Spherical Shell Structure Research Articles

Airflow Patterns around Obstacles with Large-Span Shallow Shell Roof: Wind Tunnel Measurements and Direct Simulation

Wind tunnel tests on the rigid model of large-span shallow spherical shell roof structure were carried out. The variation rule and the calculation method for the average shape coefficient of the fluctuating wind pressure under six different typical wind directions were obtained. The wind pressure distribution of the node deflection and cross section stress was numerically investigated and analyzed. Meanwhile, the effect of mechanics-flow form of the typical spherical shell structure on the wind pressure distribution was analyzed quantitatively. In this study, it is found that the results of numerical simulation agree well with the wind tunnel test data. The study on the mechanical characteristics, as well as the wind vibration research, of the spherical shell structure in different working conditions provides a reliable theoretical basis for the mechanical index of the wind vibration.

Microstructure and thermal physical properties of SiC matrix microencapsulated composites at temperature up to 1900 °C

SiC matrix microencapsulated composites with particle-free buffer (PB) layer were produced by spark plasma sintering for the first time. Microstructure and thermal physical performance of the composites from room temperature to 1900 °C were investigated. Dense composites with rational layout of tristructural isotropic (TRISO) particles and PB layer were obtained. The TRISO particles in the composites kept intact spherical shell structure. Thermal physical properties of the composites approached those of the SiC materials. The composites with high thermal conductivity and low coefficient of thermal expansion were suitable for nuclear applications. The effect of oxide additives on comprehensive performance of the composites was reappraised. Dissolution and recrystallization of SiC in the eutectic liquid phase revealed a new high temperature failure mechanism for the composites.

Dual Optical Signal-based Intraocular Pressure-sensing Principle Using Pressure-sensitive Mechanoluminescent ZnS:Cu/PDMS Soft Composite

This paper presents a novel principle for intraocular pressure (IOP)-sensing (monitoring) based on a pressure-sensitive soft composite in which a dual optical signal is produced in response to impulsive pressure input. For the initial assessment of the new IOP sensing principle, a human eye is modeled as the spherically shaped shell structure filled with the pressurized fluid, including cornea, sclera, lens and zonular fiber, and a fluid–structure interaction (FSI) analysis was performed to determine the correlation between the internal pressure and deformation (i.e., strain) rate of the spherical shell structure filled with fluid by formulating the finite element model. The FSI analysis results for human eye model are experimentally validated using a proof-of-conceptual experimental model consisting of a pressurized spherical shell structure filled with fluid and a simple air-puff actuation system. In this study, a mechanoluminescent ZnS:Cu- polydimethylsiloxane (PDMS)-based soft composite is fabricated and used to generate the dual optical signal because mechanically driven ZnS:Cu/PDMS soft composite can emit strong luminescence, suitable for soft sensor applications. Similar to the corneal behavior of the human eye, inward and outward deformations occur on the soft composite attached to the spherical shell structure in response to air puffing, resulting in a dual optical signal in the mechnoluminescence (ML) soft composite.

Analysis of stability against rotation of a spherical shell structure subjected to buoyancy

The main structure of the central detector at the Jiangmen Underground Neutrino Observatory (JUNO) is a spherical shell structure, which has a giant acrylic spherical shell connected to a stainless-steel (SS) reticulated shell with 590 SS rods. The acrylic spherical shell is submerged into water and filled with detection liquid and prone to rotation subjected to considerable buoyancy. The stability against rotation of this super-deep underground spherical shell structure needs to be fully investigated. In this study, an effective and practical method consisting of parametric analysis and optimization procedure is proposed to improve the stability against rotation. Specifically, two indicators, namely, the critical loading multiplier and the rotation angle, are proposed to evaluate the stability against rotation of the acrylic spherical shell in linear and nonlinear stability analyses, respectively. Then, parametric analysis is performed to assess the sensitivity of the stability against rotation to four parameters of interest (i.e., rod outer end constraints, liquid level difference, disc spring stiffness, and rod deviation). Based on the obtained parametric analysis results, the liquid level difference and disc spring stiffness are finally selected as design variables for the subsequent optimization process to further improve the stability against rotation. An efficient scheme combining design variable discretization and exhaustive method is adopted to identify the optimal variable values at which the acrylic spherical shell has good stability against rotation. The results indicate that the proposed method is efficient and effective for optimization of stability against rotation of such super-deep underground spherical shell structure. The proposed method is practical and easy to use for structural designers, and provides an efficient approach to the stability design of such rod-connected spherical shell structures.

