Multilayered Shells Research Articles

Boosting Acidic Hydrogen Evolution Kinetics Induced by Weak Strain Effect in PdPt Alloy for Proton Exchange Membrane Water Electrolyzers.

Strain engineering is an effective strategy for manipulating the electronic structure of active sites and altering the binding strength toward adsorbates during the hydrogen evolution reaction (HER). However, the effects of weak and strong strain engineering on the HER catalytic activity have not been fully explored. Herein, the core-shell PdPt alloys with two-layer Pt shells (PdPt2L) and multi-layer Pt shells (PdPtML) is constructed, which exhibit distinct lattice strains. Notably, PdPt2L with weak strain effect just requires a low overpotential of 18mV to reach 10mA cm-2 for the HER and shows the superior long-term stability for 510h with negligible activity degradation in 0.5M H2SO4. The intrinsic activity of PdPt2L is 6.2 and 24.5 times higher than that of PdPtML and commercial Pt/C, respectively. Furthermore, PdPt2L||IrO2 exhibits superior activity over Pt/C||IrO2 in proton exchange membrane water electrolyzers and maintains stable operation for 100h at large current density of 500mA cm-2. In situ/operando measurements verify that PdPt2L exhibits lower apparent activation energy and accelerated ad-/desorption kinetics, benefiting from the weak strain effect. Density functional theory calculations also reveal that PdPt2L displays weaker H* adsorption energy compared to PdPtML, favoring for H* desorption and promoting H2 generation.

Seismic behavior of composite shear walls with post-casting UHPC boundary elements and CRB600H steel bars

This study investigates the seismic behavior of composite shear walls reinforced with post-casting Ultra-High Performance Concrete (UHPC) boundary elements and Colded-Rolled Ribbed Bars (CRB600H). The research aims to explore the synergistic effects of UHPC and CRB600H bars on seismic performance. Six shear wall specimens with a shear span ratio of 1.56 were subjected to cyclic loading to evaluate their failure modes, crack patterns, hysteresis behavior, stiffness degradation, ductility, residual deformation, and energy dissipation capacity. The results demonstrated that the use of CRB600H bars in boundary elements of normal concrete specimens improved post-yield stiffness and reduced residual deformation. Conversely, incorporating UHPC in boundary elements enhanced load-bearing capacity and crack control but slightly reduced ductility due to the weaker interfacial connection between UHPC and the foundation. Additionally, CRB600H bars in the web region improved load-bearing capacity while maintaining ductility comparable to HRB400 bars. The findings suggest that substituting CRB600H for HRB400 in shear-dominant regions can enhance the seismic performance of shear walls. Finally, the multi-layer shell element numerical model validated by the experimental results was encouraged to conduct parametric analysis in the future. This research supports the development of more resilient building structures by integrating high-performance materials in key structural components.

Shaking table test of a full-scale lightweight bolt-connected concrete sandwich wall panel structure: Overview and seismic analyses

This study proposed a novel lightweight bolt-connected concrete sandwich wall panel structure with the advantages of thermal insulation, construction efficiency, demountability and remountability. The seismic design of the structure was employed a non-equivalent cast-in-place method, resulting in appropriate configurations of horizontal and vertical bolted joints. Subsequently, a shaking table test was carried out to investigate the damage pattern, dynamic characteristics and dynamic responses of a full-scale structure. The test results demonstrated that the overall damage was moderate, which exerted a few impacts on the structural capacity or integrity. The global responses, including small displacement response, minor torsion response, and high energy dissipation capacity were found, as well as local responses, such as small strains in the steel plates and a slight loss of bolt prestress. The maximum inter-story drift ratio was below the elastoplastic inter-story drift ratio limit θu = 1/120 defined in Chinese code GB 50011. In general, the structure presented high lateral stiffness and sufficient capacity against high-intensity ground motions. A numerical model was developed, wherein precast components were established by multi-layer shell elements and bolted joints were simulated by 3-DoF nonlinear springs. Linear modal and nonlinear time history analyses were performed and compared with the experimental results. The simulation results showed good agreement with the experimental ones, confirming the ability of the model to capture global responses.

