Vibration Output Research Articles

Development of vibration-assisted micro-milling device and effect of vibration parameters on surface quality and exit-burr

Vibration-assisted cutting is an important technology with better performance in manufacturing micro-scaled components, compared with conventional cutting technology. This article first illustrates the development of vibration-assisted micro-milling device which is made based on piezoelectric plates and shows different vibration types with vibration principle of this device. It is then tested stable to output vibration with a frequency accuracy of 100 Hz and an amplitude accuracy of 100 nm. Two groups of experiments in micro-milling 6061 aluminum alloy are carried out. Compared with conventional micro-milling, using vibration assist is verified more effective in improving surface integrity and quality. Furthermore, with a proposed method of characterizing exit-burr size, the influences of vibration frequency and amplitude on surface roughness and exit-burr size are discussed. As a result, the mean surface roughness is found positive related to vibration frequency and negative related to vibration amplitude in most of the study range. To make guidance on optimizing vibration machining parameters, cubic polynomial fitting with 95% prediction interval is of enough accuracy.

Theoretical modeling, simulation and experimental study of hybrid piezoelectric and electromagnetic energy harvester

In this paper, performances of vibration energy harvester combined piezoelectric (PE) and electromagnetic (EM) mechanism are studied by theoretical analysis, simulation and experimental test. For the designed harvester, electromechanical coupling modeling is established, and expressions of vibration response, output voltage, current and power are derived. Then, performances of the harvester are simulated and tested; moreover, the power charging rechargeable battery is realized through designed energy storage circuit. By the results, it’s found that compared with piezoelectric-only and electromagnetic-only energy harvester, the hybrid energy harvester can enhance the output power and harvesting efficiency; furthermore, at the harmonic excitation, output power of harvester linearly increases with acceleration amplitude increasing; while it enhances with acceleration spectral density increasing at the random excitation. In addition, the bigger coupling strength, the bigger output power is, and there is the optimal load resistance to make the harvester output the maximal power.

MIMOMH feed-forward adaptive vibration control of helicopter fuselage by using piezoelectric stack actuators

The vibration of a helicopter fuselage is mainly produced by the rotor exciting loads which are three forces and three moments containing harmonics in three directions at rotor hub center, and has the characteristic of large, steady and harmonic vibration. The active control of helicopter fuselage vibration by using inertia actuator needs to pay a heavy weight cost for achieving a good control effect. In this paper, a method for multi-input multi-output multi-harmonic (MIMOMH) feed-forward adaptive control of helicopter fuselage vibration by using piezoelectric stack actuators is presented. The method is composed of the harmonic coefficients identification and the MIMOMH feed-forward adaptive filtering algorithm, and has excellent characteristics such as light weight, fast response, wide working frequency range, adaptive ability and high effect. The numerical simulations for a frame structure scaled by the Z11 helicopter fuselage floor with four actuating inputs, four vibration outputs, three rotor exciting loads and the first three harmonic frequencies contained in each exciting load were performed, indicating that the vibration levels at objective points are reduced by 99% by using the method and are much lower than the results by only controlling the first harmonic frequency. When the phases, amplitudes and frequencies of exciting loads are changed, the method demonstrates an excellent adaptability to control vibration.

A three-DOF ultrasonic motor using four piezoelectric ceramic plates in bonded-type structure

A three-DOF ultrasonic motor is presented in this paper. The proposed motor consists of four piezoelectric ceramic plates and a mental base with a flange that can fix the motor on a rack. The proposed motor takes advantage of a longitudinal mode and two bending modes, different hybrids of which can realize three-DOF actuation. Because of symmetric structure of the proposed motor, the resonance frequencies of the two bending modes are identical. And the resonance frequency of the longitudinal mode was tuned closed to the ones of the bending modes by adjusting the structural parameters in modal analysis. Then trajectories of nodes on the driving foot were obtained by the transient analysis to verify the feasibility of driving principle. Experiments including vibration shape test and output characteristic test were executed. The starting voltages of the rotation along horizontal axes are about 10 Vp-p. Under driving voltages of 200 Vp-p, the output velocities of three DOF can reach 280 rpm, 277 rpm and 327 rpm, respectively. The results of the experiments indicate that the proposed motor is characterized by low starting voltages and high output velocities.

