Bilayer Cylinders Research Articles

Non-reciprocal selective frequency transmission with nonlinear bi-layer cylinder chains

Recent advancements in wave physics have led to the development of systems that break the principle of wave transmission reciprocity. In this study, we present selective frequency transmission with asymmetry in bi-layer phononic crystals, which are composed of two layers of cylinder contact chains. We demonstrate significant non-reciprocal harmonic transmission effects, as well as self-demodulated displacement amplification under excitation from different sides. These effects are achieved through a combination of contact nonlinearity and cascaded bandgaps formed by adjusting the chain lengths in both layers. We find that the evanescent waves generated through nonlinear frequency conversion in the stopband are converted into propagating waves at the interface, subsequently leading to the transmission. Our findings have implications for programmable asymmetric acoustic devices, providing a novel framework for energy mitigation, conversion, and harvesting.

Dispersion of Torsional Waves in a Hollow Bilayered Cylinder with Initial Inhomogeneous Thermal Stresses

The influence of the inhomogeneous initial thermal stresses caused by the heating or cooling of the inner and outer surfaces of a hollow bilayered cylinder on dispersion of torsional waves propagating in this cylinder is studied. The study is performed within the scope of the second version of the 3D linearized theory of elastic waves in initially stressed bodies, according to which the initial inhomogeneous thermal stresses are determined within the scope of the classical uncoupled linear theory of thermoelasticity. The equations related to the propagation of torsional waves are solved by a discrete-analytical method, and the numerical results found are presented and discussed.

The dispersion of the axisymmetric longitudinal waves propagating in the bi-layered hollow cylinder with the initial inhomogeneous thermal stresses

The paper studies the influence of the initial inhomogeneous thermal stresses on the dispersion of the axisymmetric longitudinal waves propagating in the bi-layered hollow cylinder within the scope of the 3D linearized theory of elastic waves in initially stressed bodies. The initial static thermal stresses are determined within the scope of the uncoupled classical linear theory of thermo-elasticity and it is assumed that the temperature change in the cylinder is caused by the heating or cooling of the inner and outer surfaces of the cylinder. The discrete analytical solution method is employed for the solution to the corresponding equations of the wave propagation. Concrete numerical results are obtained for the cylinder, the materials of the layers of which are steel and aluminum, as well for the cylinder made of steel only. Numerical results on the influence of the initial inhomogeneous thermal stresses on the dispersion curves related to the first, second and third modes are presented and discussed. In particular, it is established that the cooling or the heating of the outer and inner surfaces of the bi-layered hollow cylinder influences the dispersion curves not only in the quantitative sense, but also in the qualitative sense.

Torsional wave dispersion in a bi-layered hollow cylinder with inhomogeneous initial stresses caused by internal and external radial pressures

The present paper studies the influence of the inhomogeneous initial stresses in the bi-layered hollow cylinder and it is assumed that these stresses are caused by the hydrostatic pressures acting on the interior and outer free surfaces of the cylinder. The study is made by utilizing the version of the three-dimensional linearized theory of elastic waves in bodies with initial stresses for which the initial stress-strain state in bodies is determined within the scope of the classical linear theory of elasticity. For the solution to the corresponding eigenvalue problem, the discrete-analytical method is employed. Numerical results are presented and analyzed for concrete selected pairs of materials. According to these results and their analyses, it is established that, unlike homogeneous initial stresses, the influence of the inhomogeneous initial stresses on the torsional wave dispersion has not only quantitative but also qualitative character. For instance, in particular, it is established that as a result of the initial stresses caused by the hydrostatic pressure acting in the interior free surface of the cylinder, the cut-off frequency appears for the fundamental dispersive mode and the values of this frequency increase with the intensity of this pressure.

Stress control of cylinders during water entry based on the characteristics of bi-material interfaces

This paper is devoted to stress control of cylinders during water entry based on the characteristics of bi-material interfaces. Firstly, the influence factors on dynamic stress are studied from the view of elastic mechanics and wave mechanics. It is found that the dynamic stress depends on the material parameters, material layout, natural frequency and deformation. On this basis, a sandwich scheme is proposed to reduce the stress level of the cylinder entering water. Then a sandwich cylinder, two bi-layer cylinders and two monolithic cylinders during water entry are investigated by coupling of smoothed particle hydrodynamics (SPH) and finite element method (FEM). It is found that when the material parameters are given, the deformation and natural frequency of the sandwich cylinder are moderate, but its stress level is significantly lower than that of other cylinders under the same initial conditions, attributing to its unique material layout. Accordingly, the limit velocity of the sandwich cylinder colliding with water is much higher than that of other cylinders. Therefore, the stress control scheme is expected to reduce the possibility of strength failure of cylindrical structure during water entry.

