共查询到19条相似文献,搜索用时 171 毫秒
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在前一部分,本文得到复合材料蠕变的本构关系,在此基础上,本文进一步分析了复合材料蠕变本构关系的具体形式,实验测得了长纤维增强复合材料在蠕变、恢复两个阶段的应变,以用来确定本构关系中的待定参数,考虑到本构关系为复杂的非线性方程,本文提出了用离散变量和最小二乘法联合的方法确定参数,进而拟合蠕变本构关系的理论公式,分离出了蠕变过程中的弹性变形、粘弹性变形和粘塑性变形,对本构关系中的几个参函数,本文根据有限的实验数据拟合了其函数。 相似文献
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岩石材料的粘弹性和粘塑性变形是与时间相关的能量耗散行为。在Rice不可逆内变量热力学框架下,引入两组内变量分别用来描述在粘弹性和粘塑性变形过程中材料的内部结构调整。通过给定比余能的具体形式和内变量的演化方程,推导出内变量粘弹-粘塑性本构方程。粘弹性本构方程具有普遍性,能涵盖Kelvin-Voigt和Poynting-Thomson在内的经典粘弹性模型的本构方程。并指出热力学力与应力呈线性关系是组合元件模型为线性模型的根本原因。粘塑性本构方程能较好地刻画岩石材料在粘塑性变形过程中的硬化现象。对模拟岩石的模型相似材料进行单轴加卸载蠕变试验,将蠕变过程中的粘弹性和粘塑性变形分离并根据试验数据对本构方程的材料参数进行辨识。试验数据和理论曲线对比结果表明该文提出的本构方程能很好地模拟材料的蠕变行为。该类型的本构方程能为岩石工程的长期稳定性的预测、评价以及加固分析提供基础。 相似文献
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低速冲击下短纤维复合材料本构方程研究 总被引:2,自引:1,他引:1
借助ZWT非线性粘弹性一维本构关系,导出了常应变率条件下,热固性聚合物不含时间变量和积分项的、简化的、三次多项式型本构方程;采用细观力学方法,将建立在线弹性理论之上的Eshelby等效包容体理论推广应用于非线性弹性问题.在上述工作基础之上,结合应变率影响,提出了低速冲击下随机分布短纤维复合材料的一维率相关本构方程;把方程预测结果与实验结果对比,发现吻合很好,因而初步验证了所提本构方程的可靠性. 相似文献
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微薄板塑性成形本构关系研究 总被引:1,自引:0,他引:1
尺寸效应的影响使得传统的成形理论和变形机制不再适用于微塑性成形.在考虑尺寸效应对微薄板成形性能影响的基础上,对已有的CuZn36黄铜薄板微拉伸实验结果进行处理,提出了一种研究微塑性成形本构关系的方法.根据弹性和塑性变形过程,分阶段分析了t/d(板厚/晶粒大小)对屈服强度和切线模量的影响,修正了双线性弹塑性本构关系,获得了考虑尺寸效应的微塑性成形本构关系.借鉴宏观增量本构关系,结合微拉伸实验,采用Mises屈服准则和随动强化模型,得出适合微塑性成形的弹塑性增量本构方程,为微塑性成形的理论研究和实际应用奠定了基础. 相似文献
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The rate-type constitutive analysis of viscoelastic response of thin membranes, which includes an instantaneous elastic response and viscous behavior in both shear and dilatation, is developed with the aim to study the mechanical response of red blood cells. A convenient set of generalized stress and strain variables is introduced, which facilitates the derivation and integration of the governing differential equations. Gradual or sudden loading and stepwise unloading histories are considered. The performed parametric study of the mechanical response illustrates the effects of the introduced material parameters on the coefficient of viscoelastic lateral contraction and the overall membrane deformation. A closed form solution to the problem of radial stretching of a viscoelastic hollow circular membrane is derived without referral to the correspondence principle, which is of interest for the micropipette aspiration experiment of the red blood cell. The effects of the material parameters on the instantaneous elastic response and the subsequent rate of creep are discussed. 相似文献
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Assoc. Prof. Ph. D. R. Pyrz 《Acta Mechanica》1987,68(3-4):251-263
Summary A general constitutive equation for creep deformation is presented based upon the concept of tensorial internal variables. The consequences of the theory of tensor functions representation are discussed with respect to the evolution equations. In a particular case of steady evolution of internal variables the governing equation for the secondary creep rate is derived in terms of a scalar inelastic potential. The material parameters required to characterize the stationary creep behaviour of the orthotropic composite are obtained from the unidirectional tension creep tests performed on a glass woven fabric xylok composite. Further check on the theory is made for the bidirectionally loaded specimens.With 4 Figures 相似文献
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Ziliang Zhou 《International Journal of Engineering Science》1991,29(12):1661-1672
In this work, the creep and recovery properties of rubberlike viscoelastic materials in simple shear are studied by two special constitutive equations for isotropic, nonlinear incompressible viscoelastic material of the differential type. The creep and recovery processes are of significant importance to both the mechanics analysis and engineering applications. The constitutive equations introduced in this work generalize the Voigt-Kelvin solid and the 3-parameter model of classical linear viscoelasticity. They describe the uncoupled non-Newtonian viscous and nonlinear elastic response of an isotropic, incompressible material. The creep and recovery processes are treated for simple shear deformation superimposed on a longitudinal static stretch. Closed form solutions are provided and both processes are described effectively by the exponential function. 相似文献
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Creep-Damage Behaviour of Plates and Shells 总被引:1,自引:0,他引:1
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Seyed Reza Falahatgar Manouchehr Salehi Mohammad Mohammadi Aghdam 《Applied Composite Materials》2010,17(5):427-440
The Dynamic Relaxation (DR) technique together with finite difference discritization is used to study the bending behavior
of Mindlin composite plate including geometric nonlinearity. The overall behavior of the unidirectional composite is obtained
from a three-dimensional (3D) micromechanical model, in any combination of normal and shear loading conditions, based on the
assumptions of Simplified Unit Cell Method (SUCM). The composite system consists of nonlinear viscoelastic matrix reinforced
by transversely isotropic elastic fibers. A recursive formulation for the hereditary integral of the Schapery viscoelastic
