Vibration Excitation Frequency Research Articles

Piezoelectric-electromagnetic wearable harvester for energy harvesting and motion monitoring

This paper proposes a piezoelectric-electromagnetic wearable harvester (PEWH). The device is used to harvest the energy generated when the upper limb swings and can perform the function of motion monitoring. The main structure of PEWH consists of the piezoelectric power generation module and electromagnetic sensing module. Among them, the piezoelectric sheet in the piezoelectric module deforms and outputs electric energy, and the magnetic ball in the electromagnetic module moves to generate induced electromotive force to achieve sensing and energy supply. Through experimental testing, PEWH output performance is optimal when the spring wire diameter is 0.8 mm and the distance between the spring connector where the spring located and the position of the top of the shaft is 65 mm. At a vibration excitation frequency of 2 Hz, the device’s output voltage reaches a peak-to-peak value of 57.84Vpp, accompanied by a maximum power of 115.52mW. A range of application experiments were conducted to confirm the output performance of the device, which can power 82 LEDs and the temperature and humidity sensor. The prototype can be worn on the arm to enable monitoring of the current movement status. PEWH can effectively capture the energy generated by human movement for self-powered and self-sensing motion detection.

Nonlinear Crack-Wave Modulations in Shear Horizontal Wave Propagation for Fatigue Crack Detection

The nonlinear interaction of shear horizontal waves with fatigue cracks is investigated for structural damage detection. The focus is on the non-classical modulation effect in the presence of damage. The major principle of the method is explained theoretically and supported by a semi-analytical solution. The method is tested experimentally in aluminium beams with fatigue cracks. A combination of high-frequency ultrasonic and low-frequency vibration shear excitations are introduced to monitored beam components using low-profile piezoceramic shear actuators. Nonlinear vibro-acoustic responses are gathered using laser vibrometry. Vibration excitation frequencies are selected using experimental and numerical modal analysis. A series of vibro-acoustic experiments is performed for fatigue crack detection. The results show that the non-classical nonlinear vibro-acoustic effect – based on shear horizontal wave propagation – can be used for crack detection. In addition, the method also allows for damage localisation.

Continuous conveying and mixing characteristics of high‐viscosity materials under acoustic vibration excitation

AbstractInvestigating the conveying and mixing characteristics of high‐viscosity fluids in an inclined flow channel under the excitation of acoustic vibration using computational fluid dynamics methods. As the intensity of the acoustic vibration excitation increases, the free surface of the liquid transitions from generating Faraday waves to generating disordered jets. Continued increase in the amplitude leads to the liquid filling most of the vessel space, causing a blockage. However, slowly increasing the amplitude alleviates the blockage phenomenon. When high‐viscosity materials are subjected to high‐intensity acoustic vibration, the flow field is dominated by shear flow, which is accompanied by efficient stretching and folding. Changing the amplitude or frequency alone can cause blockage, and increasing the frequency of vibration excitation alone will not alleviate the blockage. Instead, increasing the amplitude can generate more mixing‐promoting reflux, effectively relieving blockage while maintaining stable conveying capacity.

Spring-like Triboelectric Nanogenerator for Monitoring Body Vibration State of the Ship Power Equipment

In the navigation process, monitoring the running state of ship power plant equipment is crucial. In bad weather, when the critical equipment is abnormal, it is especially necessary to find out the root cause of the failure as soon as possible. In this case, it is required to use rapid detection equipment to detect and judge the key parameters. This paper proposes a vibration sensor (VS-TENG) of triboelectric nanogenerators based on spring vibration. The sensor adopts the spring structure inside and vibrates with the ship power equipment to collect the low-frequency vibration energy. This paper uses the VS-TENG sensors of two different spring parameters to study the electrical signal output under the excitation conditions of varying vibration frequencies. The results show that in the frequency range of 3–500 Hz, the efficient processing of different vibration excitation frequency signals can be realized, and the vibration frequency can be accurately identified. The error of medium-high frequency identification in VS-TENG is less than 1%. Especially at the resonant frequency, the maximum voltage output value can be achieved. On the PT500 Mini test bench, VS-TENG can reasonably identify the motor frequency and shutdown state. Therefore, VS-TENG can be applied to the condition monitoring of the vibration of the ship’s power plant and has a broad application prospect.