Axisymmetric longitudinal wave dispersion in a bi-layered circular cylinder with inhomogeneous initial stresses

The paper studies the axisymmetric longitudinal wave propagation in a bi-layered hollow cylinder with inhomogeneous initial stresses by utilizing the 3D linearized theory of elastic waves in initially stressed bodies. It is assumed that the initial stresses in the cylinder are caused by the internal and external hydrostatic pressures. Assuming that the materials of the layers of the cylinder are sufficiently stiff, these initial stresses are determined within the scope of the classical linear theory of elasticity. The discrete analytical method is employed for the solution to the corresponding 3D linearized equations of motion. The dispersion equation is obtained which is solved numerically for various values of the problem parameters. As a result of this solution, the dispersion curves are constructed and, according to these curves, the character of the influence of the inhomogeneous initial stresses on the dispersion curves obtained for the lowest first and second modes is established. Analysis of the results shows that the inhomogeneous initial stresses not only quantitatively but also qualitatively act on the character of the dispersion curves.

The influence of the rheological parameters on the dispersion of the flexural waves in a viscoelastic bi-layered hollow cylinder

The paper investigates the influence of the rheological parameters which characterize the creep time, the long-term values of the mechanical properties of viscoelastic materials and a form of the creep function around the initial state of a deformation of the materials of the hollow bi-layered cylinder on the dispersion of the flexural waves propagated in this cylinder. Constitutive relations for the cylinder\'s materials are given through the fractional exponential operators by Rabotnov. The dispersive attenuation case is considered and numerical results related to the dispersion curves are presented and discussed for the first and second modes under the first harmonic in the circumferential direction. According to these results, it is established that the viscosity of the materials of the constituents causes a decrease in the flexural wave propagation velocity in the bi-layered cylinder under consideration. At the same time, the character of the influence of the rheological parameters, as well as other problem parameters such as the thickness-radius ratio and the elastic modulus ratio of the layers\' materials on the dispersion curves, are established.

Double-Layer Morphologies from a Silicon-Containing ABA Triblock Copolymer.

A combined experimental and self-consistent-field theoretical (SCFT) investigation of the phase behavior of poly(stryrene- b-dimethylsiloxane- b-styrene) (PS- b-PDMS- b-PS, or SDS32) thin films during solvent vapor annealing is presented. The morphology of the triblock copolymer is described as a function of the as-cast film thickness and the ratio of two different solvent vapors, toluene and heptane. SDS32 formed terraced bilayer morphologies even when the film thickness was much lower than the commensurate thickness. The morphology transitioned between bilayer cylinders, bilayer perforated lamellae, and bilayer lamellae, including mixed structures such as a perforated lamella on top of a layer of in-plane cylinders, as the heptane fraction during solvent annealing increased. SCFT modeling showed the same morphological trends as a function of the block volume fraction. In comparison with diblock PS- b-PDMS with the same molecular weight, the SDS32 offers a simple route to produce a diversity of well-ordered bilayer structures with smaller feature sizes, including the formation of bilayer perforated lamellae over a large process window.

On the attenuation of the axisymmetric longitudinal waves propagating in the bi-layered hollow cylinder made of viscoelastic materials

The paper studies the attenuation of the axisymmetric longitudinal waves propagating in the bi-layered hollow cylinder made of linear viscoelastic materials. Investigations are made by utilizing the exact equations of motion of the theory of viscoelasticity. The dispersion equation is obtained for an arbitrary type of hereditary operator of the materials of the constituents and a solution algorithm is developed for obtaining numerical results on the attenuation of the waves under consideration. Specific numerical results are presented and discussed for the case where the viscoelasticity of the materials is described through fractional-exponential operators by Rabotnov. In particular, how the rheological parameters influence the attenuation of the axisymmetric longitudinal waves propagating in the cylinder under consideration, is established.

