共查询到20条相似文献,搜索用时 0 毫秒
1.
D. Iean 《International Journal of Solids and Structures》2007,44(25-26):8648-8662
This paper is concerned with a linear theory of thermodynamics for elastic materials with microstructure, whose microelements possess microtemperatures. It is shown that there exists the coupling of microrotation vector field with the microtemperatures even for isotropic bodies. Uniqueness and continuous dependence results are presented. The theory is used to establish the solution corresponding to a concentrated heat source acting in an unbounded continuum. 相似文献
2.
Ramn Quintanilla 《Mechanics Research Communications》2007,34(7-8):522-527
In this note we prove the impossibility of the localization in time of the solutions of the linear thermoelasticity with voids. This means that the only solution for this problem that vanishes after a finite time is the null solution. From a thermomechanical point of view, this result says that the combination of the thermal and porous dissipation in the linear theory is not sufficiently strong to guarantee that the thermomechanical deformations will vanish after a finite time. The main idea to prove this result is to show the uniqueness of solutions for the backward in time problem. 相似文献
3.
基于弹性动力学的线性理论,建立了涂层材料中广义瑞利波传播的理论分析模型,并
且由波动方程和边界条件推导了波的频散方程.分析了慢层和快层对相速度频散的影响,给
出了不同层厚-波长比和不同涂层-基体密度比情况下广义瑞利波相速度的理论解.算例分
析分别比较了慢层和快层结构中波的相速度、群速度,以及随深度衰减的位移与应力振
幅.另外,相速度曲线和位移振幅曲线与文献中给出的结果吻合,验证了理论模型和分析过
程的正确性. 相似文献
4.
We consider wave propagation along the interface of two dissimilar anisotropic elastic half-spaces that are in sliding contact. A new secular equation is obtained that covers all special cases in one equation. One special case is when a Rayleigh wave (called the R-wave) can propagate in both half-spaces with the same wave speed. Another special case is when a slip wave (called the S-wave) can propagate in each of the half-spaces with the same wave speed. If a Rayleigh wave and a slip wave can propagate in one of the half-spaces it is called the RS-wave. In this case an interfacial slip wave exists in which the other half-space is at rest unless an RS-wave can also propagate in the other half-space. The results for general anisotropic elastic materials are applied to orthotropic materials. 相似文献
5.
6.
G. L. Komissarova 《International Applied Mechanics》2007,43(9):988-999
The properties of harmonic surface waves in an elastic cylinder made of a rigid material and filled with a fluid are studied.
The problem is solved using the dynamic equations of elasticity and the equations of motion of a perfect compressible fluid.
It is shown that two surface (Stoneley and Rayleigh) waves exist in this waveguide system. The first normal wave generates
a Stoneley wave on the inner surface of the cylinder. If the material is rigid, no normal wave exists to transform into a
Rayleigh wave. The Rayleigh wave on the outer surface forms on certain sections of different dispersion curves. The kinematic
and energy characteristics of surface waves are analyzed. As the wave number increases, the phase velocities of all normal
waves, except the first one, tend to the sonic velocity in the fluid from above
__________
Translated from Prikladnaya Mekhanika, Vol. 43, No. 9, pp. 48–62, September 2007. 相似文献
7.
郭少华 《Acta Mechanica Sinica》2010,26(2):241-246
Based on the standard spaces of the physical presentation, both the quasi-static mechanical approximation and the quasi-static electromagnetic approximation of piezoelectric solids are studied here. The complete set of uncoupled elastic wave and electromagnetic wave equations are deduced. The results show that the number and propagation speed of elastic waves and electromagnetic waves in anisotropic piezoelectric solids are determined by both the subspaces of electromagnetically anisotropic media and ones of mechanically anisotropic media. Based on these laws, we discuss the propagation behaviour of elastic waves and electromagnetic waves in the piezoelectric material of class 6 mm. 相似文献
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9.
The paper is concerned with the propagation of Rayleigh waves in an elastic half-space with impedance boundary conditions. The half-space is assumed to be orthotropic and monoclinic with the symmetry plane x3=0. The main aim of the paper is to derive explicit secular equations of the wave. For the orthotropic case, the secular equation is obtained by employing the traditional approach. It is an irrational equation. From this equation, a new version of the secular equation for isotropic materials is derived. For the monoclinic case, the method of polarization vector is used for deriving the secular equation and it is an algebraic equation of eighth-order. When the impedance parameters vanish, this equation coincides with the secular equation of Rayleigh waves with traction-free boundary conditions. 相似文献
10.
