Anisotropic Shells Research Articles

Analysis of deformability of composite laminated anisotropic cylindrical shells in the conceptual design of mechanical transducers and actuators

Analysis of axisymmetric deformability of mechanical transducers and actuators made in the form of composite anisotropic cylindrical shells subjected to axial tension or internal pressure is presented in the paper. The shells are modelled as cantilevers with one end fully clamped and another one free hanging with a rigid solid disk attached. Based on the analytical solution obtained and formulas derived, the conversion of the axisymmetric loading (axial load or internal pressure) to the shell torsion is analysed. Effects of material elastic characteristics, angle of the reinforcement orientation, and shell dimensions on the shell deformability and the value of the reactive shear force are illustrated using the analysis of anisotropic single-layered shells. It is shown that the angle of rotation and the reactive shear force have their maximum values at certain angles of the fibre orientation. Relationships between the shells’ lengths, thicknesses and the angles of the disk rotation or corresponding reactive shear forces are identified. It is shown, based on these equations, how the parameters of an anisotropic shell, delivering a required angle of the disk rotation, can be calculated.

Theory of the multilayer thin anisotropic shells, based on the asymptotic analysis of the general equations for the elasticity theory

A new theory of thin multilayer anisotropic elastic shells is proposed, based on the application of the asymptotic analysis over small geometric parameter to the general 3-dimensional equations of the elasticity theory for curvilinear coordinates. In deriving the equations of the shell theory no assumptions are made concerning to the distribution of displacements, deformations, or displacements trough thickness. Recurrent consequences of local problems of the elasticity theory for shells are formulated and an analytical solutions are obtained. The averaged equations of the asymptotic theory of shells that are of the same type as the classical equations of the Kirchhoff-Love theory of shells are derived. It is shown that the asymptotic theory makes it possible to obtain in explicit form the distributions of all 6 components of the stress tensor over the thickness of the shell. An example of the calculation of a cylindrical shell under axisymmetric bending is considered. The case of monoclinic shell layers, which have no more than 13 independent elastic constants, is considered. An algorithm is proposed for obtaining explicit analytical equations for calculating the distribution of components of the total stress tensor over the cylindrical shell. The effect of the geometric d imensions of the shell on the character of the distribution of displacements and stresses in the shell is analyzed.

Coupled Thermoelasticity Problem for Multilayer Composite Shells of Revolution. II. Applied Problems

We deduce a system of nonclassical nonlinear differential equations of coupled thermoelasticity for multilayer composite anisotropic shells of revolution in a coordinate system connected with the lines of curvature of the reference surface. The constructed nonclassical model of deformation of a multilayer shell and the nonlinear model of distribution of heat fluxes over the thickness of the shell enable us to take into account the transverse shear strains and guarantee the validity of the conditions of thermal and mechanical conjugation of the layers and the conditions of thermomechanical loading on the faces of the shell. We deduce the linearized differential equations of the axisymmetric coupled problem of thermoelasticity for a conic reinforced multilayer shell and solve the quasistatic problem of thermoelasticity for a two-layer cylindrical shell cross-reinforced in the direction of helical lines. By using the structural approach to the formulation of the criteria of strength for composite materials, we determine the loads of the onset of fracture of the binder and reinforcing elements of a two-layer metal-composite cylindrical shell.

Complex Resonances of Anisotropic Spherical Resonators

In this paper, we report the complex resonant frequencies of inhomogeneous anisotropic spherical resonators. The anisotropy can be of gyroelectric or gyromagnetic type, having one isotropic axis. Two kinds of configurations are considered: an anisotropic sphere and an anisotropic spherical shell coating a concentric perfect electric conducting core. Two full-wave methods are employed for the calculation and verification of the resonances. The first is a method based on the weak form of the coupled-field surface-volume integral equation (CFSVIE), which is solved using entire domain basis functions of Dini-type. The second is the discrete eigenfunction method (DEM) that allows the expansion of the unknown fields in the region of anisotropy in terms of spherical vector wave functions. Both the CFSVIE and the DEM are validated by comparisons with separation of variables method, regarding isotropic and metallic-isotropic resonators. It is shown that commercial packages, such as HFSS, cannot address the full spectrum of such open structures. Numerical results for complex resonances, verified by both the CFSVIE and the DEM, are given for various anisotropic configurations. Finally, magnetic plasmon resonances are particularly examined in ferromagnetic resonators.

