基于粘弹性本构模型的双搭接胶结接头应力分析

采用广义Maxwell（麦克斯韦尔）粘弹性本构模型表征胶黏剂的时间相关力学特性,采用Yeoh本构模型描述橡胶材料的超弹性,建立了钢-橡胶双搭接胶结接头的有限元计算模型.在此基础上分析了加载时间对接头粘接界面剪切应力的影响.计算结果表明,剪切应力绝对值随着加载时间的增长而减小.此外,分析了胶层厚度对接头粘接界面剪切应力的影响,随着胶层厚度的增加,剪切应力绝对值呈现明显的增大趋势.     

昆虫翼拍动中受载变形的粘弹性本构模型

昆虫翼拍动受载时发生被动变形,被看作为有助于改善飞行性能的机制之一．决定这种被动变形大小的一个关键因素是昆虫翼的材料本构关系,至今缺乏研究．基于蜻蜓翼(离体)的应力松弛实验和模型翼拍动时受载变形的有限元数值分析,揭示了粘弹性本构关系是昆虫翼材料性能的合理描述,并研究了粘弹性参数对被动变形的影响．     

考虑基体粘弹性与介电弛豫的铁电复合材料的本构模型*——Ⅰ.理论

基于细观力学方法和Laplace变换 ,将仅适用于基体为线弹性和线性介电性的铁电复合材料的本构模型推广至基体为粘弹性和介电弛豫情况 ,建立了考虑基体粘弹性和介电弛豫的铁电复合材料的本构模型 .     

具有分数导数型本构关系的粘弹性柱的动力稳定性

研究简支的受轴向周期激励的粘弹性柱动力稳定性,柱的材料满足分数导数型本构关系.建立了描述粘弹性柱动力学行为的弱奇异性Volterra积分-偏微分方程,利用Galerkin方法将其化归为弱奇异性Volterra积分-常微分方程.利用平均化方法的思想给出了粘弹性柱运动稳定状态的存在性条件.给出一种新的计算方法,克服了存储整个响应历史数据的困难,并给出了数值算例,计算结果与解析方法的结论比较吻合.     

考虑基体粘弹性和介电弛豫的铁电复合材料的本构模型*——Ⅱ.实验、计算和分析

对基体具有粘弹性和介电弛豫的铁电复合材料进行了实验分析 ,并用本文第一部分建立的本构模型对其进行了计算 .实验结果与计算值的比较表明 :建立的本构模型能够较好地反映这类铁电复合材料的力电耦合行为 ,基体的粘弹性和介电弛豫对铁电复合材料的影响是不能忽略的 .     

具有分数导数本构关系的粘弹性Timoshenko梁的静动力学行为分析

利用粘弹性材料的三维分数导数型本构关系,建立粘弹性Timoshenko梁的静、动力学行为研究的数学模型;分析Timoshenko梁在阶跃载荷作用下的准静态力学行为,得出了问题的解析解,考察了一些材料参数对梁的挠度的影响。基于模态函数讨论了粘弹性Timoshenko梁在横向简谐激励作用下的动力响应,并考察了剪切和转动惯性对梁振动响应的影响。     

一种考虑聚醚醚酮（PEEK）不同力学状态的本构模型

聚醚醚酮（简称PEEK）以其优良的性能而广泛应用于高端机械、 核工程和航空等科技领域.为了描述其在应变、应变率和温度3种因素作用下的力学行为,依据PEEK在不同温度下呈现的3种力学状态,在著名的JC(Johnson Cook)本构模型的基础上,提出了针对高分子不同力学状态的分段JC本构模型.与传统JC模型及文献中改进JC模型相比,提出的分段JC模型能够更精确地表征PEEK在中高温下的力学行为,为PEEK在复合材料中的应用和分析奠定了理论基础.     

基于Kelvin-Voigt模型的粘弹性波动力学的本征化理论

利用固体力学本征化理论,研究了具有Kelvin-Voigt粘弹性质的各向异性固体的本征特性,并由此得到了各向异性粘弹性波动力学的广义Stokes方程,展现了波动过程的立体图像．讨论了几类常见各向异性固体的粘弹性波动规律,给出了一些新的结论．     

塑性本构关系的应变路径理论

基于伊留申的两个假定,提出一个新的积分形式的塑性本构方程.由应变路径确定的应力偏量由二部分组成,它们各自按不同的规律变化.理论计算与近代实验的比较,得到令人满意的结果.本文提出的不是内时理论.     

