279 / 2019-09-27 16:56:41

Nonlinear analysis of flexoelectric beam energy harvesters

结构优化与结构行为分析 > 结构力学行为分析

Flexoelectricity refers to a spontaneous polarization in response to a non-uniform strain or strain gradient. It is a novel electromechanical coupling effect compared to piezoelectricity and universally exists in all dielectric materials. Flexoelectricity is a size-dependent effect and becomes prominent at the micro- and nano-scale. Recently, there is a growing interest to resort to flexoelectricity for harvesting energy from ambient environment, which is critical for self-powered technology and has the potential to be integrated in the micro- and nano-electro-mechanical systems. In this work, theoretical modelling and nonlinear analysis of flexoelectric beam energy harvester are presented. Firstly, we investigated a cantilever beam energy harvester based on the theory of flexoelectricity and Euler-Bernoulli beam assumption, the nonlinearity comes from the inextensibility of the centerline of the beam assumed. Nextly, a buckled flexoelectric beam energy harvester is studied based on von Karman nonlinear deformation assumption. For both cases, the nonlinear electromechanical coupling equations are derived according to the energy method. Galerkin's method is employed to obtain the discrete nonlinear equations, which are then solved numerically. Frequency response curves are plotted to reveal the nonlinear characteristics of the energy harvester and it is found that the frequency response curves exhibit a hardening behavior for a cantilevered beam energy harvester and a softening behavior for a buckled beam energy harvester. Case studies are provided and we emphasize on the influences of the load resistance, amplitude of excitation, structural size on the output performance of the energy harvester. In addition, the time histories and phase portraits of the voltage are provided. The obtained results will help understand the electromechanical coupling and nonlinear behaviors of flexoelectric beam energy harvesters.