A transformation theory for camouflaging arbitrary heat sources

Camouflage devices have attracted intensive research interest for their significant applications. However, most camouflage devices are specifically designed according to target heat sources. Here, by applying the transformation thermotics approach, we develop a coordinate transformation, and design an unspecific camouflage device which can camouflage arbitrary heat sources into a circular one with an anisotropic shell. We verify the ability of our unspecific camouflage device with both steady and transient simulations. We also find the “apparent negative thermal conductivity” under certain conditions without violating the second law of thermodynamics. To ensure the feasibility, we further put forward the effective medium approximation for sample fabrication, and only two natural materials are required. Our results have relevance to the different applications of infrared misleading, uniform heating, and so on; they may also provide guidance to the research on other diffusive fields, such as magnetostatic and electrostatic fields.

The evolution of anti-vortex like domain under electric field in polycrystalline ferroelectric

Domain wall (DW) plays an important role in the domain evolution. The anti-vortex could be a special domain structure of the mixed DWs, i.e. the Ising wall and the Mixed Ising-Neel wall. The anti-vortex domain in polycrystalline ferroelectric has been investigated by a modified first-principles-based atomistic method incorporating the anisotropic shell model. Results show that the nucleation and the disappearance of the anti-vortex happen at grain boundaries (GBs) under sinusoidal electric fields loading. As the anti-vortex motion by the electric field, it is a perfect view point for the domain evolutions. It has been found that the anti-vortex core can't pass through the GBs because of the size and disorder field. This phenomenon indicates that anti-vortex is only been obtained in grains at polycrystalline ferroelectric, and the electric field range must between −6.3 and 6.3 × 108 V/m.

Tip-Functionalized Au@Ag Nanorods as Ultrabright Surface-Enhanced Raman Scattering Probes for Bioimaging in Off-Resonance Mode

Surface-enhanced Raman scattering (SERS) performance of Au nanorods (AuNRs) can be enhanced by the tip adsorption of Raman molecules (RMs) through anisotropic polymer stabilization or through the embedding of RMs between AuNR cores and Ag shells of AuNR@RM@Ag composite particles. We propose a new strategy to design ultrabright SERS probes composed of high-aspect-ratio AuNRs with anisotropic Ag coatings, with preferred adsorption of RMs to open AuNR tips. Specifically, for 4-nitrobenzenethiol (NBT) concentrations above a threshold value c > ctr, the fabricated Au@NBT@Ag particles had NBT-functionalized open Au tips, as well as anisotropic Ag shells grown on the AuNR sides. The SERS response of these probes with an optimal Ag shell was highest in the off-resonance mode, when the excitation wavelength was far from the plasmon resonance of the Au@NBT@Ag composites. Growing the Ag shell further to completely cover the AuNRs decreased the SERS enhancement. For biocompatibility and stability, the probes were add...

Transient responses of laminated anisotropic piezothermoelastic plates and cylindrical shells with interfacial diffusion and sliding in cylindrical bending

With aid of the Stroh-type formalism and the state-space approach, a simple and elegant method is presented to obtain an exact solution for the time-dependent problem of a simply-supported laminated anisotropic piezothermoelastic plate in cylindrical bending with interfacial diffusion and sliding. The Stroh-type formalism is used to obtain the general solution of the thermoelectroelastic field in a certain layer. The state-space equation is then constructed for a laminated plate. The relaxation times and the transient thermoelectroelastic response of the laminated plate can be determined by solving the state-space equation via an analysis of a generalized eigenvalue problem. By using a similar method, we also derive an exact solution for a simply-supported laminated anisotropic piezothermoelastic cylindrical shell with interfacial diffusion and sliding under cylindrical bending.

