Analysis Of Shells Research Articles

Frequency analysis of a sandwich conical shell with nanocomposite face layers and a honeycomb core with oriented cells

In this research, the free vibration analysis is investigated for a sandwich conical shell with two nanocomposite face layers and either a hexagonal honeycomb (HH) or a re-entrant honeycomb (RH) core oriented in an arbitrary direction. Both HH and RH cores are orthotropic structures, but the RH is an auxetic structure and the HH is a non-auxetic one. The nanocomposite face layers are fabricated of a polymeric matrix strengthened with uniformly distributed agglomerated either carbon nanotubes (CNTs) or graphene nanoplatelets (GNPs). The sandwich shell is modeled via Murakami’s zig-zag theory, and the governing equations and boundary conditions are derived through Hamilton’s principle. The influences of various parameters on the natural frequencies are investigated including orientation, wall thickness, and inclined angle of the cells in the honeycomb core, thickness of the honeycomb core, mass fraction and type of the nanofibers, agglomeration intensity, and boundary conditions. It is concluded that in each vibrational mode, there are optimum values for the orientation and wall thickness of the cells and thickness of the honeycomb core which result in the highest natural frequency.

Rowing Against the Tide: The Golden Mussel (Limnoperna fortunei) Leaves DNA Footprints Along Its Invasion Route in South American Rivers

The invasion of the golden mussel has resulted in considerable environmental and socioeconomic alterations, which present a considerable threat to the native biodiversity and sustainability of the region. Understanding the distribution and biological characteristics of this Asian mussel, as well as its interaction with human activities, is of the utmost importance to developing effective strategies for mitigating and preventing its further spread. This study examines the dispersal route and incidence of golden mussels, tracing their movement from initial populations in Argentina to their arrival in the São Francisco River Basin (SFR). The presence of the mussel was confirmed through an integrative assessment that included shell taxonomic analyses and mitochondrial DNA signatures. This assessment identified populations located 7.5 km from the river’s mouth, close to the Atlantic Ocean, in areas such as shrimp farms, artisanal ports, and marinas. The analysis of mitochondrial DNA revealed the presence of South-American-specific and shared ancestral haplotypes in the SFR, Grande River, and Argentina. These findings indicate that intracontinental colonization toward the northeast region of South America originated from Asian populations that entered South America via Argentina. The absence of Asian-specific signatures in the SFR, combined with a geomorphological structure unsuitable for large ports or transoceanic vessels, supports the hypothesis of the intracontinental dispersal of Limnoperna fortunei.

Frequency analysis of tetra layered FGM cylindrical shell with S-S Edge condition

A Cylindrical shell consists of a curved surface that extends around a central axis, with its thickness being relatively small compared to its height and radius. It has wide range applications in pressure vessels and tanks, heat exchangers, aerospace etc. This article analyzes four shell surfaces, the first and third layers of functionally graded material, and the second and fourth layers of isotropic material. The natural frequency is influenced by several thick layers. The shell frequency equation is obtained by usig the Rayleigh-Ritz approach. The strain and curvature-displacement relations are derived from Sander’s shell theory. Characteristic beam functions are employed to assess the dependence of axial modal and trigonometric volume fraction law is used to attain the vibration anaylsis. Results are acquired for different thickness-to-radius and length-to-radius ratios under various edge conditions. For simply supported edge circumstances, the natural frequencies are calculated by using MATLAB software.

Performance impact analysis of shell and tube PCM heat exchanger based on hemispherical rough elements

Performance impact analysis of shell and tube PCM heat exchanger based on hemispherical rough elements

Genomic Features of Taiwanofungus gaoligongensis and the Transcriptional Regulation of Secondary Metabolite Biosynthesis