Pham Chi Vinh 《Wave Motion》2011,48(7):614-625
In this paper, formulas for the velocity of Rayleigh waves in compressible isotropic solids subject to uniform initial deformations are derived using the theory of cubic equation. They are explicit, have simple algebraic forms, and hold for a general strain energy function. Unlike the previous investigations where the derived formulas for Rayleigh wave velocity are approximate and valid for only small enough values of pre-strains, this paper establishes exact formulas for Rayleigh wave velocity being valid for any range of pre-strains. When the prestresses are absent, the obtained formulas recover the Rayleigh wave velocity formula for compressible elastic solids. Since obtained formulas are explicit, exact and hold for any range of pre-strains, they are good tools for evaluating nondestructively prestresses of structures. 相似文献
11.
Rajneesh Kumar·Rupender 《Acta Mechanica Sinica》2009,25(5):619-628
The present investigation is concerned with wave propagation in an electro-microstretch generalized thermoelastic solid half space. Two different cases have been discussed: (i) reflection of plane wave at the free surface of an electro-microstretch generalized thermoelastic solid; and (ii) propagation of Rayleigh waves in an electro-microstretch generalized thermoelastic solid half space. In case (i), the amplitude ratios of the various reflected waves have been computed numerically and depicted graphically against angle of incidence. In case (ii), the frequency equation is derived and dispersion curves giving phase velocity and attenuation coefficient as a function of wave number, have been plot- ted graphically for a specific model. Some special cases of interest are also deduced, for both the cases. 相似文献
12.
It is known that a subsonic surface (Rayleigh) wave exists in an anisotropic elastic half-space x2 0 if the first transonic state is not of Type 1. If the first transonic state is of Type 1 but the limiting wave is not exceptional, a subsonic surface wave exists. If the first transonic state is of Type 1 and the limiting wave is exceptional, a subsonic surface wave exists when . It is shown that an exceptional body wave is necessarily an exceptional transonic wave, and could be an exceptional limiting wave. Only two wave speeds are possible for an exceptional body wave. We present explicit conditions in terms of the reduced elastic compliances for the existence of an exceptional body wave. If an exceptional body wave exists, conditions are given for identifying whether the transonic state is of Type 1. Hence, through the existence of an exceptional body wave we provide explicit conditions for the existence of a subsonic surface wave with the exception when needs to be computed. 相似文献
13.
An investigation is conducted of propagation of surface waves in a porous medium consisting of a microscopically incompressible solid skeleton in which a microscopically incompressible liquid flows within the interconnected pores, and particularly the case where the solid skeleton deforms linear elastically. The frequency equations of Rayleigh- and Love-type waves are derived relating the dependence of wave numbers, being complex quantities, on frequency, as a result those waves are dispersive as well as inhomogeneous. Nevertheless, the amplitudes of both surface waves attenuate along the surface of the porous medium, whereas they decay exponentially receding from the surface of the medium. 相似文献
14.
This work investigates the dispersion properties of Rayleigh-type surface waves propagating in a layered piezoelectric nanostructure composed of a piezoelectric nanofilm over an elastic substrate. As one of the most important features of nanostructures, surface effects characterized by surface stresses and surface electric displacements are taken into account through the surface piezoelectricity theory and the nonclassical mechanical and electrical boundary conditions. Concrete expressions of th... 相似文献
15.
The scaling and similarity laws concerning the propagation of isolated spherical blast waves are briefly reviewed. Both point
source explosions and high pressure gas explosions are considered. Test data on blast overpressure from the interaction and
coalescence of spherical blast waves emanating from explosives in the form of shaped charges of different strength placed
in the vicinity of a solid propellant stack are presented. These data are discussed with regard to the scaling laws concerning
the decay of blast overpressure. The results point out the possibility of detecting source explosions from far-field pressure
measurements.
相似文献
16.