Cloaking and magnifying using radial anisotropy in non-integer dimensional space

This manuscript studies the impact of non-integer dimensional (NID) space on cloaking and magnification introduced through polarly radially anisotropic (PRA) cylindrical shell/spherically radially anisotropic (SRA) spherical shell. By selecting appropriate value of ratio, between components of tensor permittivity, these structures in ordinary space (α=3) can yield cloaking and magnification under the quasi-static limit. In case of NID space (α≠3), PRA cylindrical shell can only yield cloaking. It has been shown that bound on anisotropy ratio get effected by the NID parameter in case of PRA shell. It has also been noted that magnification cannot be achieved using PRA shell in NID space. Further, cloaking and magnification of SRA shell remains independent of parameter describing NID space.

A new model for wave propagation in functionally graded anisotropic doubly-curved shells

This research is devoted to an investigation on the wave propagation in doubly-curved shell made of Functionally Graded Anisotropic materials in the framework of an accurate higher order shear deformation theory. In this recently developed theory, an exponential formula in combination with a trigonometric function are used for modeling the displacement field. This type of theory has only five unknowns but it seems that it can have precise results in various conditions for thick and thin shells. In the functionally graded anisotropic material, all components of the elastic stiffness tensor and density are varied exponentially through the thickness direction. Hamilton’s principle is utilized with the purpose of deriving the governing equations in orthogonal curvilinear coordinates. The analytical dispersion relations are obtained by solving an eigenvalue problem. These methods are validated by comparing authors’ results with other papers available in open literature for isotropic and functionally graded plates. Detailed parametric studies are then carried out to scrutinize the influences of wave number, geometrical shape, exponential factor and volume fraction index on the circular frequencies, phase velocities and group velocities. From the best knowledge of authors, it is the first time that functionally graded anisotropic doubly-curved shells are investigated in open literature.

Directive electromagnetic radiation of a line source scattered by a PEMC cylinder coated with anisotropic media

ABSTRACTIn this paper, the electromagnetic radiation of a line source scattered by an infinite perfect electromagnetic conductor (PEMC) coated with anisotropic media is analytically analyzed. A line source is placed inside the anisotropic media. To validate the presented formulas, the radiation patterns for isotropic cases are compared to the published literature and good agreement is found between them. Also, the directivity of the electromagnetic radiation pattern is improved using the anisotropic coating. Furthermore, when the line source is placed on the surface of PEMC core and the relative tensors of anisotropic shell are appropriately chosen, the co- and cross-polarization components of the fields form the same radiation patterns.

Structural and Dynamical Nature of Hydration Shells of the Carbonate Ion in Water: An Ab Initio Molecular Dynamics Study.

The structural and dynamical nature of hydration shells of the carbonate ion in water is investigated through ab initio molecular dynamics simulation. The anisotropic solvation shell structure of the ion is resolved by calculating conically restricted pair distribution and radial/angular correlation functions. The vibrational frequency of OD modes hydrogen-bonded to the ion is found to be smaller than that of bulk water, which means the carbonate ion-water hydrogen bonds are stronger than those between water molecules. Calculations of the orientational and residence dynamics and translational diffusion reveal retarded mobility of the hydration shell water molecules compared to that of the bulk water due to stronger ion-water interactions. It is shown that the rotation of hydration shell water takes place through dual routes of hydrogen bond switching, where an OD bond initially hydrogen-bonded to a carbonate oxygen switches its hydrogen bond to another carbonate oxygen or to a water oxygen. The carbonate ion is found to have a nonzero dipole moment of 1.0 D in water, which can be attributed to its interactions with the fluctuating environment of the surrounding water. The carbonate ion is also found to have a long-range effect on neighboring water molecules that goes beyond the first solvation shell.

