Influences of interphase on dynamic effective properties of composites reinforced by dispersed spherical particles

The influences of interphase on dynamic effective properties of composites reinforced by randomly dispersed spherical particles were studied. A thin homogeneous elastic interphase with different shear and bulk moduli, located between the reinforced particle and the host matrix, was introduced to model the interfacial bonding state. The effects of such an interphase on the coherent plane waves were studied numerically. Numerical simulations were carried out for SiC-Al composites with four typical cases of interphase. It was found that the property of interphase has significant influences on the effective propagation constants of coherent waves and the dynamic effective elastic moduli of the composites. The influences on the coherent longitudinal wave and the coherent shear waves were different and dependent upon the frequency range. Moreover, several imperfect interface models, i.e., the spring model, mass model, and spring-mass model, were studied numerically and compared with the interphase model. It was found that the spring model is a more suitable model than the mass model for the light and weak interphase whereas the mass model is a more suitable model than the spring model for the heavy and strong interphase.     

双材料中多个热膨胀夹杂引起的弹性场

目的确定在双材料中由具有均匀本征应变的任意多个夹杂引起的热弹性场．方法利用Papkovitch-Neuber调和势函数得到无限大体中热膨胀夹杂产生的弹性场，通过应变核等基本解和镜像法得到双材料中多夹杂引起的热弹性场．结果阐述两相材料界面的效应、夹杂与界面的距离、弹性模量以及夹杂形状尺寸等参数对弹性场的影响．结论给出的应力公式和分布曲线，可扩展以建立双材料中热应力问题的断裂破坏准则，能有效地用来确定在双材料中由具有均匀本征应变的任意多个夹杂引起的热弹性场．     

有限变形下含非完美椭圆界面复合材料刚度的限界

应用文献［１３］中有限变形下非完美界面弹性复合材料有效模量的近似公式和微分几何方法，计算了含一般旋转椭球体夹杂弹性复合材料有效体积模量和有效剪切模量的上下限界。所得结果为研究大变形下实际弹性复合材料的刚度估值提供了定量判据。     

非完美界面多边形夹杂复合材料弹性场研究

导出了在非完美界面下，具有均匀本征应变的多边形夹杂复合材料位移场的计算公式，利用边界单元法求解了均匀剪切本征应变下多边形夹杂内应变场的分布。数值结果表明界面连结的完好与否对夹杂内部应变分布有比较明显的影响；随着界面缺陷程度的加剧，多边形内的应变偏离完好界面情形的相应应变就越大，这与实际情况相符。     

基体损伤对片状纤维复合材料弹性性能的影响

应用Ｅｓｈｅｌｂｙ等效夹杂理论和Ｍｏｒｉ－Ｔａｎａｋａ的平均化方法建立片状纤维复合材料的细观损伤力学理论，将损伤模型处理为随机“连桥”问题，给出这种宏观正交各向同性材料的９个独立弹性常数的显式表达式，并研究基体材料中孔洞形状及体积含量和裂纹密度对材料整体弹性性能的影响。     

Band gaps of elastic waves in 1-D phononic crystals with imperfect interfaces

Band gaps of elastic waves in 1-D phononic crystals with imperfect interfaces were studied.By using the transfer matrix method(TMM) and the Bloch wave theory in the periodic structure,the dispersion equation was derived for the periodically laminated binary system with imperfect interfaces(the traction vector jumps or the displacement vector jumps).The dispersion equation was solved numerically and wave band gaps were obtained in the Brillouin zone.Band gaps in the case of imperfect interfaces were compared...     

非完美界面复合材料刚度下限相关式

通过构造以夹杂纵横比为交量的函数,导出了计算非完美界面复合材料有效模量中,将任意夹杂形状转化为球形夹杂计算的普遍公式。进而得到了纤维夹杂和圆盘夹杂非完美界面复合材料有效模量4个下限之间的相关公式。     

层状横观各向同性地基轴对称问题的位移解法

通过对各向同性弹性体力学中拉甫位移函数重新修正,并利用Hankel积分变换理论,在变换域内得到了横观各向同性地基的通解,从而求得单层地基的应力和位移解,运用矩阵传递方法和Hankel积分反演变换推导了层状横观各向同性地基在轴对称荷载作用下的解析解,给出了数值计算结果.     

加层半空间交界裂纹的弹性波散射—弹性层表面位移的远场研究

本文导出了加层半空间交界裂纹的弹性波散射表面位移的表达式,利用围道积分技术及付里叶积分的渐近分析研究了远场情况下,弹性层表面位移的渐近形式,这些结果表明远场情况下弹性层表面位移主要由Rayleigh—Like—Mode波组成。本文的分析方法直接可以用于多层半空间交界裂纹的弹性波散射问题。     

SH波对界面附近脱胶圆夹杂的散射

采用Green函数法、复变函数法研究了SH波对界面附近含有半圆形脱胶的圆柱形弹性夹杂的散射,并给出了动应力集中系数的数值结果.首先,沿界面将整个空间分成上下2个部分.在上半空间,给出了在含有半圆形凸起的圆柱形弹性夹杂的弹性半空间中水平表面上任意一点承受时间谐和的出平面线源荷载作用时的位移函数.其次,取该位移函数作为Green函数,在上下空间"契合"时在界面处满足连续性条件,同时构造出半圆形脱胶,进而求出应力和位移的表达式.最后作为算例,给出了弹性夹杂周边以及脱胶结构周边的动应力集中系数的数值结果,分析了圆柱形夹杂和不同介质参数对动应力集中的影响情况.结果表明,脱胶结构对界面附近的动应力集中系数有放大作用.     

