Key Engineering Materials Vol. 685

Abstract: The fountain nonisothermal flow of a viscous fluid realized during circular pipe filling is investigated. The mathematical basis of the process is formed by equations of motion, continuity and energy with respective initial and boundary conditions with due account of the temperature dependence of viscosity, the presence of a free boundary and dissipation of mechanical energy. To solve the problem numerically a finite difference method is required. Depending on the values defining the dimensionless parameters the results of parametric studies in temperature, viscosity, dynamic and kinematic characteristics of the flow are shown. Flow patterns for the formulation of problems with different initial and boundary conditions are given. The separation of flow into the zone of spatial flow in the vicinity of the free surface and one dimensional flow away from it, and changing the shape of the free boundary, depending on the level of dissipative heating are demonstrated.

Abstract: The implicit difference scheme has been suggested for the solution of diffusion-kinetic problem describing the ion implantation by intermetallic phase formation. The model corresponds to irreversible conditions and includes finite relaxation times for mass fluxes. The linear difference equations are solved by double-sweep method. The result illustrates the convergence of difference scheme at variation of its parameters. Qualitative picture of phase evolution in the surface layer is obtained different for problem with finite relaxation times and for zero relaxation times.

Abstract: The results of analytical and numerical solutions of the problem of the redistribution of elements between the coating and the substrate under heat treatment are presented here. It is assumed that the coating consists of two elements - chromium and nitrogen, and the substrate is silicon. The model takes into account the Soret effect. The Soret’s coefficients (or the corresponding coefficients of thermal diffusion) are different for the elements. The analytical solution of the linearized coupled problem is obtained by the operational method. Numerical solution was implemented by implicit difference scheme. In the linear approximation, the results of numerical solutions are close enough to analytical ones. The effect of diffusion coefficients and thermal diffusion on the redistribution of elements in the diffusion zone has been studied.

Abstract: The problem of determining the effective properties of composite materials is actual problem for deformable body mechanics. The model, proposed by Crisher for modeling effective values of the coefficient of thermal conductivity, has been considered. Modifications of this mathematical model for two-component elastic composite were built. Model of Hill-Budiansky compresses classic fork of Voigt-Reuss, if it is added by Voigt component. Expressions of hybrid effective characteristics through the use of effective Hashin-Shtrikman moduli are built. The accuracy is estimated depending on the type of modification of the effective characteristics for the calculation of the stress-strain state of bodies (two-layer shell and three-layer plate) made from composite materials. The results are compared with the exact classical solutions, and admissible concordance is achieved.

Abstract: Method for solving a boundary value problem of inhomogeneous unsteady-state heat conduction transfer is considered. This physical process can be described by a boundary value problem for a partial differential equation of the 2^nd order. Discrete-analytical method, which turns out the mathematical formulation of the initial problem to be normal system of differential equations, was used. There is the non-iterative solution of such system, which is the set of analytic functions. The theory of matrix functions, particularly the properties of matrix exponential, was applied to get the solution. This approach allows us to model the unsteady-state heat conduction processes with unstationary boundary conditions of different types, defined as time-dependent functions. Such modeling describes the real physical processes in structural materials more accurately.

Abstract: The distinctive paper is devoted to development and verification of correct numerical methods for analysis of structural strength and stability of high-rise panel buildings. Particularly the first part of the paper contains brief introduction, description of methods of analysis and simulation software. Information about verification of corresponding computational models is presented as well.

Abstract: The paper presents the second part of study, development and verification of correct numerical methods of analysis of structural strength and stability of high-rise panel buildings. It contains the results of computational simulations of selected section of building, results of parametric study of sections of building and results of normative strength test of concrete Structures.

Abstract: The possibility of using lattice periodic functions in the processing of narrowband signals with methods of discrete Fourier transform, instantaneous spectral density, and synchronous detection providing reduction of the number of readouts being processed, is shown. Results of the method’s experimental evaluation are considered. Suggested method can be used for increasing efficiency of correlation analysis of narrow band signals and for precise measuring of mains electricity supply frequency.

Abstract: This paper considers a deformation process of an incompressible elastoviscoplastic material placed between two coaxial rigid cylinders. The material is deformed when the internal cylinder rotates around its axis while the external one is fixed. The adhesion conditions are set on both boundary surfaces. The theory of large elastoviscoplastic deformations is used to solve the problem. The mathematical model is constructed in cylindrical coordinates.

Abstract: Turbulent fluid flow inside the vertical gasifier shaft having the porous insert has been numerically analyzed. The effect of the porous medium structure on the fluid flow has been studied. The mathematical model has been formulated in dimensional primitive variables using the realizable k-ε turbulent model. The distributions of velocity and skin friction coefficient inside the gasifier shaft have been obtained. The results clearly show an essential effect of the porous medium structure on turbulent fluid flow.