共查询到20条相似文献,搜索用时 15 毫秒
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The propagation of axisymmetric waves in layered hollow cylinders with axially polarized layers is studied. Use is made of
an efficient numerical analytic method. The original problem of electroelasticity for partial differential equations is reduced
to a boundary-value eigenvalue problem for ordinary differential equations by representing the components of the stress tensor,
displacement vectors, electric-flux density, and electric potential as waves traveling in the axial direction. The problem
is solved with the stable discrete-orthogonalization method in combination with incremental search. Results of a numerical
analysis of the dispersion equations over a wide range of geometrical characteristics of the cylinders are presented 相似文献
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论文基于线性磁电弹性理论,研究了具有扇环形截面的多铁性柱形波导中的弹性波传播问题.利用波动势函数法,解析推导获得波动特征方程,进而得到弥散关系.通过算例研究了波传播的关键特性,深入分析了弥散曲线、相速度曲线和截止频率变化情况.结果显示,波的相速度和截止频率非常依赖于波导结构的扇环截面半顶角、内外径比和层合界面的弱界面系数,对于给定材料的波导结构,这些参数也是控制其弥散特性的重要影响因素.值得指出的是,在柱面应力自由的边界条件下相速度曲线中存在独特的频率带隙,而这通常是在周期结构中才会出现. 相似文献
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The problem of the free axisymmetric vibrations of longitudinally polarized piezoceramic hollow cylinders is solved by a numerical
analytic method. The spline-collocation method with respect to the longitudinal coordinate is used to reduce the original
problem of electroelasticity to an eigenvalue boundary-value problem for ordinary differential equations with respect to the
radial coordinate. This problem is solved by the stable discrete-orthogonalization and incremental search methods. Numerical
results are presented and the natural frequencies of the cylinders are analyzed for a wide range of their geometric characteristics 相似文献
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Elastic analyses of heterogeneous hollow cylinders 总被引:3,自引:0,他引:3
Two different kinds of heterogeneous elastic hollow cylinders are studied in the present paper. One is a multi-layered cylinder with different values in different layers for both elastic modulus and Poisson’s ratio. Another is an elastic hollow cylinder with continuously graded material properties. By introducing two recursive algorithms, the extrusion stresses between two neighbor layers in the multi-layered cylinder submitted to uniform pressures on the inner and outer surfaces can be simply determined. Then the exact solutions of the multi-layered structure can be found based on Lamé’s solution. For the hollow cylinder with continuously graded properties, the displacement method is used. Both Whittaker equation and hyper-geometric equation are derived and successfully solved, and then the exact solutions are found. The results obtained in the present paper are compared with the numerical solutions and good agreements are found. At the end of the present paper, some inherent properties of these two different kinds of heterogeneous elastic hollow cylinders are presented and discussed. The results obtained in the present paper are useful in the design and analysis for composites reinforced by unidirectional fiber layers. 相似文献
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The propagation of a Bleustein-Gulyaev (B-G) type wave in a structure consisting of multiple layers and a half-space of porous piezoelectric materials is theoretically studied. The solutions of the problem in terms of the mechanical displacements and electric potential functions are obtained for each layer and the half-space. The dispersion equation is obtained for electrically open and shorted boundary conditions by use of the transfer matrix method. A peculiar kind of B-G waves is investigated, which can propagate only in the layer over the half-space. The relationship between the piezoelectric constants and the dielectric constants is found for the existence of a peculiar kind of propagation modes. The numerical results in terms of the phase velocity and the electromechanical coupling factor with different thicknesses of the layer stack are presented. 相似文献
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Free nonaxisymmetric vibrations of radially polarized hollow piezoceramic cylinders of finite length
The three-dimensional problem of free nonaxisymmetric vibrations of hollow piezoceramic cylinders with axial polarization
is considered. An efficient numerical analytic method to solve boundary-value problems is proposed. The original three-dimensional
problem of electroelasticity is reduced to a two-dimensional problem by representing the displacement components as standing
circumferential waves. Spline collocation with respect to the axial coordinate is used to reduce this two-dimensional problem
to an eigenvalue boundary-value problem with respect to the radial coordinate. This problem is solved by the stable discrete-orthogonalization
