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71.
G. Korotcenkov B.K. Cho 《Progress in Crystal Growth and Characterization of Materials》2017,63(1):1-47
In this paper the results of structural analysis of the SnO2 and In2O3 films deposited by spray pyrolysis are presented. The main goals of this analysis are summarizing the results obtained in this field, highlighting a correlation between parameters of film deposition and the material structure and formulating some general regularities, typical for metal oxides. Peculiarities and mechanisms of pyrosol deposition as well as advantages and disadvantages of this technology for deposition of the films with required parameters were also discussed. It is shown that this technology has great potential for controlling structural parameters of metal oxides such as thickness, the grain size, texturing, roughness, the grain faceting and the porosity. 相似文献
72.
G.S. Wang 《Theoretical and Applied Fracture Mechanics》2004,42(3):668
In this paper, an extremely accurate and efficient method for computing the interaction of a set of or multiple sets of general doubly periodic cracks has been presented on the basis of superposition principle, pseudo-traction method, and isolating analysis technique. A great number of typical examples are given in this paper. The stress intensity factors (SIF), the minimum strain energy density factors (SED) of crack tip and the critical stress (CRS) of crack growth are calculated with the accuracy of six significant digits for the rectangularly distributed periodic cracks and five significant digits for the general doubly periodic cracks. The relation of the interaction effect of the double periodic cracks with the periods and the ratio of crack length to crack spacing is analyzed. Also in this paper, the key technique problems for this method are discussed. 相似文献
73.
74.
A novel singular superelement (SSE) formulation has been developed to overcome the loss of accuracy encountered when applying the standard finite element schemes to two-dimensional elliptic problems possessing a singularity on the boundary arising from an abrupt change of boundary conditions or a reentrant corner. The SSE consists of an inner region over which the known analytic form of the solution in the vicinity of the singular point is utilized, and a transition region in which blending functions are used to provide a smooth transition to the usual linear or quadratic isoparametric elements used over the remainder of the domain. Solution of the finite element equations yield directly the coefficients of the asymptotic series, known as the flux/stress intensity factors in linear heat transfer or elasticity theories, respectively. Numerical examples using the SSE for the Laplace equation and for computing the stress intensity factors in the linear theory of elasticity are given, demonstrating that accurate results can be attained for a moderate computational effort. 相似文献
75.
We derived for the first time the relationships among shear stress and normal stress differences for ellipsoidal interfaces
under large step shear strains considering interface velocity term and Laplace pressure term in the expression of the stress
tensor for mixtures of two Newtonian fluids. In the derivation, orientation angle of the interface is assumed to be given
by the affine deformation assumption and is independent of time based on experimental results for blends with 0.048 ≤ K ≤ 0.54 where K is the ratio of droplet viscosity to matrix viscosity. For ellipsoidal droplets, the shear stress is only proportional to
the first normal stress difference. On the other hand, for spheroidal droplets, proportionality among the shear stress, the
first and the second normal stress differences was derived, and the ratio of the second normal stress difference to the first
normal stress difference was given as a function of step strain. The shear stress and the first normal stress difference obtained
experimentally satisfy the derived relationship, indicating applicability of the stress expression for polymer blends. 相似文献
76.
An asymptotic analysis is presented for a dynamic problem of a semi-infinite isotropic thermoelastic solid with a small surface breaking crack. The exterior surface of the solid is subjected to a series of short thermal pulses. The crack surface is traction free and an ideal thermal contact is assumed across the crack. The stress intensity factor is asymptotically evaluated as a function of the crack depth and time. The effect of a boundary layer associated with the diffusive term is identified. The theoretical model is supplied with numerical simulations. 相似文献
77.
This study focuses on the development of a methodology for the determination of some in situ parameters for off-road vehicle mobility on sandy soils. The stress field in the vicinity of and at the interface between a wedge and soil was determined by solving the stress equations using the method of characteristics. The governing equations were solved numerically by using backward finite difference method. The proposed method allows the prediction of any two of the in situ soil parameters δ, φ, and γ (respectively, the interfacial friction angle between the material of a wedge penetrometer and the soil, the internal friction angle, and the unit weight of the soil), given the value of any one of them and the results of penetration tests of two different apex angle wedges. The predictions and the measured values are in agreement. 相似文献
78.
Zhen-hua Yuan De-yan Shen Ren-yuan Qian Polymer Physics Laboratory Center for Molecular Science Institute of Chemistry Chinese Academy of Sciences Beijing China 《高分子科学》2001,(4):399-405
Viscoelastic behavior of the non-Hooke deformation of amorphous PET film before yield was investigated in thetemperature region 74--80.5℃ around the glass transition temperature. The film specimen was drawn to yield point followedby unloading to zero stress, then the residual deformation was held constant, while the subsequent evolution of the stress wasrecorded. An induction period was found in the course of stress evolution fol1owed by a stress step-increase. The inductionperiod decreases with increasing drawing temperature with an activation energy of 1.10 MJ/mol·K, which is attributed tothe time needed for the relaxation of rubbery deformation through cooperative internal rotations. At temperatures lower than74℃, there is no stress increase or the induction period becomes too long to be observed. Thus the nature of anelasticity inthe non-Hooke region before yielding is attributed to stress induced rubbery deformation. The experimental results areinterpreted in terms of Perez' rheological model of a series connected Hooke spring and a Voigt element consisting of aparallel connected elastic spring and a dashpot. 相似文献
79.
E. BeyerL. Lahn C. SchepersT. Stucky 《Journal of magnetism and magnetic materials》2011,323(15):1985-1991
To reduce the core loss of electrical steel the vacuum arc ion plating technique has been used to deposit titanium nitride (TiN) layers on highly grain oriented electrical steel sheets. The layer thickness, the stresses of layers and coated sheets and the achieved reduction in core losses have been measured as functions of coating duration and applied bias voltage. Well adhered layers with high compressive stress up to 6.8 GPa have been produced. With increasing bias voltage the layer thickness decreases and the intrinsic stress of the layers increase. A further increase of bias voltage leads to a drop in stress due to thermal relaxation. In general, the tensile stress of the coated sheets rises with increasing layer thickness while the core loss of the coated material decreases with increasing tensile stress of the steel sheet and increasing bias voltage. The highest reduction of core loss has been found to be 28% (from P1.7=0.86 W/kg for commercially coated HGO electrical steel sheet with glass film to 0.62 W/kg for TiN coated material) and is due to the reduction of excess loss only. 相似文献
80.
Li-Chun Bian Zouheir Fawaz Kamran Behdinan 《Archive of Applied Mechanics (Ingenieur Archiv)》2007,77(11):809-821
The maximum energy release rate criterion, i.e., G
max
criterion, is commonly used for crack propagation analysis. This fracture criterion is based on the elastic macroscopic strength
of materials. In the present investigation, however, the G
max
criterion has been modified in order to accommodate the consideration of plastic strain energy. This modified criterion is
extended to study the fatigue crack growth characteristics of mixed-mode cracks. To predict crack propagation due to fatigue
loads, a new elasto–plastic energy model is presented. This new model includes the effects of material properties such as
strain hardening exponent n, yield strength σ
y
, and fracture toughness and stress intensity factor ranges. The results obtained are compared with those obtained using the
commonly employed crack growth law and the experimental data. 相似文献