Study on Microstructure and Properties of Mechanical Vibration-Assisted MIG Welded Joint of Aluminium Alloy Car Body

The aluminium alloy MIG welding of car body has problems such as joint softening and porosity in the weld, which directly affects the welding quality of the body structure. In this study, mechanical vibration was introduced into the aluminium alloy MIG welding process as an external excitation by improving the joint microstructure and performance of aluminum alloy MIG welding. In the research process, optical microscope and scanning electronic microscope were used to observe the microstructure of the joint, observe the size of grains, detect the number of pores, test hardness, take tensile test, and study the influence of frequency of external vibration excitation on weld forming, pore distribution, microstructure and mechanical properties. Studies have shown that mechanical vibration can effectively refine the weld grain, reduce the number of weld pores, increase the penetration depth, improve the strength and hardness of the joint, and improve the welding quality of aluminum alloy. And with the increase of vibration frequency, the grain size and number of pores of the weld gradually decrease, and the penetration depth and tensile strength and hardness of the joint gradually increase.

Vibration fatigue behavior and life prediction of directionally solidified superalloy based on the phase transformation theory

Directionally solidified nickel base superalloy DZ125L is the main material that has been widely used to manufacture aviation gas turbine blades and hot-end structural parts. Aeroengine is under vibration load for a long time in the service process, which makes vibration fatigue become one of the main failure modes of aero-engine structures. In this study, vibration fatigue behavior and excitation frequency response curves of DZ125L alloy under different stress levels were investigated through vibration fatigue tests. The fatigue crack initiation and growth mechanism of DZ125L alloy under vibration load is studied based on the results of the vibration fatigue test and finite element simulation. A vibration fatigue life prediction model based on the phase transformation theory is developed. Each parameter has clear physical significance in the model. The comparison between the model prediction results and the test results shows that the theoretical prediction results have reasonable accuracy.

Numerical experiments on the determination of rational range of mode parameters for the effective dewatering of various screening surfaces

Dehydration of mineral raw materials on a vibrating screen occurs as a result of the passage of liquid through the cells of the screening surface. With fine and ultrafine screening, this process is hindered by the surface tension of the liquid. None of the screening theories makes it possible to determine which vibration excitation modes ensure dehydration. With the help of numerical experiments on a mathematical model, the influence of vibration excitation modes on the intensity of the passage of liquid through the cells of various screening surfaces during dehydration on a vibrating screen was studied. In doing so, two tasks were solved: 1) determination of the amplitude and frequency of vibration excitation, when the required balance of water and the size of the cells of the screening surface are set; 2) determination of the remaining water on the screening surface depending on the cell size of the screening surface, the amplitude and frequency of vibration excitation. The developed mathematical model made it possible to solve both problems. On the basis of calculations and analysis, rational range of mode parameters of the vibrating screen for effective dehydration of various screening surfaces was established. The calculation algorithm is implemented on the basis of a mathematical model in the PC program «Sifting Surface» in C ++ with the connection of mathematical libraries and «Excel». The results of calculations, demonstration of the possibilities of various screening surfaces and modes are shown in the figures, which show the dependences of the residual water on the amplitude and frequency vibration excitation parameters. It is established that the vibro-impact effect, in comparison with the harmonic effect, provides better results in cleaning the cells from the liquid retained in them by surface tension forces, under less intensive modes. The results obtained will be used in the development of a mathematical model of dehydration and a method for calculating technological parameters that ensure effective removal of liquid during fine and ultrafine screening of mineral raw materials, as well as to determine the rational design and dynamic parameters of the screen.

Characteristics analysis and optimization design of bridge crane based on improved particle swarm optimization algorithm

Large redundant metal structures have high stability with large cost. An excellent mechanical structure should have the lower weight when satisfying its stability. Aiming at the large redundancy of the main beam metal structure of the double-beam bridge crane, the paper extracts six important parameters to determine its quality, and the corresponding value is set. The orthogonal test table is designed to calculate the strength and stiffness. In order to avoid resonance, the fixed vibration frequency and excitation frequency are calculated. The experimental results are fitted to obtain the six parameters of the quality, strength, stiffness, and natural frequency. Moreover, particle swarm optimization algorithm is used to solve the multi-objective optimization mathematical model with the design quality as the goal and the stiffness, strength, and easy resonance interval as constraints. In view of the long calculation time and poor convergence of particle swarm optimization algorithm, a module that limits the particle forward speed is added and the generation conditions of particles are redefined. The improved particle swarm algorithm shows that the first-order vibration frequency of the main beam increases from 18 Hz to 27.55 Hz. It improves the stability of the overall structure and avoids resonance with the motor frequency. Under the condition of satisfying the stability of the main beam, the quality of the main beam is reduced from 1.23 tons to 0.53 tons, with a reduction of 6%.

