Wave Propagation in a Magneto-Micropolar Thermoelastic Medium with Two Temperatures for Three-Phase-Lag Model

The present paper is concerned with the wave propagation in a micropolar thermoelastic solid with distinct two temperatures under the effect of the magnetic field in the presence of the gravity field and an internal heat source. The formulation of the problem is applied in the context of the three-phase-lag model and Green-Naghdi theory without dissipation. The medium is a homogeneous isotropic thermoelastic in the half-space. The exact expressions of the considered variables are obtained by using normal mode analysis. Comparisons are made with the results in the two theories in the absence and presence of the magnetic field as well as the two-temperature parameter. A comparison is also made in the two theories for different values of an internal heat source.     

Effect of mechanical force,rotation and moving internal heat source on a two-temperature fiber-reinforced thermoelastic medium with two theories

In the present paper, the three-phase-lag model and Green–Naghdi theory without energy dissipation are used to study the effect of a mechanical force and a rotation on the wave propagation in a two-temperature fiber-reinforced thermoelastic problem for a medium with an internal heat source that is moving with a constant speed. The methodology applied here is the use of the normal mode analysis to solve the problem of a thermal shock problem to obtain the exact expressions of the displacement components, force stresses, thermal temperature, and conductivity temperature. Numerical results for the considered variables are given and illustrated graphically in the absence and presence of a rotation as well as a mechanical force. A comparison is made with the results in the context of the two theories in the absence and presence of a moving internal heat source.     

Magneto-rotation-fibre-reinforced thermoelastic with gravity and energy dissipation

In this article, two theories of the generalized thermoelasticity Green-Naghdi theory (of type II and III) are applied, as well as the coupled theory to study the effect of magnetic field and rotation under influence of gravity on 2D problem of a fibre-reinforced thermoelastic. The normal mode analysis is used to obtain the expressions for the temperature, displacement components and the thermal stresses distributions. The resulting formulation is applied for two different concrete problems. The first concerns the case of a punch moving across the surface of semi-infinite thermoelastic half-space subjected to appropriate boundary conditions. The second deals with a thick plate subjected to a time-dependent heat source on each face. Numerical results are illustrated graphically for each problem considered. A comparison is made with the results predicted obtained by the two theories in the presence and absence of magnetic field, rotation and gravity field.     

Thermoelastic response in a symmetric spherical shell

This paper is concerned with the determination of thermoelastic stresses, strain and conductive temperature in a spherically symmetric spherical shell. The two-temperature three-phase-lag thermoelastic model (2T3P) and two-temperature Green–Naghdi model III (2TGNIII) are combined into a unified formulation. There is no temperature at the outer boundary, and thermal load is applied at the inner boundary. 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 the state-space approach. The numerical inversion of the transform is carried out using Fourier series expansion techniques. Because of the short duration of the second sound effects, small time approximations of the solutions are studied. The physical quantities have been computed numerically and presented graphically in a number of figures. A complete and comprehensive analysis of the results has been presented for the 2T3P and the 2TGNIII models. These results have also been compared with those of the one-temperature three-phase-lag thermoelastic model (1T3P) and one-temperature Green–Naghdi model III (1TGNIII).     

Effects of Hall current and two temperatures in transversely isotropic magnetothermoelastic with and without energy dissipation due to ramp-type heat

The present article is concerned with the investigation of disturbances in a homogeneous transversely isotropic thermoelastic rotating medium with two temperatures, in the presence of the combined effects of Hall currents and magnetic field. The formulation is applied to the thermoelasticity theories developed by Green-Naghdi theories of type-II and type-III. Laplace and Fourier transform techniques are applied to solve the problem. The analytical expressions of displacements, stress components, temperature change, and current density components are obtained in the transformed domain. A numerical inversion technique has been applied to obtain the results in the physical domain. Numerical simulated results are depicted graphically to show the effect of Hall current and two temperatures on resulting quantities. Some special cases are also deduced from the present investigation.     

Uniqueness and reciprocity theorems in generalized linear micropolar thermoviscoelasticity

A model of the equations of generalized linear micropolar thermoviscoelasticity is given. The formulation is applied to the coupled theory as well as to five generalizations, the Lord-Shulman theory with one relaxation time, the Green-Lindsay theory with two relaxation times, the Green-Naghdi theories of type II (without energy dissipation) and of type III, and the Chandrasekharaiah-Tzou theory with dual-phase-lag. Using Laplace transforms, a uniqueness theorem for this model is proved, restrictions on relaxation functions are deduced and the dynamic reciprocity theorem is derived. The cases of generalized linear micropolar thermoviscoelasticity of Kelvin-Voigt model, generalized linear micropolar thermoelasticity, generalized thermoviscoelasticity and generalized thermoelasticity can be obtained from the given general model.     

