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71.
Yi-Chao Chen Dimitris C. Lagoudas 《Journal of the mechanics and physics of solids》2008,56(5):1766-1778
A constitutive theory is developed for shape memory polymers. It is to describe the thermomechanical properties of such materials under large deformations. The theory is based on the idea, which is developed in the work of Liu et al. [2006. Thermomechanics of shape memory polymers: uniaxial experiments and constitutive modelling. Int. J. Plasticity 22, 279-313], that the coexisting active and frozen phases of the polymer and the transitions between them provide the underlying mechanisms for strain storage and recovery during a shape memory cycle. General constitutive functions for nonlinear thermoelastic materials are used for the active and frozen phases. Also used is an internal state variable which describes the volume fraction of the frozen phase. The material behavior of history dependence in the frozen phase is captured by using the concept of frozen reference configuration. The relation between the overall deformation and the stress is derived by integration of the constitutive equations of the coexisting phases. As a special case of the nonlinear constitutive model, a neo-Hookean type constitutive function for each phase is considered. The material behaviors in a shape memory cycle under uniaxial loading are examined. A linear constitutive model is derived from the nonlinear theory by considering small deformations. The predictions of this model are compared with experimental measurements. 相似文献
72.
Yi-Chao Chen Dimitris C. Lagoudas 《Journal of the mechanics and physics of solids》2008,56(5):1752-1765
A constitutive theory is developed for shape memory polymers. It is to describe the thermomechanical properties of such materials under large deformations. The theory is based on the idea, which is developed in the work of Liu et al. [2006. Thermomechanics of shape memory polymers: uniaxial experiments and constitutive modeling. Int. J. Plasticity 22, 279-313], that the coexisting active and frozen phases of the polymer and the transitions between them provide the underlying mechanisms for strain storage and recovery during a shape memory cycle. General constitutive functions for nonlinear thermoelastic materials are used for the active and frozen phases. Also used is an internal state variable which describes the volume fraction of the frozen phase. The material behavior of history dependence in the frozen phase is captured by using the concept of frozen reference configuration. The relation between the overall deformation and the stress is derived by integration of the constitutive equations of the coexisting phases. As a special case of the nonlinear constitutive model, a neo-Hookean type constitutive function for each phase is considered. The material behaviors in a shape memory cycle under uniaxial loading are examined. A linear constitutive model is derived from the nonlinear theory by considering small deformations. The predictions of this model are compared with experimental measurements. 相似文献
73.
We prove that a sum of free non-covariant duality-symmetric actions does not allow consistent, continuous and local self-interactions that deform the gauge transformations. For instance, non-abelian deformations are not allowed, even in 4 dimensions where Yang–Mills type interactions of 1-forms are allowed in the non-manifestly duality-symmetric formulation. This suggests that non-abelian duality should require to leave the standard formalism of perturbative local field theories. The analyticity of self-interactions for a single duality-symmetric gauge field in four dimensions is also analyzed. 相似文献
74.
A Model of Arterial Adaptation to Alterations in Blood Flow 总被引:3,自引:0,他引:3
Alexander Rachev 《Journal of Elasticity》2000,61(1-3):83-111
Mechanisms of arterial adaptation to changes in blood flow rates were tested by comparing the predictions of a proposed theoretical
model with available experimental data. The artery was modeled as an elastic membrane made of a nonlinear, incompressible,
elastic material. Stimulation of the vascular smooth muscle was modeled through the generation of an active component of circumferential
stress. The muscular tone was modulated by flow-induced shear stress sensed by the arterial endothelium, and is responsible
for the vasomotor adjustment of the deformed arterial diameter in response to changes in blood flow. This study addresses
the hypothesis that the synthetic and proliferative activity of smooth muscle cells, leading to a change in arterial dimensions,
is shear stress dependent and is associated with changes in the contractile state of the smooth muscle cells and changes in
the circumferential wall stress. Remodeling to a step change in flow was formulated as an initial-value problem for a system
of first order autonomous differential equations for the evolution of muscular tone and evolution of arterial geometry. The
governing equations were solved numerically for model parameters identified from experimental data available in the literature.
The model predictions for the time variation of the geometrical dimensions and their asymptotic values were found to be in
qualitative agreement with available experimental data. Experiments for validating the introduced hypotheses and further generalizations
of the model were discussed.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
75.
Marco Gigliotti Frédéric Jacquemin Jérôme Molimard Alain Vautrin 《Macromolecular Symposia》2007,247(1):199-210
Summary : The present paper is concerned with the modelling and the simulation of hygrothermal deformation of composite laminates. The temperature and moisture fields are established by employing the Fick's law for transient and cyclical environmental conditions, then the Classical Plate Theory (CLT) adapted for taking into account such conditions is applied. The hygrothermoelastic law of the composite is supposed to be constant but the diffusion coefficients depend on the temperature. The paper shows the ability of the model to handle complex environmental loading, close to service conditions. Finally, a model of plate with moderate rotations is introduced to predict the nonlinear deformations of unsymmetric plates under temperature and moisture cycling conditions. 相似文献
76.
采用Schmidt方法分析压电材料中非对称平行的双可导通裂纹的断裂性能.利用Fourier变换使问题的求解转换为求解两对以裂纹面位移之差为未知变量的对偶积分方程.为了求解对偶积分方程,直接把裂纹面位移差函数展开成Jacobi多项式形式.最终得到了裂纹的应力强度因子与电位移强度因子之间的关系.数值结果表明,应力强度因子和电位移强度因子与裂纹间的距离、裂纹的几何尺寸有关;与不可导通裂纹有关结果相比,可导通裂纹的电位移强度因子远小于相应问题不可导通裂纹的电位移强度因子.同时可以发现裂纹间的“屏蔽”效应也在压电材料中出现. 相似文献
77.
We consider a family of deformations describing cylindrical inflations within the context of finite, compressible, isotropic
elasticity. We pose the problem of finding the maximal class of materials for which these deformations are possible at equilibrium
under surface tractions only. We solve this problem for families of cylindrical inflations whose principal strain invariants
have a special dependence on the radius. These families comprise and extend all cases considered by Murphy [2].
This revised version was published online in August 2006 with corrections to the Cover Date. 相似文献
78.
Let (M,F) be a symplectic manifold and consider a Lie subalgebra of its Lie algebra of symplectic vector fields. We prove that every one-differentiable deformation of order k of the Poisson Lie algebra of M, which is invariant with respect to , extends to an invariant one-differentiable deformation of infinite order. If M admits a -invariant linear connection, a similar result holds true for differentiable deformations and for star-products. In particular, if M admits a - -invariant linear connection, there always exists a -invariant star-product. 相似文献
79.
We give a complete classification of at most second-order differential ladder operators preserving finite-dimensional spaces of monomials and closing under the Lie bracket to give a cubic polynomial of the diagonal generators. 相似文献
80.
Differential conditions are derived for a smooth deformation to be universal for a class of isotropic hyperelastic materials
that we regard as a compressible variant (a notion we make precise) of Mooney–Rivlin’s class, and that includes the materials studied originally by Tolotti in 1943
and later, independently, by Blatz. The collection of all universal deformations for an incompressible material class is shown
to contain, modulo a uniform dilation, all the universal deformations for its compressible variants. As an application of this result, by searching
the known families of universal deformations for all incompressible isotropic materials, a nontrivial universal deformation
for Tolotti materials is found.
This revised version was published online in August 2006 with corrections to the Cover Date. 相似文献