and incremental-search methods. Numerical results are presented and the natural frequencies of the cylinders are analyzed
in a wide range of their geometric characteristics 相似文献
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An experimental investigation of elastic waves produced by the axial collision of strikers with truncated 2024 aluminum cones with apex angles of 0.48, 5.38, 20, and 30 deg was performed. Wave propagation was initiated at the small end of all four cones and at the large end of the 0.48-deg and 5.38-deg cones. The striker consisted of a 1/2-in.-diam steel ball or a soft phenol-impregnated fiber cylinder. In most cases, impact was caused by firing the striker from an air gun at approximately 1300 ips; in an additional series of tests, a steel ball was dropped on the cone. The metamorphosis of the pulse at the surface of the target was recorded using both foil and semiconductor resistance strain gages. Data were obtained for periods ranging from 200 to 500 μsec; this permitted the observation of several reflections from the ends of the specimen. In several instances, cylindrical aluminum rods were glued to the cone to form a composite target; this permitted observation of the initial pulse incident on the conical section both from surface strain gage and sandwiched crystal records. Studies were also conduced to ascertain the stress distribution across the base of the 20-deg cone. Initial pulse records were employed to predict the surface response in the target using the one-dimensional equation of elastic wave propagation in a cone of infinite length. Reasonable agreement between the data and the results of calculations based on the analysis was obtained. 相似文献
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V. S. Budaev 《International Applied Mechanics》1975,11(5):533-537
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The diffraction of a monochromatic plane electromagnetic wave by a grating consisting of parallel, electrically perfectly conducting cylinders is investigated. Two separate two-dimensional scalar problems are dealt with viz. the case ofE-polarization and the case ofH-polarization. A new Green's function formulation of the problem is employed leading to integral equations for the unknown field distributions on an elementary scatterer of the grating. Numerical results are presented for a grating of cylinders with either square or circular cross-section. 相似文献
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Under the assumption of potential flow and linear wave theory, a semi-analytic method based on eigenfunciton expansion is proposed to predict the hydrody-namic forces on an array of three bottom-mounted, surface-piercing circular cylinders. The responses of the cylinders induced by wave excitation are determined by the equa-tions of motion coupled with the solutions of the wave radiation and diffraction problems. Experiments for three-cylinder cases are then designed and performed in a wave flume to determine the accuracy of this method for regular waves. 相似文献
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The stress state of longitudinally corrugated layered hollow orthotropic elliptic cylinders is determined using discrete Fourier
series for different geometrical parameters. The results obtained are presented in the form of plots and tables and analyzed 相似文献
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M. J. Manton 《Applied Scientific Research》1973,27(1):219-233
It is shown that a turbulent flow can support elastic waves for which the fluctuating stress is essentially proportional to the strain field. These fluctuations are described by a hyperbolic system and hence they do not decay away from a solid boundary. Their behaviour is also consistent with Taylor's frozen field hypothesis that turbulent fluctuations are advected with the local mean flow speed. 相似文献
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The propagation of time-harmonic elastic waves in a fiber-reinforced composite is studied. The circular fibers are assumed to be parallel to each other and randomly distributed with a statistically uniform distribution. The direction of propagation and the associated particle motion are considered to be normal to the fibers. It is shown that the average waves in the composite separate into compressional and shear types. General formulae for the complex wave number giving the phase velocity and the damping are obtained. It is shown that these formulae lead to the Hashin-Rosen expressions for the transverse bulk modulus and the lower bound for the transverse rigidity, if the correlation in the positions of the fibers can be ignored. The correlation terms, for exponential correlation, are shown to have a significant effect on the damping property of the composite, especially at high frequencies and concentrations. 相似文献