Tip Vibration Amplitude Research Articles

Terahertz nano-tomography imaging technique based on a 3D simulation model

THz scattering-type scanning near-field optical microscopy (THz s-SNOM) enables high-resolution nanoscale 2D imaging, crucial for various disciplines including biology, physics, and materials science. This study establishes a reliable 3D model to determine the maximum thickness detectable by the probe. The influences of the demodulation order, tip radius, tip vibration amplitude, and incident frequency on the maximum detectable thickness are analyzed. Using bilayer samples as examples, we successfully inverted the thickness of the first layer within the detectable maximum depth range. However, we found that inversion fails when the thickness of the first layer is too small. This underscores the distinct difference between vertical and lateral resolutions, where vertical resolution represents the minimum calculable thickness. This research unveils complex internal structures, laying the groundwork for future nanolayer imaging.

Vibration of a semi-rigid cantilever in a uniform flow

Here, we investigate the static and dynamic response of semi-rigid cantilevers at various initial inclination angles (15° <α< 90°) and flexural rigidity (EI∼O(10−8) Pa-m4) to a uniform flow using a soap film tunnel. The vertical soap film tunnel produced uniform-flow Reynolds numbers 5×103<Re<4.5×104 based on cantilever length. High speed video and image analysis were used to estimate quantities such as the average cantilever tip displacement, tip vibration amplitude and frequency ω, and vortex shedding frequency, f. Vibration frequency was then compared to vortex shedding and the cantilever’s natural frequency ωN to determine which was likely responsible for the dynamic response. A one-dimensional Euler–Bernoulli beam theory model was then used to estimate the relative magnitude of two superpositioned forcing terms with either f or ωN as the driving frequency. There was good agreement between measured and computed tip displacement.

Blade Crack Detection using Blade Tip Timing

The harsh working environment of compressor threats the integrality of bladed disk. Crack is one of the most fatal faults of rotating blades. Detecting the crack of blades at early stage could ensure the safe operation of gas turbine and save economic costs. Blade tip timing (BTT) is a noncontact blade vibration measurement technique, which is widely used in recent years. In this article, a procedure of crack detection using BTT data is proposed. First, some typical parameters are taken into consideration, including resonance frequency, amplitude change of natural frequency, amplitude of blade tip, phase, and interblade spacing. It has been found that the frequency of the blade will decrease with the increment of crack length and reduction of crack height. In addition, the resonance frequency of the bladed disk will split when the blade cracks. The amplitude of different orders of resonance frequency varies with cracks. The amplitude of the first order changes very slightly, whereas the second and third orders are relatively obvious. The blade tip vibration amplitude and phase change with cracks without obvious regularity. The interblade distance will change due to the appearance of cracks. According to the above rules, the frequency and the interblade distance are adopted as crack diagnosis indicators. First, we use the Lomb-Scargle periodogram to quickly determine whether the crack appears and then use the blade frequency and interblade distance to locate the number of the blade having crack. In the experimental test, BTT data measured on a titanium bladed disk is used to verify the effectiveness of our method.

A continuum electro-mechanical model of ultrasonic Langevin transducers to study its frequency response

In this paper, a continuum mathematical electro-mechanical model of ultrasonic Langevin transducers has been developed by considering three factors: 3D vibrations, piezoelectric effects, and elements damping. Since the equivalent-circuit methods simulate a continuous system with discrete components, they are valid near one resonance frequency. However, a continuum model is valid in broader frequency ranges. It can also describe the effect of geometries and material properties on the frequency response of transducers. By using the mathematical model, the amplitude of vibrations, mode shape, resonant and anti-resonant frequencies, mechanical quality factor, and frequency response can be achieved for a transducer with a specific geometry and material properties. It would also be reliable to design a transducer and to study its frequency response. A transducer is modeled and then numerically simulated with FEM software of COMSOL, and the results are compared with the model. Then the transducer is fabricated and tested experimentally. The results are compared with the mathematical and numerical models. The analytical resonant frequency obtained with the model is 19,378 Hz, which in comparison with 19,270 Hz of the numerical model and 19,457 Hz of the experimental test, has 0.4% and 0.5% errors, respectively. The vibration amplitude of the transducer's tip at the resonant frequency, obtained by the mathematical model, is 21.2 µm, which is 3.6% lower than the 22 µm obtained using experimental tests. The anti-resonant frequency calculated by the mathematical model is 21,748 Hz, which has a 0.7% variation with the experimental result.

