Scanning Vibrometer Research Articles

Experimental sound power from curved plates using the radiation resistance matrix and a scanning vibrometer

Vibration-based sound power (VBSP) methods based on elemental radiators and measurements from a scanning vibrometer have been shown to be accurate for flat plates and cylinders. In this paper, the VBSP method is extended to account for simple curved structures, with a constant radius of curvature. Data are also presented that suggest the VBSP method is more accurate than the ISO 3741 standard for measuring sound power when significant background noise is present. Experimental results from ISO 3741 and the VBSP methods are compared for three simple curved plate structures with different radii of curvature. The results show good agreement for all three structures over a wide frequency range. The experimental results also indicate that the VBSP method is more accurate in the low frequency range where the curved plates radiated relatively little and significant background noise was present.

Experimental study of particle dampers applied to wind turbine blades to reduce low-frequency sound emission

Sound emission from an onshore wind turbine is one of the significant hurdles to use wind energy to its full potential. The vibration caused by the generator is transmitted to the blades, which radiates the sound to the surrounding. The purpose of this experimental study is to present a passive vibration reduction concept, which is based on the high damping properties of granular materials. The efficiency of this concept will be investigated using a laser scanning vibrometer device. For the experimental purpose in the laboratory, small-scale replicas inspired by the original configurations are used as reference geometries for the wind turbine generator and the blades. Vibrations of the prototype, with and without granular material filling, will be determined and compared with each other. The influence of the amount of granular material inside the structure is also investigated. Apart from this, different types of granular filling are examined with respect to their efficiency in reducing the amplitude of vibration of the structure while being as light as possible in order to design a lightweight solution, which increases the overall mass of the wind turbine marginally.

Full-field force identification with high-speed digital holography

This paper proposes a full and large field, high spatial resolution, contact-less, and non-intrusive approach for force retrieval at different excitation regimes of mechanical structures. The inverse problem is based on the Force Analysis Technique where the measured displacement/velocity field is obtained from high-speed digital holographic vibrometry. With the full-field measurements, the analysis of harmonic and transient vibration sources is performed in both the spatial and temporal domains. The dense mesh of data points is advantageously used to solve the inverse problem of force identification (in terms of localization and quantification) which is regularized following a Bayesian approach. Experimental results for both stationary and transient regimes are provided. For the stationary regime, results are compared with those obtained from scanning vibrometer and exhibit quite good agreement, thus validating the proposed approach. For the transient regime the retrieved time dependence of the force is compared with the signal directly measured by a piezoelectric force sensor. Overall experimental results show very good agreement.

Shear-lag modelling of surface-bonded magnetostrictive transducers for shear horizontal wave generation in a non-ferromagnetic plate

The fundamental shear horizontal (SH) wave in thin-walled structures shows appealing features for structural health monitoring (SHM) applications. Its efficient generation and reception however remain a critical and challenging issue. Magnetostrictive transducers (MsTs) show proven ability in exciting strong SH waves due to the high piezomagnetic coefficient of the ferromagnetic foil. In this study, to investigate the fundamental SH wave generation using MsTs and their design, a theoretical model is established based on the shear-lag model and the normal mode expansion method. The coupling of an MsT with a host plate is achieved by a bonding layer, whose mechanical property is modelled through the continuous shear stress across the thickness. The theoretical model is validated using finite element simulations in terms of generation mechanism and some typical features associated with the fundamental SH wave component. Meanwhile, wave field is visualized using a 3D Laser scanning vibrometer system. Experimental results within a wide frequency range show a good agreement with the theoretically predicted results. Influences of the coil configuration and bonding conditions are further investigated using the proposed model. The study offers guidelines to system design and optimization for fundamental SH wave generation in views of guided-wave-based SHM applications.

Reliability Verification of Damping Capacity Assessment Through In Vitro Analysis of Implant Micromotion in Peri-implant Bone Loss Model.