Ceramic-Based Piezoelectric Material for Energy Harvesting Using Hybrid Excitation.

This paper analyzes the energy efficiency of a Micro Fiber Composite (MFC) piezoelectric system. It is based on a smart Lead Zirconate Titanate material that consists of a monolithic PZT (piezoelectric ceramic) wafer, which is a ceramic-based piezoelectric material. An experimental test rig consisting of a wind tunnel and a developed measurement system was used to conduct the experiment. The developed test rig allowed changing the air velocity around the tested bluff body and the frequency of forced vibrations as well as recording the output voltage signal and linear acceleration of the tested object. The mechanical vibrations and the air flow were used to find the optimal performance of the piezoelectric energy harvesting system. The performance of the proposed piezoelectric wind energy harvester was tested for the same design, but of different masses. The geometry of the hybrid bluff body is a combination of cuboid and cylindrical shapes. The results of testing five bluff bodies for a range of wind tunnel air flow velocities from 4 to 15 m/s with additional vibration excitation frequencies from 0 to 10 Hz are presented. The conducted tests revealed the areas of the highest voltage output under specific excitation conditions that enable supplying low-power sensors with harvested energy.

Characterization of laser Doppler vibrometers using acousto-optic modulators

We report on a new approach to characterize the performance of a laser Doppler vibrometer (LDV). The method uses two acousto-optic modulators (AOMs) to frequency shift the light from an LDV by a known quantity to create a synthetic velocity shift that is traceable to a frequency reference. Results are presented for discrete velocity shifts and for sinusoidal velocity shifts that would be equivalent to what would be observed in an ideal accelerometer vibration calibration. The method also enables the user to sweep the synthetic vibration excitation frequency to characterize the bandwidth of an LDV together with its associated electronics.

Self-Synchronization of a Vibrating Jaw Crusher with Allowance for Interaction with the Medium Processed

The vibrations of a vibrating jaw crusher model, excited by two self-synchronizing unbalanced-mass vibration exciters, with allowance for the interaction with the processed medium are examined. It is found that the frequency range of stable antiphase synchronization of the exciter rotation required for normal operation of the crusher, depends significantly on the gap between the crusher jaw and the medium element, and a decrease in the initial gap leads to an expansion of the frequency range of exciter stable antiphase synchronization. In the absence of an initial gap and the appearance of medium pressure on the jaws in the superresonance range, the appearance of a stability region of the synchronous-in-phase exciters rotation is possible. It is shown that, at a constant vibration excitation frequency, a change in the initial gap between the jaws and the processed medium can lead to a change in the type of exciter synchronization and, accordingly, vibrations of the jaws.

Analysis to the Forced Vibration of a High Temperature Superconducting System With Hysteresis

Dynamic behavior with the hysteresis of the levitation force of a high temperature magnet-superconductor system is investigated with application of a displacement harmonic excitation. The dynamic characteristics of the transient stage and the steady stage of forced vibration of the system are discussed in detail. The period-doubling and the natural frequency components are found in forced vibration. It means that the initial frozen magnetic field in superconductor plays an important role on the vibration response. The vibration amplitude vs. excitation frequency is presented. A transition excitation frequency with triple natural frequency is given to distinguish the range of vibration center. The vibration amplitude of the superconducting levitation system shows a linear increasing with the excitation amplitude, which is found to be independent on the critical current density with considerations based on the Bean's critical model. However, the critical current density greatly affects the location of the vibration center. The critical excitation amplitude vs. the field frequency to the superconductor is presented. Levitation is stable most when the sample is exposed to a low-frequency field. In this case large amplitude of the alternating field is needed to break-off of the sample.

