Layered Cylinder Research Articles

Guided Circumferential Waves in Layered Poroelastic Cylinders

The present paper investigates the propagation of time harmonic circumferential waves in a two-dimensional hollow poroelastic cylinder with an inner shaft (shaft-bearing assembly). The hollow poroelastic cylinder and inner shaft are assumed to be infinite in axial direction. The outer surface of the cylinder is stress free and at the interface, between the inner shaft and the outer cylinder, it is assumed to be free sliding and the interfacial shear stresses are zero, also the normal stress and radial displacements are continuous. The frequency equation of guided circumferential waves for a permeable and an impermeable surface is obtained. When the angular wave number vanish the frequency equation of guided circumferential waves for a permeable and an impermeable surface degenerates and the dilatational and shear waves are uncoupled. Shear waves are independent of the nature of surface. The frequency equation of a permeable and an impermeable surface for bore-piston assembly is obtained as a particular case of the model under consideration when the outer radius of the hollow poroelastic cylinder tends to infinity. Results of previous studies are obtained as a particular case of the present study. Nondimensional frequency as a function of wave number is presented graphically for two types of models and discussed. Numerical results show that, in general, the first modes are linear for permeable and impermeable surfaces and the frequency of a permeable surface is more than that of an impermeable surface.

Effects of coupled interfacial imperfections on SH wave propagation in a layered multiferroic cylinder

Although SH-wave propagation in layered multiferroic composites with imperfect interfaces has been widely investigated, the effects of interfacial imperfection couplings still remain as an un-tackled problem deserving studying. The present paper considered the SH-wave propagation in a bi-layered multiferroic cylinder that has inter-coupled magnetic, electric and mechanical imperfections on the interface. The dispersion equations of SH waves are derived and numerically solved. Parametric studies are conducted on the numerical results to reveal the effects of interfacial imperfections and their inter-couplings on phase velocity. Discussion here yields four main conclusions, which can serve as guidelines for the optimal design of multiferroic composites and the related smart devices.

Volume-Surface Combined Field Integral Equation for Plasma Scatterers

The discretization of standard differential and volume integral equations (VIEs) pertinent to the electromagnetic analysis of negative permittivity media often results in ill-conditioned and slowly convergent systems of equations. We propose the use of a volume-surface combined field integral equation (VSCFIE) consisting of coupled surface combined field integral equations and VIEs to resolve this problem. The system leverages equivalence principles to artificially change the sign of the effective permittivity of the medium in which the polarization currents radiate. Numerical results obtained by analyzing time-harmonic ${\rm TE}_{\rm z}$ scattering from various 2-D layered cylinders suggests that discretization of the proposed VSCFIE yields well-conditioned and rapidly convergent systems of equations.

О распространении осесимметричных электроупругих волн в полом слоистом цилиндре при электрическом способе возбуждения

О распространении осесимметричных электроупругих волн в полом слоистом цилиндре при электрическом способе возбуждения

Кинематический анализ распространения осесимметричных электроупругих волн в полом слоистом цилиндре при механическом способе возбуждения

Кинематический анализ распространения осесимметричных электроупругих волн в полом слоистом цилиндре при механическом способе возбуждения

Effect of initial stress on propagation behaviors of shear horizontal waves in piezoelectric/piezomagnetic layered cylinders

An analytical approach is taken to investigate shear horizontal wave (SH wave) propagation in layered cylinder with initial stress, where a piezomagnetic (PM) material thin layer is bonded to a piezoelectric (PE) cylinder. Two different material combinations are taken into account, and the phase velocities of the SH waves are numerically calculated for the magnetically open and short cases, respectively. It is found that the initial stress, the thickness ratio and the material performance have a great influence on the phase velocity. The results obtained in this paper can offer fundamental significance to the application of PE/PM composite media or structure for the acoustic wave and microwave technologies.

Guided wave propagation and mode differentiation in the layered magneto-electro-elastic hollow cylinder

In this paper, the dispersion properties of elastic waves in the layered piezoelectric/piezomagnetic (PPC) hollow cylinder are investigated. The axisymmetric formulation is based on the Scaled Boundary Finite Element method. High-order elements are utilized for the discretization. We develop the mode sorting method to distinguish modes based on the reciprocity relation of the magneto-electro-elastic media. The dispersion relationship and wave structures of various layered PPC hollow cylinders are presented. Besides, we discuss impacts of the stacking sequence and radius-thickness ratio on the dispersive behavior and discover the frequency deletion of longitudinal modes.