Fungal secondary metabolites (SMs) have broad applications in biomedicine, biocontrol, and the food industry. In this study, whole-genome sequencing and annotation of Taiwanofungus gaoligongensis were conducted, followed by comparative genomic analysis with 11 other species of Polyporales to examine genomic variations and secondary metabolite biosynthesis pathways. Additionally, transcriptome data were used to analyze the differential expression of polyketide synthase (PKS), terpene synthase (TPS) genes, and transcription factors (TFs) under different culture conditions. The results show that T. gaoligongensis differs from other fungal species in genome size (34.58 Mb) and GC content (50.72%). The antibiotics and Secondary Metabolites Analysis Shell (AntiSMASH) analysis reveals significant variation in the number of SM biosynthetic gene clusters (SMBGCs) across the 12 species (12–29), with T. gaoligongensis containing 25 SMBGCs: 4 PKS, 6 non-ribosomal peptide synthetase (NRPS), and 15 TPS clusters. The TgPKS1 gene is hypothesized to be involved in the biosynthesis of orsellinic acid or its derivatives, while TgPKS2 might catalyze the synthesis of 6-methylsalicylic acid (6MSA) and its derivatives. The TgTRI5 genes are suggested to synthesize tetracyclic sesquiterpene type B trichothecene compounds, while TgPentS may be involved in the synthesis of δ-cadinol, β-copaene, and α-murolene analogs or derivatives. Comparative genomic analysis shows that the genome size of T. gaoligongensis is similar to that of T. camphoratus, with comparable SMs. Both species share four types of PKS domains and five distinct types of TPS. Additionally, T. gaoligongensis exhibits a high degree of similarity to Laetiporus sulphureus, despite belonging to a different genus within the same family. Transcriptome analysis reveals significant variation in the expression levels of PKS and TPS genes across different cultivation conditions. The TgPKS1 and TgPKS4 genes, along with nine TgTFs, are significantly upregulated under three solid culture conditions. In contrast, under three different liquid culture conditions, the TgPKS3, TgTRI5-1, and TgTRI5-2 genes, along with twelve TgTFs, exhibit higher activity. Co-expression network analysis and TgTFs binding site prediction in the promoter regions of TgPKS and TgTPS genes suggest that TgMYB9 and TgFTD4 regulate TgPKS4 expression. TgHOX1, TgHSF2, TgHSF3, and TgZnF4 likely modulate TgPKS3 transcriptional activity. TgTRI5-1 and TgTRI5-5 expression is likely regulated by TgbZIP2 and TgZnF15, respectively. This study provides new insights into the regulatory mechanisms of SMs in T. gaoligongensis and offers potential strategies for enhancing the biosynthesis of target compounds through artificial intervention.

Biosorption of petroleum compounds from aqueous solutions using walnut shells

Herein, a walnut shell as a biosorbent was applied to remove petroleum compounds from the water medium. The characterization analyses of the walnut shells showed the macro-mesopore structure of the walnut shells, a specific surface area of 26 m2/g, and the presence of various functional groups (-OH, -COOH, -C = O). The CCD design showed that the walnut shell can remove 84.43% of petroleum compounds at pH = 3 (the optimum pH), adsorbent dosage: 2 g/L, and initial concentration of petroleum compounds: 550 mg/L. The study of kinetics and adsorption equilibrium indicated matching the experimental data with the pseudo-second-order kinetic model and Freundlich equilibrium isotherm, respectively. The maximum adsorption ability of walnut shell was 3038.29 mg/g at 45 °C. The ability to regenerate and reuse the walnut shell was investigated in 6 cycles, and the results showed a 21% decrease in adsorption ability after 6 cycles. The obtained data showed that the walnut shells could be a promising adsorbent with high adsorption ability toward petroleum components. Also, the walnut shell is a regenerable adsorbent, low-cost, and environmentally friendly, and can be effective in successive cycles. Therefore, this biosorbent can have a superb influence on wastewater treatment technology and possible applications at an industrial scale.