Dynamics of water in conical solvation shells around a benzene solute under different thermodynamic conditions.

Water molecules in different parts of the anisotropic hydration shell of an aromatic molecule experience different interactions. In the present study, we investigate the anisotropic dynamics of water molecules in different non-overlapping conical shells around a benzene solute at sub- and supercritical conditions by means of molecular dynamics simulations using both non-polarizable and polarizable models. In addition to the dynamical properties, the effects of polarizability on the hydration structure of benzene at varying thermodynamic conditions are also investigated in the current study. The presence of πH-bonding in the solvation shell is found to be an important factor that influences the anisotropic dynamics of the benzene hydration shell. The water molecules located axial to the benzene plane are found to be maximally influenced by the πH-bonding. The extent of πH-bonding is found to be somewhat reduced on inclusion of polarizability. The πH-bonded water molecules are found to reorient through large-amplitude angular jumps where the jump-angle amplitude increases at higher temperatures and lower densities. For both non-polarizable and polarizable models, it is found that the water molecules in the axial conical shells possess faster orientational and hydrogen bond dynamics compared to those in the equatorial plane. Water molecules in the axial conical shells are also found to diffuse at a faster rate than bulk molecules due to the relatively weaker benzene-water πH-bonding interactions in the axial region of the hydration shell. The residence dynamics of water molecules in different conical solvation shells around the solute is also investigated in the current study.

Features of modeling of energy profile of construction

Presentation and realization of the task of rationalization of structural parameters of reinforced concrete shells is presented. As a criterion for this task an energy principle is adopted, according to which it is assumed that from the whole set of possible values of the desired parameters of the system with a constant volume of material, the number of external and internal connections, the potential energy of deformation (DER) after the reconstruction will reach the lower limit on a rational combination of values of geometric parameters. The energy principle is taken as a criteria on for this task, according to which it is believed that out of numerous possible values of the searched parameters of the system with the constant amount of material, number of external and internal connections, the strain potential energy (SPE) after the reconstruction will reach the lower limit on the rational connection of the geometrical parameters describing the system. The determined interconnection of the rational parameters of the constructive anisotropic shell between SPE of the system of internal and external rational parameters: with ribs step value of about l ≈ 1000 mm SPE reaches the lower limit.

Atomic scale study of the anti-vortex domain structure in polycrystalline ferroelectric

A modified first-principles-based atomistic method incorporating the anisotropic shell model is developed for the simulation of the vortex-type polarisation in polycrystalline ferroelectric. Based on the modified model, a series of distinct vortex and anti-vortex polarisation configurations are obtained at atomic scale simulation in which the anti-vortex polarisation configuration in polycrystalline ferroelectric has never been reported in the open literature. In this study, a standard definition is given to the polarised anti-vortex in mathematics and polarisation topology. The accurate distribution has been obtained from the simulation and validated by analogy of the vortex field using the Landau–Ginzburg–Devonshire theory. The properties of the anti-vortex are studied to establish the relationship among the polarisation value of the vector, the radius and the streamlines curvature of the anti-vortex. Based on the polarisation mechanism, a method is proposed for experimenters to observe clearly and position accurately the polarisation anti-vortex and vortex, which could combine as novel domain structure.

Stability of Inhomogeneous Cylindrical Shells Under Distributed External Pressure in a Three-Dimensional Statement

The problem of the stability of anisotropic cylindrical shells is numerically solved in a three-dimensional statement. The shells are made of a material with one plane of elastic symmetry. By using the Bubnov–Galerkin method to approximate unknown functions with respect to the longitudinal coordinate by trigonometric series, the problem is reduced to a one-dimensional one that is solved by the discrete-orthogonalization method. The results are tested.

