Investigation of surface structure, electrokinetic and stability properties of highly dispersed Ho₂O₃-Yb₂O₃/SiO₂ nanocomposites

A series of highly dispersed Ho2O3–Yb2O3/SiO2 nanocomposites was synthesized using a liquid-phase method and examined using Fourier transform infrared (FTIR) spectroscopy, X-ray diffraction (XRD), nitrogen adsorption–desorption, transmission electron microscopy (TEM), Scanning Electron Microscopy (SEM), and photon correlation spectroscopy (PCS). X-ray fluorescence spectrometry (XRF) confirmed a similar amount of weight percentage of Ho, Yb and Si oxides in the prepared samples. Samples HoYbSi1 (Ho2O3:Yb2O3:SiO2 = 0.5:10:89.5, wt. %), HoYbSi2 (Ho2O3:Yb2O3:SiO2 = 1:10:89, wt. %) and HoYbSi3 (Ho2O3:Yb2O3:SiO2 = 2:10:88, wt. %) calcined at 550 °C are amorphous. TEM and SEM analysis confirm a sphere-like morphology with a quite homogeneous size and shape. As compared with the initial silica, the agglomerated particles of nanocomposites in the aqueous medium are in the range from 200 to 850 nm according to PCS data. The effect of anionic polyacrylic acid (PAA) adsorption on fumed silica (SiO2) and Ho2O3–Yb2O3/SiO2 nanocomposite surfaces on suspension stability was studied. The turbidymetry method was used to monitor the initial silica and triple nanooxides suspensions stability as a function of time

Boundary element analysis of anisotropic thermomagnetoelectroelastic solids with 3D shell-like inclusions

The paper presents novel boundary element technique for analysis of anisotropic thermomagnetoelectroelastic solids containing cracks and thin shell-like soft inclusions. Dual boundary integral equations of heat conduction and thermomagnetoelectroelasticity are derived, which do not contain volume integrals in the absence of distributed body heat and extended body forces. Models of 3D soft thermomagnetoelectroelastic thin inclusions are adopted. The issues on the boundary element solution of obtained equations are discussed. The efficient techniques for numerical evaluation of kernels and singular and hypersingular integrals are discussed. Nonlinear polynomial mappings are adopted for smoothing the integrand at the inclusion’s front, which is advantageous for accurate evaluation of field intensity factors. Special shape functions are introduced, which account for a square-root singularity of extended stress and heat flux at the inclusion’s front. Numerical example is presented

Self-regular stress integral equations for the axisymmetric elasticity

The stress hypersingular integral equations of axisymmetric elasticity are considered. The singular and hypersingular integrals are regularized using the imposition of auxiliary polynomial solution, and self-regular integral equations are obtained for bounded and unbounded domains. The stress-BEM formulation is considered basing on the proposed equations. Considered numerical examples show high efficiency of the proposed approach. New problem for inclusion in finite cylinder is considered

Bending of Reissner's plate containing cracks with the account of their faces contact zone width

W pracy zbadano zagadnienie zginania nieograniczonej izotropowej płyty obciążonej jednorodnie rozłożonymi momentami gnącymi w nieskończoności. Płyta jest osłabiona trzema równoległymi szczelinami, których brzegi są wolne od obciążeń zewnętrznych. Zakłada się, że brzegi szczelin w górnej swojej części kontaktują się wzdłuż całej długości, a strefa kontaktu ma stałą szerokość dla każdej szczeliny. Rozwiązanie zagadnienia jest superpozycją rozwiązań dwóch zagadnień: tarczy płaskiej oraz zagadnienia zginania płyty typu Reissnera. Wykorzystując metody teorii funkcji zmiennych zespolonych i potencjałów zespolonych, otrzymano układ osobliwych równań całkowych rozwiązywanych numerycznie metodą mecha- nicznych kwadratur. Przedstawiono wyniki analizy numerycznej przykładów dla jednej, dwóch i trzech szczelin.This paper considers the bending of unbounded isotropic plate loaded at infinity with uniformly distributed bending moments. The plate is weakened with three collinear cracks with traction-free faces. It is assumed that the crack faces are in a smooth contact on the top face of a plate along their length. The contact region for each crack has a constant height. Due to the contact of crack faces the solution of the problem is obtained as a superposition of two ones: plane stress problem and problem of Reissner plate bending. Basing on the complex variable method the system of singular integral equations is ob- tained. It is solved numerically using the mechanical qudrature technique. The analysis of numerical data is provided

Bending of Orthotropic Plate Containing a Crack Parallel to the Median Plane

This paper considers cylindrical bending of the plate containing a crack parallel to plate's faces. The analytical model of the problem is obtained using the improved theory of plates bending, which considers transverse deformation of the plate. Received analytical results are compared with the numerical data of the boundary element approach, which is modified to suit the considered contact problem. The results of analytical and numerical techniques are in a good agreement both for the isotropic and anisotropic plates

Doubly Periodic Sets of Thin Branched Inclusions in the Elastic Medium: Stress Concentration and Effective Properties

This paper considers the doubly periodic problem of elasticity for anisotropic solids containing regular sets of thin branched inclusions. A coupling principle for continua of different dimension is utilized for modeling of thin inhomogeneities and the boundary element technique is adopted for numerical solution of the problem. The branches of the inclusion can interact both inside the representative volume element and at the interface of neighbor representative elements. A particular example of the elastic medium reinforced by a doubly periodic set of I-beams is considered. Stress intensity and stress concentration inside and outside thin inclusions are determined. The dependence of the effective mechanical properties of the reinforced composite material on the volume fraction of the filament and its rigidity is obtained