Optimization design of a new type of high-frequency piezoelectric ultrasonic transducer with the compliant hinge-based mounting clamp

Piezoceramic-based ultrasonic transducers are widely used in the fabrication and packaging of the microelectronic device and their performance largely depends on the ultrasonic energy delivery efficiency (UEDE) which can be reflected by the tip vibration amplitude output (TVAO) of the transducer indirectly. Recently, it was reported that a new type of flexure hinge-based mounting clamp could enhance the TVAO of the transducer significantly. To get the best effect, this research aimed at developing an optimization method for this newly proposed mounting clamp. For the purpose, a series of researches were performed against a self-developed transducer equipped with a pair of circular notched hinge-based mounting clamps. Firstly, the influential rules of several key geometric parameters of the flexure hinge on the TVAO of the ultrasonic transducer were explored. Then, an optimization objective function together with a group of constraints was constructed. Next, the Particle Swarm Optimization (PSO) algorithm was used to optimize the geometric parameters of the circular hinge-based mounting clamp. Finally, the performance of the optimized mounting clamp was tested based on a measurement and evaluation system. The results show the optimized mounting clamp can enhance the TVAO of the transducer greatly, presenting a good improvement effect of the UEDE, and manifesting the feasibility and effectiveness of the developed method.

Observer Design for Topography Estimation in Atomic Force Microscopy Using Neural and Fuzzy Networks

In this study, a novel artificial intelligence-based approach is presented to directly estimate the surface topography. To this aim, performance of different artificial intelligence-based techniques, including the multi-layer perceptron neural, radial basis function neural, and adaptive neural fuzzy inference system networks, in estimation of the sample topography is investigated. The results demonstrate that among the designed observers, the multi-layer perceptron method can estimate surface characteristics with higher accuracy than the other methods. In the classical imaging techniques, the scanning speed of atomic force microscope is restricted due to the time required by the oscillating tip to reach the steady state motion while the closed-loop controller tries to maintain the tip vibration amplitude at a set-point value. To address this issue, we have proposed an innovative imaging technique that not only eliminates the need to a closed-loop controller but also estimates the surface topography very quick and accurate compared to the conventional imaging method. Also, the proposed technique is capable of simultaneous estimation of the topography, Hamaker parameter, and the tip-sample interaction force.

Numerical study of optimized processing condition in rolling strike ultrasonic nanocrystalline surface modification of copper

Ultrasonic nanocrystalline surface modification (UNSM) is state-of-art surface modification technique in which both the static and dynamic loads are contributed in work hardening of surface layer and amount of residual stress. The former performance causes microstructure refining while the later results to enhanced fatigue life. However, contribution of too many parameters in the process makes finding optimal parameter setting in which the process reaches to desired performance complex. In the present study, an attempt is made to find optimal combination of static force, tool tip diameter, tool tip material, linear velocity and vibration amplitude regarding the maximum plastic equivalent strain and the maximum affecting depth. The process is firstly modeled through finite element simulation in ABAQUS/EXPILICT software, and the results are further verified considering the residual stress distribution. Hereafter, a series of simulation runs are derived based on design of experiment to generate required data for optimization. In this stage, the run data are associated with response surface methodology to find optimal parameter setting regarding maximum PEEQ and maximum effective depth. The results showed that selection of 300 N static force, 9 mm tungsten carbide ball, 10 μm vibration amplitude and 1000 mm/min feed rate is optimum solution causes achieving maximum PEEQ of 3.44 at the depth of 200 μm. By finding optimal results, a series of USAT experiments have been carried out with optimum parameter setting and its hardness distribution, residual tress and microstructure has been compared with as received sample. It is found that the surface residual stress of the sample reaches from +40 MPa and reaches to –60 MPa after UNSM. On the other hand, the hardness of the sample enhances up to 50% after performing process under optimal setting.

Acoustic streaming near a sharp structure and its mixing performance characterization