A Semianalytical Approach for Free Vibration Characteristics of Functionally Graded Spherical Shell Based on First‐Order Shear Deformation Theory

This paper describes a unified solution to investigate free vibration solutions of functionally graded (FG) spherical shell with general boundary restraints. The analytical model is established based on the first‐order shear deformation theory, and the material varies uniformly along the thickness of FG spherical shell which is divided into several sections along the meridian direction. The displacement functions along circumferential and axial direction are, respectively, composed by Fourier series and Jacobi polynomial regardless of boundary restraints. The boundary restraints of FG spherical shell can be easily simulated according to penalty method of spring stiffness technique, and the vibration solutions are obtained by Rayleigh–Ritz method. To verify the reliability and accuracy of the present solutions, the convergence and numerical verification have been conducted about different boundary parameters, Jacobi parameter, etc. The results obtained by the present method closely agree with those obtained from the published literatures, experiments, and finite element method (FEM). The impacts of geometric dimensions and boundary conditions on the vibration characteristics of FG spherical shell structure are also presented.

Effectiveness and mechanism of carbamide/fly ash cenosphere with bilayer spherical shell structure as explosion suppressant of coal dust.

This study aims to eliminate or suppress explosion accidents in powder preparation and storage systems of coal dust. The modified fly ash cenosphere (FAC) was used as an inner spherical shell carrier with carbamide impregnated. Carbamide/FAC composite suppressant with bilayer spherical shell was prepared by vacuum freeze-drying. The flame propagation and explosion performances of coal were tested, respectively. The results showed that the surface-loaded carbamide particles had a particle size of ∼4 nm. With the increasing content of carbamide/FAC composite suppressant, the maximum flame length gradually decreased, and the explosion suppression effect was gradually improved. Nearly complete explosion suppression of coal could be achieved with an added amount of 40 wt% carbamide/FAC composite suppressant. The carbamide loaded in carbamide/FAC composite suppressant mainly acted in the 0-τ1 stage to weaken (dP/dt)max. FAC mainly but not solely acted on the stage of τ1-τ2 to decrease Pmax. Carbamide particles were highly efficient and responsive. The suppression mechanism of carbamide/FAC composite suppressant was proposed, which was micro-nano multiscale complementary effect and deceleration-depressurization coupling effect.

Dynamic Pressure Analysis of Hemispherical Shell Vibrating in Unbounded Compressible Fluid

This paper is the first to highlight the vibrations of a hemispherical shell structure interacting with both compressible and incompressible fluids. To precisely calculate the pressure of the shell vibrating in the air, a novel analytical approach has been established that has existed in very few publications to date. An analytical formulation that calculates pressure was developed by integrating both the ‘small-density method’ and the ‘Bessel function method’. It was considered that the hemispherical shell vibrates as a simple harmonic function, and the fluid is non-viscous. For comparison, the incompressible fluid model has been analyzed. Surprisingly, it is the first to report that the pressure of the shell surface is proportional to the vibration acceleration, and the velocity amplitude decreased at the rate of 1 r 2 when the fluid was incompressible. Otherwise, the surface pressure of the hemispherical shell was proportional to the vibration velocity, and the velocity amplitude decreased with the rate of 1 r when the fluid was compressible. The compressibility of fluid played an important role in the dynamic pressure of the shell structure. Furthermore, the scale factor derived by the theoretical approach was the product of the density and the sound velocity of the fluid ( ρ o c ) exactly. In this study, the analytical solutions were verified by the calibrated numerical simulations, and the analytical formulation were rigorously tested by extensive parametric studies. These new findings can be used to guide the optimal design of the spherical shell structure subjected to wind load, seismic load, etc.

