含界面层圆形夹杂的平面热弹性问题

研究了无穷远均匀拉伸条件下，含界面层圆形弹性夹杂的平面热弹性问题。运用Muskhelishvili复势理论的级数展开技术，将各区应力函数展开为合适的Taylor和Laurent级数，考虑边界上的力和位移连续性条件，将问题转化为线性方程组的求解，数值分析表明：总体上，软界面层可以有效的减小夹杂和基体的界面应力集中；硬界面层可以减小夹杂内的界面应力集中，但却增加了基体内的界面应力集中；此外，总体上，界面相热膨胀系数较基体相和夹杂相过高，不利于降低界面应力集中。     

半空间中椭圆夹杂与裂纹对SH波的散射

采用Green函数、复变函数和多极坐标方法求解弹性半空间中椭圆形弹性夹杂与任意方位的裂纹对SH波的散射问题。利用“保角映射”技术求解椭圆夹杂对SH波的散射位移场,并构造适合本问题的Green函数,即含椭圆形弹性夹杂的弹性半空间内任意一点承受时间谐和的反平面荷载作用时的位移基本解,结合裂纹“切割”法构造裂纹,进而得到椭圆夹杂和裂纹同时存在条件下的位移场与应力场。最后,通过具体算例,讨论了不同参数对地表位移、弹性夹杂周边动应力集中系数和裂纹尖端动应力强度因子的影响规律。     

耦合均载作用下的电磁热弹性简支圆板

耦合均载作用下的简支空心和实心圆板问题是一个经典问题,对于电磁热弹性材料尚无理论解。构造了5个含有待定常数的单调和函数,将其代入用单调和函数表示的横观各向同性电磁热弹性材料的通解,获得了表面力电磁热耦合均载作用下的简支空心圆板内耦合场的解,再将所得解代入边界条件获得确定待定常数的线性方程组。该解可以退化得到实心圆板对应问题的解。所得各解都是用初等函数表示,非常方便于工程应用。算例比较了在相同热力载荷作用下,具有相同物理常数的热弹性空心圆板、压电热弹性空心圆板和电磁热弹性空心圆板内的弹性场。     

双周期电磁弹性纤维增强复合材料的纵向剪切问题

利用等效夹杂法并结合双 (准) 周期解析函数理论,为双周期电磁弹性圆截面纤维复合材料的纵向剪切问题发展了实用有效的解析方法,获得了全场的级数解,给出了应力、电位移和磁感应强度的显式结果。利用数值算例讨论了该类非均匀材料微结构对其电磁弹性性能的影响。本文方法为电磁弹性复合材料的性能分析和微结构设计提供了一个实用有效的计算工具。      

位错与含裂纹非理想界面圆形夹杂的干涉效应

研究了基体中任意位置的螺型位错与含裂纹非理想界面圆形弹性夹杂的干涉力学问题。运用复变函数的解析延拓技术与奇性主部分析方法,获得了该问题复势函数的一般解答。作为典型例子,求出了非理想圆形界面含一条裂纹时基体和夹杂区域复势函数的封闭形式解。计算了作用在螺型位错上的位错力。讨论了含裂纹的非理想界面以及材料失配对位错力的影响规律。结果表明:与含裂纹理想界面相比,非理想界面对位错力的影响更大,对位错的捕获能力更强。硬夹杂时,可能存在非稳定平衡点,使得非理想界面、界面裂纹和夹杂对位错的作用力为零;软夹杂时,非理想界面、界面裂纹和夹杂则始终吸引位错。     

出平面线源荷载作用下半空间内浅埋圆孔对半圆形凸起的圆柱形弹性夹杂的动力影响

采用复变函数和多极坐标方法研究了在水平界面承受出平面线源荷载时弹性半空间内浅埋圆孔对半圆形凸起的圆柱形弹性夹杂的动力作用。该问题采用先“分区”再“契合”的思想求解,首先,将整个求解区域分割成两部分,其一为含半圆形凹陷和圆孔的弹性半空间,其二为圆柱形弹性夹杂;其次,构造满足含半圆形凹陷半空间水平界面应力自由和圆孔边界应力自由的散射波,构造满足圆形夹杂上半表面应力自由下半表面应力连续条件的驻波和散射波;最后,在两个区域的“公共边界”上实施“契合”,满足公共边界处位移和应力的连续性条件,同时满足圆孔边界应力自由的边界条件,建立起求解该问题的无穷代数方程组,并就具体算例讨论了圆柱形弹性夹杂周边动应力集中系数的数值结果。结果表明：圆孔的存在对“软”、“硬”夹杂周边动应力集中系数有不同的影响。     

压电螺型位错与椭圆夹杂界面导电刚性线的干涉效应

研究了无限大压电基体材料中压电螺型位错与含界面导电刚性线椭圆夹杂的电弹耦合干涉问题。运用求解复杂多连通域问题的复变函数方法,获得了椭圆夹杂和基体区域复势函数以及电弹性场的精确级数形式解答。利用广义Peach-Koehler公式导出作用于压电螺型位错上的位错力公式。主要讨论了刚性线几何尺寸和椭圆曲率对位错力的影响规律。分析结果表明:界面刚性线排斥基体中的位错,对靠近椭圆夹杂界面的螺型位错的运动和平衡位置有重要的影响。当刚性线的长度达到临界值,界面刚性线的存在会改变螺型位错与压电椭圆夹杂的干涉规律。椭圆夹杂的压缩系数变大,刚性线尺寸对位错力的影响也越大。     

