetostriction materials.
Abstract: Magnetostriction of grain-oriented 3% SiFe sheets was measured prior to assembly into model transformer cores. Core vibration was measured using a laser scanning vibrometer and harmonic spectra of acoustic noise were evaluated from the microphone outputs. Explanations show why no correlation exists between vibration harmonics profiles and A-weighted acoustic noise spectra. High localized vibration did not cause high noise due to phase differences in surface vibrations, and it is shown that this is the main reason why the A-weighted noise of a three-phase core can be less than that of an equivalent single-phase core. Noise from cores assembled from low magnetostriction materials was not always lowest because of the variable effect of electromagnetic forces.
TL;DR: In this paper, the effect of cutting parameters namely cutting speed, feed rate and helix angle on the tool life was analyzed by evaluating the amplitude of drill bit vibration and surface roughness.
TL;DR: In this article, the authors evaluated the integrity of a composite skin-stringer joint using the scattering behavior of the Lamb waves and found that the amplitude and directivity patterns of scattered fields are affected by the presence of damage, such that SHM design guidelines can be derived for efficient damage detection.
TL;DR: In this article, the authors demonstrate a method that makes an efficient use of laser nonlinear dynamics when subject to optical self-injection for subwavelength displacement sensing purposes, which combines two different phenomena taking place inside the laser cavity: optical feedback interference and laser continuous wave frequency modulation, giving rise to a wavelength sweeping effect in the laser's emission.
Abstract: We demonstrate a novel method that makes an efficient use of laser nonlinear dynamics when subject to optical self-injection for subwavelength displacement sensing purposes. The proposed methodology combines two different phenomena taking place inside the laser cavity: optical self-injection, which results in optical feedback interference, and laser continuous wave frequency modulation, giving rise to a wavelength sweeping effect in the laser’s emission. We present a combination of these phenomena to measure vibration amplitudes below $\lambda /2$ with the resolutions of a few nanometers, bandwidth dependent upon the distance of external target, amplitude, and frequency of current modulation. The basic theoretical details and a mathematical model are presented for the developed measurement principle. Experimental results with the system working as a vibrometer to measure a target vibration of amplitude ${\lambda }/{5}$ (137.5 nm) with a mean peak-to-peak error of 2.4 nm just by pointing the laser diode onto the target and applying some signal processing are also demonstrated.
TL;DR: In this paper, a gas coupled-laser acoustic detection (GCLAD) method is proposed to measure the deflection of an optical beam propagating parallel to the sample, as the refractive index of the air near the sample is affected by particle displacement on the sample surface.
Abstract: Conventional contacting transducers for ultrasonic wave detection are highly sensitive and tuned for real-time imaging with fixed array geometries. However, optical detection provides an alternative to contacting transducers when a small sensor footprint, a large frequency bandwidth, or non-contacting detection is required. Typical optical detection relies on a Doppler-shifted reflection of light from the target, but gas coupled-laser acoustic detection (GCLAD) provides an alternative optical detection method for photoacoustic (PA) and ultrasound imaging that does not involve surface reflectivity. Instead, GCLAD is a line-detector that measures the deflection of an optical beam propagating parallel to the sample, as the refractive index of the air near the sample is affected by particle displacement on the sample surface. We describe the underlying principles of GCLAD and derive a formula for quantifying the surface displacement from a remote GCLAD measurement. We discuss a design for removing the location-dependent displacement bias along the probe beam and a method for measuring the attenuation coefficient of the surrounding air. GCLAD results are used to quantify the surface displacement in a laser-ultrasound experiment, which shows 94% agreement to line-integrated data from a commercial laser vibrometer point detector. Finally, we demonstrate the feasibility of PA imaging of an artery-sized absorber using a detector 5.8 cm from a phantom surface.
TL;DR: In this paper, the authors investigated a method which controlled the energy density of ultraviolet (UV) pulse laser in real time with the control of continuous wave (CW) laser spot size in laser micro-polishing for metallic surface.
Abstract: During laser micro-polishing, the controllable laser energy density is a key technology to improve the surface roughness. In this paper, we have investigated a method which controls the energy density of ultraviolet (UV) pulse laser in real time with the control of continuous wave (CW) laser spot size in laser micro-polishing for metallic surface. The experimental and analytical considerations of several influence factors such as laser spot size, fusion zone, and focal offset were investigated. In addition, using a laser micro-polishing system manufactured with this method, the laser micro-polishing experiments on the two different surface shapes of stainless steel 316L were conducted. For the inclined or curved surface, the surface roughness improvements of up to 56.4 and 57.3 % were respectively obtained, and the analysis of the results were discussed.