Improvement in Luminous Efficacy and Thermal Performance Using Quantum Dots Spherical Shell for White Light Emitting Diodes.

White light-emitting diodes (WLEDs) based on quantum dots (QDs) are gaining increasing attention due to their excellent color quality. QDs films with planar structure are universally applied in WLEDs for color conversion, while they still face great challenges in high light extraction and thermal stability. In this study, a QDs film with a spherical shell structure was proposed to improve the optical and thermal performance for WLEDs. Compared with the conventional planar structure, the luminous efficacy of the QDs spherical shell structure is improved by 12.9% due to the reduced total reflection effect, and the angular-dependent correlated color temperature deviation is decreased from 2642 to 283 K. Moreover, the highest temperature of the WLED using a QDs spherical shell is 4.8 °C lower than that of the conventional WLED with a planar structure, which is mainly attributed to larger heat dissipation area and separated heat source. Consequently, this QDs spherical shell structure demonstrates superior performance of QDs films for WLEDs applications.

Investigation of the Dynamic Buckling of Spherical Shell Structures Due to Subsea Collisions

This paper is the first to present the dynamic buckling behavior of spherical shell structures colliding with an obstacle block under the sea. The effect of deep water has been considered as a uniform external pressure by simplifying the effect of fluid–structure interaction. The calibrated numerical simulations were carried out via the explicit finite element package LS-DYNA using different parameters, including thickness, elastic modulus, external pressure, added mass, and velocity. The closed-form analytical formula of the static buckling criteria, including point load and external pressure, has been firstly established and verified. In addition, unprecedented parametric analyses of collision show that the dynamic buckling force (peak force), mean force, and dynamic force redistribution (skewness) during collisions are proportional to the velocity, thickness, elastic modulus, and added mass of the spherical shell structure. These linear relationships are independent of other parameters. Furthermore, it can be found that the max force during the collision is about 2.1 times that of the static buckling force calculated from the analytical formula. These novel insights can help structural engineers and designers determine whether buckling will happen in the application of submarines, subsea exploration, underwater domes, etc.

A higher order transversely deformable shell-type spectral finite element for dynamic analysis of isotropic structures

This paper deals with certain aspects related to the dynamic behaviour of isotropic shell-like structures analysed by the use of a higher order transversely deformable shell-type spectral finite element newly formulated and the approach known as the Time-domain Spectral Finite Element Method (TD-SFEM). Although recently this spectral approach is reported in the literature as a very powerful numerical tool used to solve various wave propagation problems, its properties make it also very well suited to solve static and dynamic modal problems. The robustness and effectiveness of the current spectral approach has been successfully demonstrated by the authors in the case of thin-walled spherical shell structures through a series of numerical tests comprising the analysis of natural frequencies and modes of vibration of an isotropic spherical shell as well as the wave propagation analysis in the case of the same spherical shell and a half-pipe shell-like structure.

Effect of sodium dodecyl benzene sulfonate on morphology and structure of calcium silicate hydrate prepared via precipitation method

The effect of sodium dodecyl benzene sulfonate (SDBS) on morphology and structure of calcium silicate hydrate (CSH) prepared via precipitation in solution were investigated by XRD, FT-IR and SEM techniques. The formation mechanism of spherical shell of CSH was also discussed. The results suggested that different concentrations of SDBS affect differently the structure and morphology of CSH. When the SDBS concentration was less than the critical micelle concentration (CMC), the agglomeration among CSH particles reduced, the degree of order of CSH increased and the polymerization degree of Si-O decreased. When the SDBS concentration was greater than CMC, the spherical micelles were fabricated in aqueous solution, which induced CSH to form a spherical structure in the shape of spherical micelle rather than produce a layered CSH under the normal condition. After centrifugation and vacuum drying procedures, internal micelles of CSH spherical particles disappeared and turned into spherical shell structures. This experiment provides a reliable method for the preparation of CSH with specific morphology and size, which can simplify experimental conditions and increase the possibility of its application in the field of drug delivery.