This in vitro study aimed to determine the efficacy of a damping capacity assessment in evaluating the implant stability in a simulated peri-implant bone loss model. The same type of implant was placed sequentially in 0.5-mm-depth increments in polyurethane bone of a constant density, resulting in 11 specimens with varying surrounding bone levels. The implant stability was evaluated by a damping capacity assessment consisting of six consecutive impacts in one set. The damping results, including the contact time and stability index, were measured by three repeated sets of stability tests for each specimen. All implant micromotions were recorded in real time using a laser scanning vibrometer during these stability tests. The micromotions were analyzed in terms of three parameters: maximum displacement, expected mobility, and vibration frequency. Additionally, two other stability indices were acquired three times each for reference. Pearson correlation analysis was used to confirm the correlations among all the variables; P < .05 was considered statistically significant. As the peri-implant bone level increased, the contact time results decreased gradually from 502 to 290 μs, and the stability index increased from 55 to 78. The implant micromotions of all specimens showed a damped sine waveform graph, which can be divided into impact displacement and self-vibration patterns by the contact end points. As the implant stability increased, these contact end points converged toward the third peak, the maximum displacement and expected mobility decreased, and the vibration frequency increased (ρ = -0.85, -0.88, and 0.99, respectively). Two other stability indices reflected the implant stability due to peri-implant bone loss. The statistical analysis indicated significant correlations among all measured variables; in particular, the three stability indices exhibited high correlations with each other (ρ = 0.99, -0.99, and -1.00, respectively). Within the limitations of this in vitro study, the implant stability measured by a damping capacity assessment was suitable for investigating the extent of implant micromotions, which were determined by 0.5-mm horizontal changes in the peri-implant bone level.

Identification of resonant vibrations of the miniature unmanned airplane with contact and non-contact measuring techniques

The paper describes application of two different vibration measurement methods for identification of natural modes of the miniature UAV. The aim of this research was to determine resonant frequencies and modes of mini-airplane within specified range of frequency values. Special measuring equipment was used including both contact and non-contact techniques. The measuring systems on equipment of the Institute of Aviation Technology in the Faculty of Mechatronics, Armament and Aerospace of Military University of Technology (Warsaw, PL) were used to conduct measurements. In traditional GVT methods a large number of sensors can be attached to the aircraft. The weight of sensors and cables is negligible in relation to the mass of the large aircraft. But for small and lightweight unmanned aerial vehicles, this could bring a significant mass component in relation to the total mass of the tested object. In this paper the methodology of GVT was presented. Two different measuring methods were applied, i.e. the contact method and the non-contact method. Using the dedicated apparatus in relation to mini-airplane, properly prepared in terms of mass distribution, rudders deflection stiffness and proper support, some resonant characteristics can be determined. The contact measuring system consists of a multi-channel analyzer, piezoelectric accelerometers, electrodynamic exciters, amplifiers, impedance heads and a computer with the Test. Lab Software. As the non-contact method a laser scanning vibrometer was used. The principle of its operation is based on the separation of the emitted laser beam. The returning beam reflected from a vibrating object is captured by the camera and compared to the reference beam. Dedicated software analyses collected data and on the basis of it creates animations of structural vibrational shapes and spectral plots within investigated frequency range. Object used for research is the mini-UAV Rybitwa – composite mini-plane with a classic aerodynamic layout manufactured in IAT MUT. In the work both measurement methods and some sample results were presented. Results referenced to dynamic properties of the mini-UAV can be applied in the future to FE model tuning.

