Transient response of multilayered hollow cylinder using various theories of generalized thermoelasticity

The present paper deals with thermoelastic problems of finitely long hollow cylinder com-posed of two different materials with axial sym- metry. The medium is traction-free, with neglig-ible body forces and with internal and external heat generations. The governing equations for different theories of the generalized thermoe-lasticity are written in terms of displacement and temperature increment. The exact solution of the problem;using different theories of generalized thermoelasticity;has been deduced. The analytical expressions for displacements, temperature and stresses are found in final forms, and a numerical example has been taken to discuss the effect of the relaxation times. Finally, the results have been illustrated graphi- cally to find the responses of different theories.

Generalized thermoelastic functionally graded spherically isotropic solid containing a spherical cavity under thermal shock

This paper is concerned with the determination of thermoelastic displacement, stress and temperature in a functionally graded spherically isotropic infinite elastic medium having a spherical cavity, in the context of the linear theory of generalized thermoelasticity with two relaxation time parameters （Green and Lindsay theory）. The surface of cavity is stress-free and is subjected to a time-dependent thermal shock. The basic equations have been written in the form of a vector-matrix differential equation in the Laplace transform domain, which is then solved by an eigenvalue approach. Numerical inversion of the transforms is carried out using the Bellman method. Displacement, stress and temperature are computed and presented graphically. It is found that variation in the thermo-physical properties of a material strongly influences the response to loading. A comparative study with a corresponding homogeneous material is also made.

Two and Three Dimensions of Generalized Thermoelastic Medium without Energy Dissipation under the Effect of Rotation

The purpose of this paper is to study the effect of rotation on the general three-dimensional model of the equations of the generalized thermoelasticity for a homogeneous isotropic elastic half-space solid. The problem is studied in the context of the Green-Naghdi theory of type II (without energy dissipation). The normal mode analysis is used to obtain the expressions for the temperature, thermal stress, strain and displacement. The distributions of variables considered are represented graphically.

Simulation and characteristics analysis of a wavefield in a thermoelastic medium adopting the rotated staggered-grid pseudospectral method and L-S theory

The simulation of wave propagation in high-temperature media requires thermoelastic theory.In this paper,we apply the rotated-staggered-grid pseudo-spectral method(RSG-PSM)to solving thermoelastic governing equations based on L-S theory.A time splitting method is used to solve the stiffness problem of the equations,and we introduce the rotated staggered pseudo-spectral operator and centered pseudo-spectral operator to compute the first-order spatial derivatives and second-order spatial derivatives,respectively.In the case of the heterogeneous-medium model,the Crank-Nicolson explicit method is used instead of the pseudo-spectral method to compute the wavefield.The properties and propagation of the thermal coupled wavefield are discussed,and we compare the simulation results obtained using the pseudo-spectral method,staggered-grid pseudo-spectral method,and RSG-PSM.In the case of an isotropic homogeneous medium,we obtain stable and highly accurate results using the time splitting method combined with the RSG-PSM.However,the algorithm cannot be applied with a large time step when the thermal conductivity changes dramatically,and the algorithm is unstable when the reference temperature has a gradient distribution.The optimal combined application of the mesh generation mode and numerical algorithm is explored,laying a foundation for the extension of these methods to thermoporoelasticity,thermoviscoelasticity,and anisotropy.

On thermoelastic problem based on four theories with the efficiency of the magnetic field and gravity

The fundamental objective of this paper is to study the effectiveness of magnetic field and gravity on an isotropic homogeneous thermoelastic structure based on four theories of generalized thermoelasticity.In another meaning,the models of coupled dynamic theory(CDT),Lord-Shulman(LS),Green-Lindsay(GL)as well as Green-Naghdi(GN II)will be taken in the consideration.Then,applying the harmonic method(normal mode technique),the solution of the governing equations and the expressions for the components of the displacement,temperature and(Mechanical and Maxwell’s)stresses is taken into account and calculated numerically.The impacts of the gravity and magnetic field are illustrated graphically which are pronounced on the different physical quantities.Finally,the results of some research that others have previously obtained may be found some or all of them as special cases from this study.

DYNAMIC RESPONSE OF TWO-DIMENSIONAL GENERALIZED THERMOELASTIC COUPLING PROBLEM SUBJECTED TO A MOVING HEAT SOURCE

Based on the Lord and Shulman generalized thermoelasticity theory with one relaxation time, an isotropic semi-infinite plate subjected to a moving heat source has been studied by employing the finite element method directly in time domain, whose distributions of nora dimensional temperature, displacement and stress are illustrated graphically. The results show that the present method is an effective and exact numerical one for solving the thermoelastic coupling problem and is capable of overcoming the defects of traditional integrated transformation and inverse integrated transformation methods. At the same time, the temperature step of the thermal wave front is obtained exactly in contrast with conventional numerical transformation methods.

