Shell Thickness Research Articles

Analytical Study on the Buckling of Cylindrical Shells With Circumferential Thickness Variation Under Varying External Pressure

Abstract In this article, the analytical buckling load coefficient formula for a cylinder with circumferential thickness variation subjected to varying external pressure is established for the first time by developing a quadratic perturbation method. Based on the presented formula, some specific examples that consider either circumferential shell thickness variation or varying lateral pressure are studied and compared with those in the published literature. First, classical cosine thickness variation is analyzed. The computed results of buckling load coefficients indicate that most of differences between the proposed formula and finite element (FE) analyses in previous literature are less than 5%. Second, wind-type pressure load is discussed, and the maximum difference of predicted buckling load coefficients between our formula and results in published article is 2.3%. Third, both circumferential thickness variation and linear liquid pressure are analyzed by the proposed analytical formula and validated by the Galerkin method when both thickness and load variations are small. Therefore, accuracy and reliability of the established formula are validated. For the purpose of engineering application, buckling of a circular shell with local circumferential thickness variation due to weld shrinkage under wind-type pressure is analytically investigated. The effects of thickness variation amplitude, load parameter, half angle of thickness variation, and shell dimensions on buckling load coefficients are studied in detail.

Alternative Low-Order Triangular Elements for Thick and Thin Shell Analysis

In this paper, the authors discuss the development of six low-order triangular elements for the linear static analysis of thick and thin shell structures. The elements combine two triangular plane stress elements with three triangular thick plate bending elements to produce three-node flat shell elements with 18 degrees of freedom. The two plane stress components are based on the free formulation and the template formulation, while the three plate bending components are based on the free formulation, the deviatoric strain formulation and the hybrid-Trefftz formulation. The theoretical backgrounds and formulations of all elements are briefly discussed to provide a concise summary, while further details are given in the quoted references. The elements are used to analyze five standard shell benchmark examples, and the results obtained are compared to previous work in this area. The elements provide accurate and robust results for the benchmarks, with only small differences for the results as the meshes are refined. While all the proposed elements can be recommended for general shell analysis, the combination of the template plane stress element and the hybrid-Trefftz plate bending element generally provides the best results.

Performances of the sandwich panel structures under fire accident due to hydrogen leaks: Consideration of structural design and environment factor using FE analysis

Abstract This study presents a comprehensive analysis using the finite element method (FEM) to examine and evaluate the behavior of fuel carrier ship structure. Sandwich panels are effective structures for use in ship structures due to their lightweight yet robust nature. Sandwich panels used in ship structures have various core shapes, such as hexagonal, circular, and square, as needed. The sandwich panel structure can be widely implemented in ship construction, for example, on the deck, hull, and bulkhead of the ship’s cabin. Hydrogen is an alternative fuel that can replace fossil fuels. In this modern era, hydrogen is high valuable energy commodity, so accidents involving carrier ships could have significant consequences. Hydrogen is produced from liquefied natural gas (LNG), so if a leak occurs, for instance, in a storage tank or fuel tank, it has the potential to lead to accidents such as fires. Corrosion is a significant concern for the maritime industry, as it can jeopardize the structural integrity of these vessels and pose substantial safety and environmental risks. In this research, FEM was utilized to model and simulate the effects of corrosion on hydrogen carrier ships when exposed to fire, considering various environmental and operational factors. Through a systematic investigation, it is aimed to gain insights into the impact of corrosion on ship structural components during fires, such as hulls and storage tanks. The result of this study will contribute to improving corrosion and fire mitigation strategies, ensuring the safety and longevity of hydrogen and LNG carrier ships, and supporting the sustainable transportation of hydrogen to meet global energy demands. No research has been conducted on the structural behavior resulting from hydrogen fires and corrosion simultaneously. To achieve this, it is assumed to use the corrosion properties of steel in heavily traveled ship routes such as the Panama Canal Zone, Barent Sea, North Sea, and Suez Canal Zone. This study utilized an approach by modeling corrosion using shell thickness in Abaqus Quasi-Static and applying boundary conditions in the form of temperature increase up to 800°C and subsequent cooling back to the initial temperature. At the maximum temperature, the most significant mid-span displacement occurred in the circular core sandwich panel, with a value of 4 mm. The axial force in the structure was inversely proportional to the mid-span displacement. In the case of the circular core sandwich panel, the axial force was 96 kN. The most resilient core type was hexagonal because it experiences the least deformation when compared to circular and square cores.

