Journal of Vibroengineering
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Removal mechanism of ultrasonic vibration and ELID composite plane grinding based on ultrasonic vibration of nano-ceramic workpiece
Get PDFTo realize the high efficiency mirror surface grinding of hard brittle materials (such as nano-ceramic material), this work firstly constructs an experimental platform for workpiece ultrasonic vibration and ELID combined plane grinding according to the processing mechanism of ultrasonic vibration assisted grinding and ELID grinding; then, based on the removal mechanism of hard brittle material, this work analyzes the kinematics of single abrasive grit with workpiece ultrasonic vibration plane grinding, and studies the effect of ELID plane grinding on the grinding depth; finally, based on the above work, this work proposes the mathematical model of material removal rate for the workpiece ultrasonic vibration and ELID combined plane grinding. Experimental results show that the material removal rate of combined plane grinding increases with the increase of the cutting depth and workpiece speed, the material removal rate of ultrasonic vibration and ELID combined grinding is higher than that of ELID grinding under the same conditions
Vibration control of rotating piezo-composite blade beam with CUS configuration based on optimal LQG controller
Get PDFVibration control of rotating composite blade beam with piezoelectric patch embedded is investigated. Stall flutter of piezo-composite blade driven by nonlinear aerodynamic forces is analyzed based on anisotropic circumferentially uniform stiffness (CUS) configuration. The blade is modeled as single-cell thin-walled beam structure, exhibiting the couplings among three displacements of vertical bending, lateral bending and transverse shear deformation, with structural tailoring implemented. The transversely piezoelectric actuating element is embedded in a manner such that its surface is parallel to the mid-surface of the blade beam. Piezoelectric damping ratios of rotating piezo-composite blade are described, with influences of different ply angles and rotating speeds illustrated. The flutter suppression for stall aeroelastic behavior based on an optimal LQG controller (OLC) with a dynamic regulator is highlighted with obvious effects demonstrated. In contrast with conventional LQG controller, the superiority of OLC controller is apparently demonstrated by time response and piezoelectric feedback voltage. Analytical proof of the structural modeling and feasibility analysis of the physical realization of the OLC algorithm are also investigated by comparisons of different modeling theories, and demonstrated by experimental platform
A novel flexible planar loudspeaker with coils on polyimide diaphragm
Get PDFThis paper presented a low cost flexible electro-dynamic planar loudspeaker (FEPL) with coils on polyimide diaphragm. The structure was very simple to put a flexible thin film diaphragm (electroplated traces of copper coil) above a flexible magnetic (placed in the bottom of cavity), thus forming an integration of electromagnetic actuation and planar flexible structure. The advantages are as follows: (1) the new loudspeaker became a flat flexible one, which could not only directly drive the vibration film to increase the power efficiency, but reduce the total harmonic distortion (THD). (2) It could be used as flexible electronics and easily deployed on the surface of any object with magnetic property or using adhesive transfer tapes. To optimize the performance of sound pressure level (SPLs), this study made detailed analyses on the thickness of cavity, turns of coil, magnet polarization, and diaphragm dimension. Noted as the cavity height increasing, the magnetic flux densities of both vertically and horizontally polarized magnet were decreased. But they were nearly constant over the surface with the same height for the vertically polarized magnet. On the other hand, as the cavity height of the horizontally polarized magnet increased, the magnetic flux densities would be decreased rapidly at the locations moving farther away from the center point. Several kinds of planar-type loudspeakers for the coils wounded in spiral-in, spiral-in and spiral-out, and zigzag shapes and plated with copper and aluminum were applied for performance tests, and the comparisons with the traditional cone-type loudspeaker were also made. Finally, the sound pressure levels (SPLs) were compared for three rectangular coils with different dimensions and number of turns. These effects were not discussed in previous literature of study
Characterization of damage evolution during fatigue of composite structures accompanied with self-heating effect by means of acoustic emission
Get PDFDue to the increasing use of composite materials for load-carrying structures that subjected to high-magnitude cyclic loading or vibrations, it is essential to investigate the accompanying phenomena occurring during structural degradation. The phenomenon, which may significantly accelerate structural degradation is the self-heating effect, causing intensive heating due to mechanical energy dissipation. In order to prevent sudden degradation of composite structures it is essential to characterize occurring damage types and their evolution during fatigue process. In this paper, the determination of fracture mechanisms during fatigue loading was performed based on acoustic emission analysis. The obtained results allow for clustering of acoustic emission data by type of occurring damage and correlate it with accompanying self-heating appeared during loading. This allows for proper understanding of physics of observed phenomena, which may help in design and operation of composite structures subjected to fatigue loading accompanied with self-heating effect
Experimental study on damage detection of RC bridge piers under ambient vibration