Bioreducible nanocapsules for folic acid-assisted targeting and effective tumor-specific chemotherapy.

IntroductionIncreasing demands in precise control over delivery and functionalization of therapeutic agents for tumor-specific chemotherapy have led to a rapid development in nanocarriers. Herein, we report a nanocapsule (NC) system for tumor-oriented drug delivery and effective tumor therapy.Materials and methodsFunctionalized hyaluronan is utilized to build up the NC shells, in which bioreduction cleavable sites, targeting ligand folic acid (FA), and zwitterionic tentacles are integrated.ResultsThe hollow NCs obtained (~50 nm in diameter) showed well-defined spherical shell structures with a shell thickness of ~8 nm. These specially designed NCs (doxorubicin [DOX]/FA-Z-NCs) with high drug encapsulation content exhibited good biocompatibility in vitro and fast intracellular drug release behavior mediated by intracellular glutathione.ConclusionCellular uptake tests demonstrated rapid uptake of these functionalized NCs and effective escape from endosomes. Antitumor efficacy of the DOX/FA-Z-NCs was confirmed by the significant tumor growth inhibition effect as well as greatly reduced side effects, in contrast with those of the free drug DOX hydrochloride.

Viscoelastic modelling and dynamic characteristics of CNTs-CFRP-2DWF composite shell structures

Abstract The carbon nanotubes (CNTs) are well known for its application in the areas of advanced composite materials for their improved elastic properties. The large specific interfacial surface area owing to tiny dimensions of CNTs may greatly escalation the interfacial sliding which may promote the dissipation of energy in a dynamic situation that makes them very ideal for damping applications in engineering structures/systems. The present article investigates the viscoelastic modelling and dynamic responses of the CNTs – based carbon fiber reinforced two dimensional woven fabrics (CNTs-CFRP-2DWF) composite spherical shell panels where CNTs are reinforced in the polymer matrix phase. The Mori – Tanaka (MT) micromechanics in conjunction with weak interface (WI) theory has been developed for the mathematical formulations of the viscoelastic modelling of CNTs-based polymer matrix phase. Further, strength of material (SOM) method has been employed to formulate viscoelastic material behavior of the yarn and finally the viscoelastic properties of the representative unit cell (RUC) is established based on the unit cell method (UCM). An eight-node shell element with five degree of freedom per node has been formulated to study the vibration damping characteristics of spherical shell structures made by CNTs-CFRP-2DWF composite materials. The shell finite element formulation is based on the transverse shear effect as per the Mindlin's hypothesis, and stress resultant-type Koiter's shell theory. Frequency and temperature dependent material properties of such CNTs-CFRP-2DWF composite materials have been obtained and analysed. Impulse and frequency responses of such structures have been performed to study the effects of various important parameters such as volume fraction of CNTs, interfacial condition, agglomeration, temperature, geometries of shell panel on the material properties and such dynamic responses. Obtained results demonstrate that quick vibration mitigation may be possible using such CNTs-CFRP-2DWF composite material which is desirable to overcome the drawbacks of conventional CFRP woven fabric composite materials.

Viscoelastic modeling and vibration damping characteristics of hybrid CNTs-CFRP composite shell structures

The present article deals with the viscoelastic modeling and dynamic responses of the carbon nanotubes (CNTs)-based carbon fiber-reinforced polymer (CNTs-CFRP) composite spherical shell panels where CNTs are reinforced in the polymer matrix phase. The Mori–Tanaka micromechanics in conjunction with weak interface theory has been developed for the mathematical formulations of the viscoelastic modeling of CNTs-based polymer matrix phase. Further, the strength of material method has been employed to formulate the viscoelastic material behavior of the homogenized hybrid CNTs-CFRP composite materials. An eight-noded shell element with five degrees of freedom per node has been formulated to study the vibration damping characteristics of spherical shell structures made by CNTs-CFRP composite materials. Frequency- and temperature-dependent material properties of such hybrid composite materials have been obtained and analyzed. Impulse and frequency responses of such structures have been performed to study the effects of various important parameters on the material properties and such dynamic responses. Obtained results demonstrate that quick vibration mitigation may be possible using such CNTs-based proposed composite materials.