梯度增强的弹塑性损伤非局部本构模型研究

简要介绍了几种主要的梯度增强非局部模型．基于“能量耗散梯度依赖”原则,在连续介质热力学框架内推导了梯度增强损伤与塑性耦合的本构关系,同时给出了一个基于塑性的损伤模型的梯度依赖本构的具体形式．在数值计算方面,结合移动最小二乘法和泰勒级数展开方法,建立了损伤场（有限元高斯积分点上）的Laplace值的近似求解格式,分别给出了二维和三维情况下的相关公式．给出的二维的韧性断裂的梯度依赖损伤塑性的数值应用,表明了格式的有效性和实用性．还讨论了内部长度的意义及取值问题．     

Constitutive Modelling of Resins in the Compliance Domain

A rheological HWKK/H model for resins is developed taking into consideration the up-to-date analyses of experimental results. Constitutive compliance equations of linear are formulated for this model in the shear/bulk form, which describes, among other things, the first-rank reversible isothermal creep. The shear (distorsional) deformations are simulated with three independent stress history functions of fractional and normal exponential types. The volume deformations are simulated as perfectly elastic. The model is described by two elastic and six viscoelastic constants, namely three long-term creep coefficients and three retardation times.The constitutive compliance equations of viscoealsticity for resins are also formulated in the coupled form. Formulae for converting the constants of shear/bulk (uncoupled) viscoelasticity into the constants of coupled viscoelasticity are given too.An algorithm for identifying the material constants, based on the creep of uniaxially tensioned bar samples, is formulated in a way that gives unique results. The material constants are fiund for Epidian 53 epoxy and Polimal 109 polyester resins. The creep processes, simulated based on the experimental data, are presented graphically for both the resins examined.     

Parameter Identification for Inelastic Constitutive Models

The identification of material parameters of constitutive models is based on identification experiments. Since even specimens from the same lot show high deviations in the experimental data, the identification of the material parameters leads to different results for one and the same material. The number of identification experiments is usually not large enough for a statistical analysis of the deviations in the identified parameters. In order to overcome this problem we present a method of stochastic simulation which is based on time series analysis for generating artificial data with the same stochastic behaviour as the experimental data. The stochastic simulations allow an investigation of the confidence in the fits of the material parameters. We validate the stochastic simulations by comparing the results of the parameter identification from experimental data with the results from artificial data. The presented simulation method applied here turns out to be a suitable tool for generating artificial data for various kinds of analysis purposes. However, it is very important to take into account that the machines which perform the experiments do not maintain constant strain rates in the loading history of the tension and cyclic experiments.     

Constitutive model of ferroelectric composites with a viscoelastic and dielectric relaxation matrix I

Based on micromechanics and Laplace transformation, a constitutive model of ferroelectric composites with a linear elastic and linear dielectric matrix is developed and extended to the ferroelectric composites with a viscoelastic and dielectric relaxation matrix. Thus, a constitutive model for ferroelectric composites with a viscoelastic and dielectric relaxation matrix has been set up Project supported by the National Natural Science Foundation of China (Grant No. 19891180).     

黏弹性和热黏弹性方程的全局吸引子

该文证明了一类黏弹性和热黏弹性方程在没有外部阻尼情况下的全局吸引子的存在性.     

Constitutive models of ferroelectric composites with a viscoelastic and dielectric relaxation matrix (II)

Experimental analysis of ferroelectric composites with a viscoelastic and dielectric relaxation matrix is carried out, and the electromechanical coupling behavior of the ferroelectric composites is calculated by means of the constitutive model proposed in this paper. Comparisons between the experimental results and the calculations show that the constitutive model can reflect the electromechanical coupling behavior of the ferroelectric composites. The analysis indicates that the effect of viscoelasticity and dielectric relaxation of the matrix on the electromechanical coupling behavior of ferroelectric composites cannot be neglected.     

On Implicit Constitutive Theories

In classical constitutive models such as the Navier-Stokes fluid model, and the Hookean or neo-Hookean solid models, the stress is given explicitly in terms of kinematical quantities. Models for viscoelastic and inelastic responses on the other hand are usually implicit relationships between the stress and the kinematical quantities. Another class of problems wherein it would be natural to develop implicit constitutive theories, though seldom resorted to, are models for bodies that are constrained. In general, for such materials the material moduli that characterize the extra stress could depend on the constraint reaction. (E.g., in an incompressible fluid, the viscosity could depend on the constraint reaction associated with the constraint of incompressibility. In the linear case, this would be the pressure.) Here we discuss such implicit constitutive theories. We also discuss a class of bodies described by an implicit constitutive relation for the specific Helmholtz potential that depends on both the stress and strain, and which does not dissipate in any admissible process. The stress in such a material is not derivable from a potential, i.e., the body is not hyperelastic (Green elastic).     

基于形变晶粒增殖过程的弹塑性本构模型*

本文根据多晶金属变形的细观过程特征,将形变晶粒分为三类.提出塑性形变晶粒增殖的概念,并由此导出较为简洁的弹塑性本构关系.能对若干实验结果给出合理的解释.表明材料的宏观屈服、率相关和加工硬化等现象与形变晶粒演化的动力学过程密切相关.     

用于应变局部化行为分析的弹塑性损伤耦合本构研究

在已有的损伤塑性耦合本构模型基础上,进行了本构意义上的参数辨识,对不同参数取值时的材料行为进行了数值模拟,并对损伤演化律提出了改进措施．应用改进了的模型,在结构意义上进行了数值检验,模拟了简单试件拉伸时的变形局部化．数值结果表明这一理论模型有更好的数值稳定性,能较为准确地模拟金属韧性断裂的变形局部化现象．