Multilayered Shells Research Articles

Investigation of Adopting Shrink-Fit Multilayered Aluminum Shell in High-Field Common-Coil Accelerator Dipole Magnet

This paper presents the shrink-fit multilayered aluminum shell (SMAS) used for withstanding large Lorentz force in a 20-T shell-based common-coil accelerator dipole magnet. Finite element analysis (FEA) is carried out to optimize the required shell thickness when a single layer aluminum shell is used to support the 20-T dipole magnet. Also, FEA is carried out to study the performance of a three-layer SMAS used in the same dipole magnet. The analyzed results indicate that the three-layer SMAS with thickness of 75 mm can help us to reduce the peak shell stress significantly compared to a 75-mm-thick single layer aluminum shell when they provide the same preload to the coils. Some preliminary experiments have been carried out which prove that the initial stress distribution in the SMAS can be well controlled after the assembly. Hopefully, the outer diameter of the twin-aperture 20-T common-coil dipole magnet can be restricted to 900 mm if we use a three-layer SMAS as the support structure.

TESTING OF NUMERICAL SOLUTION OF THE PROBLEM OF DETERMINING SOURCES OF MAGNETOSTATIC FIELD IN MAGNETIZED MEDIUM

Purpose. Testing of numerical solution algorithm for integral equation for calculation of plane meridian magnetostatic field source distribution at interfaces of piecewise homogeneous magnetized medium by means of electrostatic analogy. Methodology. The piecewise homogeneous medium consists of three regions with different magnetic permeabilities: the shell of arbitrary meridian section, external unlimited medium outside the shell, and the medium inside the shell. For testing external homogeneous magnetic field effect on spherical shell is considered. The analytical solution of this problem on the basis of electrostatic analogy from the solution of the problem uniform electrostatic field effect on dielectric shell is obtained. We have compared results of numerical solution of integral equation with the data obtained by means of analytical solution at the variation of magnetic permeabilities of regions of medium. Results. Integral equation and the algorithm of its numerical solution for calculation of source field distribution at the boundaries of piecewise homogeneous medium is validated. Testing of integral equations correctness for calculation of fictitious magnetic charges distribution on axisymmetric boundaries of piecewise homogeneous magnetized medium and algorithms of their numerical solutions can be carried out by means of analytical solutions of problems of homogeneous electrostatic field effect analysis on piecewise homogeneous dielectric medium with central symmetry of boundaries – single-layer and multilayer spherical shells. In the case of spherical shell in wide range of values of the parameter λk, including close to ± 1, numerical solution of integral equation is stable, and relative error in calculating of fictitious magnetic charges surface density and magnetic field intensity inside the shell is from tenths of a percent up to several percent except for the cases of very small values of these quantities. Originality. The use analytical solutions for problems of calculation of external electrostatic field effect on piecewise homogeneous dielectric bodies for testing integral equations of magnetostatics and algorithms for their numerical solutions. Practical value. The described method of testing integral equations of magnetostatics and their numerical solutions can be used for calculation of magnetic fields of spacecraft control system electromagnets.

Equations of equilibrium for a strongly heterogeneous shallow shell

A linear set of equations is proposed for a strongly thickness-heterogeneous (in particular, multilayer) shallow shell. The model unifies the equations of the Mushtary−Donnell−Vlasov technical-theory and the Timoshenko−Reissner equations, which take into account transverse shear. The thickness-heterogeneous shell is replaced with an equivalent homogeneous transversally isotropic shell, the elasticity modula of which are chosen just as the previously determined elasticity modula for heterogeneous plates. In the test example for a multilayered cylindrical shell, the approximate solution according to the proposed model is compared with the exact solution of the three-dimensional problem. The model gives good results in accuracy for a reasonably wide level of inhomogeneity.

Multiple Water-in-Oil-in-Water Emulsion Gels Based on Self-Assembled Saponin Fibrillar Network for Photosensitive Cargo Protection.