Static stability behavior of aluminum alloy single-layer spherical latticed shell structure with Temcor joints

In recent years, aluminum alloy single-layer latticed shell has been extensively used in civil and industrial infrastructure. The elasticity modulus of aluminum alloy is low, the rigidity of aluminum joints are weak and the roof load transmission path is different. Therefore, the stability performance of this dome is unique. To clarify the stability performance of aluminum alloy single-layer latticed shell, over 500 aluminum alloy single-layer spherical latticed shells were analyzed with nonlinear finite method. The suggested values of rise/span ratio and initial imperfection were presented. The influencing coefficients of initial imperfection, material nonlinearity and stressed skin effect on stability bearing capacity were obtained. And the structural stability safety coefficient and the approximate calculation formula for stability bearing capacity of aluminum alloy single-layer spherical latticed shell were derived. The influences of joint semi-rigidity were investigated. All the aforementioned results provide a scientific basis for future stability design of aluminum alloy single-layer spherical latticed shell structure.

Study of the Similarities in Scale Models of a Single-Layer Spherical Lattice Shell Structure under the Effect of Internal Explosion

The similarity of each scale model is verified based on the theory of similarity, deriving the similarity law of internal explosions in a single-layer spherical lattice shell structure via dimensional theory, calculated based on models with scaling coefficients of 1, 0.8, 0.6, 0.4, 0.2, and 0.1. The results show that the shock wave propagation characteristics, the distribution of the overpressure on the inner surface, the maximum dynamic response position, and the position at which the earliest explosion venting occurs are all similar to those of the original model. With the decrease of scaling coefficients, the overpressure peak value of the shock waves of each scale model, and the specific action time of the positive pressure zone, as well as specific impulse are increasingly deviated from the original model values; when the scaling coefficient is 0.1, the maximum relative error between the overpressure peak value at the measurement point and the specific action time of the positive pressure zone as well as the specific impulse and the original model value is 4.9%. Thus, it is feasible to forecast the internal explosion effect of the original structure size model by using the experiment results of the scale model with scaling coefficient λ≥0.1.

Highly Porous Copper with Hollow Microsphere Structure from Polystyrene Templates via Electroless Plating

Hollow copper microspheres with pore size about 3 μm and spherical shell around 150 nm were successfully prepared by electroless plating using polystyrene (PS) as sacrificial templates and the kinetics were studied concerning the empirical rate law. The effects of plating bath composition on the amount, microstructure and composition of the deposited copper shells were investigated. pH was the most important factor for copper deposition rate and amount of copper deposits. The amount of by-product Cu2O decreased with increasing pH values and the deposited copper agglomerated when pH value reached 13.41. The addition of stabilizers (2, 2-bipyridine, potassium ferrocyanide and methanol) had a very negative effect on the microstructure of the deposited copper shells. PS templates were removed by sintering and the remanent copper deposits with high purity maintained good spherical shell structure. In addition, the kinetic equation of electroless copper plating (ECP) using PS as the substrate was determined and the activation energy (Ea) was 59.77 kJ·mol−1. The prepared hollow copper microspheres with high porosity are ideally suitable for synthesizing energetic materials and this method might also be used for fabricating other hollow metal microspheres.

Preparation of arginine-glycine-aspartic acid-modified biopolymeric nanoparticles containing epigalloccatechin-3-gallate for targeting vascular endothelial cells to inhibit corneal neovascularization.