A Color-Detectable Vitamin C Controlled-Release System Fabricated Using Electrospinning

This study develops a vitamin C controlled-release system, trackable via color changes as a function of vitamin C release. The system is composed of coaxial microfibers prepared via coaxial electrospinning, with a core of poly(ethylene oxide) (PEO) incorporating vitamin C, and a shell composed of polycaprolactone (PCL) containing polydiacetylene (PDA) as the color-changing material. The shell thickness is controlled by adjusting the amount of PCL ejected during electrospinning, allowing regulation of the release rate of vitamin C. When vitamin C added to PEO penetrates the PCL layer, the color of PDA changes from blue to red, indicating a color change. The results of this study can be applied to devices that require immediate detection of vitamin C release levels.

Analysis of the Dynamic Characteristics of Conical Shells of Variable Thickness on an Elastic Bed Under Unsteady Loading

Analysis of the Dynamic Characteristics of Conical Shells of Variable Thickness on an Elastic Bed Under Unsteady Loading

Parametric Optimization of System Modes for Nozzle Turbine Vane by Means of Costimulated Artificial Immune System

One requirement posed by customers is to achieve adequate durability levels as described in technical requirement documents. Modal analysis is one of the design assessments aimed at identifying the risks of high cycle fatigue (HCF). This article presents a novel application of an artificial immune system (AIS) in the optimization of a nozzle guide vane’s modal characteristics. The aim is to optimize the system’s natural frequencies in the vibration vane and adjacent hardware (turbine casing). The geometrical characteristics accounted for in the optimization process include the shell thicknesses on the turbine casing side and the nozzle outer band features (hook thickness, leaning and position). The optimization process is based on a representative model established from FEM analysis results. The framework is robust because of the applied metamodel and does not require time-consuming FEM analysis in order to evaluate the fitness function. The aim is to minimize the model area (a derivative of the system weight) with constraints imposed on the frequency (a penalty function). The optimum design is given as the solution with an increased shell thickness in the turbine casing and leaning nozzle outer band hooks to obtain the maximum stiffness of the system. The results obtained by means of the artificial immune system (AIS) and a novel variant based on an additional costimulation procedure (CAIS) are compared with the solution obtained by means of a genetic algorithm implemented in the commercial CAE software (Ansys version 19.2).

Selective aromatization of 1-hexene to BTX over core-shell structured Silicalite-1@ZSM-5 catalyst

The strong acidity on the external surface of ZSM-5 is a primary factor resulting in the low BTX selectivity and catalyst deactivation during the olefin aromatization. In this study, a membrane-restricted Silicalite-1@ZSM-5 core–shell structured catalytic catalyst was designed and constructed for 1-hexene aromatization using a hydrothermal coating method. TEM and NMR results confirmed the complete coverage of Silicalite-1 on the surface of ZSM-5, with a shell thickness of 50 nm. The further reaction of the TIPB (1,3,5-triisopropylbenzene) molecular probe reactions demonstrated the passivation of the acid sites on ZSM-5 external surface. The inert shell layer passivated the acid sites on the external surface, thereby suppressing the isomerization of PX and the side-chain alkylation reaction of light aromatics. Compared to ZSM-5, the Silicalite-1@ZSM-5 catalyst exhibited a 37.15 % increase in BTX selectivity, a 58.65 % increase in PX selectivity, significantly reduced coke deposition, and demonstrated better stability. This strategy of in-situ epitaxial growth of inert shell layers holds significant promise for enhancing the selectivity of shape-selective catalysts and extending catalyst lifetime.

