Search results for "piezoelectric"
showing 10 items of 169 documents
NON-LINEAR MECHANICAL, ELECTRICAL AND THERMAL PHENOMENA IN PIEZOELECTRIC CRYSTALS
2003
Mechanical, electrical and thermal phenomena occurring in piezoelectric crystals were examined by non-linear approximation. For this purpose, use was made of the thermodynamic function of state, which describes an anisotropic body. Considered was the Gibbs function. The calculations included strain tensor εij = f(σkl , En, T), induction vector Dm = f(σkl , En, T) and entropy S = f(σkl , En, T) as function of stress σkl , field strength En and temperature difference T. The equations obtained apply to anisotropic piezoelectric bodies provided that the “forces” σkl , En, T acting on the crystal are known. Механічні, електричні та термічні явища у п’єзоелектричних кристалах вивчаються у неліній…
A posteriori estimates for a coupled piezoelectric model
2017
Erworben im Rahmen der Schweizer Nationallizenzen (http://www.nationallizenzen.ch)
Piezoelectric Actuated Nonlinear Energy Sink With Tunable Attenuation Efficiency
2019
Abstract Comparing to linear vibration absorbers, nonlinear energy sinks (NESs) have attracted worldwide attention for their intrinsic characteristics of targeted energy transfer or energy pumping in a relatively wide frequency range. Unfortunately, they are highly dependent on the vibration amplitude to be attenuated and will play its role only if the external load exceeds a specific threshold value. Different from the passive bistable NES, a novel piezoelectric nonlinear energy sink (PNES) is designed by introducing in-phase actuation to compensate or enhance the external vibration loads, thus triggering the NES operating in high attenuation efficiency. The nonlinear mathematic model of t…
Microcracking in piezoelectric materials by the Boundary Element Method
2019
A 3D boundary element model for piezoelectric polycrystalline micro-cracking is discussed in this contribution. The model is based on the boundary integral representation of the electro-mechanical behavior of individual grains and on the use of a generalized cohesive formulation for inter-granular micro-cracking. The boundary integral formulation allows to address the electro-mechanical boundary value problem in terms of generalized grain boundary and inter-granular displacements and tractions only, which implies the natural inclusion of the cohesive laws in the formulation, the simplification of the analysis pre-processing stage, and the reduction of the number of degrees of freedom of the…
Modelling stress-corrosion microcracking in polycrystalline materials by the Boundary Element Method
2019
The boundary element method is employed in this study in conjunction with the finite element method to build a multi-physics hybrid numerical model for the computational study of stress corrosion cracking related to hydrogen diffusion in polycrystalline microstructures. More specifically a boundary integral representation is used to represent the micro-mechanics of the aggregate while an explicit finite element method is used to model inter-granular hydrogen diffusion. The inter-granular interaction between contiguous grains is represented through cohesive laws, whose physical parameters depend on the concentration of inter-granular hydrogen, diffusing along the interfaces according to the …
Piezoelectric model of rainfall energy harvester
2014
In this paper a model to predict the harvest of the energy contained in rainfall by means of piezoelectric transducers is presented. Different studies agree on the level of suitable generated voltage on the electrodes of a piezoelectric transducer subjected to rainfall, but a complete characterization on the supplied power is still missing. This work, in order to limit optimistic forecasts, compares the behavior of the transducers subjected to real and artificial rainfall, a condition that has shown promising behavior in laboratory.
A BOUNDARY ELEMENT FORMULATION FOR MICROMECHANICAL HOMOGENIZATION OF POLYCRYSTALLINE MATERIALS WITH PIEZOELECTRIC COUPLING
2019
A novel boundary element formulation for the evaluation of the effective properties of threedimensional polycrystalline aggregates with piezoelectric coupling is presented. The aggregates are modelled at the scale of their constituent crystals and are artificially generated through Voronoi-Laguerre tessellations. The electro-mechanical behaviour of each crystal is represented upon introducing an ad-hoc mesh of its boundary and a generalised integral representation of the governing equations of the piezoelectric problem. The behaviour of the whole aggregate is then retrieved upon introducing a suitable set of electro-mechanical interface conditions at the grain boundaries. With respect to cl…
A boundary element model for piezoelectric dynamic strain sensing of cracked structures
2011
A piezoelectric sensor model is here presented for the Structural Health Monitoring (SHM) of damaged structures. A boundary element approach based on the Dual Reciprocity BEM is then used to model and analyze the transient response of a piezoelectric patch bonded on a cracked beam. The BE model is written for the piezoelectric problem employing generalized displacements. The multidomain boundary element technique is implemented to model non-homogeneous and cracked configuration, taking contact conditions into account. Analyses have been carried out for an isotropic beam with a piezoelectric strip attached on it and dynamical results for the undamaged structure have been compared with FE res…
Comparison of piezosurgery and conventional rotary instruments in schneider’s membrane sinus lifting: A pilot randomized trial
2020
Background The present study aimed to evaluate and compare the postoperative effects of the piezoelectric device and conventional rotary instruments in Schneider’s membrane sinus lifting procedure. Material and Methods Twenty patients requiring bilateral maxillary bone graft augmentation in the posterior maxillary region were selected. Piezoelectric surgery was performed on one side and conventional surgery with a rotary diamond bur on the other. Postoperative pain, swelling, edema, and mouth opening were evaluated at one hour and two and seven days after the procedures. All variables were submitted to Friedman or Wilcoxon tests at a 5% significance level. Results The comparison between gro…
Sialolithiasis. Proposal for a new minimally invasive procedure: Piezoelectric surgery
2014
Sialolithiasis is the presence of stones in the ducts of the salivary glands. Most episodes are unique, and 60-80% are located exclusively in the main excretory duct. The main clinical manifestations are swelling and pain typically before, during or after meals that decreases if the obstruction is not complete. The highest prevalence of lithiasis is in the submandibular gland -87%-, whose secretion is more viscous, followed by the parotid gland -10%- and finally the sublingual gland -3%-. The most significant consequences are caused by the prolonged blockage of the duct by a stone, which can produce a persistent ductal dilatation with a swelling that does not subside, and could lead to the …