A gelled multiple water-in-oil-in-water (W1/O/W2) emulsion was successfully developed by the unique combination of emulsifying and gelation properties of natural glycyrrhizic acid (GA) nanofibrils, assembling into a fibrillar hydrogel network in the continuous phase. The multiple emulsion gels had relatively homogeneous size distribution, high yield (85.6-92.5%), and superior storage stability. The multilayer interfacial fibril shell and the GA fibrillar hydrogel in bulk can effectively protect the double emulsion droplets against flocculation, creaming, and coalescence, thus contributing to the multiple emulsion stability. Particularly, the highly viscoelastic bulk hydrogel had a high storage modulus, which was found to be able to strongly prevent the osmotic-driven water diffusion from the internal water droplets to the external water phase. We show that these multicompartmentalized emulsion gels can be used to encapsulate and protect photosensitive water-soluble cargos by loading them into the internal water droplets. These stable multiple emulsion gels based on natural, sustainable saponin nanofibrils have potential applications in the food, pharmaceutical, and personal care industries.

Delamination onset and growth in composite shells

In this paper an efficient numerical tool is proposed to investigate delamination type failure in multi-layered composite shells. In the current contribution the extended finite element method (XFEM), the mixed-mode cohesive zone model, the contact formulation, and the damage criterion are incorporated into a new algorithm to study the interfacial delamination initiation and growth with less computational effort. A flat-shell formulation is developed in the geometrically non-linear regime to study the response of shells in small strains and moderate rotations. In addition, the equivalent single layer theory (ESLT) is applied to simulate the multi-layered laminates. This formulation is enhanced through the XFEM topology to be able to model discontinuous domains and a mixed-mode bilinear cohesive formulation to track the delamination growth. In the current study, the simulation can be initiated in an intact laminate. Thus, unlike formulations in existing finite element models, incorporating cohesive zone model at all available interfaces is not necessary. The interlaminar stresses are calculated during post-processing and they are being used in the delamination onset criterion. As soon as the criterion is satisfied at a specific layer and location, the formulation of that corresponding element is locally changed to XFEM and the cohesive behaviour. Consequently, the possibility to track delamination growth is locally provided; and hence, the computational cost is reduced.

Observation on the thermal stability of multi-layer graphene with metal nanoparticles with 0D structure

We studied the effect of rapid thermal treatment on multi-layer graphene with metal particles in an oxygen gas atmosphere. The multi-layer graphene-coated copper nanoparticles (MGCNs) were produced via electrical explosion in an isopropyl alcohol liquid medium. The MGCNs usually consist of multi-layer graphene shells that tightly surround the core copper nanoparticles without obvious voids. A fracture is induced by tearing the multi-layer graphene structure and the oxidized copper metal particles of the MGCNs after thermal treatment in oxygen gas at a low temperatures, including 25, 100, 200, and 300 °C. The MGCNs were characterized via Raman spectroscopy to obtain the graphene peak and its variation according to the oxygen gas temperature. Transmission electron microscopy was conducted to confirm the effect of the oxygen on the multi-layer graphene and copper nanoparticles phase using oxygen gas. The structure of the copper nanoparticles was observed via x-ray diffraction, and x-ray photoelectron spectroscopy was used to measure the chemical bonding on the multi-layer graphene surfaces treated with oxygen gas. We can show systematically optical images of changes in multi-layer graphene morphology like the 0D structure and existence of functional groups through various analyses after rapid thermal treatment in oxygen.

The optimization method in design problems of spherical layered thermal shells

The inverse problem of designing multilayered spherical shells, intended for thermal cloaking a spherical body or concentrating heat in it, has been analyzed. The stationary heat conduction equation for an anisotropic medium is applied as an original mathematical model. The optimization method is used to reduce this inverse problem to an extreme problem, where the role of controls is played by the thermal conductivities of shell layers. A numerical algorithm for solving the problem is proposed, and the results of computational experiments are discussed.

Superior Plasmonic Photodetectors Based on Au@MoS2 Core-Shell Heterostructures.

