Performance of non-uniform functionally graded piezoelectric energy harvester beams

The appearance of functionally graded piezoelectric materials has solved the lamination problem of the conventional piezoelectric structures. Functionally graded piezoelectric materials are the new materials with unexplored capabilities. This article theoretically investigates the effects of non-uniformity on the performance of the functionally graded piezoelectric material cantilever beams subjected to harmonic excitation. The governing equations are derived based on Timoshenko and Euler–Bernoulli beam theories. The finite element method with the application of superconvergent element is employed here for the discretization and the vibration analysis of the system. This model is validated by comparing the numerical results with the experimental results of piezoelectric energy harvesters of conventional shapes available in the open literature. Parametric studies are carried out with respect to the effects of tapering ratios, the degree of non-uniformity, load resistance, and the volume fraction parameter on the electrical output power and the fundamental resonance frequency. It was observed that the application of diverging beams noticeably enhances the power output per mass of piezoelectric element extracted while decreases the natural frequency which is advantageous for scavenging energy from ambient surroundings. The results reveal that there is an optimal value for the non-homogeneous parameter leading to the maximized harvested energy under different operating conditions.

Peculiarities of surface acoustic waves, propagation in structures with functionally graded piezoelectric materials, coating from different ceramics on the basis of PZT

A model of a piezoelectric structure with an inhomogeneous coating is considered. The structure is a homogeneous half-space made of PZT-5H ferroelectric ceramics with a functionally graded coating. The properties of coating vary continuously in thickness from parameters of one material to parameters of another material in a continuously nonmonotonic or piecewise-continuous manner. As coating materials, various combinations of ceramics of different stiffness based on PZT are considered. Using the example of the problem of the propagation of sh-waves in a piezoelectric structure, we studied the influence of the ratio of the physical parameters of the coating materials, the localization region, and the size of the transition zone of one material to another on the propagation features of surface acoustic waves (SAWs) and the structure of the wave field.

A Coupling Electromechanical Inhomogeneous Cell-Based Smoothed Finite Element Method for Dynamic Analysis of Functionally Graded Piezoelectric Beams

To accurately simulate the continuous property change of functionally graded piezoelectric materials (FGPMs) and overcome the overstiffness of the finite element method (FEM), we present an electromechanical inhomogeneous cell-based smoothed FEM (ISFEM) of FGPMs. Firstly, ISFEM formulations were derived to calculate the transient response of FGPMs, and then, a modified Wilson-θ method was deduced to solve the integration of the FGPM system. The true parameters at the Gaussian integration point in FGPMs were adopted directly to replace the homogenization parameters in an element. ISFEM provides a close-to-exact stiffness of the continuous system, which could automatically and more easily generate for complicated domains and thus significantly decrease numerical errors. The accuracy and trustworthiness of ISFEM were verified as higher than the standard FEM by several numerical examples.

Geometrical nonlinear characteristics of functionally graded structure using functionally graded piezoelectric materials

In the present article, a parametric study on the geometric nonlinear static and dynamic analysis of thin functionally graded structure sandwiched between functionally graded piezoelectric materials is presented. The properties of functionally graded material are graded in the thickness direction according to a power law distribution and variation of electric field is assumed to be quadratic across the thickness of functionally graded piezoelectric materials layers. The structure is modeled using finite element modeling. The finite element formulation is derived using Hamilton’s principle using full geometric nonlinearities. This is done by using Green-Lagrangian strains instead of von-Karman strains which are usually used by most researchers while conducting similar studies. The ensued non-linear algebraic equations are then solved using the modified Newton–Raphson method. A fuzzy logic controller is used to attenuate the vibration occurring in the host structure.