Preparation and Properties of Epoxy Piezoelectric Vibration Reduction Composites

The epoxy resin (E-51) was used as polymer matrix,conductive carbon black (CB) as conductive filler,and PZT was used to prepare a composite by curing.The effects of PZT and CB content on the properties of PZT/ CB/ EP piezoelectric composite were studied.When the PZT content reaches 40 wt%,the optimized vibration attenuation properties of PZT/CB/EP materials could be achieved with a loss factor of 0.9 from room temperature to 60 ℃.With the increase of PZT content,the bending strength of PZT/CB/EP piezoelectric composite vibration reduction material firstly increased from 45 MPa to 65 MPa and then decreased to 38 MPa.At room temperature,the dielectric constant increased from 7 to 50,and the dielectric loss increased from 0.1 to 0.5.

Performance of beam-type piezoelectric vibration energy harvester based on ZnO film fabrication and improved energy harvesting circuit

We demonstrate a piezoelectric vibration energy harvester with the ZnO piezoelectric film and an improved synchronous electric charge extraction energy harvesting circuit on the basis of the beam-type mechanical structure,especially investigate its output performance in vibration harvesting and ability to generate charges.By establishing the theoretical model for each of vibration and circuit,the numerical results of voltage and power output are obtained.By fabricating the prototype of this harvester,the quality of the sputtered film is explored.Theoretical and experimental analyses are conducted in open-circuit and closed-circuit conditions,where the open-circuit mode refers to the voltage output in relation to the ZnO film and external excitation,and the power output of the closed-circuit mode is relevant to resistance.Experimental findings show good agreement with the theoretical ones,in the output tendency.It is observed that the properties of ZnO film achieve regularly direct proportion to output performance under different excitations.Furthermore,a maximum experimental power output of 4.5 mW in a resistance range of 3 kΩ-8 kΩis achieved by using an improved synchronous electric charge extraction circuit.The result is not only more than three times the power output of classic circuit,but also can broaden the resistance to a large range of 5 kΩunder an identical maximum value of power output.In this study we demonstrate the fundamental mechanism of piezoelectric materials under multiple conditions and take an example to show the methods of fabricating and testing the ZnO film.Furthermore,it may contribute to a novel energy harvesting circuit with high output performance.

Vibration analysis and active control of nearly periodic two-span beams with piezoelectric actuator/sensor pairs

The piezoelectric materials are used to investigate the active vibration control of ordered/disordered periodic two-span beams. The equation of motion of each sub-beam with piezoelectric patches is established based on Hamilton＇s principle with an assumed mode method. The velocity feedback control algorithm is used to design the controller. The free and forced vibration behaviors of the two-span beams with the piezoelectric actuators and sensors are analyzed. The vibration properties of the disordered two-span beams caused by misplacing the middle support are also researched. In addition, the effects of the length disorder degree on the vibration performances of the disordered beams are investigated. From the numerical results, it can be concluded that the disorder in the length of the periodic two-span beams will cause vibration localizations of the free and forced vibrations of the structure, and the vibration localization phenomenon will be more and more obvious when the length difference between the two sub-beams increases. Moreover, when the velocity feedback control is used, both the forced and the free vibrations will be suppressed. Meanwhile, the vibration behaviors of the two-span beam are tuned.

Application of Piezoelectric Materials in a Novel Linear Ultrasonic Motor based on Shear-induced Vibration Mode

A novel linear ultrasonic motor based on d15 effect of piezoelectric materials was presented. The design idea aimed at the direct utilization of the shear-induced vibration modes of piezoelectric material. Firstly, the inherent electromechanical coupling mechanism of piezoelectric material was investigated, and shear vibration modes of a piezoelectric shear block was specially designed. A driving point’s elliptical trajectory induced by shear vibration modes was discussed. Then a dynamic model for the piezoelectric shear stator was established with finite element（FE） method to conduct the parametric optimal design. Finally, a prototype based on d15 converse piezoelectric effect is manufactured, and the modal experiment of piezoelectric stator was conducted with laser doppler vibrometer. The experimental results show that the calculated shear-induced vibration modes can be excited completely, and the new linear ultrasonic motor reaches a speed 118 mm/s at noload, and maximal thrust 12.8 N.

Active control of wall-bounded turbulence for drag reduction with piezoelectric oscillators

An experimental investigation was performed for active control of coherent structure bursting in the near-wall region of the turbulent boundary layer. By means of synchronous and asynchronous vibrations with double piezoelectric vibrators, the influence of periodic vibration of the double piezoelectric vibrators on the mean velocity profile, drag reduction rate, and coherent structure bursting is analyzed at Reo = 2766. The case with 100 V/160 Hz-ASYN is superior to other conditions in the experiment and a relative drag reduction rate of 18.54% is exciting. Asynchronous vibration is more effective than synchronous vibration in drag reduction at the same voltage and frequency. In all controlled cases, coherent structures at large scales are regulated while the small-scale structures are stimulated. The fluctuating velocity increases significantly. A periodic regulating effect on the coherent structure can be seen in the ASYN control conditions at the frequency of 160 Hz.

