Influence Of Electrical Boundary Conditions Research Articles

Love wave propagation in a trigonal piezoelectric material layer of 32 crystal class

This paper analytically investigates the propagation characteristics of Love waves in a 32 trigonal piezoelectric layer resting on an elastic substrate. The governing electromechanical equations are derived and dispersion equations are obtained for two electrically open and short conditions. For a numerical study, a structure consisting of an α-quartz layer bonded onto a diamond substrate is considered. The influence of electrical boundary conditions on the mechanical and electrical responses is presented and discussed. The numerical results of dispersion curves indicate that phase velocities of all modes initiate at the shear wave velocity of the substrate and the phase velocity of the first mode approaches the velocity of the Bleustein–Gulyaev (BG) wave at high wavenumbers. Despite hexagonal piezoelectric material, the real and imaginary parts of the response mode shapes do not have identical distribution in a structure containing a piezoelectric material of crystal class 32. In addition, the present study provides a theoretical foundation for the design and application of surface acoustic wave (SAW) devices.

Effect of electrical boundary conditions on the domain stability of porous ferroelectric nanowires

The electrical boundary condition plays an important role in the manipulation of domain structures in low-dimensional ferroelectric materials, especially ferroelectric nanowires. Here, using phase-field simulations, we systematically investigate the influence of electrical boundary conditions on the domain structure in porous PbTiO3 ferroelectric nanowires. Our results demonstrate the formation of four types of domain structures via varying electrical boundary conditions, which possess distinguished local polarization and energy configurations. We further show that the domain structures are also dependent on the nanowire radius, including the breakdown of a metastable concentric toroidal domain structure upon reducing the radius to 14 nm. The present work provides guidance for further experimental studies on the control of polar domain structures through manipulating the electrical boundary condition and the ferroelectric size, which paves the way for developing multi-functions of low-dimensional ferroelectric systems.

Versatile non-Hermitian piezoelectric metamaterial beam with tunable asymmetric reflections

Non-Hermitian systems have been widely utilized to achieve specific functions for manipulating abnormal wave motion, such as asymmetric mode switching, unidirectional zero reflection (UZR), and unidirectional perfect absorption (UPA). In this paper, a novel non-Hermitian piezoelectric metamaterial beam is proposed to realize the tunable UZR of flexural waves. The unit cell of this non-Hermitian metamaterial beam consists of a host beam and two pairs of piezoelectric patches shunting different resistor–inductor circuits. Based on the flexural wave theory, the transfer matrix method is introduced to analyze the influence of electrical boundary conditions on the UZR and further clarify the relationship between the UZR and the exceptional point. The exceptional point depends only on the dissipative circuit, and it has no need for the balanced gain and loss like parity–time symmetric metamaterial. Furthermore, the UZR for the desired frequency is realized by applying a genetic algorithm, and its effectivity is experimentally validated. In addition, the non-Hermitian metamaterial beam is designed to realize the UPA of flexural waves. Results indicate that the proposed metamaterial beam is versatile and can achieve tunable manipulations of asymmetric wave propagations and has widely promising applications in many fields, such as non-destructive testing, enhanced sensing, wave isolation and vibration attenuation.

Influence of electrical boundary conditions on profiles of acoustic field and electric potential of shear-horizontal acoustic waves in potassium niobate plates

The profiles of an acoustic field and electric potential of the forward and backward shear-horizontal (SH) acoustic waves of a higher order propagating in X-Y potassium niobate plate have been theoretically investigated. It has been shown that by changing electrical boundary conditions on a surface of piezoelectric plates, it is possible to change the distributions of an acoustic field and electric potential of the forward and backward acoustic waves. The dependencies of the distribution of a mechanical displacement and electrical potential over the plate thickness for electrically open and electrically shorted plates have been plotted. The influence of a layer with arbitrary conductivity placed on a one or on the both plate surfaces on the profiles under study, phase and group velocities of the forward and backward acoustic waves in X-Y potassium niobate has been also investigated. The obtained results can be useful for development of the method for control of a particle or electrical charge movement inside the piezoelectric plates, as well a sensor for definition of the thin film conductivity.

Influence of electrical boundary conditions on molecular dynamics simulations of ionic liquid electrosprays.

