Papers by Keyword: Inhomogeneous

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: In this study, the inhomogeneous properties and microstructure at typical position of an Al-7.5Zn-1.6Mg-1.4Cu-0.11Zr alloy forging in T7452 condition have been investigated using OM, SEM, TEM and EBSD analysis, tensile properties testing, conductivity measurement and fracture toughness testing. The results indicate that wherein the properties near the surface layer and in the core of the alloy forging exhibit a difference of 10% or more. There are obvious differences in grain morphology, quench-introduced precipitation and recrystallization degree in the two positions. Due to the high quenching temperature, there appears a heavy quench-introduced precipitation phenomenon in the core more than surface layer of the alloy forging, which improves the electrical conductivity, but significantly reduces the strength of the final material. And there is a higher proportion of the recrystallization organization in the core of the alloy forging, seriously affecting its elongation and fracture toughness. Microstructure inhomogeneity of the alloy forging determines the uniformity of its properties.

Abstract: Influence the deposition of La³⁺ ions by monovalent K⁺ ions on magnetorefractive effect on magnetoreflaction and magnetotransmission modes in the infrared range for La_1-xK_xMnO₃ epitaxial thin-films (х=0.05, 0.10, 0.15 и 0.18) has been studied. It has been shown that the magnetorefractive effect, transversal Kerr effect and magnetoresistance reach the maximum in optimally doped films at highest Curie temperature. The good agreement between calculated in framework of magnetorefractive effect theory and experimental data takes place only for optimally doped films, with potassium concentrations of 15 % and 18 %. At the other doping levels the films become charge and magnetic inhomogeneous. Magnetic and charge homogeneity influence strongly on magnetooptical effects in films. The resonance-like lines in magnetoreflection spectra of films are connected with the shifting of reflection minimum before the phonon bands under a magnetic field has been observed.

Abstract: In this paper, we have developed a seepage-damage coupling analytical procedure based on FLAC-3D, which can simulate and analyze the crack initiation, propagation and coalescence process of jointed rock under coupling effect. It simulates the failure process of inhomogeneous specimen with two existing fractures under pore water pressure and biaxial loading. Meanwhile compare the results with corresponding non-seepage working condition. By showing the dynamic damage state and analyzing the stress-strain relationship, the mass damage and progressive failure process of jointed rock under the influence of seepage were studied.

Abstract: The inhomogeneous equilibrium point of a delayed complex network is investigated. In this letter, a novel local adaptive approach is used to make the delayed network achieve an inhomogeneous equilibrium point, where the whole nodes are divided into several groups; the nodes in the same group achieve one equilibrium point. The coupling strength between nodes varies with the information of the related nodes. By constructing a Lyapunov function, a sufficient condition about the stability of the inhomogeneous equilibrium point is obtained. When the isolated node is chaotic Lorenz system, simulations verify the effectiveness of the strategy.

Abstract: This paper presents the thermal analysis on fiber-reinforced composites containing inhomogeneous interphase subjected to a uniform temperature change. Based on the assumption of generalized plane strain, the deformations and thermal stresses of the composites subjected to a radial constraint are obtained by using iterative technique. The material properties of the interphase are assumed to be linear variation along radial direction. The effects of different volume fractions of the interphase on the stresses in the composites subjected to applied radial stress/strain are investigated.

Abstract: In this paper, J-integral of inhomogeneous welded joint is calculated by use of the combination of finite element method and virtual crack extension method, and the impact of strength matching on J-integral is studied as well. The analysis results show that the strength matching factor affects J-integral value greatly, that is, low matching of inhomogeneous welded joint of same steel can help to improve the ductility of the welded joint and the influence of the matching performance of dissimilar steel welded joint is more complex.

Abstract: Seriously inhomogeneous track rigidity of turnout will strengthen the dynamic response of wheel/rail system and shorten its service life. Combined with complicated structure characteristics of turnout, the simulation calculation model of track rigidity had been established. Main factors which influence the track rigidity were considered, such as the rail changing section, sharing baseplate, the foundation under rail. Distribution regularity of track rigidity in turnout had been obtained. The calculation result showed that track rigidity of turnout was seriously inhomogeneous. The maximum track rigidity was 162.2kN/mm in point rail of stock line, and the minimum track rigidity was 69.5kN/mm in stock rail of switch line.

Abstract: Based on the crystal plasticity theory, the slip-band traces on the specimen surface of polycrystalline copper tensioned uniaxially are investigated by using the finite deformation numerical algorithm, and the statistical distributions of the inhomogeneous strain and stress in the specimen are analyzed. The tension deformation of the polycrystalline specimen is simulated by the three dimensional FEM. Through the geometric analysis of intersect-lines between the active crystallographic slip-planes and the specimen surface, the different slip-band traces of the specimen surface are calculated and discussed. According to the results, it is confirmed that the crystal plasticity theory is feasible to study the deformation of the crystalline material.

Abstract: The tensile property of PC/ABS was investigated with an optical image analysis method in the paper. With the consideration of polymer micro mechanism, a three-stage phenomenon based model is used to describe the true stress-strain curves. The regression constants obtained with the method could be described with definite physical meanings. It is shown that two lateral contractions are not identical at the later necking stages. The fracture strain could be used as a criterion to describe uniaxial tensile fracture.