Persistent currents of ultrarelativistic plasma-encased endofullerene molecules entrapping a H atom

In this work, for the first time in the relevant literature, the persistent currents (PC) and induced magnetic fields (IMF) of an endofullerene molecule entrapping a hydrogen atom, under spherical confinement, are investigated. The endofullerene molecule is enclosed within a spherical region and embedded in a plasma environment. The plasma environment is depicted with the more general exponential cosine screened Coulomb potential, and its relevant effects are analyzed by considering plasma screening parameters. The relevant model for endohedral confinement is the Woods–Saxon confinement potential, which is compatible with experimental data. The effects of various forms of C n are thoroughly elucidated via the analysis of the confinement depth, spherical shell thickness, the inner radius, and the smoothing parameters. To find the bound states in the spherically confined endofullerene, the decoupling of the second-order Dirac equation for the large and small components of the radial atomic wave functions is considered. The Dirac equation with the interaction potential is solved numerically by using the Runge–Kutta–Fehlberg method via the decoupling formalism. The influence of spin orientations on the PC and IMF is also elucidated. The effects of spherical confinement, plasma shielding, and the structural properties of the fullerene on the PC and IMF are thoroughly viewed. Moreover, under given physical conditions, the optimal ranges of these effects are determined.

The Optimization of the One-Pot Synthesis of Au@SiO2 Core–Shell Nanostructures: Modification with Dansyl Group and Their Fluorescent Properties

This work describes the optimization of the one-pot synthesis of fine core–shell nanostructures based on nanogold (Au NPs) and silica (SiO2). The obtained core–shell nanomaterials were characterized by Transmission Electron Microscopy (TEM and by the method of spectroscopes such as UV–Vis Spectroscopy and Fourier Transform Infrared Spectroscopy (FT-IR). In addition, the measurement of the zeta potential and size of the obtained particles helped present a full characterization of Au@SiO2 nanostructures. The results show that the influence of reagents acting as reducers, stabilizers, or precursors of the silica shell affects the morphology of the obtained material. By controlling the effect of the added silica precursor, the thickness of the shell can be manipulated, the reducer has an effect on the shape and variety, and then the stabilizer affects their agglomeration. This work provides also a new approach for Au@SiO2 core–shell nanostructure preparation by further modification with dansyl chloride (DNS–Cl). The results show that, by tuning the silica shell thickness, the intensity of the fluorescence spectrum of Au@SiO2–(CH2)3–NH–DNS nanocomposite is about 12 times higher than that of DNS–Cl.

A REVIEW ON ADDITIVE MANUFACTURING (AM) MATERIAL - STATISTICS AND COMPARISIONS

Fused deposition modeling, also known as FDM, boasts a major edge in the manufacturing industry for its remarkable capacity to craft intricate components sans pricey tooling or manual labor. As is the case with any engineering process, selecting the right process parameters plays a critical role in determining the quality of FDM products. Hence, precise calibration of these parameters is essential to elevate the durability and functionality of printed parts. Our study seeks to explore the influence of five crucial FDM parameters, including layer height and shell thickness, on the tensile strength of build parts, with the ultimate goal of optimizing overall product performance. Keywords:Fusion Deposition Modeling (FDM), Shell thickness, precise calibration, durability, functionality of printed parts.

Localized Phonon Transport Study of GaN/SiO2 Core/shell Nanowires under Thermal-Stress Coupling.

In order to comprehensively explore the intricate mechanisms of thermo-mechanical interactions, this study employs the molecular dynamics method to investigate the influence of heat flux density, shell thickness and length, as well as stress on the radial interface phonon transport in GaN/SiO2 core/shell nanowire. Additionally, the surface eigenmode decomposition method is employed to analyze the interface phonon dispersion curves. The investigation reveals that with increasing heat flux density, internal thermal stresses intensify, leading to a complex distribution of thermal stresses within the system. Under the influence of thermal stress, the nonlinear acoustic properties interact with phonon scattering, resulting in the pronounced localization of interface phonons. Compressive stress causes an upshift in low-frequency phonons, while tensile stress induces a downward shift in the high-frequency optical branches at the interface. The localized phonon vibrations at the SiO2/GaN interface under nonuniform stress are identified as the primary cause for the abundant presence of nondispersive phonon modes at the radial interface. By elucidating the subtle interplay between lattice vibrations and stress fields, this study offers a novel and profound understanding of thermo-mechanical coupling effects, thereby providing innovative theoretical foundations for the design and performance management of thermoelectric devices.