Integrating plasmonic materials into semiconductor media provides a promising approach for applications such as photosensing and solar energy conversion. The resulting structures introduce enhanced light-matter interactions, additional charge trap states, and efficient charge-transfer pathways for light-harvesting devices, especially when an intimate interface is built between the plasmonic nanostructure and semiconductor. Herein, we report the development of plasmonic photodetectors using Au@MoS2 heterostructures-an Au nanoparticle core that is encapsulated by a CVD-grown multilayer MoS2 shell, which perfectly realizes the intimate and direct interfacing of Au and MoS2. We explored their favorable applications in different types of photosensing devices. The first involves the development of a large-area interdigitated field-effect phototransistor, which shows a photoresponsivity ∼10 times higher than that of planar MoS2 transistors. The other type of device geometry is a Si-supported Au@MoS2 heterojunction gateless photodiode. We demonstrated its superior photoresponse and recovery ability, with a photoresponsivity as high as 22.3 A/W, which is beyond the most distinguished values of previously reported similar gateless photodetectors. The improvement of photosensing performance can be a combined result of multiple factors, including enhanced light absorption, creation of more trap states, and, possibly, the formation of interfacial charge-transfer transition, benefiting from the intimate connection of Au and MoS2.

Surface instability of imperfectly bonded multi-layered curved films under van der Waals forces

Abstract Using a linear stability analysis and the transfer matrix method, we investigate the surface instability of an imperfectly bonded multi-layered curved film interacting with a curved rigid contactor, another imperfectly bonded multi-layered curved film or an imperfectly bonded multi-layered simply-supported cylindrical shell in each case through the action of attractive van der Waals forces. The imperfect interface is modelled as a linear spring layer with vanishing thickness characterized by normal and tangential imperfect interface parameters. Detailed numerical results are presented to demonstrate the resulting analytical solutions.

Multilayered Magnetic Nanobeads for the Delivery of Peptides Molecules Triggered by Intracellular Proteases.

In this work, the versatility of layer-by-layer technology was combined with the magnetic response of iron oxide nanobeads to prepare magnetic mesostructures with a degradable multilayer shell into which a dye quenched ovalbumin conjugate (DQ-OVA) was loaded. The system was specifically designed to prove the protease sensitivity of the hybrid mesoscale system and the easy detection of the ovalbumin released. The uptake of the nanostructures in the breast cancer cells was followed by the effective release of DQ-OVA upon activation via the intracellular proteases degradation of the polymer shells. Monitoring the fluorescence rising due to DQ-OVA digestion and the cellular dye distribution, together with the electron microscopy studying, enabled us to track the shell degradation and the endosomal uptake pathway that resulted in the release of the digested fragments of DQ ovalbumin in the cytosol.

Photochemical Preparation of Pt Electrocatalysts on SnO2 Support for PEFCs

Core-shell electrocatalyst, in which a Pt monolayer or multilayer shell covers a nano-particle core of a different metal, exhibits high mass activity due to the high utilization of Pt. However, it is still required to improve its durability. If a thermochemically-stable conductive oxide is applied to the core with high durability, such an oxide-core Pt-shell electrocatalyst may exhibit high durability. In this study, we try to realize atomic-level Pt deposition on such a stable oxide to prepare core-shell electrocatalysts, where SnO2 rather than (noble) metals is applied as the core of such electrocatalysts. A photochemical procedure is applied to deposit Pt on SnO2. The dependencies of Pt shell deposition and electrocatalytic activity are analyzed on ultraviolet (UV) irradiation time, suspension temperature during UV irradiation, and the kind and concentration of the sacrificial reagent.

A geometrically exact formulation of thin laminated composite shells

A geometrically exact approach is employed to formulate the equations of motion of thin multi-layered composite shells subject to excitations that cause large strains, displacements, and rotations. Ad hoc truncated kinematic approximations of the obtained semi-intrinsic theory delivers, as a by-product, the kinematics of the Koiter and the Naghdi theories of shells, respectively. Numerical simulations are carried out both for cylindrical and spherical shells: nonlinear equilibrium paths are constructed considering a quasi-static load increase. The comparisons between the results furnished by the geometrically exact theory and those obtained by Koiter and Naghdi theories show the high accuracy of the proposed nonlinear approach. Classical theories become increasingly inaccurate at deflection amplitudes of the order of the shell thickness, evidencing that significant misrepresentations of the system behavior are possible if reduced-order kinematics are taken into account.

