Background and Motivation Rare-earth calcium oxyborate crystals Re Ca4O（BO3）3（Re COB,Re=rare-earth elements）have been reported to be promising for high temperature piezoelectric applications,due to the merits of h...
详细信息
Background and Motivation Rare-earth calcium oxyborate crystals Re Ca4O（BO3）3（Re COB,Re=rare-earth elements）have been reported to be promising for high temperature piezoelectric applications,due to the merits of high piezoelectric coefficients(6
Background and Motivation After the discovery of piezoelectric effect in 1880,various piezoelectric devices have been designed and fabricated,such as resonators,filters,transducers,actuators and sensors *** the develo...
详细信息
Background and Motivation After the discovery of piezoelectric effect in 1880,various piezoelectric devices have been designed and fabricated,such as resonators,filters,transducers,actuators and sensors *** the developments of techniques,high temperature sensors are desired in many tech *** materials that are operational at elevated temperatures without failure are
＜正＞Background,Motivation and Objective In oil well operations,cement sheath is located between the casing and formation to provide zonal isolation through the life of a *** of cement sheath integrity is vital for a...
详细信息
＜正＞Background,Motivation and Objective In oil well operations,cement sheath is located between the casing and formation to provide zonal isolation through the life of a *** of cement sheath integrity is vital for a long-term wellbore *** of this
Piezoelectric semiconductors simultaneously exhibit strong electromechanical coupling effect and unique electric conductive behavior, and hence are useful for making novel electronic devices. In recent, Wurtzite struc...
详细信息
Piezoelectric semiconductors simultaneously exhibit strong electromechanical coupling effect and unique electric conductive behavior, and hence are useful for making novel electronic devices. In recent, Wurtzite structured piezoelectric semiconductors with one-dimensional nanostructures, film-substrate and layered structures have attracted increasing attentions due to their potential applications in electronic transport, field-effect transistors, sensors, nano-generators, flexible electronics optoelectronics and human-machine interfacing. Owing to the electromechanical coupling effect, the mechanical properties of piezoelectric semiconductors play a vital role in the device’s performance. However, it is very poor in studies on piezoelectric semiconductors from the mechanical point. In this contribution, we study acoustic wave propagations in piezoelectric semiconductor multilayers within the framework of linear continuum theory. The transfer matric method is employed to derive the dispersion equation under different boundary conditions. The effect of the charge density and conductivity on the dispersion frequency are systematically studied.
Background,Motivation and Objective Recently,much attention has been paid to the relaxor ferroelectric single crystals for their ultrahigh piezoelectric *** quality and large size Pb(Mg1/3Nb2/3)O3-x Pb Ti O3(PMN-PT)si...
详细信息
Background,Motivation and Objective Recently,much attention has been paid to the relaxor ferroelectric single crystals for their ultrahigh piezoelectric *** quality and large size Pb(Mg1/3Nb2/3)O3-x Pb Ti O3(PMN-PT)single crystals has been grown well
Because of the gradually changing material properties, functionally graded materials（FGM） have many advanced applications. Guided wave propagation in FGM structures attracted considerable research efforts for the pu...
详细信息
Because of the gradually changing material properties, functionally graded materials（FGM） have many advanced applications. Guided wave propagation in FGM structures attracted considerable research efforts for the purpose of the ultrasonic NDT＆E. But the limitation of manufacturing technology results in the existence of initial stresses in FGM structures. The influences of the initial stresses on the wave propagation in FGM structures must be paid enough attention. Based on "Mechanics of Incremental Deformations", the circumferential SH waves in FGM cylindrical curved plates with axially and radially initial stresses are investigated. The Legendre polynomial series method is used to solve the coupled wave equation with variable coefficients. Through numerical examples, the convergence of the polynomial method is discussed. The influences of initial stress on dispersion curves and stress distributions are investigated, respectively. Numerical results show that the curves of frequency vs initial stresses in both directions are not entirely linear and that the influence of the compressive stress on the SH wave is almost entirely contrary to that of the tensile stress. The influence of the radial initial stress is contrary to that of the axial initial stress both on dispersion curves and on displacement, stress distributions. The influence of the radial initial stress becomes stronger with the increasing of the mode order but the influence of the axial initial stress becomes stronger with the increasing of the wavenumber.
In analogy to photonic crystals, phononic crystals may exhibit complete band gaps in their transmission spectra where the propagation of acoustic or elastic waves is strictly forbidden in all directions. The complete ...
详细信息
In analogy to photonic crystals, phononic crystals may exhibit complete band gaps in their transmission spectra where the propagation of acoustic or elastic waves is strictly forbidden in all directions. The complete band gaps could be engineered to provide a vibrationless environment for high precision mechanical systems in given frequency ranges. Understanding the full band structures is expected to lead to the design of new generations of sound shields, filters, transducers, refractive devices such as acoustic lenses and acoustic interferometers, etc. By breaking the periodicity of the systems, it is possible to create highly localized defect or guided modes within the acoustic band gaps, which are analogous to localized modes in a photonic crystal and to localized impurity states in a semiconductor. This makes the phononic crystals potential candidates for the design of elastic or acoustic wave guides. In the case of solid/solid systems, the existence of full band gaps and localized defect modes and the possibility of guiding waves have been investigated theoretically using the different methods. In the present paper, this boundary element method is extended to the calculation of the defect states in two-dimensional phononic crystals. We consider a 2D phononic crystal consisting of a square array. Both scatterers and matrix are homogeneous, isotropic and linear elastic solids. Due to the periodicity of the system, we can restrict our attention to a supercell. For the solid/solid system, when the binary components perfectly contact, the boundary conditions along the interface are that the displacements and the stresses are *** addition, the periodicity of the structures implies that any field quantity(e.g. the displacement, stress, pressure and their derivatives) should obey the following Bloch theorem. The Bloch theorem allows us to solve the problem in a supercell. We bulid the boundary integral equations of the matrix and every scatter. Then the boun
暂无评论