Generalized magneto-thermoviscoelastic plane waves under the effect of rotation without energy dissipation

A new model of the equations of generalized thermoviscoelasticity for a thermally, isotropic and electrically conducting half-space solid whose surface is subjected to a thermal shock is given. The formulation is applied to the generalized thermoelasticity based on the Green and Naghdi (GN) theory under the effect of rotation, where there is an initial magnetic field parallel to the plane boundary of the half-space. The medium is deformed because of thermal shock and due to the application of the magnetic field, it results in induced magnetic and electric fields in the medium. The normal mode analysis is used to obtain the expressions for the variables considered. The distributions of temperature, displacement, stress, induced magnetic and electric fields are represented graphically. Comparisons are made with the results predicted by the types II and III in the presence and absence of rotation.     

Reflection of plane waves in thermo-diffusion elasticity without dissipation under the effect of rotation

The governing equations of rotating thermoelastic solids with diffusion are solved in context of the Green–Naghdi theory (Type II) to show the numerical existence of four coupled plane waves. The required boundary conditions at the stress free and thermally insulated surface of the model are satisfied to obtain the reflection coefficients of various reflected waves for an incident plane wave. These coefficients are found to depend on rotation parameter, the angle of incidence of striking waves, thermo-diffusion parameters, and other material constants. Complex absolute values of speeds and reflection coefficients are computed for a particular material representing the model. Graphical representation of numerical results show the effects of rotation and diffusion on speed and reflection coefficients of plane waves.     

Generalized thermoelastic waves in spherical curved plates without energy dissipation

In this article, the propagation of thermoelastic waves in orthotropic spherical curved plates subjected to stress-free, isothermal boundary conditions is investigated in the context of the Green–Naghdi (GN) generalized thermoelastic theory (without energy dissipation). The theoretical formulation is based on the linear GN thermoelastic theory. The coupled wave equation and heat conduction equation expressed by the displacement and temperature are obtained. By the Legendre orthogonal polynomial series expansion approach, the coupled controlling equations are solved. The convergence of the method is demonstrated through a numerical example. The dispersion curves of thermal modes and elastic modes are illustrated simultaneously. Dispersion curves of the corresponding purely elastic spherical plate are also shown to analyze the influence of thermoelasticity on elastic modes. The displacement, temperature and stress distributions of both elastic modes and thermal modes are calculated to show their differences. A thermoelastic spherical plate with a different ratio of radius to thickness is considered to show the influence of the ratio on the characteristics of thermoelastic waves.     

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.     

Thermo-poroacoustic acceleration waves in elastic materials with voids without energy dissipation

We present a model for acoustic wave propagation in a porous material which also allows for propagation of a thermal displacement wave. The thermodynamics is based on an approach of A.E. Green, F.R.S. and P.M. Naghdi and is presented for a modification of the theory of elastic materials with voids.     

Coupled thermoelasticity and second sound in finite length functionally graded thick hollow cylinders (without energy dissipation)

In this article, the coupled thermoelasticity behavior of functionally graded thick hollow cylinders is studied. The governing coupled thermoelasticity and the energy equations are solved for a finite length functionally graded cylinder subjected to thermal shock load. The coupled thermoelastic equations are considered based on Green–Naghdi theory. The mechanical properties of cylinder are graded across the thickness as a power law function of radius. The cylinder is assumed to be made of many isotropic sub-cylinders (layers) across the thickness. Functionally graded properties are created by suitable arrangement of layers and governing equations are expanded in longitudinal direction by means of trigonometric function expansion. The Galerkin Finite Element and Newmark Methods are used to analyze the cylinder. The dynamic behavior of temperature distribution, mechanical displacement and thermal stresses is obtained and discussed. The second sound and elastic wave propagation are determined for various kinds of variation in the mechanical properties. The comparison of present results with published data shows the excellent agreement.     

Propagation of harmonic plane waves under thermoelasticity with dual-phase-lags

The present paper deals with the investigation of the propagation of harmonic plane waves with assigned frequency by employing the thermoelasticity theory with dual-phase-lags (Tzou [7], Chandrasekharaiah [10]). The exact dispersion relation solutions for the plane wave are obtained analytically and asymptotic expressions of several characterizations of the wave fields, such as phase velocity, specific loss, penetration depth and amplitude ratios are obtained for both the high frequency as well as low frequency values. In order to illustrate the analytical results, the computational tool Mathematica is used to find the numerical values of different wave fields at intermediate values of frequency and results are depicted in different figures. A detailed analysis of the effects of phase-lags on plane wave is presented on the basis of analytical and numerical results and significant points are highlighted.     

Effect of ramp-type heating on the vibration of functionally graded microbeams without energy dissipation

In the present work, a generalized solution for the vibration of functionally graded microbeam is studied. A vibrational response is presented for a microbeam subjected to a ramp-type heating and which has functionally varying material properties through its thickness. The governing equations of the generalized thermoelasticity without energy dissipation proposed by Green and Naghdi are presented. An analytical technique based on Laplace transform is used to calculate the vibration of deflection and the temperature. The inverses of Laplace transforms are computed numerically using Fourier expansion techniques. The effect of the ramping time parameter is studied on the lateral vibration, the temperature, the displacement, the stress, the bending thermal moment, and the strain energy of the functionally graded microbeam. The influence of the thickness of the beam is also analyzed.     

装配式梁柱转动摩擦耗能节点抗震性能试验研究

为了减轻传统钢框架的梁柱节点在强震作用下的损伤与破坏,提出了一种装配式梁柱转动摩擦耗能节点,阐述了该节点的构造形式与工作机理,对其进行了低周反复加载试验,系统研究了该节点的抗震性能,建立了其恢复力模型,并与试验结果进行了对比分析.研究结果表明,装配式梁柱转动摩擦耗能节点利用连接钢板与黄铜板之间的转动摩擦耗能,其滞回曲线...     

