Thick-walled spherical shell problem

Uniform TiO2–PANI composite capsules and hollow spheres

This study aimed to investigate the forces of a high-speed catamaran under the action of regular head waves at speed of 20 kn, and provided data support for the structural design of high-speed catamarans. This paper employs Computational Fluid Dynamics (CFD) and Finite Element Analysis (FEA) methods to construct a unidirectional fluid-structure interaction (FSI) numerical model for a high-speed hull with an aluminum alloy shell material, based on the Reynolds-averaged Navier–Stokes (RANS) equations. Structural dynamic analysis is performed using the numerical results, focusing on the study of the hull’s structural forces and deformation characteristics under head wave regular wave conditions. By adjusting the local structure of the hull frame, a high-speed vessel design and optimization were achieved in accordance with regulatory requirements. The results show that the maximum equivalent stress and maximum shear stress both were occurred when the wavelength-to-ship-length ratio was approximately 1.25. The maximum stress was occurred at the wavelength from 14 to 16 m. The maximum deformation was 3 mm at the bow of longitudinal girder under the wave load. The maximum equivalent stress and shear stress were typically at the bow of ship bottom. Through appropriate structural reinforcement, the equivalent stress could be significantly reduced, thereby improving the structural strength.

The fabrication of mesoporous core–shell and hollow spheres with ordered mesostructures and tunable large pore sizes is highly desirable for fundamental research and practical applications. A direct triblock-copolymer-templating coating approach has been provided for the synthesis of carbon sphere@mesoporous silica core–shell (CS@SBA-15) and hollow structures in an acidic medium at room temperature. These CS@SBA-15 core–shell structures possess large mesopores (6.3–8.4 nm), high surface areas (318.1–438.4 m2 g−1) and large pore volumes (0.31–0.36 cm3 g−1). The corresponding hollow mesoporous silica spheres (HMSS) with controllable mesopores (6.0–8.2 nm), high surface areas (239.9–326.5 m2 g−1) and pore volumes (0.37–0.62 cm3 g−1) can be obtained after the removal of the carbon sphere cores through calcination at 700 °C in air. The current research results provide an effective methodology for the synthesis of other mesoporous silica core–shell structures with large pore sizes and multilayer core–shells, and even nanorattle structures.

Formation of hollow silica spheres with ordered mesoporous structure by treatment with dimethyl carbonate for selective decomposition of mesoporous silica core

Finite-element method (FEM) and experimental investigation of 2024 Al subjected to equal-channel angular pressing (ECAP) has been carried out. The maximum equivalent normal stress and the maximum shear stress at an optionally given displacement of ECAP have been obtained through FEM for various given initial length of ECAP samples. The cracking criterion for the materials subjected to ECAP is further discussed with the help of experimental investigation. It is observed that at all given displacement of ECAP, the maximum equivalent normal stress is always less than the ultimate tensile strength of materials for all ECAPed samples with various initial length, while the maximum shear stress is always present at the angular channel zone of ECAP die, and its value decreases with the decrease of initial length of ECAPed samples. When the used initial length is small enough, the computed maximum shear stress becomes less than the shear strength of the materials, which is in very good agreement with the experimental observation that the frequency of sample cracking is decreased greatly. It is concluded that the non-cracking criterion of the materials subjected to ECAP could be expressed as "the maximum shear stress is less than the shear strength of materials". It is also suggested that a rational research should be involved in the actual measurement of stress-strain curve and the optimization in the configuration of ECAP die, the technology of materials pretreatment and the length of samples based on the above-motioned non-cracking criterion.

Facile synthesis of multi-shelled MnO2–Co3O4 hollow spheres with superior catalytic activity for CO oxidation

Finite element analysis of maxillary first molar with a 4-wall defect and 1.5-mm-high ferrule restored with fiber-reinforced composite resin posts and resin core: The number and placement of the posts

Motivated by the success of the spherical model in predicting the volumetric compaction behavior of both porous rocks and metals to a hydrostatic pressure, we consider the applicability of the spherical model to nonhydrostatic loading conditions. Specifically, the spherical model is used to examine the influence of the presence of a shear stress on the volumetric compression of a porous solid. We first obtain the linear, elastic solution for a hollow sphere subject to homogeneous tractions on the outer boundary. Then, assuming that the matrix material is governed by the Drucker‐Prager yield criterion, we use the elastic solution to derive an analytic expression for the onset of yield in the hollow sphere. The expression for the initial yield surface shows that the presence of a shear stress hastens the onset of yield in the sphere in comparison to a hydrostatic loading condition. This result agrees well with experimental data which shows that, for porous solids, permanent crush‐up begins at a lower mean stress under a nonhydrostatic loading than when the applied loading is a hydrostatic pressure. At this point, due to difficulty in obtaining an analytic solution, we turn to a numerical scheme (finite element method) to extend the analysis of the hollow sphere problem into the elasto‐plastic range. The spherical model results clearly exhibit the experimental finding that the presence of a shear stress tends to enhance the volumetric compaction of porous solids in comparison to a hydrostatic loading condition. For both a porous rock and metal sample, agreement between the spherical model and experimental results is excellent.

Fabrication and characterization of millimeter-scale translucent La2O3-doped Al2O3 ceramic hollow spheres

We propose a mathematical model that makes it possible to reduce the problem of the stressed state and limit equilibrium of a cylindrical anisotropic elastoplastic shell with internal crack to a system of nonlinear singular integral equations with discontinuous functions on the right-hand sides. We construct an algorithm for numerical solution of such systems together with the conditions of plasticity and boundedness of stresses near the crack. For a transversally isotropic shell, we carry out a numerical analysis of the dependence of the opening of the internal crack front on the load and geometric and mechanical parameters.

Coupled critical plane-pseudo excitation method for multiaxial fatigue analysis of structures under random vibration

Uniform Y(2)O(3) hollow microspheres have been successfully prepared via a urea-based homogeneous precipitation technique with colloidal melamine formaldehyde (MF) microspheres as templates followed by a subsequent calcination process. X-ray diffraction, energy dispersive X-ray analysis, and Fourier transform infrared spectroscopy results show that the MF templates can be effectively removed, and the amorphous precursor has converted to crystalline Y(2)O(3) during the annealing process. Scanning electron microscopy and transmission electron microscopy images indicate that the Y(2)O(3) hollow spheres inherit a spherical shape and good dispersion of MF templates, and the shell of the hollow spheres is composed of a large amount of uniform nanoparticles. The lanthanide activator ion Ln(3+)-doped Y(2)O(3) hollow microspheres exhibit bright down- and upconversion luminescence with different colors coming from different activator ions under ultraviolet or 980 nm light excitation, which may find potential applications in fields such as light phosphor powders, advanced flat panel displays, or drug delivery.

Elastic-brittle-plastic analysis of the radial subgrade modulus for a circular cavity based on the generalized nonlinear unified strength criterion

N-doped hollow mesoporous carbon spheres prepared by polybenzoxazines precursor for energy storage

A novel approach for modelling coal permeability during transition from elastic to post-failure state using a modified logistic growth function