基于分数阶理论的两端固定杆热弹动力响应

基于Ezzat型分数阶广义热弹性理论和Green-Lindsay广义热弹性理论,借助拉普拉斯积分变换及其数值反变换法研究了移动热源作用下两端固定的温度相关性杆一维热弹动力响应问题,得到了无量纲位移、应力和温度沿x方向的分布情况。分别研究了分数阶参数α、2个不同的热松弛时间因子τ0和τ1、温度相关性参数以及移动热源传播速度υ对无量纲位移、应力和温度的影响,结果表明:分数阶参数α对所考虑的无量纲物理量均有明显影响;热松弛时间因子τ0对无量纲温度外的其他2个物理量影响显著,热松弛时间因子τ1仅对无量纲温度的影响最为显著;随着温度相关性参数和移动热源传播速度υ增大,各物理量呈逐渐减小的状态。

受移动热源作用的两端固定杆的广义热-弹耦合问题

基于带有一个热松弛时间的Lord-Shulman广义热弹性理论,研究了受移动热源作用的两端固定的均质各向同性杆的热-弹动态响应。该文给出了杆的广义热-弹耦合的控制方程,借助拉普拉斯积分变换及其数值反变换对控制方程进行了求解。计算得到了杆内温度、应力及位移的分布规律,从其分布图上可以看出,温度、应力及位移随移动热源速度的增大而减小。

定常温度热弹性板的精化理论

本文首先给出了定常温度热弹性 Ｂｉｏｔ［１］通解的一种新的简化形式，它看起来与各向同 性弹性力学的Ｐａｐｋｏｖｉｃｈ－Ｎｅｕｂｅｒ 通解十分相象，而后由此出发，由一般的各向同性弹性板推 广到本文的热弹性板问题，研究了热弹性板的问题，在没有任何预先假设的前提下，应用Ｌｕｒ’ｅ 算子法，证明了此通解不失一般性，导出了热弹性板精化理论的控制微分方程。

有限厚度圆柱壳热冲击问题的广义热弹性解

针对包含有界边界的轴对称结构受热冲击作用的广义热弹性问题进行了研究分析.基于Lord-Shulman广义热弹性理论(L-S理论),构建了热冲击下有限厚度圆柱壳热弹性响应的广义热弹性模型.借助Laplace(拉普拉斯)变换技术以及Bessel函数的渐进特性,推导了温变载荷作用下,圆柱壳内部位移、温度以及应力场的解析表达式.该表达式不仅可以清楚地揭示热冲击下热波、热弹性波在壳体内部的传播、反射以及叠加的作用过程,更可准确地捕捉到热波、热弹性波波前位置处的阶跃现象,并对热冲击诱发的动态热应力峰值进行有效预测.

一维半无限压电杆的广义的热冲击问题

采用具有两个热松弛时间的G-L广义热弹性理论,研究了一维半无限长压电杆在其端部受到热冲击时的边值问题.借助于拉普拉斯正、反变换技术,在所考虑时间非常短的情况下,对问题进行了求解,得到了位移及温度分布的近似解析解,发现位移及温度分布中分别存在两个阶跃点,并通过数值计算,把温度的分布规律用图形反映了出来.从温度的分布图上可以看出,当任何x的值大于第二个阶跃点的位置值时,温度值都是零,也即在当前所给定的时刻,热以波的形式沿压电杆仅传播到了第二阶跃点的位置,而在第二个阶跃点之后,压电杆上的温度分布保持初始温度;给定不同时刻,热波波前的位置也将相应的在压电杆上移动,也即热波波前在压电杆上的位置随考虑时刻不同而不同.这与经典的热传导是完全不同的,它说明热是以波的形式以有限的速度、而不是以无限的速度在介质中进行传播的.

定常温度热弹性梁的精化理论

首先给出了定常温度热弹性Biot通解的一种新的简化形式,它看起来与各向同性弹性力学的Papkovich-Neuber通解十分相似。不作预先假设,从热弹性理论出发,利用Biot通解和Lur’e算子方法构造了梁的精化理论,得出了自由表面热弹性梁的三个精确方程:四阶方程、超越方程和温度方程。由一般的各向同性弹性梁推广到热弹性梁,导出了在反对称载荷和介质温度作用下热弹性梁的近似控制微分方程。

无限长旋转圆柱体的广义热弹耦合问题

应用Lord和Shulman(L-S)广义热弹性理论,研究无限长旋转圆柱体的热弹耦合问题.建立L-S型广义的热弹耦合的控制方程,借助拉普拉斯积分变换及其数值反变换技术对问题进行求解,得到瞬态热冲击作用下无限长旋转圆柱体中的温度、应力、位移的分布规律.从其分布图上可以看出,介质中呈现出热的波动性和热弹耦合效应,由于旋转效应,位移、应力的幅值有明显提高,而旋转对温度几乎没有影响.