Neovascularization (NV) of the cornea can disrupt visual function, causing ocular diseases, including blindness. Therefore, treatment of corneal NV has a high public health impact. Epigalloccatechin-3-gallate (EGCG), presenting antiangiogenesis effects, was chosen as an inhibitor to treat human vascular endothelial cells for corneal NV treatment. An arginine–glycine–aspartic acid (RGD) peptide–hyaluronic acid (HA)-conjugated complex coating on the gelatin/EGCG self-assembly nanoparticles (GEH-RGD NPs) was synthesized for targeting the αvβ3 integrin on human umbilical vein endothelial cells (HUVECs) in this study, and a corneal NV mouse model was used to evaluate the therapeutic effect of this nanomedicine used as eyedrops. HA-RGD conjugation via COOH and amine groups was confirmed by 1H-nuclear magnetic resonance and Fourier-transform infrared spectroscopy. The average diameter of GEH-RGD NPs was 168.87±22.5 nm with positive charge (19.7±2 mV), with an EGCG-loading efficiency up to 95%. Images of GEH-RGD NPs acquired from transmission electron microscopy showed a spherical shape and shell structure of about 200 nm. A slow-release pattern was observed in the nanoformulation at about 30% after 30 hours. Surface plasmon resonance confirmed that GEH-RGD NPs specifically bound to the integrin αvβ3. In vitro cell-viability assay showed that GEH-RGD efficiently inhibited HUVEC proliferation at low EGCG concentrations (20 μg/mL) when compared with EGCG or non-RGD-modified NPs. Furthermore, GEH-RGD NPs significantly inhibited HUVEC migration down to 58%, lasting for 24 hours. In the corneal NV mouse model, fewer and thinner vessels were observed in the alkali-burned cornea after treatment with GEH-RGD NP eyedrops. Overall, this study indicates that GEH-RGD NPs were successfully developed and synthesized as an inhibitor of vascular endothelial cells with specific targeting capacity. Moreover, they can be used in eyedrops to inhibit angiogenesis in corneal NV mice.

Morphology conserving aminopropyl functionalization of hollow silica nanospheres in toluene

Inorganic nanostructures containing cavities of monodisperse diameter distribution find applications in e.g. catalysis, adsorption and drug delivery. One of their possible synthesis routes is the template assisted core-shell synthesis. We synthesized hollow silica spheres around polystyrene cores by the sol-gel method. The polystyrene template was removed by heat treatment leaving behind a hollow spherical shell structure. The surface of the spheres was then modified by adding aminopropyl groups. Here we present the first experimental evidence that toluene is a suitable alternative functionalization medium for the resulting thin shells, and report the comprehensive characterization of the amino-functionalized hollow silica spheres based on scanning electron microscopy, transmission electron microscopy, N2 adsorption, FT-IR spectroscopy, Raman spectroscopy and electrokinetic potential measurement. Both the presence of the amino groups and the preservation of the hollow spherical morphology were unambiguously proven. The introduction of the amine functionality adds amphoteric character to the shell as shown by the zeta potential vs. pH function. Unlike pristine silica particles, amino-functionalized nanosphere aqueous sols can be stable at both acidic and basic conditions.

Overpressure peak formula of surface shock waves in single layer spherical lattice shell under the effect of internal explosion

This paper uses the LS-DYNA analysis software to make numerical simulation and analysis on the blast effect of single layer spherical lattice shell structure under the action of internal explosion, summarized overpressure peak distribution characteristics of surface shock waves in lattice shell under internal explosion: shock waves overpressure peak of lattice shell top is mainly secondary wave overpressure peak, while at rest locations, it is mainly first wave overpressure peak; shock waves overpressure peak distribution in lattice shell and side wall is big at both ends and small in the middle. Finally, according to distribution law of shock waves overpressure peak, we proposed simplified calculation formula for surface shock waves overpressure peak in singer layer spherical lattice shell, to provide reference for antiknock and explosion-proof of engineering structures.