Thermosensitive polymer stabilized core-shell AuNR@Ag nanostructures as “smart” recyclable catalyst

Core-shell AuNR@Ag nanostructures were synthesized and surface-grafted with thermosensitive poly(N-isopropylacrylamide) to enhance stability and endow stimuli-responsive property. The AuNR cores showed average dimensions of 8-nm diameter and 33-nm length, while the anisotropic silver shells displayed 1–2 nm thin side and maximal 8 nm fat side. The obtained polymer-stabilized AuNR@Ag nanostructures as catalysts showed normal Arrhenius change of apparent rate constant, k app, in catalyzed reaction between 20 and 30 °C, but displayed a decrease of k app with respect to the temperature increasing between 32.5–40 °C, showing self-inhibition of the observed catalytic activity. Such “smart” self-inhibition of catalytic activity at enhanced temperature can be attributed to the thermosensitive response of the grafted polymer molecules and should be significant to control the reaction rate and avoid superheat for exothermic reactions. Such polymer-stabilized nanocatalyst also could be recovered and reused in the catalytic system.

Dynamics of Geometrically Nonlinear Elastic Nonthin Anisotropic Shells of Variable Thickness

A theory of dynamic elastic geometrically nonlinear deformation of nonthin anisotropic shells with variable thickness is constructed. Shells are assumed asymmetric about the reference surface. Functions are expanded into Legendre series. The basic equations are written in a coordinate system aligned with the lines of curvature of the reference surface. The equations of motion and appropriate boundary conditions are obtained using the Hamilton–Ostrogradsky variational principle. The change in metric across the thickness is taken into account. The theory assumes that the refinement process is regular and allows deriving equations including products of terms of Legendre series of unknown functions of arbitrary order. The behavior of a square metallic plate acted upon by a pressure pulse distributed over its face is studied.

Semi-analytical postbuckling strength analysis of anisotropic shell structures

An investigation of the forms of shell buckling has been the subject of many experimental and theoretical studies. On the basis of analysing of the forms of equilibrium it is possible to determine the stability of a structure as a whole, especially if a statistical analysis is used. The numerical analysis of the shells considered is based on a semi-analytical treatment of displacement and stress field. This method is proven for static and dynamic nonlinear analysis of general shells of revolution and leads to important advantages in efficiency and accuracy compared with a common finite element analysis, especially in the case of geometrically imperfect shells. The method developed permits determination of stresses in a shell by means of an experimental deflection function. Failure criterion allows predicting the sites of fracture and maintenance of a shell upon loss of stability.

Synthesis and Luminescence Properties of Water Soluble \u03b1-NaGdF4/\u03b2-NaYF4:Yb,Er Core\u2013Shell Nanoparticles

Hexagonal phase (β) sodium rare earth tetrafluorides (NaREF4, RE = Y, Gd, Lu, et al.) are considered the ideal matrices for lanthanide (Ln) ions doped upconversion (UC) luminescence materials, because they can provide favorable crystal lattice structures for the doped luminescent Ln ions to make intensive emissions. However, the cubic phase (α) NaREF4 always preferentially forms at low reaction temperature in short time as it is dynamically stable. Therefore, it is hard to obtain small sized β-NaREF4 via the traditional solvothermal method. In this paper, small sized β-NaYF4:Yb,Er nanoparticles were synthesized by a heterogeneous-core-induced method via the solvothermal reaction. The heterogeneous α-NaGdF4/β-NaYF4: Yb, Er core–shell structure was confirmed by the local elemental mapping. The formation mechanism of β-NaYF4:Yb,Er shell on the surface of α-NaGdF4 core was explained in detail. We reasoned that a hetero interface with a lower lattice symmetric structure was produced by cation exchanges between the core and shell, which caused the preferential growth of anisotropic hexagonal phase shell. The existence of this hetero interface has also been proven by observation of Gd3+ UC emission.