Calcium-carbonate and phytoelements to improve egg production in backyard laying hens under heat stress

Calcium-carbonate and phytoelements to improve egg production in backyard laying hens under heat stress

Inclusion of metal nanoparticles at the core-shell interface of GaAs0.99Bi0.01/ZnO/ITO core-shell nanowire solar cell for photovoltaic performance enhancement

Optoelectronic performance analysis of perpendicularly aligned conformally coated GaAs0.99Bi0.01/ZnO/ITO core–shell nanowire solar cell having a core length of 1 μm, core diameter of 160 nm, shell thickness of 10 nm and period of 280 nm, decorated with Au metal nanoparticles(MNPs) of variable diameters at the core–shell interface is done employing FDTD method. Diameter optimization of MNPs with four different diameters values around core GaAs0.99Bi0.01 nanowire is accomplished in terms of maximum short circuit current density (Jsc), which offered an optimized diameter combination of D1 = D2 = 50 nm and D3 = 34 nm, D4 = 10 nm, resulting in a maximum Jsc of 32.6 mA cm−2. A detailed analysis of the electric field profile including its top view and longitudinal view is presented to investigate the distribution of electric field upon optical illumination at different wavelength range. The overall photo generation rate profile is also presented to focus on the localized surface plasmon resonance effect caused by the metal nanoparticles (MNPs). In order to boost the electrical performance, a thin coating of electron selective ZnO shell is used around p type GaAs0.99Bi0.01core, which aids in charge carrier separation, thereby improving open circuit voltage (Voc) and overall power conversion efficiency (PCE). The electrical characteristics of bare NW and MNP decorated GaAs0.99Bi0.01/ZnO core–shell nanowire solar cell for different MNP diameters have been compared. For the optimized diameter combination, as stated above, a Voc of 941 mV, Jsc of 28 mA cm−2, FF of 84.35% and PCE of 22.19% is obtained for SRV of 105 cm s−1 at the interfaces and SRH recombination lifetime as less as 10 ns. For SRV of 105 cm s−1 at the interfaces and SRH recombination lifetime of 1 μs, this proposed structure can achieve a Voc of 1.06 V, Jsc of 31.5 mA cm−2, PCE of 29.37% and FF of 87.88% for equal diameters of D1 = D2 = D3 = D4 = 50 nm.

High-order accurate transient and free-vibration analysis of plates and shells

The limited availability of analytical solutions and the high cost associated with experimental testing motivate the use of computational tools to assess the dynamic behavior of load-bearing components, especially when a wide design space must be explored, as is often the case with composite structures. In this context, a novel high-order accurate discontinuous Galerkin formulation for transient and free-vibration analysis of multilayered plates and shells is presented and numerical validated. The starting point of the formulation is a generalized structural theory for multilayered shells with arbitrary curvature based on the expansion of the displacement covariant components throughout the shell thickness. The variational statement of three-dimensional elastodynamics allows deriving the strong form of the governing differential equations, which form the basis to obtain the corresponding discontinuous Galerkin weak statements. As the order of the through-the-thickness expansion and the order of the discontinuous Galerkin basis functions are free parameters, the proposed approach allows tuning the order of accuracy of the computed solution throughout both the shell thickness and the shell modeling domain. Numerical results are reported and discussed for several validation test cases in terms of h- and p-convergence analyses, demonstrating the high-order accuracy, robustness, and computational savings of the formulation.