Seismic performance of precast shear wall with sleeves connection based on experimental and numerical studies

• Development of force-displacement mixed control methods for controlling both axial forces, rotations and lateral deformations of reinforced concrete shear wall specimens subjected to quasi-static cyclic tests. • The precast reinforced concrete shear walls endowed with grout-filled sleeves connections behaves similarly to the standard cast-in-situ solution with respect to failure mode, interstory drift angle, ultimate force, ductility and energy dissipation capacity. • The proposed single-row grout-filled sleeves connection method is suitable for six-story box-modularized precast reinforced concrete shear walls. • The multi-layer shell element combined with the proposed truss elements at the boundaries is effective for the proper simulation of precast reinforced concrete shear walls endowed with grout-filled sleeves connection. The seismic behavior of a full-scale precast reinforced concrete shear wall (PRCSW) endowed with single-row grout-filled sleeves connection, which was developed for six-story precast box-modularized structures with reinforced concrete shear walls (PBSRCSWs), is investigated in this paper. In order to accurately reproduce the axial-flexure-shear boundary conditions of PRCSW specimens under quasi-static loading, this paper proposes a force-displacement mixed control method. Relevant experimental results showed that desired axial forces, rotations and lateral deformations were effectively accomplished on the specimens. Moreover, the PRCSW specimen resembled the cast-in-situ shear wall specimen in terms of failure modes, interstory drift angle, ultimate force, ductility and dissipated hysteretic energy. In particular, the maximum interstory drift angle of the PRCSW specimen reached 17.86 mrad. Finally, experimental results and numerical simulations indicated that the proposed grout-filled sleeves connection method can be safely employed in six-story PBSRCSWs.

Composition-Graded PdxNi1–x Nanospheres with Pt Monolayer Shells as High-Performance Electrocatalysts for Oxygen Reduction Reaction

It is undoubtedly desirable, albeit very challenging, to appropriately balance the catalytic activity, electrochemical durability, and noble-metal (NM) utilization when developing Pt-based catalysts for oxygen reduction reaction (ORR). Accordingly, in this work, a versatile and effective strategy that promises the nanostructure of both composition-graded core and mono- or multilayer shell is proposed to synthesize highly uniform, sub-10 nm PdxNi1–x@Pt nanospheres (NSs) as high-performance ORR electrocatalysts. Highly uniform and composition-graded PdxNi1–x NSs are previously obtained via a facile one-pot Ni-substitution-based process, and then Pt mono- or multilayer shells are coated onto them through Cu underpotential deposition coupled with Pt2+ galvanic displacement. Results show that carbon-supported PdxNi1–x@Pt electrocatalysts possess both high catalytic activity and highly efficient NM utilization toward ORR. The optimized Pd0.42Ni0.58@Pt/C exhibits 0.61 mA cm–2, 0.42 A mg–1Pd+Pt, and 1.45 A mg–1Pt...

Chitosan-based nanocapsules of core-shell architecture

N-dodecyl derivative of cationically modified chitosan was used to prepare core-shell nanocapsules templated on liquid cores. Surfactant-free method based on ultrasound-assisted direct emulsification of aqueous solution of polysaccharide with oleic acid was applied. Formation of spherical capsules was confirmed by scanning and transmission electron microscopies. Dynamic light scattering measurements were used to determine physicochemical parameters of the obtained particles as well as to follow the process of multilayer shell formation. Confocal microscopy was applied to examine the ability of encapsulation of hydrophobic compounds inside the cores of the nanocapsules. Performed studies confirmed that hydrophobically modified cationic chitosan provides long-term stabilization of oil-in-water emulsion for biomedical applications as no toxic effect was observed in acute oral toxicity studies.

TiN coating effect on the elastoplastic behaviour of Ti film for electron beam exit window

The paper theoretically and experimentally studies the effect of coating on elastoplastic behaviour of the exit window membrane of an electron accelerator under loading by atmospheric pressure and heating due to partial absorption of beam energy by membrane material. The study uses finite-element analysis of benchmark problems formulated within the theory of multi-layer plates and shells to determine the profile, maximum deflection and residual (plastic) strain depending on the properties of materials, thickness of membrane and coating and radiation power. The estimates satisfactorily agree with experimental data and particularly witness that thin (about 1 μm) TiN coating significantly reduces the elastoplastic strain of the titanium membrane and electron beam energy losses in it.