Free vibration optimization of 2D tri-axial braided composite fan blade with ANN-Anal-FEM-GA integrated model

This research aimed to increase the natural frequencies of a non-rotating 2D tri-axial braided composite (2DTBC) fan blade. The investigation utilized a multidisciplinary approach, integrating Artificial Neural Network (ANN) modeling, analytical method, Finite Element (FE) analysis, optimization techniques, and experimental validation. The ANN captured the complex relationship between the braiding machine and structure parameters. The mechanical properties of the 2DTBC were determined through the micromechanical modeling, and the thin-shell analysis was applied to describe the blade’s displacement and strain characteristics. Micromechanical modeling examines material behavior at the microscopic level, and thin shell analysis focuses on modeling and analyzing thin, curved structures using simplified equations. The FE method facilitated the formulation of the equation of motion and the calculation of natural frequencies. A genetic algorithm, focused on a single-objective optimization, was employed to refine the braiding structure parameters and the number of composite layers, thereby enhancing the blade’s natural frequencies. The optimized 2DTBC blade was subsequently fabricated and validated through impact hammer modal testing, showing strong agreement with the predictions from the combined ANN-analytical-FEM-GA model. The optimization of the braiding parameters led to a significant increase in the blade’s natural frequencies.

Spatiotemporal changes in riverine input into the Eocene North Sea revealed by strontium isotope and barium analysis of bivalve shells

Reconstructing hydrological conditions of past warm periods, such as the Eocene ‘hot house’ provides empirical data to compare to state of the art climate models. However, reconstructing these changes in deep time is challenging, for example, given the complex interplay between evapotranspiration, precipitation and runoff. As a proxy for past changes in these hydrological systems, the dynamics of fresh water input into marginal seas can be used to identify the spatiotemporal distribution of riverine runoff. Elemental barium (Ba) and radiogenic strontium (87Sr) are, depending on the amount of runoff and the background geology of the catchment area, typically enriched in river waters in comparison to seawater and can thus be utilized to determine changes in riverine fresh water discharge. Here, we use barium to calcium ratios (Ba/Ca) and radiogenic strontium isotopes (87Sr/86Sr) measured in fossil bivalve shells to reconstruct patterns of fresh water input into the paleo North Sea during the early to middle Eocene. Our reconstruction shows the potential of Ba/Ca and 87Sr/86Sr to serve as proxies for riverine runoff and highlights the spatiotemporal complexity of Eocene hydrological conditions in western Europe. In particular, our results enable changes in riverine input along geological to perennial time scales for different coastal regions to be determined, revealing a steady influx of fresh water, but with distinct spatiotemporal differences.

Paleoecology, bioerosion, and paleoenvironments in the Late Miocene of Dar Pahn Unit, Makran, SE Iran

This study focuses on sedimentation patterns and paleoecological conditions during the Upper Miocene in Southeast Iran, specifically analyzing the Rudig section. The sedimentation was predominantly terrigenous and occurred in marine conditions, forming multiple shallowing upwards sequences comprising silty marl, siltstone, and sandstone. The analysis of molluscan shells from this period indicates minimal bioerosion, with encrusters represented solely by Balanus sp. This low level of encrustation suggests rapid sedimentation and brief exposure times. Bioerosion was limited, with Caulostrepsis taeniola borings found only in the shells of vermetid Thylacodes sp. and predatory gastropod Conus sp. Predatory drillings, identified as Oichnus paraboloides were present in the shells of Turritella sp., Corbula sp., and Bursa sp., along with occasional shell aperture peeling repairs in Turritella sp. The presence of abundant large Thalassinoides burrows in the sandstone facies, along with moderate ichnodiversity supports the interpretation of the sandstone facies as shoreface. The rare occurrence of Ophiomorpha nodosa in siltstone facies, and the dominance of burrowing crustaceans in shallow water facies and suspension-feeding mollusks in deeper facies, provides further insight into the paleoenvironment. This study offers a detailed reconstruction of the sedimentary and ecological dynamics during the Upper Miocene in this region, enhancing our understanding of paleoenvironmental conditions and faunal interactions. Keywords: biofacies, sedimentary facies, bioerosion, encrustation, predation, Cenozoic.