Moving sensors for improved estimation of dynamic structures: Experimental validation

In the monitoring of structural systems, the use of multiple high-end sensors may prove to be economically prohibitive. The alternative approach would be to use fewer devices capable of moving across the span of the structural system. In the proposed approach, a velocity sensor that is able to move across the spatial domain and obtain point-wise velocity measurements is combined to a novel dynamic observer. Based on the measured velocities, a state estimator is developed, the gain of which depends on the motion of the sensor. The motion of the sensor is defined using Lyapunov redesign methods and depends only on the estimation error at the current sensor position. The guidance policy is performance based and steers the sensor to spatial regions of the structure with larger estimation errors. The proposed approach is validated with a one-dimensional flexible structure, mathematically described by an Euler–Bernoulli partial differential equation. The moving sensor is realized through the use of a laser scanning vibrometer that provides both the moving measurements and additional measurements against which the proposed approach will be validated. Once measurements over a large number of locations are acquired, the experimental results are fed to the algorithm that selects the instantaneous sensor location. Experimental results for linear and nonlinear beam cases are presented to show the feasibility and robustness of the proposed approach.

Dental Condition as A Factor Modifying the Transmission of the Sound Vibration in the Skull Bones

Dental deficiencies coexist with hearing loss, and dental treatment can improve hearing acuity. To prove that different dentition affects the transmission of acoustic vibrations through bone conduction, we prepared six dry human skulls to reconstruct teeth and soft tissues. We measured the transmission of vibrations from the maxilla to the cochlea, in the toothless jaw (TJ), jaw with lateral defects with frame dentures (FD), toothless jaw with complete dentures (CD), and jaw with reconstructed dentition (RD). Each skull was flexibly suspended. The maxilla was stimulated with the bone vibrator Radioear B71. The vibrations of the pyramid were measured perpendicularly using the Polytec PSV-400-M2 scanning vibrometer. Characteristics of frequencies differed simultaneously on the left (l) and right (r) side of each skull. In all states (from 234 Hz to 5 kHz), we identified 10–21 resonant (R) and 9–21 antiresonant (AR) frequencies unilaterally (+/− 5%). In about 30% of cases, they were each time inconsistent with the “physiological” state-RD. In the 500 Hz–2 kHz frequency range (necessary for understanding speech), the effective vibrations velocities vRMS (mm/s) near cochlea were significantly lower in RD than in tree states, where (depending on the dentures) the least energy reached cochlea in FD and the most in TJ.

Analysis of the Oscillation Behavior of Hybrid Aluminum/Steel Joints Realized by Ultrasound Enhanced Friction Stir Welding

Friction stir welding (FSW) is an innovative solid-state joining process, which is suitable for joining dissimilar materials with strongly differing physical and chemical properties such as aluminum and steel. Where other joining methods such as fusion welding struggle to achieve appropriate joint strengths due to the excessive formation of brittle aluminum-rich intermetallic phases (IMP), FSW joints of aluminum and steel only show small layers of IMP, thus, sufficient tensile strengths in proximity to the maximum tensile strength of the weaker aluminum base material can be reached. With the aim to optimize the mechanical and microstructural properties of such dissimilar joints for widening the field for possible industrial applications, several hybrid friction stir welding methods have been developed which include an additional energy input, whereas the ultrasound enhancement (USE-FSW) is one of the most promising. The current work was carried out on AA6061/DC04 joints which were successfully friction stir welded with and without ultrasound support, in respect to the influence of varying the ultrasound transmission side. The functionality of the USE-FSW setup could be verified by multi point laser vibrometer measurements. Additionally, a higher proportion of transversal oscillation for the transmission of power ultrasound into aluminum could be detected using a scanning vibrometer. In comparison to the conventionally friction stir welded joints the ultrasound enhancement led to an avoidance of weld defects and an increase of the steel particle volume in the stir zone. The joint produced with power ultrasound transmission via aluminum resulted in a more uniform interface.

Selective Generation of Lamb Wave Modes in a Finite-Width Plate by Angle-Beam Excitation Method.

