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991.
Nicola Bellomo Nils Calander Eugen Mamontov Magnus Willander 《Comptes Rendus Mecanique》2003,331(7):461-467
992.
The fundamental assumption of the paper is that the extra stress tensor of an electrorheological fluid is an isotropic tensor valued function of the rate of strain tensor D and the vector n (which characterizes the orientation
and length N of the fibers formed by application of an electric field). The resulting constitutive equation for is supplemented by the solution of the previously studied time evolution equation for n. Plastic behavior for the shear and normal stresses is predicted. Anticipating that the action of increasing shear rate
is i) to orient the fibers more and more in the direction of flow and ii) simultaneously to break up the fibers leads to the conclusion that for
the same behavior is encountered as without an electric field. Using realistically possible approximation formulas for the dependence of
and N on
leads to the Bingham behavior for
and power law behavior for large shear rates.
相似文献
Basim Abu-JdayilEmail: |
993.
I. W. Stewart 《Continuum Mechanics and Thermodynamics》2007,18(6):343-360
A dynamic continuum theory is presented for smectic A liquid crystals in which the usual director n and unit layer normal
a do not always necessarily coincide. Most previous dynamic continuum theories equate n with a; the theory developed in this
article allows n and a to differ in non-equilibrium situations, work that has been motivated by the recent investigations
by Auernhammer et al. (Rheol. Acta 39, 215–222, 2000; Phys. Rev. E 66, 061707, 2002) and Soddemann et al. (Eur. Phys. J. E
13, 141–151, 2004). The usual Oseen constraint () for smectics is not imposed upon the unit normal a. Permeation is also included. After a summary of the complete dynamic
equations, an application is given via an example which shows that planar aligned layers of smectic A subjected to an arbitrary
periodic disturbance are linearly stable.
相似文献
994.
FEA calculations have been carried out for a model rubber shear spring, consisting of a block of a highly elastic material, bonded between two rigid parallel plates and sheared by displacing one of the plates parallel to the other in its own plane. The block was prevented from deforming in the perpendicular direction, and thus was deformed in plane strain. Stress distributions along the bond-line and the center-line are reported and compared with those expected from the theory of large elastic deformations. Unexpected tensile stresses were found to develop in the interior of the sheared block. They are attributed to the absence on the end surfaces of the stresses needed to maintain a simple shear, causing a pronounced change in the reference pressure—a consequence that is usually overlooked. Because the internal stresses are governed by the boundary conditions, they were strongly affected by the shape of the end surfaces. In addition, they were reduced markedly by assigning values to Poisson's ratio slightly lower than 0.5, thus allowing some volume expansion of the rubber. Strain energy release rates were also evaluated for growth of a crack along the bond-line, starting at the edges, and compared with those reported previously by Lindley and Teo [Energy for crack growth at the bonds of rubber springs, Plast. Rubber Mat. Appl. 4 (1979) 29-37], Muhr et al. [A fracture mechanics study of natural rubber-to-metal bond failure, J. Adhes. Sci. Technol. 10 (1996) 593-616], Gregory and Muhr [Stiffness and fracture analysis of bonded rubber blocks in simple shear, in: D. Boast, V.A. Coveny (Eds.), Finite Element Analysis of Elastomers, Professional Engineering Publications, Bury St. Edmunds, UK, 1999, pp. 265-274] and Gough and Muhr [Initiation of failure of rubber close to bondlines, in: Proceedings of the International Rubber Conference, Maastricht, Netherlands, June 2005, IOM Communications Ltd., London, 2005, pp. 165-174]. They confirm that a long crack at the compression edge will grow faster than one at the tension edge, but the results for short cracks were inconclusive. 相似文献
995.
大型渡槽动力设计方法研究 总被引:5,自引:0,他引:5
根据大型渡槽结构的特点,在缺乏适用的抗震分析模型前提下,提出支撑-渡槽-水伪三维流固耦合动力分析方法。模型基于结构动力分析理论和流固耦合分析理论,整体结构分析采用Newmark方法进行动力时程分析,分析中考虑渡槽结构整体受力性能,包括下部支撑结构、地基等多种因素的影响作用;渡槽-水耦合体子结构分析采用任意拉格朗日-欧拉(Arbitrary Lagrangian Eulerian,ALE)有限元方法进行动力分析,考虑渡槽-水的耦合相互作用,模拟渡槽中水体的大幅晃动作用,相应得出渡槽中动力压力值及其分布。以某排架支撑矩形渡槽为例,采用本文提出的伪三维模型进行地震时程分析,计算结果与三维模型计算结果吻合良好。本文提出的伪三维动力分析方法计算效率高,满足渡槽结构抗震设计要求,便于工程应用,是大型渡槽结构动力分析研究和抗震设计的实用静、动力分析方法。 相似文献
996.
Huang Mojia Fu Mingfu Zheng Chaomei 《Acta Mechanica Solida Sinica》2006,19(1):75-85
By the nonlinear optimization theory, we predict the yield function of single BCC crystals in Hill's criterion form. Then we give a formula on the macroscopic yield function of a BCC polycrystal Ω under Sachs' model, where the volume average of the yield functions of all BCC crystallites in Ω is taken as the macroscopic yield function of the BCC polycrystal. In constructing the formula, we try to find the relationship among the macroscopic yield function, the orientation distribution function (ODF), and the single BCC crystal's plasticity. An expression for the yield stress of a uniaxial tensile problem is derived under Taylor's model in order to compare the expression with that of the macroscopic yield function. 相似文献
997.
998.
999.
为了提高对边坡体力学行为的认识,借助于FLAC有限差分软件的数值模拟,并结和相似理论的推导验证,研究了在仅有自重体积力作用的条件下,线弹性边坡体的一些力学特征及其与相关变量或物理力学参数的相关关系。没有外载荷影响时边坡地表最大主应力和最小主应力分别平行和垂直于地表,当深度增加时,主应力的取向逐渐变成竖直和水平两个方向,坡面处既有张应力区也有拉应力区,坡脚处亦存在较大的张应力,这是自重体积力作用下边坡体应力分布的一般性特征,在本文和前人的研究中都能体现。本文还重点揭露了:坡角线性增加时坡顶最大张应力的变化速率表现为:快——慢——快; 沿坡顶面竖直向下张应力随深度增加线性减小; 小变形条件下边坡应力场与弹性模量无关; 最后验证了满足相似理论的坡体,坡面对应点的位移比是其几何尺寸比的平方倍。本文不仅是对既有研究成果的进一步补充,而且为以后研究复杂条件下边坡体的力学特征奠定了基础,对于理论和实践都有一定的启发意义。 相似文献
1000.