Yielding onset in FGM thick-walled spherical shells under thermo-mechanical loading

Based on von Mises yield criterion, a thermoelasto-plastic analysis of a thick-walled spherical shell composed of functionally graded material (FGM) subjected to internal pressure and thermal gradient is conducted in order to accurately predict the onset radius of yielding within the vessel wall. The modulus of elasticity, thermal conductivity and thermal expansion coefficients, and yield stress of FGM are assumed to follow power-law functions in radius according to Erdogan’s model. The equilibrium differential equation of the shell under thermo-mechanical loading in steady-state conduction heat transfer are derived analytically and then solved to determine through-thickness variations of the radial and circumferential stresses and radial displacement in elastic and perfectly plastic zones in the vessel wall. The presented approach leads to the definition of new formulation to predict the onset radius of yielding. Moreover, a neural network (NN) solution to reliable quantify the influence of all uncertain input parameters with respect to uncertain output parameter is utilized. The numerical results showed that for various FGM parameters and specific thermal gradient, the plastic zone can commence from inside radius, outside radius, simultaneously in both radii, or may be launched in the intermediate radius of the spherical shell wall.

A comprehensive study of beam modal functions in the free vibration analysis of cylindrical shells: Critical examination on the applicability to the clamped-free boundary condition

Over the past few decades, approximate methods that can provide solutions of sufficient accuracy have received considerable attention in the free vibration analysis of cylindrical shells, where a great deal of studies adopted the beam modal functions as the trial functions for the axial mode shapes of cylindrical shells. Nevertheless, most studies were restricted to the application of single term beam modal function and failed to simulate elastic boundary conditions of cylindrical shells, while the accuracy of the corresponding methods has recently sparked significant controversy, especially for cylindrical shells under the clamped-free boundary condition. This paper presents a comparative study of three forms of beam modal functions in the free vibration analysis of cylindrical shells, one of which is proposed for the first time to simulate elastic boundary conditions of cylindrical shells. A unified model is developed using the general Rayleigh–Ritz method, incorporating the breathing modes with circumferential orders being zero, and four types of commonly used thin shell theories, namely the Donnell, Reissner, Love, and Sanders theories. From both perspectives of natural frequencies and mode shapes, numerical results are validated by comparison with those existing in the literature and those calculated from the finite element method (FEM). The results not only clarify the distinction of different forms of beam modal functions used in the Rayleigh-Ritz method, but also provide explanations for the controversy raised in recent studies. Furthermore, the unified formulations can be extended to vibration analysis of various forms of shell structures, and can also be helpful to the vibration analysis of beams and plates with elastic boundary conditions.

Weak form quadrature shell elements based on absolute nodal coordinate formulation

Weak form quadrature elements for moderately thick shells with arbitrary initial configurations are developed under the framework of continuum mechanics and the absolute nodal coordinate formulation (ANCF). Locking problems of shell analysis are discussed. Nonlinear analysis of various shell structures is conducted. The joint constraint equations for shells with discontinuous slopes are established. Five examples encompassing static and dynamic shell analysis, post-buckling analysis of shells, as well as analysis of shells with discontinuous mid-surface slopes are examined to assess the performance of the proposed elements. Satisfactory results are obtained, validating the efficacy of the proposed elements.

Free vibration and supersonic flutter analyses of a sandwich cylindrical shell with CNT-reinforced honeycomb core integrated with piezoelectric layers

In this research, the free vibration and supersonic flutter analyses of a cylindrical sandwich shell with a reinforced honeycomb core (RHC) integrated with piezoelectric face sheets are investigated. The core is a honeycomb structure enriched with fibers and carbon nanotubes (CNTs). The layers of the shell are modeled based on the Cooper-Naghdi shell theory and the continuity conditions between the layers are considered. The aerodynamic pressure of the supersonic flow is modeled using the linear piston theory. Hamilton’s principle is used to derive the governing equations. A semi-analytical solution is presented including an exact solution in the circumferential direction followed by a numerical solution in the longitudinal direction via the differential quadrature method (DQM). The effects of several parameters on the frequencies, the corresponding damping coefficients, and the critical aerodynamic pressure are investigated. It is concluded that improving the stiffness of the honeycomb core with the CNTs does not necessarily improve the aeroelastic stability of the shell. The presented results can be used in the design and analysis of aerospace structures.