A Lamb wave in a plate with a finite width has both thickness and width modes, whereas only thickness modes exist in an infinitely wide plate. The thickness and width modes are numerously formed in a finite-width plate, and they all have different cut-off frequencies, wave velocities, and wave structures. These different characteristics can be utilized in various applications, but a selective generation method for a particular Lamb wave mode in a finite-width plate has not been sufficiently studied, and only a method using multiple elements has been reported. This paper presents the selective generation of a certain Lamb wave mode in a finite-width plate by an angle-beam excitation method using single or dual wedges. In the proposed generation method, a specially designed wedge with grooves or a patch having insulation layers is employed for partial acoustic insulation of the ultrasonic energy incident into the plate. The feasibility of the proposed method was investigated through finite element method (FEM) simulations for Lamb wave excitation and propagation, and then experimentally demonstrated by the measurement of Lamb wave propagation using a laser scanning vibrometer.

Modal Characteristics of Carbon Fiber Reinforced Composite Structure at High Temperature

Flight vehicles that fly at high Mach speeds will be exposed to a severe aerodynamic heating problem, which leads to high surface temperatures and large temperature gradients. Thermal load will induce thermal stress, thermal deformation, and even thermal buckling. Therefore, the dynamic stiffness and the modal characteristics will be affected. In this paper, several tests are carried out for a plain woven carbon-fiber-reinforced silicon carbide (C/SiC) composite plate under elevated temperature. The plate is heated by a quartz-lamp radiation heating system. A three-dimensional digital image correlation system is first employed to obtain the relationship between displacements and temperature to get the critical buckled temperature. Then, the thermal modal tests are performed by a laser scanning vibrometer to investigate the effect of thermal loads on modal parameters: especially the effect of the critical buckled temperature. A specific fixture with water cooled is designed in order to avoid the influence of the uncertainty of the boundary condition since the modal parameters are very sensitive to the boundary condition. Finally, the numerical simulation process of the high-temperature modal tests for the buckled plate is presented to investigate the contributions from temperature-dependent material properties and thermal stresses. As the temperature increases, the modal frequencies reduce. After the critical buckled temperature, the modal frequencies increase. A parametric study is further performed using the presented numerical model to investigate the thermal modal characteristics of C/SiC composite plates with various thickness and boundary conditions.

Development of Nanoporous AAO Membrane for Nano Filtration Using the Acoustophoresis Method.

A concept of a nanoporous anodic aluminum oxide (AAO) membrane as a vibro-active micro/nano-filter in a micro hydro mechanical system for the filtration, separation, and manipulation of bioparticles is reported in this paper. For the fabrication of a nanoporous AAO, a two-step mild anodization (MA) and hard anodization (HA) technique was used. Atomic force microscopy (AFM) and scanning electron microscopy (SEM) were used to analyze the surface morphology of nanoporous AAO. A nanoporous structure with a pore diameter in the range of 50–90 nm, an interpore distance of 110 nm, and an oxide layer thickness of 0.12 mm with 60.72% porosity was obtained. Fourier-transform infrared spectroscopy (FTIR) and energy-dispersive X-ray spectroscopy (EDS) were employed to evaluate AAO chemical properties. The obtained results showed that the AAO structure is of hexagonal symmetry and showed where Al2O3 is dominant. The hydrophobic properties of the nanoporous surface were characterized by water contact angle measurement. It was observed that the surface of the nanoporous AAO membrane is hydrophilic. Furthermore, to determine whether a nanomembrane could function as a vibro-active nano filter, a numerical simulation was performed using COMSOL Multiphysics 5.4 (COMSOL Inc, Stockholm, Sweden). Here, a membrane was excited at a frequency range of 0–100 kHz for surface acoustics wave (SAW) distribution on the surface of the nanoporous AAO using a PZT 5H cylinder (Piezo Hannas, Wuhan, China). The SAW, standing acoustic waves, and travelling acoustic waves of different wavelengths were excited to the fabricated AAO membrane and the results were compared with experimental ones, obtained from non-destructive testing method 3D scanning vibrometer (PSV-500-3D-HV, Polytec GmbH, Waldbronn, Germany) and holographic interferometry system (PRISM, Hy-Tech Forming Systems (USA), Phoenix, AZ, USA). Finally, a simulation of a single nanotube was performed to analyze the acoustic pressure distribution and time, needed to center nanoparticles in the nanotube.