Acoustic streaming can be generated in microchannels by low-frequency acoustic transducer in the vicinity of sharp structures. Close to the tip, the strong curvature induces bent trajectories on the time-periodic acoustic flow, locally enhancing the streaming-generating force. In this study, we investigate the influence of the sharp structure and vibration velocity on the streaming flow. The vibration velocities are characterized by directly visualizing the displacement of tracing particles and the generated acoustic streaming is observed using particle image velocimetry, under various operating conditions. By measuring the concentration of a fluorescence dye, we evaluate the mixing performance for different values of tip angle, vibration amplitude, and flow rate through the microchannel. Our results confirm that intense streaming is generated under low-frequency (2.5 kHz) acoustic condition when the local curvature of the boundary is close to or smaller than the viscous boundary-layer thickness. It is shown that the sharpest the edge tip, the largest the vortices size and the spatial extent of the induced streaming, therefore greatly enhancing the mixing between two miscible liquids. The mixing index, linearly characterizing the mixing degree between 1 (totally separated) and 0 (perfectly mixed), jumps from 0.73 (without acoustic excitation) to 0.38 (with acoustic excitation), resulting in a highly mixed homogeneous fluid just after the sharp edge. This emphasizes the promising potential of acoustic streaming to enhance mass transfer inside microchannels which is usually limited by the laminar flow conditions.

A new method to enhance the tip vibration amplitude output of the high frequency piezoelectric ultrasonic transducer used in the thermosonic bonding

The vibration amplitude output of the high frequency piezoelectric ultrasonic transducer used in the thermosonic bonding system can be reduced owing to many factors, among which the mounting clamp, taking charge of installing the whole transducer on the mounting bracket in bonding machine, is one such factor. To minimize the negative effect of the coupling between the transducer and the mounting bracket through the mounting clamp, and enhance the vibration amplitude output of the transducer, a new kind of flexible mounting clamp is proposed, which combines the traditional mounting clamp and the flexure hinge. Several high frequency ultrasonic transducers with different flexible clamps were designed and fabricated. A measurement system was specially set up to investigate the vibration characteristics of the transducers. Results show that the proposed flexible mounting clamps are able to increase the tip vibration amplitude output of the transducer significantly, whether the transducer vibrates at resonance or not. The promotion effect is closely related to the compliance and the decoupling potential of the clamp. The method newly proposed is a meaningful and useful attempt, and it also can be used for the ultrasonic transducers in other applications.

Cavitation and acoustic streaming generated by different sonotrode tips

Aiming at improving the efficiency of cavitation treatment, this work investigates characteristics of acoustic streaming and cavitation generated in water by dumbbell-shaped sonotrodes with plane, truncated and conical tips. The main emphasis was placed on elucidating the effects of tip shape and vibration amplitude ranged from 40 to 60 μm. The PIV technique and Weissler reaction were used to measure flow pattern and velocity of acoustic streaming, and cavitation efficiency, respectively. To provide a theoretical explanation to the experimental results, a self-developed mathematical model was used to simulate the acoustic streaming and predict the size of cavitation zone numerically.Both the experimental and numerical results revealed that the sonotrode tip shape affects the acoustic streaming significantly, altering the flow magnitude and direction from fast and downward under the plane and truncated tips to relatively slow and upward near the conical tip. Besides, the conical tip provides a more efficient cavitation treatment in comparison with the plane and truncated tips. The simulation results showed that widening of cavitation zone and altering of acoustic streaming velocity and direction near the sonotrode tip are responsible for the enhancement of cavitation treatment efficiency.

Ultrasonic Cutting of Switchgrass and Miscanthus Stems

Abstract. Ultrasound-assisted cutting has been used to cut materials with high precision, improved quality and reduced cutting forces. The research objective was to investigate the effects of high-frequency vibrations on the cutting force and cutting energy of switchgrass and miscanthus stems. Laboratory experiments were conducted on individual biomass stems at cutting speeds between 3 and 400 mm/s. An experimental cutting system with an ultrasound generator, an ultrasonic blade, a load cell, and a data acquisition system was developed. The custom designed blade was 5-cm wide and vibrated at 19.551 kHz with 2.8 µm tip vibration amplitude. There were significant measured differences in the cutting forces and cutting energies between conventional cutting and ultrasonic cutting of switchgrass and miscanthus stems (p &amp;lt; 0.05). These results suggest that the use of high-frequency vibrations reduce cutting force and cutting energy of both switchgrass and miscanthus stems. Ultrasound-assisted cutting reduced the cutting energy of switchgrass by 66.85% at 100 mm/s and miscanthus by 80.58% at 30 mm/s. However, ultrasonic cutting did not have a significant effect on the cutting force and cutting energy when the cutting speed was equal to or greater than the blade tip vibration speed. The results of this research should be useful for adapting the ultrasonic technology in biomass harvesting, particle size reduction, and processing equipment. Keywords: Biomass, Blades, Energy, Finite element analysis, Miscanthus, Switchgrass, Ultrasonics.

Electrostatic and aerodynamic forced vibrations of a thin flexible electrode: Quasi-periodic vs. chaotic oscillations.