Towards Prevention of Oil/Gas Pipelines Vandalism

Abstract Simulation of the detection, identification and classification of the vibration signature of oil/gas pipelines in response to acts of vandalism is presented in this paper. Real vibration signal data were acquired from a sample oil/gas steel pipe subjected to different excitation forces during a real experimental field work. The data acquired from the use of a drilling machine were used as input to an intelligent system modeled to classify the vibration data during simulation process by use of the MATLAB fuzzy logic toolbox. Results from the simulation show that a relatively uniform vibration output value of 1.0 (on a scale of 0 to 1), being the desired output, was achieved. This value is ideal for the design of a system to detect and diagnose an act of vandalism on oil/gas pipelines. Installing such a system spatially on a pipeline network will forestall the incessant occurrences of intrusion on the pipes, and consequently lead to an improvement on the safety of the lives and properties of those who live in communities across which the pipelines run.

Analyzing of micro-electro-mechanical systems (MEMS) sensor for pumping aggregates

PurposeThe purpose of this research paper is to develop and analyze micro-electro-mechanical systems sensor for vibration monitoring of pumping aggregate.Design/methodology/approachThe system is based on smart sensor and smart mobile phone.FindingsThe numerous measurements on a wide range of turbo aggregates were performed to establish the operating condition of pumping aggregates.Originality/valueAfterwards, the influence of vibration at different positions on the output vibration of the pumping aggregate was analyzed by adaptive neuro fuzzy inference system method.

A piezoelectric energy harvester for broadband rotational excitation using buckled beam

This paper proposes a rotational energy harvester using a piezoelectric bistable buckled beam to harvest low-speed rotational energy. The proposed harvester consists of a piezoelectric buckled beam with a center magnet, and a rotary magnet pair with opposite magnetic poles mounted on a revolving host. The magnetic plucking is used to harvest the angular kinetic energy of the host. The nonlinear snap-through mechanism is utilized to improve the vibration displacement and output voltage of the piezoelectric layer over a wide rotation frequency range. Theoretical simulation and experimental results show that the proposed energy harvester can yield a stable average output power ranging between 6.91-48.01 μW over a rotation frequency range of 1-14 Hz across a resistance load of 110 kΩ. Furthermore, dual attraction magnets were employed to overcome the suppression phenomenon at higher frequencies, which yields a broadband and flat frequency response over 6-14 Hz with the output power reaching 42.19-65.44 μW, demonstrating the great potential of the bistable buckled beam for wideband rotation motion energy harvesting.

A Comparative Study of Regularization Method in Structure Load Identification

This study aims to correlate the vibration data with quantitative indicators of structural health by comparing and validating the feasibility of identifying unknown excitation forces using output vibration responses. First, numerical analysis was performed to investigate the accuracy, convergence, and robustness of the load identification results for different noise levels, sensors numbers, and initial estimates of structural parameters. Then, the laboratory beam structure experiments were conducted. The results show that using the two identification methods Tikhonov (L‐curve) and TSVD (GCV‐curve) can successfully and accurately identify the different excitation forces of the external hammer. The TSVD based on GCV method has more advantages than the Tikhonov based on L‐curve method. The proposed two kinds of load identification procedure based on vibration response can be applied to the safety performance evaluation of the railway track structure in future inverse problems research.

Improving and Predicting Fluid Atomization via Hysteresis‐Free Thickness Vibration of Lithium Niobate

AbstractAcoustically driven atomization from the broad perspective of materials choice, vibration mode, and fluid characteristics is considered to identify a simple method for improving both the understanding of the atomization phenomena and the overall efficiency of atomization. Whether by the definition of a “figure of merit” (a function of the transducer quality factor and electromechanical coupling coefficient), its output vibration displacement at a given input power, or the fluid flow rate during atomization, it is found that the combination of single‐crystal 127.86° Y‐rotated lithium niobate and thickness‐mode vibration produces an order of magnitude greater atomization flow rate and efficiency in comparison to all known atomizers, including classic lead zirconate‐based devices and newer, Rayleigh wave or Rayleigh/Lamb spurious‐mode‐based devices alike. By using this improved approach, for the first time, fluids with viscosities up to 48 cP are reported to be atomized, and an atomization Reynolds number ReA is defined which can be used to both predict the atomization flow rate for ReA ≳ 40 and the inability to atomize a given fluid at a particular vibration amplitude when ReA ≲ 40.

