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131.
Y. Ootao R. Kawamura Y. Tanigawa T. Nakamura 《Archive of Applied Mechanics (Ingenieur Archiv)》1998,68(10):662-676
Summary A neural network model is applied to optimization problems of material compositions for a functionally graded material plate
with arbitrarily distributed and continuously varied material properties in the thickness direction. Unsteady temperature
distribution is evaluated by taking into account the bounds of the number of the layers. Thermal stress components for an
infinite functionally graded material plate are formulated under traction-free mechanical conditions. As a numerical example,
a plate composed of zirconium oxide and titanium alloy is considered. In the optimization problem of minimizing the thermal
stress distribution, the numerical calculations are carried out making use of the neural network. The optimum material composition
is determined by taking into account the effect of temperature-dependence of material properties. The results obtained by
neural network and ordinary nonlinear programming method are compared.
Received 3 March 1998; accepted for publication 22 May 1998 相似文献
132.
This work studies the asymptotic stress and displacement fields near the tip of a stationary crack in an elastic–plastic nonhomogeneous material with the emphasis on the effect of material nonhomogeneities on the dominance of the crack tip field. While the HRR singular field still prevails near the crack tip if the material properties are continuous and piecewise continuously differentiable, a simple asymptotic analysis shows that the size of the HRR dominance zone decreases with increasing magnitude of material property gradients. The HRR field dominates at points that satisfy |α−1 ∂α/∂xδ|1/r, |α−1 ∂2α/(∂xδ ∂xγ)|1/r2, |n−1 ∂n/∂xδ|1/[r|ln(r/A)|] and |n−1 ∂2n/(∂xδ ∂xγ)|1/[r2|ln(r/A)|], in addition to other general requirements for asymptotic solutions, where α is a material property in the Ramberg–Osgood model, n is the strain hardening exponent, r is the distance from the crack tip, xδ are Cartesian coordinates, and A is a length parameter. For linear hardening materials, the crack tip field dominates at points that satisfy |Etan−1 ∂Etan/∂xδ|1/r, |Etan−1 ∂2Etan/(∂xδ ∂xγ)|1/r2, |E−1 ∂E/∂xδ|1/r, and |E−1 ∂2E/(∂xδ ∂xγ)|1/r2, where Etan is the tangent modulus and E is Young’s modulus. 相似文献
133.
The purpose of this research is to further investigate the effects of material inhomogeneity on the decay of Saint-Venant
end effects in linear isotropic elasticity. This is carried out within the context of anti-plane shear deformations of an
inhomogeneous isotropic elastic solid. The mathematical issues involve the effects of spatial inhomogeneity on the decay rates
of solutions to Dirichlet or Neumann boundary-value problems for a second-order linear elliptic partial differential equation
with variable coefficients on a semi-infinite strip. In previous work [1], the elastic coefficients were assumed to be smooth
functions of the transverse coordinate so that the material was inhomogeneous in the lateral direction only. Here we develop
a new technique, based on a change of variable, to study generally inhomogeneous isotropic materials. The governing partial
differential equation is transformed to a Helmholtz equation with a variable coefficient, which facilitates analysis of the
influence of material inhomogeneity on the diffusion of end effects. For certain classes of inhomogeneous materials, an explicit
optimal decay estimate is established. The results of this paper are applicable to continuously inhomogeneous materials and,
in particular, to functionally graded materials.
This revised version was published online in August 2006 with corrections to the Cover Date. 相似文献
134.
采用氢化物发生-原子荧光光谱法测定低合金钢中砷的含量。样品经盐酸-硝酸混合酸消解,以盐酸(5+95)溶液为反应介质,15g·L~(-1)硼氢化钾-2g·L~(-1)氢氧化钾的混合溶液为还原剂,采用柠檬酸作为掩蔽剂。砷的质量浓度在60.0μg·L~(-1)以内与荧光强度呈线性关系,方法的检出限(3s/k)为0.023μg·L~(-1)。应用此法对标准钢样进行了分析,测定结果与认定值相符合,可满足钢铁中微量砷(质量分数0.001%~0.04%)的测定要求。 相似文献
135.