In this paper, transverse vibrations of an electrostatically actuated thin flexible cantilever perturbed by low-speed air flow are studied using both experiments and numerical modeling. In the experiments, the dynamic characteristics of the cantilever are studied by supplying a DC voltage with an AC component for electrostatic forcing and a constant uniform air flow around the cantilever system for aerodynamic forcing. A range of control parameters leading to stable vibrations are established using a dimensionless operating parameter that is the ratio of the induced and the free stream velocities. Numerical results are validated with experimental data. Assuming the amplitude of vibrations are small, then a non-linear dynamic Euler-Bernoulli beam equation with viscous damping and gravitational effects is used to model the equation of motion. Aerodynamic forcing is modelled as a temporally sinusoidal and uniform force acting perpendicular to the beam length. The forcing amplitude is found to be proportional to the square of the air flow velocity. Numerical results strongly agree with the experiments predicting accurate vibration amplitude, displacement frequency, and quasi-periodic displacement of the cantilever tip.

A novel technique for micro-hole forming on skull with the assistance of ultrasonic vibration

Micro-hole opening on skull is technically challenging and is hard to realize by micro-drilling. Low-stiffness of the drill bit is a serious drawback in micro-drilling. To deal with this problem, a novel ultrasonic vibration assisted micro-hole forming technique has been developed. Tip geometry and vibration amplitude are two key factors affecting the performance of this hole forming technique. To investigate their effects, experiment was carried out with 300μm diameter tools of three different tip geometries at three different vibration amplitudes. Hole forming performance was evaluated by the required thrust force, dimensional accuracy, exit burr and micro-structure of bone tissue around the generated hole. Based on the findings from current study, the 60° conically tipped tool helps generate a micro-hole of better quality at a smaller thrust force, and it is more suitable for hole forming than the 120° conically tipped tool and the blunt tipped tool. As for the vibration amplitude, when a larger amplitude is used, a micro-hole of better quality and higher dimensional accuracy can be formed at a smaller thrust force. Findings from this study would lay a technical foundation for accurately generating a high-quality micro-hole on skull, which enables minimally invasive insertion of a microelectrode into brain for neural activity measuring.

Model-based broadband estimation of cutting forces and tool vibration in milling through in-process indirect multiple-sensors measurements

In machining processes, cutting forces measurement is essential to allow cutting process and tool conditions monitoring. Moreover, in order to have information about the quality of the milled part, the amplitude of the tool tip vibration would be very useful. Since both the measurements are extremely complicated especially in an industrial scenario, in this study, an in-process model-based estimator of cutting forces and tool tip vibration was designed and properly tested. The developed estimator relies on both a machine dynamic model and on indirect measurements coming from multiple sensors placed in the machine. The machine dynamic model was obtained through an experimental modal analysis session. The estimator was developed according to the Kalman filter approach. The fusion of multiple sensors data allowed the compensation of machine tool dynamics over an extended frequency range. The accuracy of the observer estimations was checked performing two different experimental sessions in which both the force applied to the tool and the tool tip vibration amplitude were measured. In the first session, the tool was excited with different sensorized hammers in order to appreciate the broad bandwidth of the performed estimations. In the second one, real cutting tests (steel milling) were done and the cutting forces were measured through a dynamometer; tool tip vibrations were measured as well. The experimental results showed that the indirect estimation of cutting forces and tool tip vibrations exhibit a good agreement with respect to the corresponding measured quantities in low and high frequency ranges. The contribution of this research is twofold. Firstly, the conceived observer allows estimating the tool tip vibrations that is a useful information strictly connected to the surfaces quality of the processed workpiece. Secondly, thanks to a multi-sensors approach, the frequency bandwidth is extended especially in the low frequency range.

Manipulation of DNA origami nanotubes in liquid using programmable tapping‐mode atomic force microscopy

The nanoscale manipulation of 1D soft and flexible ‘DNA origami nanotubes’ (DONs) that are 6 nm in diameter and 400 nm in length, and placed on a mica substrate in a TE/Mg2+ buffer solution, was executed by an atomic force microscopy (AFM) tip using a programmable tapping-mode manipulation strategy. The AFM's tip tapping amplitude was controlled to be less than or equal to 10 nm while vibrating in a solution with Mg2+ concentration of 10–20 mM. A series of single-point and one-step manipulation experiments revealed that manipulation can be achieved with an 80% successful rate under the condition that the AFM tip vibration amplitude is 3–4 nm and the Mg2+ concentration is 10 mM. Utilising this optimised condition, multipoint and multistep manipulation based on the programmable tapping-mode AFM process was conducted and nanomanipulation of DONs was successfully demonstrated.