Get PDFThis paper presents an experimental method for damage detection of bridge piers as the basic and strategic elements in such engineering structures. Definition of percentage and location of damage are considered as initial data to solve damage detection problems. Nowadays, regarding the development of inverse methods for damage detection such as definition of objective functions and optimization approaches, the present experimental study can be utilized as initial stage of such methods. In this study, three 1/3 scaled test specimens of RC bridge piers are casted. Spacing of transverse reinforcements is considered as the main variable parameter for test specimens. The constant vertical loads and low vibrations as cyclic loads are applied to the specimens and the results including the hysteresis behavior of specimens and the backbone curves are investigated. The damage percentage per first four steps is also extracted to utilize the results using Banon-Veneziano method. Also increase in lateral displacement during first steps initiated micro cracks propagated along nearly one tenth of the piers length (0.1L) above the foundation. The cracks were propagated after an increase in displacement from fourth step and were separately observed. Finally, the ultimate failures were observed along nearly one fifth of the piers length (0.2L). Finally, the results revealed that the proposed method is an appropriate method to determine the severity of damage and its location as the primary information in reverse-optimization methods
High performance estimations of natural frequency of basalt FRP laminated plates with intermediate elastic support using response surfaces method
Get PDFStudying the changes of the natural frequencies due to intermediate elastic support of laminated composites is usually need a lot of computational processes or difficult to estimate. The present study employs a new high performance method for natural frequency estimating in basalt fiber reinforced polymer (FRP) laminated, variable thickness plates with intermediate elastic support based on the finite strip transition matrix (FSTM) with response surfaces (RS) method. Author has found that the FSTM method is very effective. However, a large error of estimation remains for estimation of natural frequency due to the large number of an iteration implemented in FSTM algorithm to estimate the natural frequency. In the present study, a new data processing procedure is proposed to improve performance of estimations of natural frequency. The estimation responses for four of classical boundary conditions at the plate ends with different elastic restraint coefficients (KT) are computed to obtain the first six frequency parameters (Ω). As a result, the method reveals excellent performance of estimations of natural frequencies
Bending vibrations of an orthotropic plate with Braille elements
Get PDFPurpose of this research is to investigate the vibrations of the orthotropic plate which has Braille elements formed on its surface. Results of investigations are applied in the process of formation of Braille elements. Bending of orthotropic plate is investigated. Supplementary stiffness from the static loading in the plane stress problem caused by centrifugal forces is taken into account. Experimental investigations on a special designed experimental setup were performed. Correspondence of the experimental results with the numerical ones is determined
Tooth surface friction and its influence on dynamic transmission error of double power input transmission system
Get PDFAccording to the meshing characteristics of spur gears and helical gears, calculation formulas of time varying friction stiffness and friction torque coefficient are derived. Based on the theory of the concentrated parameter, considering the influence of the time-varying coefficient of friction, time-varying meshing stiffness and the integrated error of the integrated, a three-dimensional dynamic model for a double power input transmission system with multi degrees of freedom and variable parameters was developed, including the flexional, torsional and axial motions. The Fourier series method is used to solve the equations by transforming the time varying system into a linear time invariant system, and the total system response of the system is obtained after the superposition of each order excitation response. The change law of friction torque coefficient and friction stiffness is obtained too. The results show that the friction stiffness curve of herringbone gear changes gently without mutations, and the direction is constant which what makes the resultant friction force direction be of the friction no unchanged. The tooth surface roughness has a certain influence on the dynamic transmission error. The first and second harmonic order frequencies of the split torque stage gears have an important influence on the dynamic transmission errors
Parallel simulation based adaptive prediction for equipment remaining useful life
Get PDFThe latest demands for remaining useful life (RUL) prediction are online prediction, real-time prediction and adaptive prediction. This paper addresses the demands of RUL prediction and proposes a novel framework of parallel simulation based adaptive prediction for equipment RUL. In the framework, a Wiener state space model (WSSM) is developed to achieve the aim, which considers the whole historical data and monitoring noise. Driven by the online observation data, the degradation state is estimated by the Kalman filter based data assimilation and the WSSM parameters are updated by the expectation maximum algorithm. An analytical RUL distribution considering the distribution of the degradation state is obtained based on the concept of the first hitting time. A case study for GaAs laser device is provided to substantiate the superiority of the proposed method compared with the competing method of traditional Wiener process. The results show that the parallel simulation method can provide better RUL prognostic accuracy
Variational mode decomposition denoising combined with the Euclidean distance for diesel engine vibration signal
Get PDFVariational mode decomposition (VMD) is a recently introduced adaptive signal decomposition algorithm with a solid theoretical foundation and good noise robustness compared with empirical mode decomposition (EMD). There is a lot of background noise in the vibration signal of diesel engine. To solve the problem, a denoising algorithm based on VMD and Euclidean Distance is proposed. Firstly, a multi-component, non-Gauss, and noisy simulation signal is established, and decomposed into a given number K of band-limited intrinsic mode functions by VMD. Then the Euclidean distance between the probability density function of each mode and that of the simulation signal are calculated. The signal is reconstructed using the relevant modes, which are selected on the basis of noticeable similarities between the probability density function of the simulation signal and that of each mode. Finally, the vibration signals of diesel engine connecting rod bearing faults are analyzed by the proposed method. The results show that compared with other denoising algorithms, the proposed method has better denoising effect, and the fault characteristics of vibration signals of diesel engine connecting rod bearings can be effectively enhanced