지르코니아 프라이머 종류에 따른 복합레진-지르코니아의 전단결합강도

Purpose: The aim of this research was to evaluate the influence of different surface treatments on the shear bond strength of zirconia ceramic to composite resin. Methods: Seventy two cylinder-shape (diameter: 5 mm; height: 12 mm) blocks of experimental industrially manufactured Y-TZP ceramic were abraded with <TEX>$125{\mu}m\;Al_2O_3$</TEX> particles and randomly divided into 4 groups. All the materials were categorized as group Gc(control group - composite resin veneering on zirconia surface), Gr - composite resin veneering after surface treatment of Rocatec system (3M ESPE, Seefeld, Germany) group; Gz - composite resin veneering after surface treatment of Zirconia primer (Z-primer, Bisco, U.S.A) group; Gm - composite resin veneering after surface treatment of zirconia primer (Monobond plus, ivoclar vivadent AG, Liechtenstein) group. Two different zirconia primers and Rocatec system were used to zirconia cylinders (n=16) onto the zirconia surface. Zirconia specimens, polished and roughened, were pretreated and composite bilayer cylinders bonded using conventional adhesive techniques. Results: Shear bond strengths were analyzed using single-factor ANOVA(p<0.05). Bond strength values achieved after airbone particle abrasion and zirconia surface pre-treatments(p<0.05). Conclusion: Shear bond strength tests denmonstrated that zirconia primer is a viable method to improved bond strength between zirconia ceramic core and veneering composites.

On the dispersion of the axisymmetric longitudinal wave propagating in a bi-layered hollow cylinder made of viscoelastic materials

The paper deals with the study of axisymmetric longitudinal fundamental wave propagation (dispersion) in the bi-layered hollow circular cylinder made of linear viscoelastic materials. The investigations are made by utilizing the exact equations of linear viscoelasto-dynamics. The corresponding dispersion equation is derived for an arbitrary type of hereditary operator and the algorithm is developed for its numerical solution. Concrete numerical investigations are made for the case where constitutive relations of the layers’ materials of the cylinder are described through fractional exponential operators. The influence of the viscosity of the layers’ materials of the hollow cylinder on the wave dispersion is studied through the rheological parameters which indicate the characteristic creep time and long-term values of the elastic constants of these materials. Dispersion curves are presented for certain selected dispersive and non-dispersive attenuation cases under various values of the problem parameters and the influence of the aforementioned rheological parameters on these curves is discussed. As a result of the numerical investigations, in particular, it is established that in the case where the rheological parameters of the layers are the same, the viscosity of the layers’ materials causes the axisymmetric wave propagation velocity to decrease.

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.

Electret electrostatic cloak

We report that a bi-layer electret cylinder can cloak electrostatic field. We fabricated two hollow electret cylinders, the two hollow electret cylinders nested a bi-layer hollow electret cylinder. The direction of the polarization intensity is parallel to one of the diameters. Experimental results show that the bi-layer hollow electret cylinder can cloak electrostatic field.

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.

Derivation of the diffusion impedance of multi-layer cylinders. Application to the electrochemical permeation of hydrogen through Pd and PdAg hollow cylinders

The purpose of this research paper is to report on the diffusion impedance of multi-layer cylinders. Analytical expressions of the diffusion impedance in multi-layer solid cylinders (sorption/desorption experiments) and through multi-layer hollow cylinders (permeation experiments) have been obtained by integration of Fick's diffusion equation in cylindrical coordinates. The resulting impedances are expressed as a function of the characteristics of individual active layers (layer thickness, diffusion coefficient and solubility of diffusing species in each layer). These impedance expressions can be used to characterize a large variety of experimental systems. In this work, model impedances have been used to fit experimental impedances of hydrogen permeation through Pd and Pd77Ag23/Pd mono- and bi-layer hollow cylinders, yielding the values of microscopic rate parameters (surface charge transfer resistances, diffusion coefficient). Analytical expressions of low frequency limits (stationary conditions of flow) have been derived. Practical conditions required for the separation of the contributions of the different layers are analyzed. Some limitations and perspectives offered by this work are discussed.

