Smart control of functionally graded sandwich plates by incorporating Murakami zig-zag function

This study is aimed at incorporating the zig-zag effect by Murakami zig-zag function in the development of a finite element model for active constraining layer damping treatment of functionally graded sandwich plates. The present sandwich construction consists of functionally graded facings distanced by a ceramic core. The substrate functionally graded plate is subjected to active constraining layer damping treatment, which in itself is a two-layered material system comprised of a viscoelastic layer and a 1–3 piezoelectric composite layer. The deformation kinematics of the functionally graded sandwich plate active constraining layer damping system is shaped using Murakami zig-zag function , and the finite element model is obtained by the virtual work principle. A standard feedback control system has been implemented, and a MATLAB subroutine has been developed to present the open- and closed-loop responses. Substrate plates with functionally graded configurations 1-1-1, 1-2-1, and 2-1-2 are considered to evaluate the effect of active constraining layer damping on damping the frequency responses of these plates. Investigation on damping performance has been carried out, bearing in mind the change in power-law index with top and bottom ceramic-/metal-rich surfaces. Also, the effect of variation in fiber orientation angle (obliquely reinforced) of the piezoelectric composite material on the active constraining layer damping performance has been examined thoroughly.

Broadband tunable acoustic metasurface based on piezoelectric composite structure with two resonant modes

In this letter, we propose a deep-wavelength tunable acoustic metasurface composed of a fixed piezoelectric composite structure with a broad operating frequency range. The metasurface unit has two tunable resonant frequencies determined by specific external inductors and can continuously modulate the phase of transmitted wave. The influence of the inductors on the resonant frequencies are studied by simulation and experiment. Moreover, the functions of acoustic beam steering and focusing by the designed metasurface at three arbitrarily chosen frequencies are verified in simulation. This work may have good potential in design of acoustic metasurfaces with broadband operating frequencies.

A Piezoelectric Wave Energy Harvester Using Plucking-Driven and Frequency Up-Conversion Mechanism

In this study, a plucking-driven piezoelectric wave energy harvester (PDPWEH) consisted of a buoy, a gear train frequency up-conversion mechanism, and an array of piezoelectric cantilever beams was developed. The gear train frequency up-conversion mechanism with compact components included a rack, three gears, and a geared cam provide less energy loss to improve electrical output. Six individual piezoelectric composite beams were plucked by geared cam to generate electrical power in the array of piezoelectric cantilever beams. A sol-gel method was used to create the piezoelectric composite beams. To investigate PDPWEH, a mathematical model based on the Euler–Bernoulli beam theory was derived. The developed PDPWEH was tested in a wave flume. The wave heights were set to 100 and 75 mm, the wave periods were set to 1.0, 1.5, and 2.0 s. The maximum output voltage of the measured value was 12.4 V. The maximum RMS voltage was 5.01 V, which was measured by connecting to an external 200 kΩ resistive load. The maximum average electrical power was 125.5 μw.

Experimental validation of axially polarized multilayer piezoelectric composite cylindrical transducers with adjustable multifrequency

The axially polarized multilayer piezoelectric composite cylindrical transducers with adjustable multifrequency capability have been proposed by adjusting the external electric resistance and the ratio of piezoelectric layer numbers between the actuator part and the sensor part, which have promising potential in designing the novel cymbal transducer for underwater sound projector and ultrasonic radiator applications. In the previous studies, the multilayer models were established to guide the design of the transducers with arbitrary layer number, and analyzed the dynamic characteristics theoretically. In this work, an experimental study is performed to validate the theoretical models and predictions. Piezoelectric rings with multiple concentric annular electrodes are designed to characterize the multilayer piezoelectric composite cylindrical transducers. The top surface of the piezoelectric rings is divided into two separate parts. One part is covered by multiple concentric annular electrodes, corresponding to the piezoelectric layers, and the other part is uncovered, corresponding to the elastic layers. Four prototypes are fabricated and each consists of four concentric annular electrodes. The impedance spectra are measured by the impedance analyzer to obtain the resonance and anti-resonance frequencies. Effects of two adjusting methods on the dynamic characteristics are evaluated experimentally. The experimental results basically coincide with the theoretical ones. This comprehensive experimental work assures the feasibility of using axially polarized multilayer piezoelectric composite cylindrical transducers with adjustable multifrequencies and confirms the benefit of the developed theoretical models for guiding the fabrication and optimization of this type of transducers.