Green synthesis of sacrificial UV-sensitive core and biobased shell for obtaining optically hollow nanoparticles

Hollow nanoparticles have been extensively studied in recent years. Obtaining such structures with biobased materials, following greener synthetic routes, is still challenging, especially if accurate particle dimensions are required. This work reports the use of an innovative hybrid silica core (Si@azo) containing UV-sensitive molecule, wrapped in biobased multilayer shell composed of polysaccharides. It is a promising strategy for obtaining optically hollow nanoparticles. Indeed, Si@azo cores have the ability to be partially degraded when irradiated with UV light. Combined with a well-controlled and monodisperse diameter, they provide a good basis for layer-by-layer assembly, leading to a multilayer shell with controlled composition and thickness. Finally, UV irradiation of such a core–shell structure is harmless to the polysaccharide shell, but does impact the hybrid silica core, as revealed by turbidity measurements, among other. Each step, i.e. core synthesis, shell addition, and core–shell irradiation, has been carefully characterized at the macro (Fourier-transform infrared spectroscopy – FTIR, Dynamic Light Scattering – DLS, Zeta-potential measurement, Surface Plasmon Resonance – SPR, turbidity) and microscale (Transmission and Scanning Electron Microscopies). Emphasis is put on how turbidity measurements can be related to the core refractive index (ncore), giving information on the state of core degradation and whether the core–shell particle is optically hollow.

Design and implementation of a high-performance miniaturized multi-layer magnetic shielding spherical shell with minimal pores based on target magnetic field

Achieving the spin-exchange relaxation-free (SERF) state in atomic comagnetometers (ACMs) necessitates a stable and weak magnetic environment. This paper presents the design of a miniaturized permalloy magnetic shielding spherical shell (MSSS) with minimal apertures, tailored to meet these requirements. By employing a combination of analytical solutions and finite element analysis (FEA), we achieved superior magnetic shielding while maintaining a compact form factor. The analytical solution for the shielding factor indicated that a four-layer permalloy sphere shell with optimized air gaps was necessary. A numerical analysis model of the MSSS was developed and validated using COMSOL software, confirming the suitability of the air gaps. The size, shape, and orientation of the openings in the perforated sphere shell were meticulously designed and optimized to minimize residual magnetism. The optimal structure was fabricated, resulting in triaxial shielding factors of 47619, 52631, and 21739, meeting the anticipated requirements. A comparison of simulation results with experimental tests demonstrated the efficacy of the design methodology. This study has significant implications for ultra-sensitive magnetic field detection devices requiring weak magnetic field environments, such as atomic gyroscopes, magnetometers, atomic interferometers, and atomic clocks.

Determining the effect of longitudinal stiffeners on the deformation of multilayer ellipsoidal shells under non-stationary loads

The object of this study is the deformation of multilayer ellipsoidal shells under non-stationary distributed load. It is proposed to reinforce the shell with longitudinal stiffeners to enhance the strength of it. The application of Timoshenko's theory of shells and cores enabled the investigation of the influence of longitudinal stiffeners on the deformation of multilayer ellipsoidal shells under non-stationary loads with the discrete positioning of the stiffeners. A mathematical model of shell oscillations under various types of short-term non-stationary loads was based on the Hamilton-Ostrogradsky variational principle. The numerical algorithm based on the application of the integral-interpolation approach to the construction of finite difference schemes in spatial coordinates, combined with an explicit finite-difference scheme for the time coordinate, was used to solve the task set. It has been determined that reinforcing stiffeners significantly affect the deformed state of the multilayer ellipsoidal shell. The "shell-stiffeners" relation was taken into account as a base for research. The maximum deformation ε11 of the smooth three-layer ellipsoidal shell was on average 1.4 times greater than the deformation ε11 of the reinforced three-layer ellipsoidal shell throughout the entire studied time interval. It was determined that over time the presence of reinforcing stiffeners has a more significant impact on the deformed state of the reinforced ellipsoidal shell. A distinctive feature of this research is the consideration of the discrete placement of reinforcing stiffeners which made it possible to investigate the impact of longitudinal stiffeners on the deformation of multilayer ellipsoidal shells under non-stationary loads. The results could be used for the investigation of applied problems in research organizations and design bureaus when designing shell structures

Natural Vibrations and Stability of Composite Cylindrical Shells Containing a Quiescent Fluid

This paper presents the results of investigation of the natural vibrations and stability of circular vertical multilayered cylindrical shells, fully or partially filled with a quiescent compressible fluid subjected to hydrostatic and external static loads. The behavior of the elastic structure and fluid medium is described based on the classical shell theory and Euler’s equations. The linearized equations of motion of the shell, together with the corresponding geometrical and physical relations are reduced to a system of ordinary differential equations with respect to new unknowns. The acoustic wave equation is transformed to a system of differential equations using the method of generalized differential quadrature. The solution of the formulated boundary value problem is developed using Godunov’s orthogonal sweep method. The dependences of the lowest vibration frequencies and critical external pressure on the ply angle and the filling level of two-layer and three-layer cylindrical shells are analyzed in detail. It is demonstrated that, in contrast to the ply angle and a given combination of boundary conditions, the lay-up scheme of composite materials plays different parts in the problems of maximizing the fundamental frequency of vibrations and extending the stability boundaries.