Numerical and experimental investigations in the damping behavior of particle dampers attached to a vibrating structure

Particle damping is a passive damping technique at which granular material is either filled in a box attached to a vibrating structure or it is filled in holes embedded in the vibrating structure. Due to the structural vibrations, momentum is transferred to the granular material which interacts with each other. As a result, energy is dissipated by impacts and frictional phenomena between the particles.In this paper, a discrete element model is combined with a reduced finite element model. It can be analyzed for a wide frequency range. The accuracy is validated by experiments. The testbed consists of a beam with a free-free boundary condition excited by a shaker and its velocity profile is measured with a laser scanning vibrometer. The particle damper is filled with different steel balls. The discrete element code uses continuous contact models. An efficient contact algorithm is used while a coupling with a finite element model of the structure enables the prediction of the overall system movement.The system is analyzed over a wide frequency range for multiple eigenmodes. The first comparisons of experiments and simulations are performed showing a good agreement of the frequency response and modal parameters. A high dependency of the damping on the position of the particle box and its filling ratio is obtained.

Amplitude Uniformity in Ultrasonic Assisted Fused Deposition Modeling

Fused Deposition Modeling (FDM) is one of the Additive Manufacturing (AM) technology. Ultrasonic-assisted FDM system has been proven to improve the mechanical properties of the printed specimens. This study aims to explore the uniformity of the amplitude of ultrasonic vibration that was used during the printing process. The uniformity of vibration affected the improvement of the mechanical properties of the 3D printed part. If there is a bad uniformity of ultrasonic vibration, it will influence and increase the variation of the tensile test result. An open-source FDM printer attached with the piezoelectric transducer in various locations of the printer platform was set up. Five different positions and numbers of piezoelectric transducer were set up in order to determine the best position and number of the piezoelectric transducer for transmitting the vibration uniformly to the printing platform. A laser scanning vibrometer was used to determine the amplitude of ultrasonic vibration that transmitted over the printing platform of an open-source FDM 3D printer. From the results, it shows that with two piezoelectric transducers at “Position 4” improved the uniformity of ultrasonic vibration as it had the lowest standard deviation. The test also revealed that the ultrasonic vibration effect uniformly on the 3D printed specimens. In addition, it also reduces the variation and provide better tensile test results of the printed specimens

Optimization of a flexible piezoelectric module structure based on a lead-free piezoceramic embedded in nanofiber composites

Abstract To realize flexible piezoelectric materials with energy harvesting properties and vibrational characteristics, a piezoelectric module structure based on a lead-free piezoceramic embedded in a nanofiber composite was optimized according to the electrode structure and the module array arrangement. Lead-free piezoceramic particles embedded in nanofiber composites were prepared by an electrospinning process and then modularized by adding upper and lower electrodes via lamination. The energy harvesting properties of the flexible piezoelectric single modules with electrode structures consisting of top and bottom electrodes or interdigitated electrodes with various electrode widths and electrode intervals were characterized according to the oscillation frequency and the bending motion. The displacement and vibrational mode shapes of the flexible single modules were analyzed using a laser scanning vibrometer. Based on the optimized electrode structures of the flexible single modules, flexible piezoelectric dual modules were fabricated according to x- and z-axis array arrangements and to serial and parallel connection methods. The energy harvesting properties were measured and structural health monitoring sensor tests were conducted for several simulated situations. Among the examined modules, the flexible piezoelectric dual module with a serially connected x-axis array showed the best performance. This work provides a new guideline for using module structure design to enhance the piezoelectric effect in flexible modules.