横观各向同性三维热弹性力学通解及其势理论法

通过引入两个位移函数,对用位移表达的运动平衡方程作了简化.利用算子理论,严格地导出了横观各向同性非耦合热弹性动力学问题的通解.对于静力学问题,通解的形式可进一步简化成用4个准调和函数来表示.具体考察了横观各向同性体内平面裂纹上下表面有对称分布温度作用的问题,推广了势理论方法,导出了一个积分方程和一个微分-积分方程.针对币状裂纹表面受均布温度作用情形,给出了具体的解.

半无限长旋转杆件中的广义电磁热弹耦合问题

应用Lord和Shulman(L-S)广义热弹性理论,研究半无限长旋转理想杆件的电磁热弹耦合问题.给出介质中的Maxwell方程组,建立了L-S型广义电磁热弹耦合的控制方程,借助拉普拉斯变换和数值反变换技术对问题进行求解,得到瞬态热冲击作用下半无限长旋转杆件中的温度、应力、位移、感应磁场和电场的分布规律.结果表明,介质呈现热的波动性和电磁热弹耦合效应,由于考虑旋转,对位移和应力提高较大,但对杆的感应磁场和电场的影响较小,对温度基本没有影响.

半无限长压电杆的瞬态热冲击问题

采用具有一个热松弛时间的L S广义热弹性理论 ,研究了一维半无限长压电杆在一端受到热冲击时的边值问题 .借助拉普拉斯正、反变换技术 ,在所考虑时间非常短的情况下 ,对问题进行了求解 ,得到了压电杆上的位移、压力及温度分布的近似解析解 ,发现应力及温度分布中分别存在两个阶跃点 ,并给出了算例 .

功能梯度材料广义热弹性响应

基于Lord-Shulman热弹性理论,选取温度和位移及其一阶导数作为状态变量,结合Laplace积分变换,采用状态空间法建立功能梯度材料的一维广义热弹性响应的层合模型.作为应用,考虑组分材料体积份数按幂率变化的功能梯度无限大平板,数值分析在冲击性热机载荷作用下的温度、应力以及位移响应.结果表明,在冲击性热机载荷作用下,热流延迟项以及组分材料的体积含量变化对功能梯度结构的热弹性响应有着显著的影响.

荷载作用下多孔饱和地基的热-水-力耦合动力响应分析

基于广义热弹性理论,结合达西定律,对Biot波动方程进行修正,研究了一个受到荷载作用的多孔饱和地基的热-水-力多场耦合动态响应问题。建立了多孔饱和地基在荷载作用下的热-水-力耦合模型及控制方程,该模型可退化为热弹性耦合模型。采用正则模态法求解,得到了问题的解析解,讨论了热-水-力耦合模型和热弹性耦合模型的区别,分析了荷载频率变化对地基中各物理量的影响。最终给出了无量纲的竖向位移、超孔隙水压力、竖向应力和温度等物理量的分布规律。

基于广义热弹性理论的多孔地基在移动荷载作用下的特性研究

基于广义热弹性理论,引入热松弛时间,对Biot波动方程进行修正,建立了考虑温度效应的多孔饱和地基在移动荷载作用下的动力控制方程。利用Fourier变换方法,得到地基中温度增量、应力、位移和孔隙水压力在变换域中的一般解,结合热源输入条件和地基边界条件,确立时域内的温度增量、应力、位移和孔隙水压力的积分形式解答。利用Fourier逆变换方法和自适应数值积分算法得到了相应的数值结果。结果可退化为静荷载作用下的弹性地基解答,并与经典Flamant解进行比较,显示出较好的一致性。通过数值计算讨论不同的热源输入对地基温度增量场、应力场、位移场以及孔隙水压力的影响。结果表明:温度增量场受热源输入条件的影响很小,而应力、位移和孔隙水压力受热源输入的影响很明显。

半无限大体广义电磁热弹耦合的二维问题

基于Lord和Shulman广义热弹性理论,研究了热、电可导的半无限大体电磁热弹耦合的二维问题。半无限大体受热和外加恒定磁场的作用,文中建立了电磁热弹性耦合的控制方程,利用正则模态法求解得到了所考虑物理量的解析解,并用图形反映了各物理量的分布规律,从分布图上可以看出,介质中出现了电磁热弹耦合效应,各物理量的非零值仅在一个有限的区域内。