Using piezoelectric sensor and actuator for ultrasonic assisted system

ABSTRACTAn ultrasonic assisted system mainly consists of the transducer and the match-fitting cutter is designed to provide miniature vibration amplitude. In the transducer, a set of piezoelectric ceramics is used as actuator in charge of generating large enough vibration amplitude, which will be immediately measured by the neighboring sensor also made by piezoelectric ceramics. Since the driving frequency is easily affected by the changing working environment, variation of the vibration output is detected in time by the PZT sensor to support the feedback autoresonance control purpose. However, measurement on the transducer is not equivalent to that on the cutter. Further investigation on the measured output of the cutter in comparison with that of the transducer is carried out. It is found that there exists a reasonable and predictable relation between them. ANSYS is used for modal and harmonic analysis. The estimated resonance frequency and vibration amplitude are approximate to the experimental results, which verifies the accuracy of the proposed measurement method.

Quantifying and managing uncertainty in operational modal analysis

Abstract Operational modal analysis aims at identifying the modal properties (natural frequency, damping, etc.) of a structure using only the (output) vibration response measured under ambient conditions. Highly economical and feasible, it is becoming a common practice in full-scale vibration testing. In the absence of (input) loading information, however, the modal properties have significantly higher uncertainty than their counterparts identified from free or forced vibration (known input) tests. Mastering the relationship between identification uncertainty and test configuration is of great interest to both scientists and engineers, e.g., for achievable precision limits and test planning/budgeting. Addressing this challenge beyond the current state-of-the-art that are mostly concerned with identification algorithms, this work obtains closed form analytical expressions for the identification uncertainty (variance) of modal parameters that fundamentally explains the effect of test configuration. Collectively referred as ‘uncertainty laws’, these expressions are asymptotically correct for well-separated modes, small damping and long data; and are applicable under non-asymptotic situations. They provide a scientific basis for planning and standardization of ambient vibration tests, where factors such as channel noise, sensor number and location can be quantitatively accounted for. The work is reported comprehensively with verification through synthetic and experimental data (laboratory and field), scientific implications and practical guidelines for planning ambient vibration tests.

Bifurcations and chaos in a gear assembly with clearances for solar array drive assembly

Solar array drive assembly is an important part of the spacecraft. It is used to rotate the solar panels. The gear assembly in solar array drive assembly plays a key role in transferring power safely. Nonlinear behavior of gear assembly, like the chaotic motion, can highly affect the stability and operating life of solar array drive assembly. Clearances in gear assembly which were neglected for simplification in past years have increased the risk of failure and become a problem in accurate control. To investigate the clearances effect on nonlinear behavior, this paper establishes a new dynamic model of the gear assembly with bilateral clearances. The main difference comparing to general spur gears is its unique hysteresis stiffness may also influence the clearance effects. Transformation of the hysteresis loop is observed from theoretical equations using different parameters. Bifurcations and chaotic analysis of the system are carried out by numerical simulations in this study. The results show that the variation of clearances may induce the chaotic behavior into gear transmission even when the primary response is stable. When the system step into the chaotic region, it has a high risk of unstable vibration and fuzzy output. The influence of excitation frequency on the chaotic motion of the system is also provided. Chaos thresholds are calculated to avoid nonlinear behavior of the system in design and control. This study makes it possible to predict the unstable clearance interval in this system and avoid the system stepping into chaotic motion. Analyzing and predicting the chaotic behaviors can contribute to the further studies on design and control of the solar array drive assembly.