出平面线源荷载对半空间中半圆形凸起的圆柱形弹性夹杂的散射

采用复变函数法和Green函数法,求解出平面线源荷载对半空间中半圆形凸起的圆柱形弹性夹杂的散射。首先,给出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,取该位移函数作为Green函数;然后,采用分区的思想,分别构造出夹杂内的驻波和夹杂外的散射波,满足"公共边界"处位移和应力的连续性条件,建立起求解该问题的无穷代数方程组;最后,给出了动应力集中系数和水平地面位移幅值的数值结果,并进行了讨论。     

圆柱型各向异性材料中螺型位错与非理想界面圆形夹杂的干涉效应

研究了圆柱型各向异性材料中螺型位错与含非理想界面圆形夹杂的弹性干涉问题。利用复变函数方法,获得了圆形夹杂和无限大基体区域复势函数的精确级数形式解答。利用Peach-Koehler公式导出作用于螺型位错上的位错力公式。主要讨论了材料各向异性性质与界面非理想性对位错力的影响规律。分析结果表明,界面非理想性吸引位错,而各向异性夹杂排斥各向同性基体材料中的位错。当夹杂的各向异性程度大于基体时,位错在非理想界面附近存在一个平衡位置。当界面非理想程度系数不变时,夹杂各向异性程度系数存在一个临界值改变作用在位错上位错力的方向。     

一维六方准晶复合材料界面层中螺型位错分析

本文研究了一维六方准晶复合材料夹杂界面层中螺型位错与夹杂以及无限大基体的干涉效应。运用复变函数方法,得了该问题的解析解答,所得退化结果与已有文献结果一致,并得到了作用在圆环形界面层中螺型位错的位错力的精确表达式。讨论了一维六方准晶材料弹性常数对位错运动以及位错力的影响规律。结果表明,一维六方准晶中的材料弹性常数对位错力的变化影响是显著的。随着相位子场弹性常数或者声子场-相位子场耦合弹性常数的增大,其相应区域对位错的排斥或者吸引作用也分别增强。在夹杂界面或者基体界面附近,随着相位子场弹性常数和声子场-相位子场耦合弹性常数同时增大,夹杂或者基体对位错的吸引作用增强,但是并不改变位错平衡点的位置。     

Study of deflection and damping in microbeam resonator based on microstretch thermoelastic theory

This article deals with the deflection and thermoelastic damping analysis in homogeneous, isotropic, micropolar microstretch generalized thermoelastic thin beam based on Euler–Bernoulli theory. Analytical expressions for deflection, thermoelastic damping, frequency shift, temperature distribution and microstretch functions have been obtained for various boundary conditions viz. clamped, simply supported and cantilever beam by using Laplace transform technique. The analytical results have been numerically analyzed with the help of MATLAB software in case of magnesium like materials. The computed results have been presented graphically in view of various boundary conditions.     

Hierarchical nano-/micromaterials based on electrospun polymer fibers: Predictive models for thermomechanical behavior

Summary Applications of small electrospun polymer fibers in hierarchical composite materials are discussed. Micromechanics models for effective elastic, thermal, and thermoelastic behavior of these materials are developed. The principle of effective homogeneity is applied to connect scales in the materials. Effective thermoelastic characteristics of nano- and microfiber composite are analyzed to illustrate the developed approach. Strong hybrid effects are observed in the dependence of effective modulus and thermal expansion coefficient on fractional content of fibers of different diameters. The extrema are located at the higher fractions of larger reinforcing elements. The methodology developed can be utilized for connecting scales in modeling other hierarchical materials.     

Pressure dependence of the thermoelastic quotient for three glasses

The interrelationship between the mechanical work done on a material in the elastic range and changes in its thermodynamic properties, that is, between stress and strain, on the one hand, and temperature and entropy, on the other, is known as the Thermoelastic effect. The phenomenon is exactly adiabatic and is characterized by the thermoelastic quotient commonly referred to as thermoelastic constant. The thermoelastic effect can be used for stress analysis by monitoring the stress fluctuations by means of infrared radiometry, Also, it can be applied to study the anharmonicity in materials by measuring the temperature changes associated with adiabatic pressure changes, In this paper thermodynamic expressions are derived for the pressure derivative of the thermoelastic quotient under adiabatic as well as isothermal conditions, The derived expressions are applied to investigate the thermoelastic effect for the three glasses, namely, silica glass, soda-lime silica glass, and lead-silica glass, The isothermal pressure derivative of the thermoelastic quotient is evaluated for the three glasses. The isothermal volume derivative of the Gruneisen function is calculated.     