Size effect on creep energy dissipation during stable crack growth

Creep energy dissipation (CED) due to crack tip creep zone is determined under steady state conditions for centre cracked thin specimen of 1.25CrO.5Mo steel, with different widths and crack length to width ratios. The creep energy rate increases when the increment in crack length Δa increases and the slope increases with increase in aspect ratio a/W and decreases with increase in width W.     

Study on the reflection of photothermal waves in a semiconducting medium under generalized thermoelastic theory

In this article, coupled generalized thermoelastic with thermal relaxation time and plasma theories were used to study the reflection problem at the surface of a semiinfinite semiconconducting medium during a photothermal process. Using the harmonic wave method, the reflection coefficient ratios were obtained analytically for the incident CI wave and incident rotational wave. The variations of the amplitude of reflection coefficient ratios with the angle of incidence are shown graphically for silicon. Effects of several parameters (thermal relaxation time, thermoelastic coupling parameter, and thermoelectric coupling parameter) on reflection coefficient ratios were given by numerical results.     

A DRBEM model for harbor oscillation with the effect of energy dissipation

Abstract

In this study, the numerical scheme of dual reciprocity boundary element method (DRBEM) is adopted to investigate the resonant problem in a harbor while considering the effect of energy dissipation. The numerical model employed the mild slope equation as a basic equation. To avoid complicated procedures for solving the equation, DRBEM is used to improve numerical efficiency. Computation results are compared with the existing experimental data and other theoretical results. It shows that the present model is valid and effective to solve the harbor oscillation problem.     

The reflection of nonlinear irregular surface water waves

This paper concerns the reflection of irregular surface water waves from an impermeable vertical wall and investigates the similarities between this case and the direct, head-on collision of two identical wave groups travelling in opposite directions. A new set of experimental measurements is presented and compared with fully nonlinear numerical predictions based upon a multiple-flux boundary element method (BEM). Comparisons concern both the spatial and the temporal water surface elevations in the vicinity of the focused wave event; the latter occurring at the location of the wall. Linear and second-order irregular wave theories, commonly adopted as the basis for design solutions, are shown to significantly under-predict both the wave steepness and the maximum crest elevation in the vicinity of the wall. In contrast, the fully nonlinear numerical predictions are shown to be in very good agreement with the experimental measurements; the present results having been achieved without the need for smoothing, filtering or regridding.     

振动荷载下路基的能量耗散率空间分布规律的研究

为研究振动荷载作用下的路基内部的能量状态分布,基于Parseval定理,分别以动应变/加速度为变量,推导建立了周期性和非周期性的路基内振动信号的能量耗散率计算公式;根据土体的动力互易性原理,进行了振动荷载下路基动力响应现场试验,利用试验测试结果,分析研究了该路基的能量耗散率空间分布规律.研究结果表明:①能量耗散率沿深度...     

Dispersion of surface waves at a dielectric-high temperature superconductor interface with allowance for energy dissipation

The dispersion characteristics of surface waves at a dielectric-high temperature superconductor (HTSC) interface have been studied with allowance for energy dissipation. Conditions of the existence of surface waves and the corresponding dispersion relations are determined at temperatures below the HTSC critical temperature. The frequency dependences of the penetration depth in each medium and the free path of surface polaritons are described. In the frequency range studied, these quantities can vary within several orders of magnitude.     

On the propagation of waves in layered anisotropic media in generalized thermoelasticity

In view of the increased usage of anisotropic materials in the development of advanced engineering materials such as fibers and composite and other multilayered, propagation of thermoelastic waves in arbitrary anisotropic layered plate is investigated in the context of the generalized theory of thermoelasticity. Beginning with a formal analysis of waves in a heat-conducting N-layered plate of an arbitrary anisotropic media, the dispersion relations of thermoelastic waves are obtained by invoking continuity at the interface and boundary conditions on the surfaces of layered plate. The calculation is then carried forward for more specialized case of a monoclinic layered plate. The obtained solutions which can be used for material systems of higher symmetry (orthotropic, transversely isotropic, cubic, and isotropic) are contained implicitly in our analysis. The case of normal incidence is also considered separately. Some special cases have also been deduced and discussed. We also demonstrate that the particle motions for SH modes decouple from rest of the motion, and are not influenced by thermal variations if the propagation occurs along an in-plane axis of symmetry. The results of the strain energy distribution in generalized thermoelasticity are useful in determining the arrangements of the layer in thermal environment.     

全轻纤维混凝土的SHPB冲击强度与耗能效应

以LC30全轻页岩陶粒混凝土为基准,对聚丙烯纤维、钢纤维和多壁碳纳米管不同组合掺入方式,分别进行了静力和分离式Hopkinson压杆(SHPB)冲击试验,利用HJC模型和LS-DYNA软件对素混凝土和钢纤维混凝土的动态应力-应变曲线进行了数值模拟。结果表明:全轻纤维混凝土不仅具有应变率效应和临界值,而且还具有强度效应和能量效应;并随应变率提高,其动态峰值应力和峰值应变、总能耗随之增大,且动态应力增长系数与应变率的对数具有显著相关性,但纤维掺入方式具有明显的差异性。其中,单掺时以聚丙烯纤维为最好,双掺时差异不大,三掺时为最好。数值模拟与试验曲线相近,但峰值应力较大和下降段差异较大,表明HJC模型对全轻混凝土及其纤维混凝土具有一定的局限性。