Low-Frequency Stable Internally Combined Volume-Surface Integral Equation for High-Contrast Scatterers

Volume integral equations (VIEs) are commonly used to analyze scattering from inhomogeneous dielectric objects. Unfortunately, when VIEs are applied to high-contrast scatterers, their discretization results in ill-conditioned systems of equations. Oftentimes volume-surface integral equations (VSIEs) are used to eliminate this effect. However, when the scatterer’s mesh has elements that are much smaller than the wavelength, VSIEs become ill-conditioned, too. This letter introduces a new set of internally combined VSIEs (ICVSIEs) that exhibit neither of these ill-conditioning phenomena. Just like in previous VSIE methods, surface currents are used to artificially increase the effective permittivity of the background medium in which volume polarization currents radiate. To remove ill-conditioning due to electrical size, coupling between the surface and volume is accounted for by judiciously adding contributions due to “exterior” and “interior” surface currents. Numerical data obtained by analyzing time-harmonic TE scattering from various 2-D layered cylinders suggests that discretization of the new ICVSIE yields matrices that are unaffected by the scatterer’s maximum permittivity and electrical size.

Dynamic Analysis of a Layered Cylinder Reinforced by Functionally Graded Carbon Nanotubes Distributions Subjected to Shock Loading using MLPG Method

Dynamic Analysis of a Layered Cylinder Reinforced by Functionally Graded Carbon Nanotubes Distributions Subjected to Shock Loading using MLPG Method

Coupled interfacial imperfections and their effects on the fracture behavior of a layered multiferroic cylinder

An interfacial imperfection coupling model is proposed to characterize the imperfect interface in a bi-layered multiferroic cylinder by extending the generalized linear spring model of the uncoupled imperfect interface. Based on the model, fracture analysis is performed on the multiferroic cylinder containing intra-layer cracks. Parametric studies on the stress intensity factor (SIF) yield three main conclusions: (a) the mechanical imperfection can enhance the SIF independently; (b) the magnetic or electric imperfection can reduce the SIF only through its coupling with the mechanical imperfection; and (c) the magneto-electric imperfection coupling does not affect the SIF in any case.

Feeding in rolling contact of layered printing cylinders

Many web handling processes involve nips through which the web passes. Due to contact deformations, the speed at which the nip cylinders feed the web may differ from the peripheral speed of the cylinders. This paper examines in detail the feeding phenomenon in the case of layered cylinders. In particular, we focus on offset printing cylinders which are covered by a thin rubbery layer. We begin our analysis by considering existing limiting solutions of thin layered cylinders undergoing small strains, and thereafter study the large deformation rolling contact problem using the finite element method. It turns out that the feeding tendency of layered cylinders is dominated by the compressibility of the layer. However, feeding characteristics of layered cylinders are not constant but rather depend on the applied indentation: an increase in indentation may even alter the feeding tendency of the cylinders. The results also indicate that the feeding type affects web strain. Consequently, we conclude that in order to attain better web handling, the feeding characteristics of the cylinders should be known.

Nonhomogeneous atherosclerotic plaque analysis via enhanced 1D structural models

The static analysis of structures with arbitrary cross-section geometry and material lamination via a refined one-dimensional (1D) approach is presented in this paper. Higher-order 1D models with a variable order of expansion for the displacement field are developed on the basis of Carrera Unified Formulation (CUF). Classical Euler-Bernoulli and Timoshenko beam theories are obtained as particular cases of the first-order model. Numerical results of displacement, strain and stress are provided by using the finite element method (FEM) along the longitudinal direction for different configurations in excellent agreement with three-dimensional (3D) finite element solutions. In particular, a layered thin-walled cylinder is considered as first assessment with a laminated conventional cross-section. An atherosclerotic plaque is introduced as a typical structure with arbitrary cross-section geometry and studied for both the homogeneous and nonhomogeneous material cases through the 1D variable kinematic models. The analyses highlight limitations of classical beam theories and the importance of higher-order terms in accurately detecting in-plane cross-section deformation without introducing additional numerical problems. Comparisons with 3D finite element solutions prove that 1D CUF provides remarkable three-dimensional accuracy in the analysis of even short and nonhomogeneous structures with arbitrary geometry through a significant reduction in computational cost.

Nonaxisymmetric Waves in Layered Hollow Cylinders with Axially Polarized Piezoceramic Layers

Nonaxisymmetric Waves in Layered Hollow Cylinders with Axially Polarized Piezoceramic Layers

Extension of the layer removal technique for the measurement of residual stresses in layered anisotropic cylinders

An extension of the layer removal technique is presented that allows the residual stresses within multilayered anisotropic pipes of any wall thickness to be determined. The method inherently satisfies the self-equilibrium requirement and limits the effects of measurement errors to the region local to the error. The thickness of each layer that is removed need not be uniform and is entirely independent of the thickness of each ply of material. Four example problems are considered. The first three allow results to be compared between the present method and previous work. The fourth problem demonstrates the method on a thick walled anisotropic pipe built up of +45°/-45° plies for which no solution was previously available.