Three-dimensional elasticity solutions for doubly-curved composite shells by extended differential quadrature method

This paper presents the three-dimensional (3D) stress analysis of doubly-curved composite shells with general boundary conditions using the strong sampling surfaces (SaS) formulation. The SaS method is based on the choice of SaS parallel to the middle surface and located at Chebyshev polynomial nodes to introduce the displacements of these surfaces as unknown functions that leads to a non-conventional shell formulation, in which strain–displacement and stress–strain relationships are represented in terms of SaS displacements. This is due to the use of Lagrange polynomials in approximating displacements, strains and stresses in the thickness direction. The outer surfaces are not included into a set of SaS that makes it possible to uniformly minimize the error used by Lagrange interpolation. The strong SaS formulation, based on direct integration of elasticity equilibrium equations in the thickness direction by the extended differential quadrature (EDQ) method, can be applied efficiently for high-precision calculations of doubly-curved composite shells with clamped and free edges. This is because in the SaS/EDQ formulation, displacements, strains and stresses of SaS are interpolated in a rectangular domain specified in a curvilinear coordinate system using a Chebyshev-Gauss-Lobatto grid and Lagrange polynomials are also used as basis functions. The proposed approach deals with equilibrium equations in terms of SaS stresses, avoiding the integration of second order differential equations in terms of SaS displacements, that greatly simplifies the implementation of the EDQ method.

Buckling analysis of PMMA hemispherical pressure shells with thickness variation

The buckling behaviour of polymethyl methacrylate (PMMA) hemispherical pressure shells under uniform external pressure was investigated experimentally and numerically. Six PMMA hemispherical pressure shells were prepared via the free blow-forming process. The geometry and wall thickness of each hemispherical shell were measured. The collapse loads and final failure modes of all shells were obtained via a hydrostatic pressure device. In addition, through optical 3D scanning, a numerical model of the hemispherical shell that reflects the actual geometric imperfection was established and used in the finite element buckling analysis. The numerical results were in agreement with the test results. These findings provide a reference for evaluating the buckling load of PMMA hemispherical shells prepared via the free blow-forming process.

RFOR-DQHFEM: Hybrid relaxed first-Order reliability and differential quadrature hierarchical finite element method for multi-physics reliability analysis of conical shells

In this current work, a hybrid reliability analysis and theoretical frequency technique are suggested for the reliability response of conical shells. Two levels of analyses are proposed as the main loop of the reliability method for finding the failure probability and the second level applied in the main loop for giving the performance function of frequency applied in conical shell structures with multi-physics vibration analysis. A dynamical adjusting procedure is proposed for computing the relaxed factor using the enough descent condition inside the reliability method. The superior convergence rate is considered for selecting the relaxed factor of the proposed first-order reliability method named RFORM. An elastic-electro-mechanical model based on the Higher-Order Shear Deformation Theory (HSDT) is extended for frequency analysis of conical shells. The innovative numerical procedure named Differential Quadrature Hierarchical Finite Element Method (DQHFEM) as a robust framework for giving the vibration behavior of studied mechanical structures is applied for solving motion equations. The developing DQHFEM and RFORM are applied for the laminated, nanocomposite, and piezoelectric conical shell structures with multi-source uncertainties. Increasing the volume percentage of nanoparticles from 0% to 10% significantly enhances the reliability index, with carbon nanoparticles showing a 132% increase, silica nanoparticles showing a 97% increase, and other nanoparticles showing an approximate 40% increase. Also, as moisture content increases from 0% to 30%, the reliability index for a thickness-to-large-radius ratio of 0.2 drops by about five times. Excessive moisture levels (above 20%) result in a negative reliability index, indicating a hazardous condition.

