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991.
Ignacio Gonzlez M. Eugenia Muoz Antonio Santamaría J. Adolfo Pomposo Hans Grande Javier Rodríguez‐Parra 《Macromolecular rapid communications》2002,23(12):659-663
An improved method, based on mechanical stirring and a controlled solvent evaporation process, is proposed to obtain PANI(CSA)0.5/m‐cresol solutions, which lead to gels with conductivities in the range 3 to 150 S/cm, preserving the elasticity associated to the gel network. Such high conductivity values have only been found for brittle films cast from PANI solutions. According to our experimental results, there is no justification for an analogy between the elastic modulus and the conductivity of physical networks. 相似文献
992.
The “dual constraint” model developed by Mead, Van Dyke et al. is here extended by inclusion of “early-time” contour-length
fluctuations and constraint-release Rouse relaxation, and then evaluated by comparing its predictions with literature data
for over 50 different linear and star polymers. By combining the reptation model of Doi and Edwards with contour-length fluctuations
and constraint release, the model provides a systematic approach to prediction of the rheological properties of polymers.
The parameters are taken from the literature and used consistently for linear polymers, star polymers, and their mixtures
having the same chemical compositions. In most cases, the predictions of the model appears to agree well with data for monodisperse,
bidisperse, and polydisperse linear and star polymers, except at low molecular weights.
Received: 23 December 1999 Accepted: 28 March 2000 相似文献
993.
Large-amplitude oscillatory squeezing flow data are reported for a complex biological material, which is highly shear-thinning
in oscillatory shear flow. This soft tissue has a linear viscoelastic limit at a strain of approximately 0.2%. The oscillatory
squeezing flow data at large strain are analyzed using two constitutive models: a bi-viscosity Newtonian model, and a non-linear
Maxwell model. It is found that although both models may have the same response in shape, the later matches with our non-linear
experimental data better. It is also concluded that the non-linear response of the material in large amplitude oscillatory
flow is mainly due to the shear thinning of the material.
Received: 9 February 2000/Accepted: 22 February 2000 相似文献
994.
粘弹性圆薄板的动力学行为 总被引:4,自引:0,他引:4
基于线性粘弹性力学的Boltzmann叠加原理,给出粘弹性圆薄板动力学分析的初边值问题。通过一定的简化后得到描述薄板力学行为的四维非线性非自治动力系统。综合使用非线性动力学中的数值分析方法,研究了参数对粘弹性圆薄板动力学行为的影响。同时计算了吸引子的Lyapunov维、相关维和点形维。 相似文献
995.
大变形下初始斜交异性本构方程 总被引:3,自引:0,他引:3
采用材料主轴法,建立了初始斜交异性材料在变形构形(Euler描述)下的斜交异性本构方程,以及在初始构形(Lagrange描述)下的形式。具体给出了斜交异性线弹性材料方程的显式,它在Lagrange描述下形式简洁,可方便地用于有限元计算。文中指出,在变形构形下是线弹性的材料,在Lagrange描述下其本构方程一般已成为非线性,我们称之为本构转换非线性。这种非线性在实际的有限元计算中还未引起重视。为理论简明,本构方程是对二维给出的。 相似文献
996.
Biaxial Mechanical Evaluation of Planar Biological Materials 总被引:12,自引:0,他引:12
Michael S. Sacks 《Journal of Elasticity》2000,61(1-3):199-246
A fundamental goal in constitutive modeling is to predict the mechanical behavior of a material under a generalized loading
state. To achieve this goal, rigorous experimentation involving all relevant deformations is necessary to obtain both the
form and material constants of a strain-energy density function. For both natural biological tissues and tissue-derived soft
biomaterials, there exist many physiological, surgical, and medical device applications where rigorous constitutive models
are required. Since biological tissues are generally considered incompressible, planar biaxial testing allows for a two-dimensional
stress-state that can be used to characterize fully their mechanical properties. Application of biaxial testing to biological
tissues initially developed as an extension of the techniques developed for the investigation of rubber elasticity [43, 57].
However, whereas for rubber-like materials the continuum scale is that of large polymer molecules, it is at the fiber-level
(∼1 μm) for soft biological tissues. This is underscored by the fact that the fibers that comprise biological tissues exhibit
finite nonlinear stress-strain responses and undergo large strains and rotations, which together induce complex mechanical
behaviors not easily accounted for in classic constitutive models. Accounting for these behaviors by careful experimental
evaluation and formulation of a constitutive model continues to be a challenging area in biomechanics. The focus of this paper
is to describe a history of the application of biaxial testing techniques to soft planar tissues, their relation to relevant
modern biomechanical constitutive theories, and important future trends.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
997.
998.
Linear surface gravity waves on a semi-infinite incompressible Voigt medium are studied in this paper. Three dimensionless
parameters, the dimensionless viscoelastic parameter ϑ, the dimensionless wave number and the dimensionless surface tension
are introduced. A dimensionless characteristic equation describing the waves is derived. This is a sixth order complex algebraic
equation which is solved to give the complex dispersion relation. Based on the numerical solution, two critical values of
ϑ, ϑ
A
=0.607 and ϑ
B
=2.380, which represent the appearance of the cutoff region and the disappearance of the strong dispersion region, are found.
The effects of ϑ on the characteristic equation and the properties of the waves are discussed.
The project supported by the National Natural Science Foundation of China (59709006) 相似文献
999.
1000.
Fan Jiashen Professor 《应用数学和力学(英文版)》2000,21(4):461-470
Introducing the nonlinear Rayleigh damping into the governing equation of the Mode Ⅲ dynamic rupture for standard viscoelastic solid, this equation is a partial differential and integral equation. First, eliminating the integral term, a PDE of third-order is obtained. Then, applying the small parameter expansion method, linearized asymptotic governing equation for each order of the small parameter is obtained. Dividing the third-order PDE into an elastic part with known solution, the rest part pertains to viscous effect which is neither a Mathieu equation nor a Hill one. The WKBJ method is still adopted to solve it analytically. 相似文献