A broadband piezoelectric energy harvester with movable mass for frequency active self-tuning

A broadband active self-tuning frequency piezoelectric energy harvester (AST-PEH) is proposed in this paper. It consists of a piezoelectric cantilever beam, an energy harvesting and control circuit (EHCC), a miniature stepper motor, a screw rod and a T-section mass. It can actively adjust the position of the T-section mass according to the ambient vibration frequency. It matches the AST-PEH’s resonant frequency with the ambient vibration excitation frequency, and it widens the operating frequency range of the AST-PEH. The expression of the AST-PEH’s resonant frequency function is constructed based on the dynamic and static theoretical analysis. The theoretical model of the AST-PEH under different position of the T-section mass is analyzed by ANSYS15.0 APDL, which is verified by two different materials and sizes. The tested two type substrate materials are steel and polylactic acid (PLA). The experimental results show that the frequency range of the two type harvesters are 4.8 Hz–6.3 Hz and 8.17 Hz–14.3 Hz respectively, and the widening rates of the working frequency are 31.25% and 75% respectively. The tested maximum output power of steel type AST-PEH is 0.32 mW at 6.3 Hz under 0.32 g acceleration and with a 100 KΩ load resistance.

A Sensorless Self-Tuning Resonance System for Piezoelectric Broadband Vibration Energy Harvesting

This article presents a broadband piezoelectric vibration energy harvesting system. It can actively tune its resonant frequency to match the frequency of the ambient vibration excitation. The energy harvester is comprised of a movable mass attached to a piezoelectric cantilever beam. And a microstepper is employed to adjust the position of the mass for regulating the resonant frequency. Furthermore, in this article, a new method is proposed for the online dynamic detection of the piezoelectric transducer (PZT) vibration statement without any additional sensors. A circuit is proposed to detect the ambient vibration excitation frequency deviation against the resonant frequency only by measuring the phase difference between the open-circuit voltage and the short-circuit current of the PZT. Experimental results indicate a frequency broadening rate of up to 60.56%, while the maximum extraction efficiency is 84.8%. It can harvest vibration energy and self-power the system in a wide broadband ambient excitation vibration frequency for the wireless sensor network nodes.

An Improved Computational Method for Vibration Response and Radiation Noise Analysis of Two-Stage Gearbox

In this work, an improved computational method for the prediction of the vibration and noise of a gearbox that considers the flexibility of the shaft is developed. Based on the finite element method (FEM), a coupled dynamic model of a spur gear-shaft-bearing system is established, and the time-varying mesh stiffness (TVMS), the time-varying bearing stiffness (TVBS), and the flexibility of the shaft are considered. The Newmark integration method (NIM) is utilized to obtain the dynamic load of the bearing. Furthermore, the proposed model is validated by experiments. The bearing load is then considered to be the excitation of the housing, and the radiated noise is calculated via the finite element method/boundary element method (FEM/BEM). The effects of the shaft flexibility on the bearing response and radiated noise are discussed based on the proposed method. The results demonstrate that, when the shaft flexibility is considered, the system undergoes the bending vibration of the shaft, and the vibration amplitude and excitation frequency components of the bearing load decrease significantly. Additionally, the main resonance mode of the gearbox is changed, and the radiated noise is enhanced. The effects of the input speed and shaft stiffness on the bearing response and radiated noise are also investigated. The results provide a theoretical basis for the further development of the vibration and noise reduction of gearboxes.

Chatter stability of synchronized elliptical vibration assisted milling

This paper presents the dynamics to analyze the stability of ultrasonic elliptical vibration-assisted milling operations. The elliptical vibrations are delivered to the tool-tip with a piezo actuator integrated to tool holder at about 16.5 kHz with amplitudes of 10 μm and 5 μm in radial and tangential directions, respectively, with 90° phase difference. The chip thickness is modeled by considering the rigid body motion of the tool, regenerative and ultrasonic vibration amplitudes. The loss of tool contact with the workpiece at the ultrasonic vibration excitation frequency is considered in evaluating the directional factors in the regeneration of chip and process damping. The stability of the system is solved using the semi-discrete time-domain method and experimentally validated in milling Aluminum Al-7050 and AISI-1045 steel. It is shown that the ultrasonic vibrations can increase the stable depth of cuts if the periodic loss of contact between the tool and workpiece is maintained by selecting cutting speed, which is less than the tangential vibration velocity delivered by the actuator.

전기 자동차용 인휠 모터 시스템의 소음 저감

In this study, we identified the noise sources of an in-wheel motor system and proposed a low-noise design guideline through structural modification. To identify the noise sources, we not only measured the noise and vibration signals, but we also performed modal testing. Using waterfall plots for the frequency spectra of noise and vibration signals, we identified the vibration excitation frequencies owing to the gear mesh and the motor electromagnetic force of the motor. We obtained the natural frequencies of the in-wheel motor system from the modal test results. The results of the signal analysis and modal test showed that noise was generated by the resonance between the excitation and natural frequencies. To avoid this resonance, we proposed a design guideline for noise reduction in an in-wheel motor system by using a finite element simulation.