constitutive equation in multiaxial stress state is used to model the nonlinear viscoelastic matrix material in the material
level. The creep tests data is used for verification of the predicted response of the current approach. Under uniform lateral
pressure, the laminated plate deformation with clamped and hinged edged constraints is predicted for various time steps. 相似文献
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The stress and creep analysis of structures made of micro-heterogeneous composite materials is treated as a two-scale problem, defined as a mechanical investigation on different length scales. Reinforced composites show by definition a heterogeneous texture on the microlevel, determined by the constitutive behaviour of the matrix material and the embedded fibres as well as the characteristics of the bonding properties in the interphase. All these heterogeneities are neglected by the finite element analysis of structural elements on the macroscale, since a ficticious and homogeneous continuum with averaged properties is assumed. Therefore, the constitutive equations of the substitute material should well reflect the mechanical behaviour of the existing micro-heterogeneous composite in an average sense.The paper at hand starts with the brief outline of a micromechanical model, named generalized method of cells (GMC), which provides the macrostress responses due to macrostrain processes as well as the homogenised constitutive tensor of the substitute material. The macroscopic stresses and strains are obtained as volume averages of the corresponding microfields within a representative volume element. The effective material tensor constitutes the mapping between the macro-strains and the macro-stresses. The cells method is used for the homogenisation of the unidirectionally reinforced single layers of laminates made of viscoelastic resins and flexibly embedded elastic fibres. The algorithm for the homogenisation of the constitutive properties runs simultaneously to the finite element analysis at each point of numerical integration and provides the macro-stresses and the homogenised constitutive properties. The validity of the proposed two-scale simulation is investigated by solving boundary value problems and comparing the numerical results for the structures to the experimental data of creep and relaxation tests or analytical solutions. 相似文献
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A viscoelastic continuum damage model and its application to uniaxial behavior of asphalt concrete 总被引:9,自引:0,他引:9
Sun Woo Park Y. Richard Kim Richard A. Schapery 《Mechanics of materials : an international journal》1996,24(4):241-255
An existing viscoelastic constitutive model which accounts for the effects of rate-dependent damage growth is described and applied successfully to characterize the uniaxial stress, constant strain rate behavior of asphalt concrete. The special case of an elastic continuum damage model with multiaxial loading, which is based upon thermodynamics of irreversible processes with internal state variables, is first reviewed and then it is shown how this model has been extended to a corresponding viscoelastic damage model through the use of an elastic-viscoelastic correspondence principle. The general mathematical model is next specialized to uniaxial loading. A rate-type evolution law, similar in form to a crack growth law for a viscoelastic medium, is adopted for describing the damage growth within the body. Results from laboratory tests of uniaxial specimens under axial tension at different strain rates are then shown to be consistent with the theory. The discussion of data analysis describes the specific procedure used here to obtain the material parameters in the constitutive model for uniaxial loading and how the method may be generalized for multiaxial loading. 相似文献
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This study presents an integrated micromechanical model-finite element framework for analyzing coupled heat conduction and deformations of particle-reinforced composite structures. A simplified micromechanical model consisting of four sub-cells, i.e., one particle and three matrix sub-cells is formulated to obtain the effective thermomechanical properties and micro–macro field variables due to coupled heat conduction and nonlinear thermoviscoelastic deformation of a particulate composite that takes into account the dissipation of energy from the viscoelastic constituents. A time integration algorithm for simultaneously solving the equations that govern heat conduction and thermoviscoelastic deformations of isotropic homogeneous materials is developed. The algorithm is then integrated to the proposed micromechanical model. A significant temperature generation due to the dissipation effect in the viscoelastic matrix was observed when the composite body is subjected to cyclic mechanical loadings. Heat conduction due to the dissipation of the energy cannot be ignored in predicting the factual temperature and deformation fields within the composite structure, subjected to cyclic loading for a long period. A higher creep resistant matrix material or adding elastic particles can lower the temperature generation. Our analyses suggest that using particulate composites and functionally graded materials can reduce the heat generation due to energy dissipation. 相似文献