Dynamics of Three-layer Cylindrical Shells Elliptical Cross-Section With a Longitudinal-Transverse Discrete Ribbed Filler

In this paper, we consider the equations of non-axisymmetric oscillations of discretely reinforced multilayer cylindrical shells of elliptical section. When analyzing the elements of the elastic structure, a refinement model of the theory of shells and rods of the Timoshenko type is used. The numerical method of solving the dynamic equations is based on the integro- interpolation method of constructing the finite-difference schemes for equations with discontinuous coefficients. The problem of dynamic behavior of a three-layer longitudinal-transversal reinforced cylindrical shell of an elliptical section under a distributed nonstationary load is investigated. A solution of the problem on dynamic behaviour of the three-layered cylindrical shell with some discrete longitudinal-transverse ribbed filler is considered for distributed non-stationary loading.

Analysis of carbon fines obtained from the off-gas dust of calcium carbide furnace

The off-gas dust of calcium carbide furnace is a hazardous waste of large quantities in China. It, however, contains valuable materials and should be recovered not only for environmental and safety reasons but also for economic reasons. This work examines carbon fines separated from the off-gas dust of a calcium carbide furnace by acid leaching using HCl and HF solutions. The carbon fines are characterized using various instrumental techniques. It is found that the carbon fines mainly consist of hollow spheres of 0.5–3.5 µm in size with multilayer graphitic shells, a BET surface area of 124.5 m2/g and a mean pore size of 4.0 nm. Some of the carbon fines enclosed smaller carbon spheres that are either hollow or enclosed with inorganic species, such as magnetic Fe3C, which can be separated magnetically. The carbon fines are good sorbent as demonstrated by quick adsorption of Congo Red in an aqueous solution to capacities of 216 or 296 mg/g with or without the magnetic separation, respectively. A mechanism for the formation of carbon spheres is proposed.

Isogeometric analysis of laminated composite and functionally graded sandwich plates based on a layerwise displacement theory

A multi-layered shell formulation is developed based on a layerwise deformation theory (Reddy, 2004) within the framework of isogeometric analysis (IGA). IGA utilizes Non-Uniform Rational B-splines (NURBS) to represent the geometry as well as to describe the field variables (Hughes et al., 2005). The high-order smoothness of NURBS offered the opportunity of capturing the structural deformation efficiently in a rotation-free manner. The derivation also follows a layerwise theory, which assumes a separate displacement field expansion within each layer, and considers transverse displacement component as C0-continuous at layer interfaces, thus resulting in a layerwise continuous transverse strain states. Since the in-plane and through-thickness integrations are carried out individually, this approach is capable of capturing the complete three-dimensional stress states in a two-dimensional setting, which improves the computational efficiency. A knot insertion technique is utilized for the discretization in the through-thickness direction, and C0-continuity is enforced by means of knot repetition at dissimilar material interfaces. The performance of the proposed model is demonstrated using multiple laminated composites and sandwich plates (including functionally graded material core) as examples. Numerical results prove the accuracy of the proposed formulation and show that the isogeometric layerwise shell is superior to its finite element counterpart.

Analysis of laminated composite structures with embedded piezoelectric sheets by variable kinematic shell elements

In this article, the static analysis of multilayered shell structure embedding piezoelectric layers is performed using some advanced theories, obtained by expanding the unknown variables along the thickness direction using equivalent single-layer models, layer-wise models, and variable kinematic models. The variable kinematic models permit to reduce the computational cost of the analyses by grouping some layers of the multilayered structure with equivalent single-layer models and keeping the layer-wise models in other zones of the multilayer. This model is here extended to the static analysis of electro-mechanical problems. The used refined models are grouped in the Carrera Unified Formulation, and they accurately describe the displacement field, the stress distributions, and the electric potential along the thickness of the multilayered shell. The shell element has nine nodes, and the mixed interpolation of tensorial components method is used to contrast the membrane and shear locking phenomenon. The governing equations are derived from the principle of virtual displacement, and the finite element method is employed to solve them. Cross-ply plates and shells, with piezoelectric skins and simply supported edges, subjected to bi-sinusoidal mechanical or electrical load are analyzed. Various aspect ratios and radius-to-thickness ratios are considered. The results, obtained with different theories within Carrera Unified Formulation context, are compared with the elasticity solutions given in the literature. From the results, it is possible to conclude that the shell element based on Carrera Unified Formulation is very efficient in the study of electro-mechanical problems of composite structures. The variable kinematic models combining the equivalent single-layer with the layer-wise models permit to have a reduction of the computational costs, with respect to the full layer-wise theories, preserving the accuracy of the results in localized layers.