Field dynamics in Layered Cylinder Resonator

We present the field dynamics in a layered cylinder resonator. The resonators can be re­garded as concentric ring resonators. We found that it is possible to excite the rings with clockwise and counterclockwise modes, and these modes can be separated promoting the coupling of each of these to the output ports of the buffers of the resonators.

Nonaxisymmetric Waves in Layered Hollow Cylinders with Radially Polarized Piezoceramic Layers

The problem of the propagation of nonaxisymmetric waves in layered hollow cylinders with axially polarized piezoceramic layers is solved using an effective numerical-analytic method. The three-dimensional problem of electroelasticity for partial differential equations is reduced to a boundary-value eigenvalue problem for ordinary differential equations by representing the components of the stiffness tensor, displacement vectors, electric-flux density, and electrostatic potential as a combination of standing circumferential waves and traveling axial waves. The problem is solved with the stable discrete-orthogonalization and incremental search methods. The dispersion equations are analyzed numerically over a wide range of geometrical characteristics of the cylinders.

A New Look at Azimuthal Wave Propagation Constants of an n-Layered Dielectric Coated PEC Cylinder

A method for determining the azimuthal wave propagation constants supported by an n-layered dielectric coated PEC cylinder is presented. The method, based on a Green's function described in <citerefgrp xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><citeref refid="ref1"/> </citerefgrp> , is designed to optimally handle layered cylinders where the number of layers is extremely large as might be encountered in structures designed using transformational optics. The method is also tractable for any stratification profile without the need for individual layer analysis. We implement a recently developed numerical method to calculate Bessel functions of complex order and argument. Our method is verified by comparison with previously published results. We also present new results for a 5-layer case demonstrating self consistency and improved accuracy over published methods. Finally, to illustrate the method's benefits, we present a brief analysis of two multilayer structures; a multilayer variation of the coated cylinder presented in <citerefgrp xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <citeref refid="ref2"/></citerefgrp> and an example of a 7-layer case that approximates a material parameter gradient.

DQEM for analyzing dynamic characteristics of layered fluid-saturated porous elastic media

Based on the Porous Media Theory presented by de Boer, the governing differential equations for a layered space-axisymmetrical fluid-saturated porous elastic body are firstly established, in which the suitable interface conditions between layers are presented. Then, a differential quadrature element method (DQEM) is developed, and the DQEM and the second-order backward difference scheme are applied to discretize the governing differential equations of the problem in the spatial and temporal domain, respectively. In order to show the validity of the present analysis, the dynamic response of a fluid-saturated porous medium is analyzed, and the obtained numerical results are directly compared with the existing analytical results. The effects of the numbers of the elements and grid points on the convergence of the numerical results are considered. Finally, the dynamic characteristics of a layered fluid-saturated elastic soil cylinder subjected to a water pressure or a dynamic loading are studied, and the effects of material parameters are considered in detail. From the above numerical results, it can be found that the DQEM has advantages, such as little amount in computation, good stability and convergence as well as high accuracy, so it is a very efficient method for solving the problems in soil mechanics, especially such problems with discontinuities.

Failure Analysis of a Composite Cylinder

Composite cylinders are high-strength containers made from a mixture of fibre glass or carbon fibers and a plastic resin typically epoxy. A lamina is assumed to be homogeneous and the mechanical behavior is characterized by a set of equivalent or effective moduli and strength properties. In the phenomenological approach, the lamina properties are determined experimentally by conducting tests on a single lamina or a laminate. Once the mechanical properties of the ply are known the initial failure of the ply within a laminate or structure can be predicted by applying an appropriate failure criterion. Failure types are dependent on loading, stacking sequence, and specimen geometry. There are many proposed theories to predict the one-set of failures. Most of failure criteria are based on the stress state in a lamina. The present work aims to determine the effect of diameter-to-thickness ratio 'S' with respect to failure pressure of a four layers, introduction of hoop layers at ends on four layered cylinder and introduction of hoop layers at middle of six layered angle-ply laminated cylinder which is analyzed by using Finite Element software ANSYS. The variation of failure pressure with respect to fiber angles was also presented in this work.

Stress state of layered hollow cylinders with irregularly shaped cross-section

The stress state of longitudinally corrugated layered hollow orthotropic elliptic cylinders is determined using discrete Fourier series for different geometrical parameters. The results obtained are presented in the form of plots and tables and analyzed