New OpenSees material model for simulating reinforced concrete shear walls subjected to coupled axial tension and cyclic lateral loads

In high-rise buildings, reinforced concrete (RC) shear walls, particularly those forming part of coupled wall systems or core wall systems, may be subjected to coupled axial tension and cyclic lateral loads during strong seismic events. A new two-dimensional material model named the “Fixed Angle Model Considering Crack Sliding” (FAM-CS) was proposed for simulating the nonlinear behavior of RC walls subjected to axial tension and cyclic lateral loads. The proposed model was implemented in the OpenSees platform. Nonlinear constitutive models for shear aggregate interlock effects of concrete and dowel action of rebars were incorporated into the proposed model to represent the shear transfer mechanisms along concrete cracks. The proposed model was validated against the test data of six wall specimens subjected to coupled axial tension and cyclic lateral loads. The results indicated that the proposed model reasonably predicted the lateral strength capacity (an average error of 6.2 %) and the residual strength at the maximum drift loading (an average error of 12.3 %) of the specimens. For comparison, three other commonly used models, the Shear-Flexure Interaction Multiple-Vertical-Line-Element-Model, the multi-layer shell element model and the Cyclic Softened Membrane Model were adopted for the simulation of the specimens. Compared with the three existing OpenSees models, the newly implemented material model provided improved predictions of the wall hysteretic behavior with respect to lateral strength capacity, lateral strength degradation, pinching characteristics and cyclic stiffness degradation. In addition, the proposed model reasonably captured the localized failure pattern as well as the energy dissipation characteristics of the test specimens. Finally, a mesh sensitivity study was conducted to assess the robustness of the proposed model. The results revealed that the proposed model was robust regarding the lateral load-drift responses of RC walls, with a mesh size ranging from approximately one to three times the average crack spacing.

Hierarchical Bi2O3 nanosheets and ZIF-8 derived porous nitrogen-doped carbon fibers as novel assembled nanocomposites for high-performance flexible supercapacitors

The unique design of the core–shell heterostructure is significant for obtaining electrode materials with excellent electrochemical properties. In this paper, porous carbon nanofibers (NPC@PPZ) embedded with N-doped porous carbon nanoparticles are used to construct flexible electrodes (NPC@PPZ@Bi2O3). Zeolite imidazole skeleton (ZIF)-8 and poly(methyl methacrylate) (PMMA) derived porous carbon fibers and Bi2O3 nanosheets, were utilized as the porous core and multilayer shell, respectively. The unique core and shell result in abundant pores and channels for fast ion transport and storage, high specific surface area, and additional electroactive sites. This perfect structural design enables the NPC@PPZ@Bi2O3 composite electrode to have excellent electrochemical performance. The results show that this electrode can obtain a high specific capacitance of 697 F g−1 at a current density of 1 A g−1 and a stable cycling performance at a high current density of 5 A g−1. The strategy developed in this study provides a new approach for the design and fabrication of flexible supercapacitors by electrostatic spinning combined with hierarchical porous structures.

Baseline-free damage localization in multilayer metallic spherical shell structures using guided wave tomography

Multi-layer metal spherical shell structure is widely used as the core component of pressure-bearing equipment, deep-sea exploration equipment and other critical areas due to its plane stress uniformity and high specific strength. Its long-term service in complex and harsh environments will inevitably produce a variety of defects and damages, which will affect the safety of the equipment in service. Ultrasonic guided wave inspection is a potential non-destructive testing method, but the multilayer metal bonding structure between the metal and non-metal bonding layer impedance difference is large, resulting in defects located in the internal reflection signal is difficult to propagate to the outer layer with a sensor, the multilayer spherical shell structure itself leads to the complexity of the guided wave propagation characteristics, it is difficult to extract the individual modes of the time information for the defects of the detection and localization. Therefore, in this paper, we propose a probabilistic damage existence imaging method for spherical shell structures and combine it with the virtual time reversal technique to detect and localize the defects on the inner and outer surfaces of multilayered metallic spherical shell structures without benchmarks. The results show that the newly proposed method can realize the accurate localization imaging of internal/external defects of multilayer metal spherical shell structures.

