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81.
推导多维梯度折射率介质内稳态辐射传递的扩散近似方程.使用有限元法对扩散近似进行离散和求解,利用两个二维半透明介质的稳态辐射传递问题验证该扩散近似的精度及适用性.算例考虑介质为均匀折射率及梯度折射率两种情况.利用扩散近似分别求解辐射平衡时的边界热流、介质内温度场分布,并与辐射传递方程的求解结果进行对比分析.结果表明:介质折射率变化、散射特性、光学厚度及散射反照率均直接影响扩散近似的精度;在光学厚及强散射条件下,该扩散近似可以作为一种快速算法应用于梯度折射率介质稳态辐射传递的求解. 相似文献
82.
A New Higher Order Shear Deformation Model for Static Behavior of Functionally Graded Plates 下载免费PDF全文
Tahar Hassaine Daouadji Abdelouahed Tounsi & El Abbes Adda Bedia 《advances in applied mathematics and mechanics.》2013,5(3):351-364
In this paper, a new displacement based high-order shear deformation theory is introduced
for the static response of functionally graded plate. Unlike any other theory, the number
of unknown functions involved is only four, as against five in case of other shear deformation
theories. The theory presented is variationally consistent, has strong similarity with
classical plate theory in many aspects, does not require shear correction factor, and
gives rise to transverse shear stress variation such that the transverse shear stresses
vary parabolically across the thickness satisfying shear stress free surface conditions.
The mechanical properties of the plate are assumed to vary continuously in the thickness
direction by a simple power-law distribution in terms of the volume fractions of the
constituents. Numerical illustrations concerned flexural behavior of FG plates with
Metal-Ceramic composition. Parametric studies are performed for varying ceramic volume
fraction, volume fraction profiles, aspect ratios and length to thickness ratios. The
validity of the present theory is investigated by comparing some of the present results
with those of the classical, the first-order and the other higher-order theories. It
can be concluded that the proposed theory is accurate and simple in solving the static
behavior of functionally graded plates. 相似文献
83.
功能梯度简支矩形板的非线性动力响应 总被引:1,自引:0,他引:1
研究了功能梯度简支矩形板在横向简谐激励作用下的非线性动力响应问题。采用幂律分布规律描述功能梯度材料的等效材料参数,基于Galerkin法建立了系统广义坐标的常微分控制方程。利用平均法得到了系统的幅频响应特性,分析了功能梯度矩形薄板的非线性主共振特性。数值算例验证了平均化方法的正确性,揭示了功能梯度平板主共振响应中的多值性和跳跃现象;同时分析发现初始条件会改变功能梯度平板主共振的响应幅值。最后讨论了功能梯度材料的梯度指数对系统幅值响应的影响。 相似文献
84.
M. N. M. Allam A. M. Zenkour & R. Tantawy 《advances in applied mathematics and mechanics.》2014,6(2):233-246
This paper presents an analytical solution for the interaction of electric potentials,
electric displacement, elastic deformations, and describes hygrothermal effect responses
in hollow and solid cylinders, subjected to mechanical load and electric potential. Exact
solutions for displacement, stresses and electric potentials in functionally graded
piezoelectric material are determined using the infinitesimal theory. The material properties
coefficients of the present cylinder are assumed to be graded in the radial direction by a
power law distribution. Numerical examples display the significant of influence of material
inhomogeneity. It is interesting to note that selecting a specific value of inhomogeneity
parameter can optimize the piezoelectric hollow and solid cylinders responses, which will
be of particular importance in modern engineering designs. 相似文献
85.
Love’s first approximation theory is used to analyze the natural frequencies of rotating functionally graded cylindrical shells.To verify the validity of the present method,the natural frequencies of the simply supported non-rotating isotropic cylindrical shell and the functionally graded cylindrical shell are compared with available published results.Good agreement is obtained.The effects of the power law index,the wave numbers along the x-and θ-directions,and the thickness-to-radius ratio on the natural frequencies of the simply supported rotating functionally graded cylindrical shell are investigated by several numerical examples.It is found that the fundamental frequencies of the backward waves increase with the increasing rotating speed,the fundamental frequencies of the forward waves decrease with the increasing rotating speed,and the forward and backward waves frequencies increase with the increasing thickness-to-radius ratio. 相似文献
86.
Exact solutions for generally supported functionally graded plane beams are given within the framework of symplectic elasticity. The Young’s modulus is assumed to exponentially vary along the longitudinal direction while the Poisson’s ratio remains constant. The state equation with a shift-Hamiltonian operator matrix has been established in the previous work, which is limited to the Saint-Venant solution. Here, a complete rational analysis of the displacement and stress distributions in the beam is presented by exploring the eigensolutions that are usually covered up by the Saint-Venant principle. These solutions play a significant role in the local behavior of materials that is usually ignored in the conventional elasticity methods but possibly crucial to the material/structure failures. The analysis makes full use of the symplectic orthogonality of the eigensolutions. Two illustrative examples are presented to compare the displacement and stress results with those for homogenous materials, demonstrating the effects of material inhomogeneity. 相似文献
87.
88.
In this paper, the effective pyroelectric coefficient
and polarization offset of
the compositionally step-like graded multilayer ferroelectric structures
have been studied by use of the first-principles approach.
It is exhibited that the dielectric gradient has a nontrivial influence
on the effective pyroelectric coefficient, but has a little influence
on the polarization offset; and the polarization gradient
plays an important role in the abnormal hysteresis loop phenomenon
of the compositionally step-like graded ferroelectric structures.
Moreover, the origin of the polarization offset is explored,
which can be attributed to the polarization gradient
in the compositionally step-like graded structure. 相似文献
89.
非均质、各向异性材料梯度多墙结构充分利用了材料性质连续、渐进、变化的物理力学性能,现已广泛应用于飞行机翼结构和汽车轻量化结构.在层合板屈曲理论的基础上,针对梯度多墙结构这一具体结构形式,采用当量刚度方法,建立了相应的本构关系和非线性屈曲控制方程,求解得到不同复杂边界条件及组合载荷下的屈曲临界载荷,通过试验分析验证,计算结果可以较好地满足工程设计.研究结果表明:梯度材料能有效地减小界面中的应力集中,减弱材料中初始缺陷的作用,从而不同程度地提高了材料的强度和韧性. 相似文献
90.
This paper presents a theory on accurately analysing the dispersion relation and the
interaction impedance of electromagnetic waves propagating through a helical groove
waveguide with arbitrary groove shape, in which the complex groove profile is
synthesized by a series of rectangular steps. By introducing the influence of
high-order evanescent modes on the connection of any two neighbouring steps by an
equivalent susceptance under a modified admittance matching condition, the
assumption of the neglecting discontinuity capacitance in previously published
analysis is avoided, and the accurate dispersion equation is obtained by means of a
combination of field-matching method and admittance-matching technique. The validity
of this theory is proved by comparison between the measurements and the numerical
calculations for two kinds of helical groove waveguides with different groove
shapes. 相似文献