Boundary integral equation formulation for the generalized micro-polar thermoviscoelasticity

A formulation of the boundary integral equation method for generalized linear micro-polar thermoviscoelasticity is given. Fundamental solutions, in Laplace transform domain, of the corresponding differential equations are obtained. The initial, mixed boundary value problem is considered as an example illustrating the BIE formulation. The results are applicable to the generalized thermoelasticity theories: Lord-Shulman with one relaxation time, Green-Lindsay with two relaxation times, Green-Naghdi theories, and Chandrasekharaiah and Tzou with dual-phase lag, as well as to the dynamic coupled theory. The cases of generalized linear micro-polar thermoviscoelasticity of Kelvin-Voigt model, generalized linear thermoviscoelasticity and generalized thermoelasticity can be obtained from the given results.     

Effect of Gravitational Field and Temperature Dependent Properties on Two-Temperature Thermoelastic Medium with Voids under G-N Theory

This investigation is aimed to study the two dimensional problem of thermoelastic medium with voids under the effect of the gravity. The modulus of elasticity is taken as a linear function of the reference temperature and employing the two-temperature generalized thermoelasticity. The problem is studied in the context of Green-Naghdi (G-N) theory of types II and III. The normal mode analysis method is used to obtain the exact expressions for the physical quantities which have been shown graphically by comparison between two types of the (G-N) theory in the presence and the absence of the gravity, the temperature dependent properties and the two-temperature effect.     

Plane wave propagation and domain of influence in fractional order thermoelastic materials with three-phase-lag heat transfer

The domain of influence theorem for the fractional order theory of anisotropic thermoelastic materials with three-phase-lag heat transfer is proposed. The fractional order theory of thermoelasticity with three-phase-lag heat transfer has been used to investigate the problem. The plane wave propagation in anisotropic thermoelastic medium having a fractional order derivative in the context of three-phase-lag model of thermoelasticity is studied. The governing equations for a transversely isotropic three-phase-lag model are reduced as a special case. Some wave characteristics are computed numerically and presented graphically.     

Magneto-thermo-elastic response in a perfectly conducting medium with three-phase-lag effect

This paper deals with the problem of magneto-thermo-elastic interactions in an unbounded, perfectly conducting elastic medium due to the presence of periodically varying heat sources in the context of linear theory of generalized thermo-elasticity with energy dissipation (TEWED or GN-III model), without energy dissipation (TEWOED or GN-II model) and three-phase-lag model (3P model). The governing equations of generalized thermo-elasticity of the above models under the influence of a magnetic field are established. The Laplace-Fourier double transform technique has been used to get the solution. The inversion of the Fourier transform has been done by using residual calculus, where poles of the integrand are obtained numerically in a complex domain by using Laguerre’s method, and the inversion of the Laplace transformation is done numerically using a method based on Fourier series expansion technique. Displacement, temperature, stress and strain distributions have been computed numerically and presented graphically in numbers of figures. A comparison of the results for different theories (GN-II, GN-III and 3P model) and the effect of magnetic field and damping coefficient on the physical quantities has been discussed.     

Generalized thermo-microstretch elastic medium with temperature dependent properties for different theories

A general model of the equations of generalized thermo–microstretch for a homogeneous isotropic elastic half–space is given. The modulus of elasticity is taken as a linear function of reference temperature. The formulation is applied to generalized thermoelasticity theories, the Lord–?hulman and Green–Lindsay theories, as well as the classical dynamical coupled theory. The normal mode analysis is used to obtain the exact expressions for the displacement components, force stresses, temperature, couple stresses and microstress distribution. The variations of the considered variables through the horizontal distance are illustrated graphically. A comparison is made with the results predicted by the three theories in case of temperature–independent modulus of elasticity.     

Two-Temperature Effects on Plane Waves in Generalized Thermo-Microstretch Elastic Solid

In this article, the effect of two temperatures on plane waves propagating through a generalized-thermo-microstretch elastic half-space solid has been investigated. The surface of the medium is subjected to a mode-I crack, and the $z$ axis is pointing vertically into the medium. Two fascinating theories of generalized thermo-elasticity presented by Green and Naghdi and named as without energy dissipation (GN-II) and with energy dissipation (GN-III) have been used. Governing equations for each particular case are also derived, and a solution is obtained. An analytical technique of normal mode analysis is used to obtain the exact expressions for the displacement components, force stresses, the temperature, and the couple stresses distribution. The variations of the considered variables against the vertical distance are illustrated graphically. Comparisons are made with the results between type II and III in generalized-thermo-microstretch and in a particular case (without microstretch constants). Numerical work is also performed for a suitable material with the aim of illustrating the results. It is found that the maximum amplitude is obtained for the maximum value of the two temperature parametric constant.     