The primary resonance response of simply supported circular cylindrical shells is investigated using the perturbation method. Donnell's non-linear shallow-shell theory is used to derive the governing partial differential equations of motion. The Galerkin technique is then employed to transform the equations of motion into a set of temporal ordinary differential equations. Considering only the primary resonance case, the method of multiple scales is used to study the periodic solutions and their stability. The necessary and sufficient conditions for appearance of the so-called companion mode are also discussed. To this end, a range of the possible multi-mode solution is obtained for response and excitation amplitudes and also excitation frequency as a function of damping, geometry and material properties of the shell. Parametric studies are performed to illustrate the effect of different values of thickness, length and material composition on the possibility of the companion mode participation in primary resonance response. 相似文献
136.
Dao Huy Bich 《International Journal of Non》2011,46(9):1195-1204
This paper presents an analytical approach to investigate the non-linear axisymmetric response of functionally graded shallow spherical shells subjected to uniform external pressure incorporating the effects of temperature. Material properties are assumed to be temperature-independent, and graded in the thickness direction according to a simple power law distribution in terms of the volume fractions of constituents. Equilibrium and compatibility equations for shallow spherical shells are derived by using the classical shell theory and specialized for axisymmetric deformation with both geometrical non-linearity and initial geometrical imperfection are taken into consideration. One-term deflection mode is assumed and explicit expressions of buckling loads and load-deflection curves are determined due to Galerkin method. Stability analysis for a clamped spherical shell shows the effects of material and geometric parameters, edge restraint and temperature conditions, and imperfection on the behavior of the shells. 相似文献
137.
Mohammad R. Torshizian Mohammad H. Kargarnovin Cyrus Nasirai 《Mechanics Research Communications》2011,38(3):164-169
In this paper, a two dimensional functionally graded material (2D-FGM) under an anti-plane load with an internal crack is considered. The crack is oriented in an arbitrary direction. The material properties are assumed to vary exponentially in two planar directions. The problem is analyzed and solved by two different methods namely Fourier integral transforms with singular integral equation technique, and then by the finite element method. The effects of crack orientation, material non-homogeneity, and other parameters on the value of stress intensity factor (SIF) are studied. Finally, the obtained results for Mode III stress intensity factor of different methods are compared. 相似文献
138.
Carlos A. Almeida Juan C.R. Albino Ivan F.M. Menezes Glaucio H. Paulino 《Mechanics Research Communications》2011,38(8):553-559
This paper presents a geometric nonlinear analysis formulation for beams of functionally graded cross-sections by means of a Total Lagrangian formulation. The influence of material gradation on the numerical response is investigated in detail. Two examples are given that illustrate the main features of the formulation, in which the behavior of beams of graded cross-sections is compared with homogeneous material beams. A motivation for this work is the potential development of functionally graded risers for the offshore oil exploration industry. 相似文献
139.
The thermal fracture of a bimaterial consisting of a homogeneous material and a functionally graded material (FGM) with a system of internal cracks and an interface crack is investigated. The bimaterial is subjected to a heat flux. The thermal properties of FGM are assumed to be continues functions of the thickness coordinate, while the elastic properties are constants. The method of the solution is based on the singular integral equations. For a special case where the interface crack is much larger than the internal cracks in the FGM the asymptotic analytical solution of the problem is obtained as series in a small parameter (the ratio between sizes of the internal and interface crack) and the thermal stress intensity factors (TSIFs) are derived as functions of geometry of the problem and material characteristics. A parametric analysis of the effects of the location and orientation of the cracks and of the inhomogeneity parameter of FGM’s thermal conductivity on the TSIFs is performed. The results are applicable to such kinds FGMs as ceramic/ceramic FGMs, e.g., TiC/SiC, MoSi2/Al2O3 and MoSi2/SiC, and also some ceramic/metal FGMs. 相似文献
140.
We investigate the Morita context and graded cases for weak group corings and derive some equivalent conditions for μ to be
surjective. Furthermore, we develop Galois theory for weak group corings. As an application, we give Galois theory for comodulelike
algebras over a weak Hopf group coalgebra. 相似文献