Molecular dynamics (MD) simulations are coupled to solutions of Poisson's equation to study the effects of the electrical boundary conditions on the emission modes of an electrospray thruster fed with an ionic liquid. A comparison of a new tip boundary condition with an analytical model based on a semihyperboloidal shape offers good agreement, although the analytical model overestimates the maximum value of the tangential electric field since it does not take into account the space charge that reduces the field at the liquid surface. It is found that a constant electric field model gives similar agreement to the more rigorous and computationally expensive tip boundary condition at lower flow rates. However, at higher mass flow rates the constant electric field produces extruded particles with higher Coulomb energy per ion, consistent with droplet formation. Furthermore, the MD simulations show that ion emission sites differ based on the boundary condition and snapshots offer an explanation as to why some boundary condition models will predict emission in a purely ionic mode, whereas others suggest a mixed ion-droplet regime. Finally, specific impulses and thrusts are compared for the different models and are found to vary up to 30% due to differences in the average charge to mass ratio.

Fundamental electro-elastic field in an infinite transversely isotropic piezoelectric medium with a permeable external circular crack

For the first time, exact and fundamental solutions are developed for an infinite transversely isotropic piezoelectric medium, weakened by a circular external crack. The crack is assumed to be electrically permeable and is subjected to mechanical loadings applied symmetrically with respect to the crack face. The problem is transformed into a mixed boundary value problem, which is solved by the generalized potential theory method along with the general piezoelectricity solutions. Three-dimensional non-axisymmetric electro-elastic field is completely and explicitly presented in terms of elementary functions. Singular behaviors on the crack tip and the crack face displacement are examined. For a specific piezoelectric material, numerical calculations are performed to confirm the validity of the present solutions, and to show the electromechanical coupling effect and the influence of electric boundary conditions. The present solutions can serve as benchmarks to clarify various simplified analyses and numerical simulations.

On the influence of electric boundary conditions on dynamic SIFs in piezoelectric materials

Dynamic stress intensity factors (SIFs) for a straight crack in a piezoelectric material under time-harmonic L- and SH-wave loading are determined for different electric boundary conditions. Impermeable, permeable and limited permeable cracks are compared. The problem is formulated and numerically solved using a nonhypersingular traction-based boundary integral equation method where the fundamental solution is obtained by Radon transform. A parametric study in the frequency domain shows the dependence of the SIFs on the choice of the electrical boundary conditions at the crack faces.

Effect of metallization on the power flow angle of SH0 waves in thin piezoelectric plates

The anisotropy of the angle between the phase and group velocity (power flow angle, PFA) as well as the influence of electrical boundary conditions on this angle have been studied for shear-horizontal fundamental (SH0) acoustic waves in thin piezoelectric plates of lithium niobate (LNO) and potassium niobate (KNO). Both LNO and KNO crystals possess orientations at which the PFA for SH0 waves reaches large values (17° and 48°, respectively). It is established that metallization of the piezoelectric plate surface can significantly change PFA values, in particular, by 18° and 55° for Y-X + 25° cut plates of LNO and KNO, respectively.

Fracture behaviour of cracks in piezoelectric media with electromechanically coupled boundary conditions

Existing studies on slit crack problems have been limited mostly to the electrically impermeable and permeable crack models, which represent the limiting cases of the physical boundary condition. This paper studies the generalized plane problem of a crack in a piezoelectric medium, with the electric boundary condition along the crack surfaces being governed by its opening displacement. The theoretical formulation of this nonlinear problem is based on the use of Fourier transforms and the solution of a system of integral equations, which are solved using Chebyshev polynomials. The analytical solution of the problem clearly shows the transition between permeable and impermeable models with increasing crack opening. Depending on the applied mechanical and electric loads, different modes of crack deformation are predicted and discussed.

On a plane crack in piezoelectric solids

A new analytical solution for a piezoelectric plane with an elliptical void is derived by removing the commonly held assumptions that the void boundary is impermeable and a void axis is perpendicular to the poling direction. The approach of Lekhnitskii's complex potential functions is used in the derivation. Applicability of the common practice of reducing a void solution to a crack solution is examined. It is shown that a recently reported solution for exact electric boundary conditions is actually the well known solution for a permeable crack. A unified formulation for plane cracks containing air or vacuum is then developed to account for different electric boundary conditions. Crack closure is taken into consideration in the analysis. The influence of electric boundary conditions and crack orientation on fracture parameters is discussed.

Influence of electrical boundary conditions on structure of surface acoustic waves in potassium niobate

It has been found that variations in the electrical boundary conditions can significantly change the structure of surface acoustic waves propagating in potassium niobate. For example, a generalised Rayleigh wave propagating along the X+15/spl deg/ direction in the Y-cut may be transformed into a quasi-shear Bleustein-Gulyaev wave by electrical shorting of the surface.