纤维铺放压紧力及预浸带加热温度对复合材料力学性能的影响

采用三因素四水平正交实验与单因素实验相结合, 通过力学性能测试及SEM和光学显微镜微观形貌观察研究了复合材料铺放过程中压紧力、 预浸带加热温度及芯模温度对复合材料力学性能的影响。实验结果表明: 压紧力与加热温度对层间剪切强度(ILSS)影响很大, 而芯模温度影响较小; 当压紧力为600 N、 预浸带加热温度为30℃、 芯模温度为18℃时, 复合材料综合力学性能达到最佳。微观形貌观察结果表明: 随着压紧力和预浸带加热温度升高, 纤维与树脂接触充分, 树脂与纤维分布均匀性较好, 层间富树脂区的厚度较小, ILSS逐渐增加; 但当预浸温度上升到40℃以后, 压紧力作用导致树脂与纤维的分布均匀性变差, 层间富树脂区的厚度较大, 从而导致ILSS下降。     

温度极化对膜蒸馏过程的影响研究

采用直接接触式膜蒸馏，以纯水为料液，考察了材料及结构不同的5种微孔疏水膜的渗透性能．分析结果认为，膜的渗透系数和温度极化系数共同影响着膜通量的大小．实验还考察了料液温度和流率对膜通量及热效率的影响，利用膜及膜两侧边界层内传热传质理论对此进行了分析讨论．因温度极化系数随操作温度变化，可通过控制适宜操作温度获得大膜通量和高热效率．增大料液流率可强化传热，使温度极化减弱，膜通量增加．     

The Effect of Mechanical Force on Generalized Thermoelasticity in a Fiber-Reinforcement Under Three Theories

The present paper is concerned with effect of mechanical force on generalized thermoelasticity in a fiber-reinforcement. The formulation is applied to generalized thermoelasticity based on the coupled theory, Lord–Shulman theory, and Green–Lindsay theory. The analytical expression of the displacement components, stresses, and temperature are obtained in the physical domain and illustrated graphically using normal mode analysis. Comparisons are made among the three theories for the field quantities in the absence and in the presence of a fiber-reinforcement as well as for different values of mechanical force.     

有效亮度温度理论

经典亮度温度和有效波长理论忽略了环境辐射的影响,且实际测温理论偏离了亮度温度的定义.考虑了环境辐射影响,提出新的有效亮度温度概念,使有效亮度温度适用于存在环境辐射的任意温度测量;进一步提出了基于带通辐射温度计测量的积分有效亮度温度和等效波长理论,使辐射温度计的"主观"测量结果与物体的客观辐射特性相联系,避免了实际测量理论偏离被测量定义.     

温度对平板电磁成形中电磁力影响的数值分析

为了确定高温电磁成形技术中温度对电磁力的影响,采用ANSYS软件对不同温度下板坯中的电磁力进行了模拟.采用霍尔器件测量了常温下线圈-工件间隙的磁感应强度,验证了电磁力的分布规律.模拟结果表明,工件均温时,随温度升高,轴向电磁力峰值减小,负径向电磁力峰值增大.较高温度下轴向力峰值的下降速率小于较低温度情况.工件非均温时,工件中涡流密度较大位置和电磁力峰值位置向低温区偏移.工件存在高斯温度分布时,电磁力的分布特征与常温下相似.     

Thermal buckling and postbuckling analysis of a laminated composite beam with embedded SMA actuators

In this paper, the thermal buckling and postbuckling behaviours of a composite beam with embedded shape memory alloy (SMA) wires are investigated analytically. For the purpose of enhancing the critical buckling temperature and reducing the lateral deflection for the thermal buckling, the characteristics of thermal buckling are investigated through the use of the shape recovery force associated with SMA wire actuators. The results of both thermal buckling and postbuckling behaviours present quantitatively how the shape recovery force affects the thermal buckling behaviour. The analytical results show that the shape recovery force reduces the thermal expansion of the composite laminated beam, which results in both an increment of the critical buckling temperature and also a reduction of the lateral deflection of postbuckling behaviours. A new formula is also proposed to describe the critical buckling temperature of the laminated composite beam with embedded SMA wire actuators.     

Effect of low temperature on plastic deformation in structural materials in a complex state of stress

The results of experimental studies of elastoplastic deformation in structural materials of different grades in a complex state of stress at low temperatures are analyzed. It is shown that the degree of the effect of temperature and force conditions on the character of materials’ strain hardening at low temperature depends on their nature and structural state. The principal hypotheses and postulates that form the basis of the modern plasticity theories are examined for low temperatures. Two new models are introduced to describe the elastoplastic deformation of quasi-brittle and metastable materials under the simple loading with consideration for the effect of low temperatures on their structural state and mechanical properties.     

离子束溅射制备CuInSe_2薄膜的研究

利用离子束溅射沉积技术,设计三元复合靶,直接制备CuInSe_2(CIS)薄膜.通过X射线衍射仪(XRD)、原子力显微镜(AFM)和分光光度计检测在不同衬底温度和退火温度条件下制备的CIS薄膜的微结构、表面形貌和光学性能.实验结果表明:使用离子束溅射沉积技术制备的CIS薄膜具有黄铜矿结构,在一定的条件下,适当温度的热处理可以制备结构紧密、颗粒均匀、致密性和结晶性良好的CIS薄膜,具有强烈的单一晶向生长现象.