2D general solution and fundamental solution for orthotropic thermoelastic materials

The 2D general solution for the plane problem of thermoelastic materials is derived in terms of three harmonic functions using strict differential operator theory for the case of distinct eigenvalues. Based on the obtained general solution, the 2D fundamental solution for a steady line heat source in an infinite and a semi-infinite thermoelastic plane is obtained by three newly introduced harmonic functions. All components of coupled fields are expressed in terms of elementary functions and they are convenient to be used.     

Thermoelastic Stress Analysis of a GRP Tee Joint

A detailed study of the stresses that are developed in a glass reinforced plastic (GRP) tee joint under service loads is described. The joints are fabricated by laminating a boundary angle over a radiused fillet on either side of the ‘tee’. Full-field stress characterisation data is provided by a thermoelastic analysis of the tee joint. Calibration procedures that allow the thermoelastic data to be compared with the results of a finite element analysis are detailed. The results of the thermoelastic analysis are compared with values obtained from the finite element analysis. The applicability of thermoelastic analysis as a validation tool for finite element models of composite materials is assessed.     

Existence of longitudinal and transverse waves in anisotropic thermoelastic media

Four waves propagate in an anisotropic thermoelastic medium. The fastest among them is a quasi-longitudinal wave. The slowest of them is a thermal wave. The remaining two are called quasi-transverse waves. The prefix ‘quasi’ refers to their polarizations being nearly, but not exactly, parallel or perpendicular to the direction of propagation. The polarizations of these four waves are not mutually orthogonal. Hence, unlike anisotropic elastic media, the existence of a longitudinal wave may not imply the existence of a transverse wave, by default. The existence of a purely longitudinal wave in an anisotropic thermoelastic medium is ensured by the stationary characters of three expressions. These expressions involve components of phase direction with elastic (stiffness and coupling) and thermal coefficients of the thermoelastic medium. The existence of a purely transverse wave is ensured by the two equations restricting the choice of thermoelastic (stiffness and coupling) coefficients. The existence of longitudinal and transverse waves along the coordinate axes and in the coordinate planes are discussed for general anisotropy. The discussion is extended to orthotropic materials, and the existence of pure phases is explored along few specific phase directions.     

Thermal stress induced birefringence in double cladding fiber with non-circular inner cladding

Thermal stress induced birefringence due to the thermoelastic difference between the outer cladding and the non-circular inner cladding of a double cladding fiber (DCF) is theoretically investigated. A modified slab model is proposed to estimate the influence of the outer cladding on the birefringence property of the core. Numerical simulation is carried out to investigate the thermoelastic and geometric contributions of the cladding to thermal induced birefringence in rectangular and D-shaped ytterbium-doped DCFs. The thermoelastic relations deduced in the modified slab model are also qualitatively verified. Research shows that the influence of the outer cladding on the thermal-induced birefringence in DCF varies greatly depending on the choice of outer cladding materials, inner cladding shapes and temperature variation.     

Generalized thermoelastic waves in functionally graded plates without energy dissipation

In this paper, a dynamic solution of the propagating thermoelastic waves in functionally graded material (FGM) plate subjected to stress-free, isothermal boundary conditions is presented in the context of the Green–Naghdi (GN) generalized thermoelastic theory. The FGM plate is composed of two orthotropic materials. The materials properties are assumed to vary in the direction of the thickness according to a known variation law. The coupled wave equation and heat conduction equation are solved by the Legendre orthogonal polynomial series expansion approach. The convergency of the method is discussed through a numerical example. The dispersion curves of the inhomogeneous thermoelastic plate and the corresponding pure elastic plate are compared to show the characteristics of thermal modes and the influence of the thermoelasticity on elastic modes. The displacement, temperature and stress distributions of elastic modes and thermal modes are shown to discuss their differences. A plate with a different gradient variation is calculated to illustrate the influence of the gradient field on the wave characteristics.     

Thermal conversion efficiency of an ideal thermoelastic marmem cycle

The thermal conversion efficiency of an ideal stress-strain-temperature cycle based on the mechanical shape memory effect associated with a thermoelastic martensite transformation (thermoelastic marmem cycle) has been studied. A relationship between the upper limit of the thermal efficiency and a set of materials properties has been derived. It is shown that a higher thermoelastic marmem efficiency and a closer approach to the corresponding Carnot efficiency are favoured by: (1) higher yield stress of the high-temperature phase, (2) larger recoverable strain, (3) smaller transformation temperature range and thermal hysteresis associated with the transformation, and (4) smaller transformation latent heat. The thermal efficiency has been calculated for a cycle utilizing a Ti-50.4 at % Ni alloy. The highest efficiency for this particular alloy was found to be about 9%; this amounts to 45% of the corresponding Carnot efficiency. Thus it is concluded that efficiencies can be obtained which are comparable with those of cycles operating at small temperature differences with fluids as working media.Marmem is derived from martensite memory [21].     

Eshelby's formula for an ellipsoidal elastic inclusion in anisotropic poroelasticity and thermoelasticity

Eshelby's formula that relates the strain inside of an ellipsoidal inclusion in an unbounded elastic medium to the uniform strain imposed at infinity is generalized to the cases of poroelastic and thermoelastic materials. This result holds for an arbitrary anisotropy of the inclusion and of the host material.