TL;DR: In this article, the dispersion curves for the propagation mechanism of an ultrasonic guided wave in the evaporator are determined through numerical calculation, and the shear stress and vibration characteristics under ultrasonic excitation are analyzed using finite element method (FEM).
TL;DR: In this paper, a 100J-level Nd:glass laser system in nanosecond-scale pulse width has been constructed to perform as a standard source of high-fluence-laser science experiments.
Abstract: A 100-J-level Nd:glass laser system in nanosecond-scale pulse width has been constructed to perform as a standard source of high-fluence-laser science experiments. The laser system, operating with typical pulse durations of 3–5 ns and beam diameter 60 mm, employs a sequence of successive rod amplifiers to achieve 100-J-level energy at 1053 nm at 3 ns. The frequency conversion can provide energy of 50-J level at 351 nm. In addition to the high stability of the energy output, the most valuable of the laser system is the high spatiotemporal beam quality of the output, which contains the uniform square pulse waveform, the uniform flat-top spatial fluence distribution and the uniform flat-top wavefront.
TL;DR: It is demonstrated that the viscoelastic properties of single adherent cells can be extracted by measuring a difference in vibrational amplitude of the resonant sensor platform.
Abstract: Many recent studies on the viscoelasticity of individual cells link mechanics with cellular function and health. Here, we introduce a measurement of the viscoelastic properties of individual human colon cancer cells (HT-29) using silicon pedestal microelectromechanical systems (MEMS) resonant sensors. We demonstrate that the viscoelastic properties of single adherent cells can be extracted by measuring a difference in vibrational amplitude of our resonant sensor platform. The magnitude of vibration of the pedestal sensor is measured using a laser Doppler vibrometer (LDV). A change in amplitude of the sensor, compared with the driving amplitude (amplitude ratio), is influenced by the mechanical properties of the adhered cells. The amplitude ratio of the fixed cells was greater than the live cells, with a p-value <0.0001. By combining the amplitude shift with the resonant frequency shift measure, we determined the elastic modulus and viscosity values of 100 Pa and 0.0031 Pa s, respectively. Our method using...
Patent•
21 Nov 2016
TL;DR: In this article, the authors proposed a method to direct a laser beam to a target along a scan path at a variable scan velocity and adjust a digital modulation during movement of the laser beam along the scan path and in relation to the variable scan speed.
Abstract: Methods include directing a laser beam to a target along a scan path at a variable scan velocity and adjusting a digital modulation during movement of the laser beam along the scan path and in relation to the variable scan velocity so as to provide a fluence at the target within a predetermined fluence range along the scan path. Some methods include adjusting a width of the laser beam with a zoom beam expander. Apparatus include a laser source situated to emit a laser beam, a 3D scanner situated to receive the laser beam and to direct the laser beam along a scan path in a scanning plane at the target, and a laser source digital modulator coupled to the laser source so as to produce a fluence at the scanning plane along the scan path that is in a predetermined fluence range as the laser beam scan speed changes along the scan path.
TL;DR: In this paper, the authors report on higher orders of the roof tile-shaped bending mode in piezoelectrically actuated MEMS plate-type resonators with quasi free-free support.
Abstract: This paper reports on higher orders of the roof tile-shaped bending mode in piezoelectrically actuated MEMS plate-type resonators with quasi free–free support, achieving an increased piezoelectric response of ∼25% compared to a one-sided clamped cantilever structure with the same geometry and similar quality factor. Aluminum nitride (AlN) is used for the excitation of the devices offering different anchor designs. These MEMS resonators are characterised by electrical and optical measurements in air and in several liquids (i.e., isopropanol and viscosity standards: D5, N10, N35, N100, D500). Nodal analyses are presented and compared to both Finite Element Methods simulations and Laser Doppler Vibrometer measurements, demonstrating an excellent agreement between the positions of the plate supports with those of the nodal lines of the specific mode, which ensures a quasi free–free vibration. An optimized electrode design (OED) is established and compared to non-optimized actuation, showing superior performance for plates with OED. The evaluation of the quality factor Q and the strain related conductance peak Δ G of the investigated modes results in the highest value for the 4th order mode ( Q ∼ 100; Δ G = 0.35 mS). Finally the piezoelectric response Δ G / Q (∼4 μS for 4th order mode) is presented, showing great potential for a large variety of challenging resonator based physical and chemical sensing applications.
TL;DR: In this paper, a two-dimensional non-contact areal scan system was developed to image and quantify impact damage in a composite plate using an enhanced zero-lag cross-correlation reverse-time migration (E-CCRTM) technique.