Cyclic Behavior of Partially Prefabricated Steel Shape-Reinforced Concrete Composite Shear Walls: Experiments and Finite Element Analysis

Due to the higher lateral stiffness, load-carrying, and energy dissipation capacities compared with traditional reinforced concrete (R.C.) shear walls, steel shape-reinforced concrete (SRC) shear walls, in which steel profiles are encased in the boundary elements, have been widely applied in high-rise buildings. In order to simplify the on-site construction procedure, this paper proposes a novel partially prefabricated steel shape-reinforced concrete (PPSRC) shear wall using throat connectors. Based on the pseudo-static tests of two large-scale specimens, the effect of construction methods (prefabricated or cast in place) on the cyclic behavior of PPSRC shear walls was investigated by the hysteretic loops, skeleton curves, stiffness degradation, energy dissipation, and deformation decomposition. The test results indicated that PPSRC shear walls could exhibit a comparative cyclic response with the cast-in-place SRC shear walls, and the proposed throat connectors could effectively transfer the stress of the longitudinal reinforcements. Finally, a macro-modeling of PPSRC shear walls based on the multi-layer shell elements in OpenSees 3.3.0 was established and validated by the test results, and the parametric analysis of the axial compression, steel ratio, and concrete strength of prefabricated and cast-in-place parts was then conducted.

Simultaneous removal of 2,4-DCP and Cr(VI) in water by gBC@nZVI: Cr(V) mediated ROS formation

In the actual polluted environment, the composite pollution system was usually composed of heavy metals and organic pollutants, especially Cr(VI) and chlorophenols often co-existed in industrial wastewater. In this study, a composite material consisting of multilayer graphene carbon shells coated with nZVI (gBC@nZVI) with various excellent properties was applied to deal with the composite system of Cr(VI) and 2,4-dichlorophenol (2,4-DCP) coexisting in the wastewater, and the intrinsic mechanism for the simultaneous removal of heavy metals and organic pollutants was systematically investigated. The results showed that in the composite pollution system (Cr(VI) = 20 mg/L, 2,4-DCP = 15 mg/L), complete removal of Cr(VI) could be achieved in 60 min, while 2,4-DCP achieved 95.2 % removal, with the contribution of oxidative degradation being 76.4 %. It was found that during the efficient adsorption and reduction of Cr(VI) by gBC@nZVI, the generation of the metastable intermediate Cr(V) was verified by probe compounds, electron spin resonance and UV–visible spectroscopy, and further experiments demonstrated that the generation of •OH was closely related to Cr(V) and promoted the oxidative degradation of the coexisting 2,4-DCP. Quenching experiments with the addition of specific scavengers indicated that •OH was the active species directly dominating the oxidative degradation of 2,4-DCP, whereas Cr(V) was indirectly involved in the degradation of 2,4-DCP by promoting the generation of •OH. In addition, the increase of solution pH negatively affected the degradation of 2,4-DCP in the composite polluted system, mainly due to the hindered generation of •OH in the alkaline environment. This work provided theoretical support for the promising application of gBC@nZVI in real environments contaminated with a combination of Cr(VI) and chlorophenols.

Multi-Layered Shell Model and Seismic Limit States of a Containment Building in Nuclear Power Plant Considering Deterioration and Voids

Multi-Layered Shell Model and Seismic Limit States of a Containment Building in Nuclear Power Plant Considering Deterioration and Voids

Nonlinear poro-thermo-forced vibration in curved sandwich magneto-electro-elastic shells under hygrothermal environment

This research employs a multiple scales perturbation approach to evaluate the nonlinear wave propagation behaviors of a doubly curved sandwich composite piezoelectric shell with a flexible core in a hygrothermal environment. Stress and strain calculations for the flexible core and face sheets are carried out using Reddy's third-order shear deformation theory (TSDT) and third-order polynomial theory, respectively. The study explores the synergistic effects of a multilayered shell, flexible core, and magneto-rheological layer (MR) in revealing the nonlinearity of both in-plane and vertical moment within the core. The Halpin–Tsai model is employed to derive the properties of polymer/carbon nanotube/fiber (PCF) and polymer/graphene platelet/fiber (PGF) three-phase composite shells. The governing equations for the multiscale shell are derived using Hamilton's formulation. The research investigates temperature variations, diverse distribution patterns, curvature ratios, and magnetic fields through numerical analysis, presenting the results graphically and prior research has demonstrated the accuracy of these methods. Notably, these factors exert significant influence on the frequency-amplitude curves of the smart structure.