Energy Enhancement of a Piezoelectric Cantilever Generator with Magnetic Coupling

Vibration energy harvesting has played a major role due to the almost universal presence of mechanical vibrations. It is demonstrated experimentally that a piezoceramic cantilever generator can be substantially enhanced by introducing a magnetic coupling force in this paper. The piezo-electromagnetic generator consists of a 44mm×20mm×0.7mm bimorph piezoelectric ceramic and two Φ8mm×4mm permanent magnets located at the tip of the beam. The greater bending deformation will be caused because of the permanent magnets and applied magnetic field. Then the generated charge is increased because it is proportional to the vibration amplitude of the tip of the beam. Experimental results show that the generated voltage enhances from 3.04V to 4V for the attractive force and changes from 3.04V to 3.78V for the repulsive force when the distance between the magnets is 20mm, increased by 31.6% and 24.3%, respectively. It also shows that the attractive force is better than the repulsive force from the view of enhancing the generation capacity. It proves that the method is effective for improving the output energy of the piezoelectric cantilever.

Visibility of weak contrasts in subsurface scattering near-field microscopy

We present a systematic study of the effect of the tip vibration amplitude in scattering-type scanning near-field optical microscopy (s-SNOM) on the visibility of buried structures in terms of image contrast, signal strength, and noise. When varying the tip vibration amplitude the visibility of structures and the image contrast change in opposite directions. We address the question how to optimize the tip vibration amplitude in practice and discuss the respective advantages of either high contrast or low noise. Besides for subsurface imaging, our findings can also be applied to the imaging of structures with a low material contrast on the surface.

Quasi-analytical model for scattering infrared near-field microscopy on layered systems

We present a quantitative quasi-analytical model to predict and analyze signals on layered samples measured by infrared scattering-type scanning near-field optical microscopy. Our model predictions are compared to experimental data and to fully retarded calculations based on a point dipole approximation of the tip. The model is used to study the influence of the tip vibration amplitude and of the tip radius on the near-field contrasts of samples with particularly small variations in the layer thickness. Additionally the influence of a dielectric capping layer on the tip-substrate coupling is analyzed. When inversely applied, our calculation opens the possibility to extract the local layer thickness of thin films or the dielectric functions that allow one to draw conclusions on the material composition, conductivity or crystal structure on the nanoscale.

MEMS Ring Resonators for Laserless AFM With Sub-nanoNewton Force Resolution

A concept of atomic force microscopy (AFM) oscillating sensors using electromechanical silicon microresonators is presented, and imaging capabilities are demonstrated. The microresonators are designed to feature MHz resonance frequencies, and they are batch fabricated using standard silicon microtechnologies. Integrated capacitive transducers allow to drive the resonator and to sense its vibration amplitude. A nanotip is located at a maximum of displacement for sensing near-field forces when interacting with a surface. The device has been mounted on a commercial AFM setup through a dedicated probe holder and a preprocessing electronic circuit. Experiments show that intermittent contact AFM is possible with a tip vibration amplitude of a few nanometers. AFM images have been acquired on silicon micro and nanopatterns. A force resolution of 0.2 nN/√Hz is deduced from the measurements.

Dynamic Response Analysis of Large Wind Turbine Blade Based on Davenport Wind Speed Model

Fluctuating wind speed spectrum, which is closer to the actual working conditions, was simulated by davenport wind speed model, and displacement and stress distribution of blade under fluctuating wind speed were calculated by finite element analysis software. The numerical results indicate that the growth trend of vibration amplitude for whole blade at flapping direction is nonlinear along the wingspan. The max von-mises stress appears when the vibration amplitude of tip reaches the maximum, and it is mainly concentrated in the central part of the blade. The stress at trailing edge and tip is smaller than the central part. Above results provide a reference for the strength safety design of wind turbine blade.,Fluctuating wind speed spectrum, which is closer to the actual working conditions, was simulated by davenport wind speed model, and displacement and stress distribution of blade under fluctuating wind speed were calculated by finite element analysis software. The numerical results indicate that the growth trend of vibration amplitude for whole blade at flapping direction is nonlinear along the wingspan. The max von-mises stress appears when the vibration amplitude of tip reaches the maximum, and it is mainly concentrated in the central part of the blade. The stress at trailing edge and tip is smaller than the central part. Above results provide a reference for the strength safety design of wind turbine blade.