Papers by Keyword: Piezoceramics

Abstract: Testing methods used for assessment of buildings considered as a cultural heritage are focused mainly on non-destructive testing methods. Old buildings are usually sensitive to destructive in-situ testing, and a variety of non-destructive techniques (NDT) are frequently used. One of the most commonly used sensors are accelerometers, which can measure vibrations of different part of structures. These can be used in either continuous monitoring or in short-time assessment. Impact-Echo is a well-known method which can locate defects, caverns, or damaged parts not only in industry-level structures, but also in preservation of cultural heritage. This type of measurement requires attaching a sensor to the surface of the observed element. This is in most cases done by adhesives which can damage the more porous structures. In this paper a comparison of two different sensor types in testing of reference concrete elements is presented: contact piezoceramic accelerometer; non-contact MEMS type microphone. Signals recorded by each sensor type are assessed by the statistical method of feature extraction.

Abstract: 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.

Abstract: The time-dependent effects of piezoceramic material under the constant electric field are analyzed. The new rate-dependent ferroelectroelastic phenomenological model is proposed and compared with known models and experimental data.