Free vibration analysis of fiber-reinforced composite multilayer cylindrical shells under hydrostatic pressure

With the development and application of composite materials in deepwater submersibles, the influence of high external pressure from deepwater environments on the vibration characteristics of composite pressure-resistant cylindrical shells cannot be ignored. In this paper, the free vibration characteristics of prestressed composite multilayer shells are methodically examined by establishing partial differential equations based on the three-dimensional elasticity theory. To solve these equations, the state-space technique and double Fourier series expansion are employed to transform them into state-space ordinary differential equations. These equations are utilized to analyze vibration problems of simply supported composite multilayer cylindrical shells with arbitrary layered angles. The initial stress equilibrium equation is solved to determine the prestress induced by the hydrostatic pressure. This overcomes the limitation of membrane stress and considers non-uniform distributions of radial and interlaminar prestresses. The proposed theoretical model and solution strategies are validated by comparing with theoretical and experimental results from the existing literature and the finite element method. Additionally, the present investigation reveals that the natural frequencies of thick shells can be calculated more accurately using the prestress derived by the proposed approach, especially subjected to noticeable hydrostatic pressure. Finally, the performed investigations indicate that the circumferential prestressing has a more pronounced effect on the shell's natural frequencies than axial prestressing.

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.

Damage Development in a Cellular Axisymmetric Tank Additive-Manufactured from Plastic Filament. Part 1. Damage Development in Cellular Axisymmetric Multilayer Shells Under Critical Mechanical Loads and Quivalent Properties of Model Layers for Stress-Strain State Estimation

Damage Development in a Cellular Axisymmetric Tank Additive-Manufactured from Plastic Filament. Part 1. Damage Development in Cellular Axisymmetric Multilayer Shells Under Critical Mechanical Loads and Quivalent Properties of Model Layers for Stress-Strain State Estimation

Seismic behavior of reinforced concrete shear walls using a combined model of multi-layer shell and fiber beam elements

Seismic behavior of reinforced concrete shear walls using a combined model of multi-layer shell and fiber beam elements

Universal three-dimensional finite element for analyzing of elastic inhomogeneous shells under thermomechanical loads

The work is devoted to the development of a new modification of the finite element intended for the calculation of inhomogeneous composite shells of thin and medium thickness. The element is constructed on the basis of a universal three-dimensional isoparametric 8-node multilayer finite element of a continuous medium. The layers of the modified finite element are made of composite materials reinforced with continuous unidirectional fibers. Within the framework of a finite element model of a multilayer shell of stepwise variable thickness, a technique for modeling the properties of a unidirectional fibrous composite material has been developed, based on a method for structuring material inhomogeneities iby thickness and by plan. The shell can consist of an arbitrary number of layers of varying thickness bonded into a single piece. Each layer can have its own type of material: traditional or composite. Effective physical and mechanical characteristics of the layer material are determined using known micromechanical methods for predicting the thermoelastic constants of a fiber composite through the known physical characteristics of the matrix and fiber. The fibrous material of the layer is presented as homogeneous transversely isotropic with planes of isotropy normal to the direction of reinforcement. Additional variable parameters of the "basic" universal finite element are supplemented with new attributes that determine the thermoelastic properties of the composite components. The new parameters are related to the choice of the type of fibrous composite material in the layer of the finite element, to the setting of structural micromechanical parameters of its components, and to the setting of the reinforcement orientation angle. This allows the calculations to use both traditional and fiber-composite materials in layers of inhomogeneous shells. Numerical examples demonstrate the effectiveness of the developed approach.

Mixture electrolyte suppressing water-induced parasitic reactions on Zn anode by tuning multilayer solvating structure

Though aqueous zinc ion batteries have been identified as a feasible option for energy storage, there are still some challenges that block the development of aqueous zinc ion battery, especially the issues from zinc metal anode. Tuning solvating structure of Zn2+ and adjusting the electrolyte in recent years is considered to be a simple but potential strategy to improve stability of zinc anode. In this work, a mixture electrolyte was obtained by dessolving LiTFSI/TEGDME Li-O2 battery electrolyte into 2 M aqueous ZnSO4 solution to tune solvating structure and adjust the striping/plating process of anode. Molecular spectrum and X-ray based method clarified that the mixture electrolyte plays dual functions to protect anode during electrochemical process. From one aspect, TEGDME partially replaced water and reconstructed a new multilayer solvating shell with TFSI-, which is beneficial for fast dendrite-free deposition. From the other aspect, surface spectrum also revealed that due to the participation of Li+ and TFSI-, a surface layer with ZnOHS framework and ZnF2 fillings formed on anode which further inhibit the dendrite growth and stabilize anode. This work combines the method of tuning solvation structure and construct SEI together and opens a new view designing new electrolytes for aqueous Zn-ion battery.