Buckling analysis and parametric optimization of the metal-composite shell with voids under hydraulic pressure combined with sensitivity analysis

Structural design parameters always impact the buckling properties of the composite shells due to the differences in the anisotropy of the materials and the varying enhancement capabilities of each component. This paper aims to analyze the parametric effect on the buckling load and optimize the design parameters of metal-composite shells with voids under hydraulic pressure. Firstly, the theoretical model of buckling load is established based on the microscopic model of hybrid materials and the Galerkin method. Then, four design parameters including fiber volume content, winding angles, and CNTs volume content are selected to discuss the parametric effect on the critical buckling load. Further, the global sensitivity analysis is conducted to determine the influence rank, and the GA-PSO algorithm is used to confirm the optimal parametric combination. The results imply that the fiber volume content and internal and external helical symmetrical angles significantly affect the buckling load. Besides, The winding layers of internal and external helical symmetrical angles enhance the hydraulic resistance of the anti-symmetric structure. The middle helical layer can be influenced by the outer layer, leading to directional changes in the critical buckling load at an angle of around 50°.

Correlation study of graphitic shell encapsulated nickel: A multi-spectroscopic approach

Graphite-encapsulated metal nanoparticles hold great potential across various applications due to their unique combination of metal and graphitic properties. While Raman spectroscopy is widely used to assess the graphitic shells, metrics derived from prominent Raman bands often prove unreliable when analyzing such structures with a large number of heterogeneous flakes and are mostly applicable to few-layer graphene. However, researchers continue to face challenges in identifying reliable metrics that accurately reflect two key properties of graphitic shells: thickness and degree of graphitization. In this study, graphitic shells were synthesized via plasma-enhanced chemical vapor deposition (PECVD) at low temperatures (500 °C), seeded by nickel nano-islands. A full-factorial experiment was designed to explore a diverse sample space by varying two key input factors: the initial thickness of the nickel seeding film and the duration of carbon deposition. Using resource-intensive surface characterization techniques (SEM, EDS, XPS, and AFM), we verified encapsulation efficiency and morphology, identifying strong correlations between the input factors and properties of the shells. To gain insights into structural characteristics, we employed conventional spectroscopy techniques (Raman, UV–Vis-nIR transmission, and Transient Absorption Spectroscopy), introducing 107 metrics derived from spectral data. Principal Component Analysis (PCA) aligned the input factors, and their corresponding shell properties, with the first two principal components. Accordingly, we identified the most relevant metrics including new candidates derived from less prominent Raman bands. Additionally, inter-metric correlations enable interchangeable use of spectroscopy techniques. This study marks the first multi-spectroscopic correlation analysis of graphitic shells and provides a novel framework for evaluating their properties.

A Financial Analysis and Valuation of Shell

In todays era of global energy transition, the strategic choices made by energy giants like Shell carry immense significance, shaping not only their own future blueprint but also profoundly influencing the overall energy sectors trends. The article provides a comprehensive analysis of Shell plc with liquidity, solvency, profitability, and valuation analysis of 2023 with its main competitors in the oil and gas industry. Despite facing challenges from fluctuating commodity prices and regulatory changes, Shell maintains a competitive advantage and favorable market position. The company demonstrates robust financial health, with strong liquidity, solvency, and profitability ratios compared to industry peers. Nevertheless, the analysis reveals the companys profitability ratios lag behind competitors, indicating room for improvement. Although facing uncertainties in future commodity prices and regulatory environments, the analysis highlights Shells commitment to balancing environmental goals with shareholder value, as evidenced by its energy transition strategy. Shells stock is still fairly valued according to the analysis, presenting a compelling investment opportunity with its well-constructed financial framework. Overall, Shells strategic plans and adjustments aim to ensure resilience and adaptability, promising investors sustainable development amidst evolving market dynamics.

A Meshfree Approach for Dynamic Analysis of Sandwich Conical and Cylindrical Shells with Varying Thicknesses

A Meshfree Approach for Dynamic Analysis of Sandwich Conical and Cylindrical Shells with Varying Thicknesses