Abstract: A two-dimensional (2D) non-contact areal scan system was developed to image and quantify impact damage in a composite plate using an enhanced zero-lag cross-correlation reverse-time migration (E-CCRTM) technique. The system comprises a single piezoelectric wafer mounted on the composite plate and a laser Doppler vibrometer (LDV) for scanning a region in the vicinity of the PZT to capture the scattered wavefield. The proposed damage imaging technique takes into account the amplitude, phase, geometric spreading, and all of the frequency content of the Lamb waves propagating in the plate; thus, a reflectivity coefficients of the delamination is calculated and potentially related to damage severity. Comparisons are made in terms of damage imaging quality between 2D areal scans and 1D line scans as well as between the proposed and existing imaging conditions. The experimental results show that the 2D E-CCRTM performs robustly when imaging and quantifying impact damage in large-scale composites using a single PZT actuator with a nearby areal scan using LDV.
01 Jul 2016-Microsystem Technologies-micro-and Nanosystems-information Storage and Processing Systems
TL;DR: In this article, a four-leaf clover (FLC EH-MEMS) was proposed to enable multiple resonant modes in the typical range of vibrations scattered in the environment (i.e., up to 4-5 kHz).
Abstract: In this contribution, we discuss a novel design concept of a high-performance wideband MEMS vibration energy harvester (EH), named four-leaf clover (FLC EH-MEMS) after its circular shape featuring four petal-like mass-spring systems. The goal is to enable multiple resonant modes in the typical range of vibrations scattered in the environment (i.e., up to 4---5 kHz). This boosts the FLC conversion capability from mechanical into electrical energy exploiting the piezoelectric effect, thus overcoming the common limitation of cantilever-like EHs that exhibit good performance only in a very narrow band of vibration (i.e., fundamental resonant mode). The FLC concept is first discussed framing it into the current state of the art, highlighting its strengths. Then, after a brief theoretical introduction on mechanical resonators, the FLC EH-MEMS device is described in details. Finite Element Method (FEM) analyses are conducted in the ANSYS Workbench framework. A suitable 3D model is built up to perform modal simulations, aimed to identify mechanical resonant modes, as well as harmonic analyses, devoted to study the mechanical and electrical behaviour of the FLC EH-MEMS (coupled field analysis). The work reports on experimental activities, as well. Physical samples of the FLC EH-MEMS device are fabricated within a technology platform that combines surface and bulk micromachining. Thereafter, specimens are tested both with a laser doppler vibrometer measurement setup as well as with a dedicated shaker-based setup, and the results are compared with simulations for validation purposes. In conclusion, the FLC EH-MEMS exhibits a large number of resonant modes scattered in the tested range of vibrations (up to 15 kHz) already starting from frequencies as low as 200 Hz, and expected levels of converted power better than 10 µW.
TL;DR: In this paper, a comparison between analytical, numerical and experimental data of a cantilever with integrated thermal actuator and piezoresistive sensor, suitable for fast scanning probe microscopy (SPM) and lithography (SPL) is presented.
TL;DR: In this paper, the in-plane and out-of-plane vibration components are used for 3D vibration measurements by using three laser scanning vibrometers (LSVs) or by moving a single LSV to three different locations.
TL;DR: The results show that the edge-filter enhanced self- Mixing Interferometry technique opens new possibilities for self-mixing detection where longer ranges, lower backscattering laser powers and higher velocities are involved.
Abstract: A laser Doppler velocimetry (LDV) sensor using the edge-filter enhanced self-mixing interferometry (ESMI) is presented based on speed measurements of single microparticles. The ESMI detection utilizes an acetylene edge-filter that maps the frequency modulation of a semiconductor laser into an intensity modulation as the laser wavelength is tuned to the steep edge of the absorption profile. In this work, the ESMI signal was analyzed for aerosol particles of different sizes from 1 μm to 10 μm at a distance of 2.5 m. At this operation range, the signal from single particles of all sizes was successfully acquired enabling particle velocity measurements through the Doppler shifted frequency along the beam axis. For the particular case of 10 μm particles, single aerosol particles were still detected at an unprecedented range of 10 m. A theoretical treatment describing the relation between Mie scattering theory and the self-mixing phenomenon on single-particle detection is presented supporting the experimental results. The results show that the edge-filter enhanced self-mixing technique opens new possibilities for self-mixing detection where longer ranges, lower backscattering laser powers and higher velocities are involved. For example, it can be used as a robust and inexpensive anemometer for LDV applications for airflows with low-number density of microparticles.