Spectro-Temporal Responses of Curved Railway Tracks with Variable Radii of Arc Curves

On curved railway tracks, wheel/rail interface can usually cause a traveling source of sound and vibration, which constitutes high-pitch or tonal noise pollution causing considerable concern to rail asset owners, commuters and people living or working along the railway corridor. The sound and vibration can be in various forms and spectra. The undesirable tonal sound on curves caused by excessive lateral wheel/rail dynamics in resonance with falling friction states are often called ‘squeal noises’. This paper evaluates the transient effect of curve radii on the possible occurrence of lateral track resonances, which is a principal cause of dynamic wheel/rail mode coupling that could trigger ‘curve squeal’. This study is devoted to systems thinking approach and better insight into dynamic phenomena of railway tracks that could resolve the railway curve noise problems. Curved track models in three-dimensional space have been developed using a finite element package, STRAND7. The dynamic responses of curved track have been simulated by applying a moving train load. The transient loading model of a common wheel/rail slip has been adopted. The simulations of railway tracks with different curve radii have been carried out to develop state-of-the-art understanding of lateral track dynamics, including rail dynamics, cant dynamics and overall track responses. Parametric studies have been conducted to evaluate lateral displacements, velocities and accelerations of rail over sleeper and rail at midspan, both in static and dynamic conditions. The study firstly reveals that the lateral resonance of tangent tracks is relatively rare and the mode coupling behavior is unlikely to occur on moderately curved tracks. The lateral vibration responses have been presented in terms of time histories and spectro-temporal responses (also called “Spectogram”). The dynamic lateral responses of the track are found to be sensitive to the change of curved radii. The resonance peak in the lateral direction is related to the agreement of corresponding natural frequencies of rail and the vibration excitation frequencies under an individual rolling velocity. The outcome of this study establishes new insight into the dominant influences of different track parameters to track lateral dynamic behaviors.

Numerical and experimental analysis of vibration damping performance of polyurethane adhesive in machine operations

Machining operations inherently cause structural vibrations of the work piece and machine involved, especially during roughening operations. This clearly adversely affects the surface roughness, tolerances and tooling lifetime. These effects are even more prominent in case the stiffness of the work piece to be machined is low and machining vibration excitation frequency range strongly overlaps the range of structural resonance frequencies of the work piece. This is typically the case for lightweight (sheet) metal structures. Additional fixation is costly, time-consuming and moreover it may induce structural loading and deformation which, after finishing, causes an out-of-tolerance work piece.This work presents an alternative approach which applies Polyurethane foam adhesive bonding as a temporary measure to reduce structural vibrations during milling operations of a large welded sheet metal construction.The first part of this work analyses the actual structural vibrations that occur during milling operations. Experimental and numerical modal analysis is carried out in order to determine the excitation and resonant vibration behaviour of the sheet metal structure. A dedicated Finite Element Model (FE – model) is set up which enables the necessary insights in where and how critical vibration levels may be reduced and how the work piece supports can be optimized. The second part of the work discusses the development and application of suitable vibration dampening supports applying Polyurethane foam adhesive. For this purpose, experiments are carried out to determine the vibration dampening performance of different foam layer thicknesses. These involve hammer excitation of dedicated small-scale adhesively bonded samples. FE modelling is applied to optimize the mounting of bonded Polyurethane dampers and to predict the effect on structural vibrations during milling operations. This part extensively outlines the specific experiments involved and the strategy for modelling the viscoelastic foam dampeners in the structural numerical model in a robust but effective way. The third part describes the validation measurement campaign and extensively compares structural vibration levels before and after providing the foam dampening measures. It concludes by showing that critical vibration levels may be reduced by over 58% with the method applied.

Stability Analysis of Rotating Blade Vibrations Using Lyapunov Exponents

This paper presents an analysis of the vibration stability of a rotating blade due to shaft torsional vibration excitation. The governing equation adopted in the study is a Hill’s type linear second order ordinary differential equation with multiple harmonically variable coefficient terms. The differential equation of the system is rewritten as two coupled first order ordinary differential equations. The stable and unstable regions are determined by the Lyapunov characteristics exponents on parameter space (grid) relating to the rotor speed, the torsional vibration excitation frequency and the blade natural frequency. The results are contrasted to those obtained by the strained parameter method (a perturbation technique), an excellent match is observed for small torsional vibration amplitudes .