In this paper, the propagation and localization of Rayleigh waves in disordered piezoelectric phononic crystals with material 6 mm are studied taking the electromechanical coupling into account. The electric field is approximated as quasi-static. The analytical solutions of Rayleigh waves are obtained. The 6×6 transfer matrix between two consecutive unit cells is obtained by means of the mechanical and electrical continuity conditions. The expression of the localization factor in disordered periodic structures is presented by regarding the variables of the mechanical and electrical fields as the elements of the state vector. The numerical results for a piezoelectric phononic crystal—PVDF-PZT-2 piezocomposite—are presented and analyzed. From the results we can see that the localization is strengthened with the increase of the disorder degree. The characteristics of the passbands and stopbands are influenced by different ratios of the thickness of the polymers to that of the piezoelectric ceramics. Disorder in elastic constant c11 of PZT-2 can also result in the localization phenomenon. The propagation and localization of Rayleigh waves in piezoelectric phononic crystals may be controlled by properly designing some structural parameters. 相似文献
17.
《Wave Motion》2018
In this paper, the propagation of Rayleigh waves in orthotropic non-viscous fluid-saturated porous half-spaces with sealed surface-pores and with impervious surface is investigated. The main aim of the investigation is to derive explicit secular equations and based on them to examine the effect of the material parameters and the boundary conditions on the propagation of Rayleigh waves. By employing the method of polarization vector the explicit secular equations have been derived. These equations recover the ones corresponding to Rayleigh waves propagating in purely elastic half-spaces. It is shown from numerical examples that the Rayleigh wave velocity depends strongly on the porosity, the elastic constants, the anisotropy, the boundary conditions and it differs considerably from the one corresponding to purely elastic half-spaces. Remarkably, in the fluid saturated porous half-spaces, Rayleigh waves may travel with a larger velocity than that of the shear wave, a fact that is impossible for the purely elastic half-spaces. 相似文献
18.
The paper presents the effect of a rigid boundary on the propagation of torsional surface waves in a porous elastic layer
over a porous elastic half-space using the mechanics of the medium derived by Cowin and Nunziato (Cowin, S. C. and Nunziato,
J. W. Linear elastic materials with voids. Journal of Elasticity, 13(2), 125–147 (1983)). The velocity equation is derived, and the results are discussed. It is observed that there may be two
torsional surface wave fronts in the medium whereas three wave fronts of torsional surface waves in the absence of the rigid
boundary plane given by Dey et al. (Dey, S., Gupta, S., Gupta, A. K., Kar, S. K., and De, P. K. Propagation of torsional surface
waves in an elastic layer with void pores over an elastic half-space with void pores. Tamkang Journal of Science and Engineering, 6(4), 241–249 (2003)). The results also reveal that in the porous layer, the Love wave is also available along with the torsional
surface waves. It is remarkable that the phase speed of the Love wave in a porous layer with a rigid surface is different
from that in a porous layer with a free surface. The torsional waves are observed to be dispersive in nature, and the velocity
decreases as the oscillation frequency increases. 相似文献
19.
P.N. Andriotaki 《Theoretical and Applied Fracture Mechanics》2005,43(3):308
Second-order ordinary differential equations (ODEs) with strongly nonlinear damping (cubic nonlinearities) govern surface wave motions that entail nonlinear surface seismic motions. They apply to dynamic crack propagation and nonlinear oscillation problems in physics and nonlinear mechanics. It is shown that the nonlinear surface seismic wave equation (Rayleigh equation) admits several functional transformations and it is possible to reduce it to an equivalent first-order Abel ODE of the second kind in normal form. Based on a recently developed methodology concerning the construction of exact analytic solutions for the type of Abel equations under consideration, exact solutions are obtained for the nonlinear seismic wave (NLSW) equation for initial conditions of the physical problem. The method employed is general and can be applied to a large class of relevant ODEs in mathematical physics and nonlinear mechanics. 相似文献
20.
E. Rodrigues Ferreira 《International Journal of Non》2009,44(5):450-455
In this paper, waves propagating in Mooney-Rivlin and neo-Hookean non-linear elastic materials subjected to a homogeneous pre-strain are considered. In a previous paper, Boulanger and Hayes [Finite-amplitude waves in deformed Mooney-Rivlin materials, Q. J. Mech. Appl. Math. 45 (1992) 575-593] showed, for deformed Mooney-Rivlin materials, that the superposition of two finite-amplitude shear waves polarized in different directions (orthogonal to each other) and propagating along the same direction is an exact solution of the equations of motion. The two waves do not interact. Here, we are interested in superpositions of waves propagating in different directions. Two types of superpositions are considered: superpositions of waves polarized in the same direction, and also superposition of waves polarized in different directions. It is shown that such superpositions are exact solutions of the equations of motion with appropriate choices of the propagation and polarization directions. 相似文献