Research on and application of low-temperature calcination on waste Taiwanese hard clam shell during Taiwanese hard clam aquaculture

This study uses a circular economy-regenerative value addition approach. Pre-treated waste clam shells were calcined at a low temperature (about 300 °C) and then crushed into clamshell powder. Taiwanese hard clam shell (THCS) powder and commercially available calcium carbonate products, such as low-temperature calcined oyster shell (OS) powder, slaked lime, and calcium carbonate, were compared experimentally, and the safety of THCS powder was determined. In the safety evaluation, the Vibrio-like bacteria test results showed that no colony growth was found for the low-temperature-calcined THCS powder, indicating that it did not contain Vibrio-like bacteria. Tolerance test results showed that high-dose slaked lime will cause high Taiwanese hard clam mortality, and the survival rates of other groups were all 100%. In addition, slaked lime had the most significant effect on increasing the water pH. OS powder had the greatest effect on increasing the calcium ion concentration in the water, followed by THCS power. The aquaculture benefit-related experimental results showed that the low-temperature calcined OS powder and THCS powder groups had the most favorable performance in terms of Taiwanese hard clam growth rate, shell weight, and shell thickness. This study used different calcium carbonate products as additives in Taiwanese hard clam aquaculture ponds and observed growth differences between the different groups. These results indicated that the low-temperature calcination of THCS in Taiwanese hard clam aquaculture can effectively replace the commonly used OS powder, slaked lime, and calcium carbonate products in traditional aquaculture. Furthermore, it can effectively solve the problem of THCS waste accumulation, promote environmental beautification, create a circular economy and aquaculture application value, and conform to the economic benefits of aquaculture.

Vibrations and thermoelastic quality factors of hemispherical shells with fillets

In engineering applications, hemispherical shell resonators are typically machined with fillets to reduce stress concentration and enhance structure strength. The fillets will inevitably affect the dynamic properties and the mechanical quality factor of hemispherical shell resonators, which has been seldom investigated before. In this paper, an effective analytical method is developed to explore the free vibration and thermoelastic damping (TED) characteristics of the hemispherical shell with fillets. The fillets are characterized by the variation in the thickness of the hemispherical shell during modelling. The first-order shear deformation theory (FSDT) is used to describe the theoretical formulas of the hemispherical shell with fillets. By employing the unified Jacobi polynomials and Fourier series as the assumed mode shape functions, the equation of motion of the structure is established by Hamilton's principle and the assumed mode method. The analytical model for thermoelastic quality factor (QTED) which is determined by TED is obtained by computing the dissipated energy and the maximum elastic potential energy of the hemispherical shell with fillets. The validity and accuracy of the present method are confirmed by comparing the present solutions with the published results and those obtained from the finite element method (FEM). The influences of fillets on the vibration behaviors and QTED characteristics of the hemispherical shells are analyzed in detail. The present model can be used to optimize the design of the fillets of the hemispherical shell resonators with high quality factors.

Estimating yolk weight of duck eggs using VIS-NIR Spectroscopyand RGB images and whole egg weights

Duck eggs are widely-consumed food and cooking ingredient. The heavier yolk weight (YW) corresponds to a larger size and greater value. However, there is no non-destructive method available to estimate the weight of the yolk. Accurate weight prediction of duck egg yolks must combine both phenotypic and internal information. In this research, we used Visible-Near Infrared (VIS-NIR) spectroscopy to obtain internal information of duck eggs, and a high-definition camera to capture their phenotypic features. YW was predicted by combiningthe reduced spectral and RGB image information with the whole egg weight. We also investigated the impact of color and thickness of the duck egg on spectral transmittance (ST), as these factors can influence the extent of ST. The results showed that the spectral curves of duck eggs produced two peaks and one valley, which may be caused by the dual-frequency absorption of the C-H group and O-H group, and can be used to symbolize the internal information of duck eggs. The ST was somewhat affected by the color and thickness of the duck eggshell. Before modelling, Principal Component Analysis (PCA) was used to significantly reduce the dimensionality of the RGB image with spectral data. A Partial Least Squares Regression (PLSR) model was utilized to fit all the features. The test set yielded a coefficient of determination (R²) of 0.82 and a Root Mean Squared Error (RMSE) of 1.05 g. After removing the eggshell's color and thickness features, the model showed an R² of 0.79 and an RMSE of 1.11 g. This study demonstrated that the yolk weight of duck eggs can be estimated using VIS-NIR spectroscopy, RGB images and whole egg weight. Furthermore, the effects of shell color and thickness can be neglected.