On the harmonic magnetoelastic behavior of a composite cylinder with an embedded polynomial eigenstrain

This article presents closed-form solutions of displacement and stress components for a dynamic eigenstrain problem in a bi-layered coaxial cylinder. The cylinder could be axisymmetric and infinitely long with plane strain condition, or axisymmetric and thin with plane stress condition. The inner layer experiences a harmonic eigenstrain with cubic polynomial distribution in the radial direction. The layers are assumed to be imperfectly bonded and the cylinder is subjected to an external constant magnetic field. The harmonic governing differential equations including the Lorentz force effect are analytically solved. The results illustrate the effect of external magnetic field, cubic polynomial eigenstrain, and imperfect boundary conditions on the magnetoelastic response of the composite cylinders with plane strain and plane stress conditions.

Electric field induced pearling instability in cylindrical vesicles

A theoretical and experimental study on the effect of an electric field on a cylindrical vesicle is presented. Experiments show that a cylindrical vesicle when subjected to an axial electric field, displays an axisymmetric pearling instability (the Rayleigh–Plateau instability) beyond a threshold electric field. Unlike fluid jets, in which electric fields are known to stabilize the Rayleigh–Plateau instability, cylindrical vesicles exhibit dual effects of electric field. The tension required to induce the instability is produced by the electric field. At higher values of field strength however, a stabilizing action of the electric field is seen. This renders the fastest growing wavenumber, km, independent of the electric field at high electric field strength. Theoretical results predict, albeit qualitatively, a weak dependence of km on the electric field. It also explains the substantially higher experimental values of km (around 0.64–1.0) observed in vesicles as compared to km = 0.56 for fluid cylinders. Theory and experiments show that the instability is induced using a much lower value of pulsed DC field as compared to an AC field. At long times, a pearled state is observed, with the pearls separated by short cylindrical nanotubules. The pearled structure is converted into crowded, taut spherical globules, which are connected by very thin short bilayer cylinders when the field is switched off, before they eventually disappear and the original cylindrical vesicle is recovered. All of the morphological changes in cylindrical vesicles in electric fields are completely reversible. This study demonstrates the dominance of tension and stretching at short and long timescales respectively.

The amphipathic helix of an enzyme that regulates phosphatidylcholine synthesis remodels membranes into highly curved nanotubules

CTP:phosphocholine cytidylyltransferase (CCT) is an amphitropic protein regulating phosphatidylcholine synthesis. Lipid-induced folding of its amphipathic helical (AH) membrane-binding domain activates the enzyme. In this study we examined the membrane deforming property of CCT in vitro by monitoring conversion of vesicles to tubules, using transmission electron microscopy. Vesicle tubulation was proportional to the membrane density of CCT and proceeded either as growth from a pre-formed surface bud, or as a global transformation of roughly spherical vesicles into progressively thinner tubules. The tubulation pathway depended on the lipid compositional heterogeneity of the vesicles, with heterogeneous mixtures supporting the bud-extension pathway. Co-existence of vesicles alongside thick and thin tubules suggested that CCT can discriminate between flat membrane surfaces and those with emerging curvature, binding preferentially to the latter. Thin tubules had a limiting diameter of ~12nm, likely representing bilayer cylinders with a very high density of 1 CCT/50 lipids. The AH segment was necessary and sufficient for tubulation. AH regions from diverse CCT sources, including C. elegans, had tubulation activity that correlated with α-helical length. The AH motifs in CCT and the Parkinson's-related protein, α-synuclein, have similar features, however the CCT AH was more effective in its membrane remodeling function. That CCT can deform vesicles of physiologically relevant composition suggests that CCT binding to membranes may initiate deformations required for organelle morphogenesis and at the same time stimulate synthesis of the PC required for the development of these regions.

Electromagnetic analysis of specular resonance by periodic bilayer cylinders

Specular resonance by periodic bilayer cylinders is electromagnetically analyzed for the first time to our knowledge. The phenomenon occurs when the radius is roughly 0.8 times the wavelength. It is also discovered that the structure behaves as a good guided-mode resonant grating filter when the radius is around 0.4 times the wavelength.

Bulk waves excited by a laser line pulse in a bi-layer cylinder

In this paper, the transient displacement excited by a laser line source is calculated for a bi-layer cylinder made of homogeneous and isotropic materials. A sample made by welding tin in a copper tube and a sample of cooper rod are considered. Experimental displacements are observed by the laser ultrasonic technique, and corresponding theoretical waveforms are calculated. Good agreement is found in the arrival time, shape and relative amplitude of various longitudinal and shear bulk waves propagating through the sample or reflected by the interface.