Modeling Energy Harvesting Devices with Non-Uniformly Polarized Piezoceramic Materials

Non-uniformly polarized piezoceramic materials can be used in effective energy harvesting devices. Axisymmetric and plane models of electro elastic bodies were studied using applied theory and finite element method (FEM). Applied theory for devices made of parts with longitudinal and transverse polarization was developed. It was based on bending of electro elastic plates models. Numerical experiments for FEM models were performed in ACELAN package. Comparison of applied theory and FEM results showed satisfactory accuracy. First model consists of three parts: transversally polarized part and two parts with opposite longitudinal polarization. It was compared with uniformly polarized model of the same size. Both electro-mechanical coupling coefficient and output voltage produced by forced oscillations were greater in case of non-uniform polarization. Geometrical parameters – such as relative size of parts, electrode positioning and thickness of the device - were varied in series of numerical experiments to determine range of applicability for developed models and to perform initial analyses of most effective set of parameters. Model was analyzed for different boundary conditions. Automation tools for applied theory computations were developed. Second model is a disk with transvers polarization in the central part and opposite longitudinal polarization in two layers of outer part. It also showed output voltage growth. Appling polarization to the device is an important part of manufacturing process. In some cases, parts can be polarized with imperfections as incomplete polarization of deviation of polarization direction. Polarization process for predefined model geometry and electrode scheme can be performed in ACELAN package. Vector field of the polarization were transferred to finite element meshes and used for solving problems with non-uniform polarization. Difference between simplified block model presented in applied theory and full model solved with FEM was estimated. Some problems can be reduced from full to simplified model without significant accuracy loss. Described programs, models and techniques are developed for advanced analysis of non-uniformly polarized energy storage devices.