Effects of Transient Obliquity Tides Within Mimas' Warm, Icy Interior Preserved as a Frozen Fossil Figure

AbstractMimas has a high eccentricity and an anomalously high physical libration like its neighbor, Enceladus, but does not appear to have a geologically active surface. We investigate Mimas' interior with a technique that infers spatial variations in tidal heating from its global shape. To account for its hydrostatic shape, we find Mimas' normalized moment of inertia is 0.375 ± 0.0025, indicating a relatively undifferentiated world. Its remaining topography is consistent with a ∼30 km thick conductive ice shell in Airy isostasy atop a weakly convecting ∼30 km thick layer that itself mantles a ∼140 km radius ice‐rock interior. The convective shell's density must be closer to the interior density to satisfy our moment of inertia and provide a denser compensating layer for Airy isostasy. This ice‐rock interior is elongated along the Mimas‐Saturn axis, which can match Mimas' observed physical libration without appealing to an ocean. The inferred ice shell thickness variations indicate a high obliquity (≈1.7°). We suggest that the obliquity damped rapidly, after which topography froze in when internal heat was conducted out of Mimas quicker than isostatic ice shell thickness variations could relax. We speculate on several possible explanations for this transient high obliquity, including excitation by ring‐forming material following the recent tidal disruption of an eccentric satellite. We cannot rule out a young Mimantean ocean, but our inferred moment of inertia favors a Mimas that was solid when it experienced a period of high obliquity, did not significantly melt during a recent resonance with Enceladus, and is solid today.

Amorphous/Graphitic carbon phase engineering of Corrosion-Resistant Fe@C Core-Shell nanowires for optimized dipole polarization and enhanced microwave absorption

The study of designing and developing ferromagnetic nanocomposites with both microwave absorption (MA) and corrosion protection properties through microscopic heterogeneous interfacial engineering and crystal phase engineering remains challenging. In this study, Fe@C core–shell nanowires (FCNWs) are obtained by magnetic field-controlled in situ reduction method and annealing process to de-regulate the carbon shell thickness and carbon morphology. The enhancement of Fe-C heterogeneous relative interfacial effects and dielectric/magnetic response is revealed using density functional theory and simulated electromagnetic field distribution, and the modulation of the amorphous carbon/graphitic carbon ratio achieves the enhancement of dipole polarization in the low-frequency region. The FCNWs absorber had a minimum reflection loss (RLmin) of −47.6 dB at a thickness of 4.9 mm, and the maximum effective absorption bandwidth (EABmax) was achieved at 5.5 mm up to 4.0 GHz. In addition, the shielding effect of the graphitic carbon shell on the corrosion medium and the addition of additional electron conduction pathways allow the FCNWs absorber to obtain smaller corrosion currents and larger polarization resistances compared to Fe nanowires. Thus, modulation of atomic-scale heterogeneous interfaces and crystal phases has great potential in modulating the dielectric response.

Yolk-shell electron-rich Ru@hollow pyridinic-N-doped carbon nanospheres with tunable shell thickness and ultrahigh surface area for biomass-derived levulinic acid hydrogenation under mild conditions

Aiming to efficiently upgrade renewable biomass-derived levulinic acid (LA) into γ-valerolactone (GVL), we have devised yolk-shell electron-rich Ru@hollow pyridinic-N-doped carbon nanospheres, featuring a tunable shell thickness (20−70nm) and an ultrahigh surface area (4016 m2 g−1). Experimental and theoretical investigations reveal that the strategic formation of the yolk-shell structure and appropriate thinning of the carbon shell facilitate the generation of electron-rich Ru0 and a positive shift of the d-band center towards the Fermi level by increasing surface pyridinic-N species. These modifications suitably intensify Ru0−H interaction, promote reactant adsorption, stimulate electron transfer between active H and the C=O group of LA, and ultimately reduce apparent activation energy. Consequently, a high LA turnover frequency (18733.4h−1 at 30 °C) and GVL selectivity (99.9%), alongside excellent stability up to eight cycles, are achieved, markedly outperforming externally-supported analogues. These findings afford valuable insights into designing yolk-shell nanostructures for biomass upgrading through microenvironment engineering.