Incipient Fault Feature Extraction for Rotating Machinery Based on Improved AR-Minimum Entropy Deconvolution Combined with Variational Mode Decomposition Approach

Aiming at the issue of extracting the incipient single-fault and multi-fault of rotating machinery from the nonlinear and non-stationary vibration signals with a strong background noise, a new fault diagnosis method based on improved autoregressive-Minimum entropy deconvolution (improved AR-MED) and variational mode decomposition (VMD) is proposed. Due to the complexity of rotating machinery systems, the periodic transient impulses of single-fault and multiple-faults always emerge in the acquired vibration signals. The improved autoregressive minimum entropy deconvolution (AR-MED) technique can effectively deconvolve the influence of the background noise, which aims to enhance the peak value of the multiple transient impulses. Nevertheless, the envelope spectrum of simulation and experimental in this work shows that there are many interference components exist on both left and right of fault characteristic frequencies when the background noise is strong. To overcome this shortcoming, the VMD is thus applied to adaptively decompose the filtered output vibration signal into a number of quasi-orthogonal intrinsic modes so as to better detect the single- and multiple-faults via those sub-band signals. The experimental and engineering application results demonstrate that the proposed method dramatically sharpens the fault characteristic frequencies (FCFs) from the impacts of bearing outer race and gearbox faults compared to the traditional methods, which show a significant improvement in early incipient faults of rotating machinery.

Exploring the phenomenon of ultrasonic atomization for viscous fluids

We consider the choice of vibration modes and piezoelectric materials for acoustically driven atomization, an attractive method for a broad range of applications, particularly pulmonary drug delivery. Whether by the definition of a figure of merit, a product of the resonator quality factor and electromechanical coupling coefficient, its output vibration displacement at a given input power, or the fluid flow rate during atomization, we find that the combination of single-crystal 127.86-deg. Y-rotated lithium niobate and thickness-mode vibration produces an order of magnitude greater atomization flow rate and efficiency in comparison to classic lead zirconate-based devices and newer, Rayleigh wave or Rayleigh/Lamb spurious-mode based devices alike. For the first time, fluids with viscosities up to 48 cP are reported to be atomized, and we define an atomization Reynolds number ReA that can be used to both predict the atomization flow rate for ReA>40 and the inability to atomize a given fluid at a particular vibration amplitude when ReA<40.

Enhancing and multi-objective optimising of the performance of Stirling engine using third-order thermodynamic analysis

ABSTRACTStirling engine is an external combustion engine which uses eternal heat sources like solar radiation for heating a compressible fluid inside cylinders. In the recent years, significant attention is drawn to Stirling engines due to the clear advantages, high efficiency potential, flexible fuel, lower nitrogen oxides, quiet and minimal vibration, high reliability and highest specific output work for any closed regenerative cycle. The third order thermal analysis is one of the analyses which has been applied in several studies which have been carried out on Stirling engines. NSGA-II algorithm is applied to optimise the differential regenerator pressure (bar) and the power output (kW) for a Stirling engine system. In this study, three decision-making techniques are utilised to optimise the solutions, obtained of the results. At last, the employed techniques are compared with the data of an experimental research work.

Development of a new 3D model for the prediction of residual stress and fracture behaviour in Ti-6Al-4V after ultrasonic peening treatment

Experimental and numerical studies have been carried out to determine the residual stress in Ti-6Al-4V after Ultrasonic Peening Treatment (UPT). Ultrasonic vibration output from the test equipment transducer was employed as the load to simulate the test conditions and the residual compressive stress in the material was measured by X-ray diffraction (XRD). A Johnson-Cook constitutive model was used to describe the rate-dependent stress-strain and failure behaviour of a sample. Based on motion analysis of the peening needle, a new 3D peen-rebound-peen (PRP) finite element model was developed to predict the stress field during and after the UPT process, using ABAQUS. The residual stresses predicted by the PRP model are in good agreement with the XRD results for the same peening and sample conditions. The effect of the gap width between the needle and the sample, the constitutive model parameters, and the peening duration were also studied.