Influences of shaker armature dynamics on periodic force measurement

In this article, we investigate the influence of the shaker armature’s mechanical structure on periodic force measurement, with particular emphasis on measurement uncertainty. In order to perform modal and harmonic analyses of the measurement setup, a finite element model was iteratively developed. The model was validated by measurements with a scanning vibrometer. The results show that the dynamic behaviour of the shaker armature should be taken into consideration before carrying out a periodic force measurement.

Soft Haptic Actuator Based on Knitted PVC Gel Fabric

An electroactive and actuator made of knitted polyvinyl chloride (PVC) gel fabric is proposed herein. This haptic actuator consists of an upper layer, a lower layer, and fabric made by twisting long and slender PVC gel strings. The PVC gel fabric changes its shape according to the input voltage waveform, and exerts an electrostatic force between the upper and lower layers. When the applied voltage is removed, the PVC gel fabric rapidly restores to its initial configuration. Consequently, these effects generate vibrations that are sufficiently strong for human perception. In this paper, we conducted quantitative experiments to investigate the performance of our soft haptic actuator using an accelerometer and a laser scanning vibrometer. Furthermore, we performed a perceptual evaluation and the results indicate that our proposed actuator can stimulate the human skin with sufficient perceptual strength.

Outstanding Piezoelectric Performance in Lead‐Free 0.95(K,Na)(Sb,Nb)O3‐0.05(Bi,Na,K)ZrO3 Thick Films with Oriented Nanophase Coexistence

AbstractLead‐free 0.95(K0.48Na0.52)(Nb0.95Sb0.05)O3‐0.05Bi0.5(Na0.82K0.18)0.5ZrO3 (KNSN‐BNKZ0.05) piezoelectric films with preferred crystal orientation and enhanced thickness are fabricated on silicon substrates from a chemical solution approach. Adequate K excess is introduced to obtain a single perovskite phase in the resulting thicker films. The effects of thickness, crystal orientation, and structure of the films on the performance are investigated. Outstandingly large effective piezoelectric strain coefficient up to 250 pm V−1 is demonstrated over a macroscopic scale using a laser scanning vibrometer in the [100]‐KNSN‐BNKZ0.05 film with an enhanced thickness of 2.7 µm, competitive to the benchmark oriented lead zirconate titanate films on silicon. Atomically resolved electron microscopy reveals the coexistence of oriented ferroelectric rhombohedral (R) and tetragonal (T) phases at the nanometer scale with gradual polarization rotation, which can lower the domain wall energy and facilitate the large piezoelectric response. The increased film thickness reduces the in‐plane mechanical clamping to enable more free deformation in the thickness direction and improve domain wall mobility, both further contributing to enhanced piezoelectric response.

Investigation of Ultrasonic Sonotrode Design to Improve the Performance of Ultrasonic Fouling Removal

Fouling build-up is a well-known industrial problem and its accumulation is dependent on the conditions surrounding the structure. Conventional fouling removal methods are costly and also require an operational halt to carry out the procedure. The use of Ultrasonics has gained popularity in recent years as a non-invasive means of fouling removal but further research and development are required to improve and optimize the technology. Currently in industry, Ultrasonic horns are designed and optimized to generate high amplitude vibrations for various applications including welding, cutting and sonochemistry. Some research has been done to design horns for the generation of cavitation, but none specifically for fouling removal applications. This work investigates the addition of half-wavelength transducer horns of varying shapes (cylindrical, conical, exponential and stepped) to an existing 40 kHz cleaning transducer. Numerical modelling is carried out to optimize the length of the horn before manufacturing final geometries. Experiments were conducted to attach an ultrasonic horn to the transducer and to a carbon steel plate (300 mm × 300 mm × 2 mm), and to measure wave propagation across the structure using a PSV-400 3D Laser Scanning Vibrometer. This has shown that the addition of an ultrasonic horn improves the out-of-plane displacement across the structure, which correlates to an improvement in fouling removal for steel tube ultrasonic cleaning.

Vibration Damping Measurement on Car Windshields

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.