双材料非弹性主方向半无限界面裂纹应力场

利用坐标轴不平行于弹性主方向的应力、应变变换公式,并结合复合材料断裂复变方法,对正交异性双材料非弹性主方向半无限界面裂纹问题进行了研究,得到了用弹性主方向坐标系工程参数表示界面裂纹尖端的应力场、位移场。并给出双材料参数对半无限界面裂纹尖端应力场的影响规律。     

压电、压磁弹性体的空间问题研究

从横观各向同性压电、压磁弹性体空间问题的基本方程出发,建立由位移、电势和磁势函数所表示的控制偏微分方程组,通过引入势函数来研究压电,压磁弹性体的空间问题一般解.针对压电、压磁半无限体受法向集中力作用,导出位移、应力、电位移、电势、磁感和磁势函数的具体表达式.     

四阶各向同性张量的Hil分解定理及其应用

证明了四阶各向同性张量的Ｈｉｌ分解与一般分解的等效性。根据Ｈｉｌ分解归纳提出了两个定理，并应用它们导出了具有非完美界面结合的两相各向同性复合材料有效弹性模量的上、下界限     

Estimation of interfacial damage in composites with reinforced particles based on ultrasonic data

The scattering of elastic waves by a spherical particle with imperfect interface and the nondestructive detection of interfacial damage were studied. First, the scattering of elastic waves by a spherical particle with imperfect interface, i.e. spring interface model, was studied. Then, multiple scattering by random distributed particles was investigated and the equations to evaluate the velocity and attenuation of effective waves defined by statistic averaging were given. Furthermore, on the basis of the established relation between the velocity and interfacial constants, a method to evaluate the interfacial damage nondestructively from the ultrasonic data was pro- posed. Numerical simulation was performed for the SiC-Al composites. The velocities of the effective waves were computed to show the influence of the interface constants. Using the genetic algorithm, the interfacial damage was evaluated from the synthetic experi- mental data with various noise levels. The numerical results showed the feasibility of the method proposed.     

部分界面不连续夹杂问题的弹性一般解

在应变分析基础上,利用Eshelby等效夹杂原理和Green函数方法,得到了部分界面不连续椭圆形夹杂问题的弹性一般解,并同时给出不连续界面的相对位移解。它们对多相材料力学的研究具有重要的意义。     

An anisotropic micromechanical model for calculation of effective elastic moduli of Ni-based single crystal superalloys

An anisotropic micromechanical model based on Mori-Tanaka method is developed to calculate the effective elastic moduli of Ni-based single crystal superalloys. In the micromechanical model, the γ' precipitate with very high volume fraction is regarded as matrix, γ phase is divided into three parts as three different kinds of inclusions, and the actual cubic structure and orthogonal anisotropy properties of γ phase and γ′ precipitate are taken into account. Based on this anisotropic micromechanical model, the effective elastic moduli of Ni-based single crystal superalloys composite materials is obtained, and the influences of volume fraction and elastic constants of γ′ precipitate on the effective elastic moduli are also discussed. The results provide useful information for understanding mechanical behavior of composite materials in Ni-based single crystal superalloys and other anisotropic polygonal inclusion problem.     

叠层压电球壳的三维热释电分析

从球壳热传导方程出发,建立一个关于温度场的二阶齐次状态方程,并采用级数展开技术和矩阵理论进行精确求解.利用界面连续条件导出叠层球壳内、外表面温度场状态矢量的传递关系,进而利用内、外表面的温度边界条件精确确定球壳内的温度分布.基于热释电弹性体的三维基本方程,引入3个位移函数与2个应力函数,导出1个二阶齐次状态方程和1个六阶非齐次状态方程,并采用几乎相同的求解策略得到了边界温度作用下球壳内精确的电弹性场.通过数值算例考察了单层薄/厚球壳在内、外恒定温度作用下的稳态响应,以及相同厚度的单层与叠层球壳的不同热释电响应,发现厚度与结构形式不同可以显著改变其热释电效应.     

一类复合缺陷对SH波散射及动应力强度因子

运用Ｇｒｅｅｎ函数法研究圆形弹性夹杂及其侧边径向裂纹,一种新复合型缺陷对ＳＨ波散射问题,求解侧边裂纹的散射和裂纹尖端场动应力强度因子。首先,给出在表面处含有半圆形弹性夹杂的弹性半空间的水平表面上任意一点,承受时间谐和的出平面线源荷载作用时的位移函数。其次,取该位移函数作Ｇｒｅｅｎ函数,推导出该问题的定解积分方程。最后,分析介质参数对面圆形弹性夹杂的动应力强度因子的影响。     

任意荷载下黏弹性饱和土体中球壳的动力响应研究

工程实践中经常需要解决无限大弹性体内球壳的动力响应问题.采用Biot波动理论，对黏弹性饱和
土体中球壳的动力响应问题进行研究分析.利用Helmholtz分解原理，通过引入势函数，在Laplace变换域
中得到任意响应模式下球壳的动力响应解答.最后利用Laplace数值逆变换得到时间域中的数值结果，讨
论了在球壳内作用有轴对称荷载和流体压力两种情况时不同响应模式条件下球壳动力响应.球壳内作用有
轴对称荷载时接触面上的径向位移随n值的增大而减小，孔隙水压力开始有较大振荡；球壳内作用有流体
压力时在瞬时响应模式下位移趋近于零，而孔隙水压力变化相对平缓.结果表明,对于黏弹性饱和土体中
的球壳在不同的边界条件和响应模式下动力响应差别很大.     

正交异性双材料非弹性主方向裂纹尖端应力场

研究了正交异性双材料非弹性主方向界面裂纹问题。利用转轴变换公式,在特征方程组的判别式都大于零时,给出了正交异性双材料非弹性主方向界面裂纹应力场和位移场理论解表达式。