Temperature dependence of mode coupling effect in piezoelectric vibrator made of[001]c-poled Mn-doped 0.24PIN-0.46PMN-0.30PT ternary single crystals with high electromechanical coupling factor

The influence of temperature on mode coupling effect in piezoelectric vibrators remains unclear.In this work,we discuss the influence of temperature on two-dimensional(2D)mode coupling effect and electromechanical coupling coefficient of cylindrical[001]c-poled Mn-doped 0.24PIN-0.46PMN-0.30PT piezoelectric single-crystal vibrator with an arbitrary configuration ratio.The electromechanical coupling coefficient kt decreases with temperature increasing,whereas k33 is largely invariant in a temperature range of 25℃-55℃.With the increase of temperature,the shift in the‘mode dividing point’increases the scale of the poling direction of the piezoelectric vibrator.The temperature has little effect on coupling constantΓ.At a given temperature,the coupling constantΓof the cylindrical vibrator is slightly greater than that of the rectangular vibrator.When the temperature changes,the applicability index(M)values of the two piezoelectric vibrators are close to 1,indicating that the coupling theory can be applied to piezoelectric vibrators made of late-model piezoelectric single crystals.

MULTI-LAYER PIEZOELECTRIC ACTUATOR AND ITS APPLICATION IN CONTROLLABLE CONSTRAINED DAMPING TREATMENT

A kind of novel multi-layer piezoelectric actuator is proposed and integrated with controllable constrained damping treatment to perform hybrid vibration control. The governing equation of the system is derived based on the constitutive equations of elastic, viscoelastic and piezoelectric materials, which shows that the magnitude of control force exerted by multi-layer piezoelectric actuator is the quadratic function of the number of piezoelectric laminates used but in direct proportion to control voltage. This means that the multi-layer actuator can produce greater actuating force than that by piezoelectric laminate actuator with the same area under the identical control voltage. The optimal location placement of the multi-layer piezoelectric actuator is also discussed. As an example, the hybrid vibration control of a cantilever rectangular thin-plate is numerically simulated and carried out experimentally. The simulated and experimental results validate the power of multi-layer piezoelectric actuator and indicate that the present hybrid damping technique can effectively suppress the low frequency modal vibration of the experimental thin-plate structure.

Further studies on thickness vibrations of piezoelectric plate excited by parallel field

In this paper, the thickness vibrations of the piezoclectric plate excited by a parallel field are further analysed. The new formula of resonant frequency equation and electromechanical coupling factor of the coupling modes are obtained. The characteristics of piezoelectrically-tunable frequency for the pure and coupling modes are investigated and ap plied to two examples.

Computational analysis of vibration modes of disk-shaped piezoelectric traveling wave motors

According to Kirchhoff-Love's assumptions, this paper establishes linear system of equations for solving eigen frequency constant and corresponding mode shape. Using engineer-ing and numerical analysis software Matlab5.2 and method of coefficient determinant searching arithmetic, eigen frequency constant and mode shape of the stator with i.d./ o.d. ratio of 0.1, 0.3, 0.35, 0.6 and different vibration modes are accurately solved and analyzed. By means of Newton interpolation method, contributions of transverse deflection amplitude and vibration energy corresponding to various modes are determined. This paper offers a valid theoretical foundation for the optimum design of the stator of disk-shaped ultrasonic motors. Furthermore, according to results of numerical analysis, several choosing principles of vibration modes are summarized.

Experimental investigation of wall-bounded turbulence drag reduction by active control of double piezoelectric vibrator

In order to manipulate the large-scale coherent structures in the wall-bounded turbulence and reduce the skin-friction,an active-control experimental investigation is performed by using the synchronous and asynchronous vibrations of double piezoelectric vibrators embedded spanwisely on a smooth flat plate surface.A TSI-IFA300 hot-wire anemometer and a TSI-1621 A-Tl.5 hot-wire probe are used to measure the time series of the instantaneous velocity at different locations.The influences of the vibrations on the wall-bounded turbulence are compared in a multi-scale point of view.A disturbance Reynolds Number Red=pd2 f/μis introduced to represent the disturbance.A probability density functions(PDFs)of the multi-scale components of the turbulence velocity and the multi-scale conditional phase-averaged waveform are studied in detail using the wavelet transform.The results show that the maximum drag reduction rate 18.54%is obtained at 100 V/160 Hz and Red=0.54 in the asynchronous vibration mode.The disturbances generated by the vibrators have a significant influence on the sweep events of the burst.The asynchronous vibration model is more effective than the synchronous vibration one.A possible physical mechanism is suggested to explain why the disturbance frequency of 160 Hz leads to an optimal parameter set for the drag reduction.