Active vibration control for piezoelectricity cantilever beam: an adaptive feedforward control method

This work is focused on the active vibration control of piezoelectric cantilever beam, where an adaptive feedforward controller (AFC) is utilized to reject the vibration with unknown multiple frequencies. First, the experiment setup and its mathematical model are introduced. Due to that the channel between the disturbance and the vibration output is unknown in practice, a concept of equivalent input disturbance (EID) is employed to put an equivalent disturbance into the input channel. In this situation, the vibration control can be achieved by setting the control input be the identified EID. Then, for the EID with known multiple frequencies, the AFC is introduced to perfectly reject the vibration but is sensitive to the frequencies. In order to accurately identify the unknown frequencies of EID in presence of the random disturbances and un-modeled nonlinear dynamics, the time–frequency-analysis (TFA) method is employed to precisely identify the unknown frequencies. Consequently, a TFA-based AFC algorithm is proposed to the active vibration control with unknown frequencies. Finally, four cases are given to illustrate the efficiency of the proposed TFA-based AFC algorithm by experiment.

High spatial resolution modal identification of a stadium suspension roof: Assessment of the estimates uncertainty and of modal contributions

In Operational Modal Analysis (OMA) engineers are usually confronted with the challenge of extracting as much information as possible from the data collected in ambient vibration tests in order to characterize the modal behaviour of the tested structures under environmental and operational conditions. There exist several tools for this purpose that combined can be used to estimate valuable information regarding modal behaviour of the tested structures from the output vibration responses measured in these tests. In this context, this paper describes the strategies and techniques employed, as well as the results obtained from the OMA performed to identify the modal properties of a football stadium suspension roof. The main focus of the paper is the employment of state-of-the-art identification techniques, in time and frequency domain, in order to estimate the modal parameters of the roof structure with high spatial resolution for the mode shapes of vibration together with their uncertainties bounds, as well as to assess the contribution of the identified modes to the measured responses under different environmental and operational conditions. A particular challenge of the presented example is the need to simultaneously process a large number of time series (15 datasets with 12 sensors – 180 time series). At the end of the paper, the estimates provided by the ambient vibration test are compared with the ones obtained with a permanent monitoring system operating during one year, in order to evaluate the representativeness of the results provided by a single ambient vibration test.

Dynamic Characteristics Analysis of a Seismic Vibrator-Ground Coupling System

A mathematical model to describe the seismic vibrator and ground coupling is proposed based on dynamic analyses of the vibrator baseplate structure and properties of soil. This mathematical model is solved using Newmark’s method. It produces reasonable results and the trend of amplitude envelope follows the experimental data. With this model, characterization of the vibrator-ground coupling is performed. Modal analysis study shows that the motions between the vibrator reaction mass and baseplate experience a combination of a first-order vibration mode and a second-order vibration mode. The corresponding frequencies of two vibration modes are located at 2.77 Hz and 488.7 Hz, respectively. As the frequency goes up, the motion behavior of the reaction mass and baseplate is dominated by the second-order vibration mode. It is realized that the second-order vibration mode is responsible for the phase difference between the input sweep signal and the output force signal. Furthermore, the impact of the coupling system parameters on the vibrator output force is also investigated. It is observed that the vibrator output force decreases as the sweep frequency increases. The weight ratio of the reaction mass and the baseplate has an impact on the vibrator output force.

Examination of a broadband sweep with and without Force Control

This article proposes that this known significant discrepancy between the Weighted Sum Ground Force (WSGF) prediction of the vibrator output (the Sallas Approximation; see Sallas, 1984) and downhole measurements of the output is not so much a ‘lie’, as it is simply the natural consequence of the limitations and inaccuracies of the WSGF model. The authors believe that these model deficiencies arise from a woefully incomplete understanding of the complex interaction of the vibrator mechanism with the ground. If this is correct, than an improved understanding of the interactions of the vibrator mechanism and the ground during a sweep should lead to a more complete model of the vibrator/earth interactions, with significant improvements in both the actual energy content of the propagating wavelet as well as more ‘truthful’ quality control reporting thereof. Modern vibrator control systems use both phase and force control systems in controlling the output motions of the reaction mass (RM) and baseplate (BP). Feedback from various sensors on the vibrator mechanism is used to adjust the input hydraulic controls so that the WSGF ‘mimics’ the desired reference sweep. In this paper we examine the response of a downhole vertical geophone to a broadband sweep generated on the surface, initially with both force and phase control operating, and then with force control disabled, to observe what effects force control has on the vibrator mechanism and the propagating seismic wavelet, as well as to develop an improved understanding of the interaction of the vibrator mechanism with the ground during a sweep.