弹性地基上的自由矩形板

在弹性地基上的自由矩形板的弯曲,在弹性薄板理论中也是个难题.本文以叠加法提供一个精确解.它满足微分方程,自由边界的条件以及自由角点条件.这样将导致一系列无穷联立方程.所解的问题为在板的中点作用一集中力这问题.我们并以地基反力应与这集中力相平衡.校核所作的计算是否正确.     

扇形板的富里哀—贝塞尔级数解

本文以加补充项的富里哀—贝塞尔双重级数的位移模式,对扇形弹性薄板在各种边界件条下的弯曲和振动问题,提出了一种应用范围比较广的、便于计算的、解析形式的解法.作为算例,文中给出了各种角度的径向边界简支或固定的扇形板在均布荷载或集中荷载作用下产生的挠度和弯矩的分布曲线,并与有关文献的数值结果进行了比较.本文推广了加补充项的富氏级数法的应用范围,并计算出各种角度的径向边界简支的扇形板的自振频率和节线的图表.     

Uncovering the finite difference model equivalent to Hencky bar-net model for axisymmetric bending of circular and annular plates

As there are a few finite difference models in the literature for axisymmetric bending of plates, only one of these models is equivalent to the Hencky bar-net model (HBM) that comprises a finite number of rigid circular arcs and straight radial segments joined by frictionless hinges with elastic rotational springs. This paper is concerned with uncovering the one finite difference model (FDM) that is equivalent to the HBM. Based on the energy formulation, the governing equation for HBM is derived and it will be used to identify the FDM that has the same discrete set of equations. By using this equivalency between the HBM and the identified FDM, the expressions of edge spring stiffnesses of HBM are derived for various boundary conditions. As illustrative examples, the HBM is used to solve the bending problems of circular plates under uniformly and linearly increasing distributed loads. The analytical solutions of HBM avoids the singularity problem faced in FDM at the plate center. This paper also presents some benchmark bending solutions for annular plates with and without an internal ring support for different boundary restraints by using the HBM.     

任意形状弹性薄板弯曲的精确解*

本文提供了一个求解任意形状弹性薄板弯曲的新方法,在求得了极坐标系中弹性薄板弯曲微分方程的精确解后,将解代入薄板的边界条件,利用Fourier级数将边界方程展开,可确定出各待定常数,所得结果是精确的。     

Dynamic and static nonlinear analysis of generally laminated imperfect plates having nonuniform boundary conditions and resting on elastic foundation

A multimode solution to the dynamic von Kármán-type nonlinear equations is presented for the titled plates. The plate edges subjected to inplane forces are elastically restrained against rotation. The variation of rotational stiffness is assumed identical along parallel edges. Generalized double Fourier series with the time-dependent coefficients and the method of harmonic balance are used in the formulation of the solution. Nonlinear bending and postbuckling of the laminate are treated as special cases. Numerical results are presented for nonlinear free vibration and postbuckling of antisymmetric angle-ply and cross-ply laminates.     

Elastic and inelastic local buckling of stiffened plates subjected to non-uniform compression using the Galerkin method

A solution for the elastic and inelastic local buckling of flat rectangular plates with centerline boundary conditions subjected to non-uniform in-plane compression and shear stress is presented. The loaded edges are simply supported, the longitudinal edges may have any boundary conditions and the centerline is simply supported with a variable rotational stiffness. The Galerkin method, an effective method for solving differential equations, is applied to establish an eigenvalue problem. In order to obtain plate buckling coefficients, combined trigonometric and polynomial functions that satisfy the boundary conditions are used. The method is programmed, and several numerical examples including elastic and inelastic local buckling, are presented to illustrate the scope and efficacy of the procedure. The variation of buckling coefficients with aspect ratio is presented for various stress gradient ratios. The solution is applicable to stiffened plates and the flange of the I-shaped beams that are subjected to biaxial bending or combined flexure and torsion and shear stresses, and is important to estimate the reduction in elastic buckling capacity due to stress gradient.     

矩形片筏基础的挠度分析

工程上对片筏的力学分析，通常采用温克勒地基模型，且假定床基系数是常量。本则认为床基系数是坐标的函数，考虑了具有线性变化床基系数的地基上的片筏，利用伽辽金法求得周边固支片筏在均布荷载作用下的挠度。所得结果颇具一般性且实用价值更高。     

Attenuation and Diffraction of Bending Waves at Gaps in Fluid Loaded Plates

The scattering of a bending wave by a finite number of parallelrectilinear gaps in an infinite fluid-loaded plate is discussed.For the purpose of analysis, the widths of the gaps are assumedto be infinitesimal, but there is no physical contact betweenabutting edges of neighbouring sections of the plate. A sectionedge may be restrained by resilient supports or loadings, eitherindividually or jointly with the neighbouring edge. The theorydetermines the attenuation of the bending wave by the gaps andthe sound radiated into the ambient fluid during the interaction.Specific results are given for a steel plate which has a singlegap in air and in water, such that either (1) the abutting edgesare free to vibrate independently, (2) both edges are clamped,or (3) one edge is clamped and the other free. In each of thesecases the coupling between the two halves of the plate is providedsolely by the fluid loading: the bending wave would be totallyreflected at the gap in vacuo. The results are relevant to thecontrol and suppression of structure-borne sound     

Free vibration of functionally graded rectangular plates using first-order shear deformation plate theory

The main objective of this research work is to present analytical solutions for free vibration analysis of moderately thick rectangular plates, which are composed of functionally graded materials (FGMs) and supported by either Winkler or Pasternak elastic foundations. The proposed rectangular plates have two opposite edges simply-supported, while all possible combinations of free, simply-supported and clamped boundary conditions are applied to the other two edges. In order to capture fundamental frequencies of the functionally graded (FG) rectangular plates resting on elastic foundation, the analysis procedure is based on the first-order shear deformation plate theory (FSDT) to derive and solve exactly the equations of motion. The mechanical properties of the FG plates are assumed to vary continuously through the thickness of the plate and obey a power law distribution of the volume fraction of the constituents, whereas Poisson’s ratio is set to be constant. First, a new formula for the shear correction factors, used in the Mindlin plate theory, is obtained for FG plates. Then the excellent accuracy of the present analytical solutions is confirmed by making some comparisons of the results with those available in literature. The effect of foundation stiffness parameters on the free vibration of the FG plates, constrained by different combinations of classical boundary conditions, is also presented for various values of aspect ratios, gradient indices, and thickness to length ratios.     

Nonlinear bending analysis of FGM elliptical plates resting on two-parameter elastic foundations

Nonlinear bending analysis is first presented for functionally graded elliptical plates resting on two-parameter elastic foundations, and investigations on FGM elliptical plates with immovable simply supported edge are also new in literature. Material properties are assumed to be temperature-dependent and graded in the thickness direction. The governing equations of a functionally graded plate are based on Reddy’s high-order shear deformation plate theory that includes thermal effects. Ritz method is employed to determine the central deflection-load and bending moment-load curves, the validity can be confirmed by comparison with related researchers’ results, and it is worth noting that the forms of approximate solutions are well-chosen in consideration of both simplicity and accuracy. Influences played by different supported boundaries, thermal environmental conditions, foundation stiffness, ratio of major to minor axis and volume fraction index are discussed in detail.     

均布载荷下两邻边固定、一边简支、一边自由的矩形板的弯曲

用广义简支边概念和叠加法给出的均布载荷下两邻边固定、一边简支、一边自由矩形板的精确解。对正方形自由的挠度和回定边的弯矩进行了数学计算。     

On the energy flux vector for bending vibrations of a plate : PMM vol. 40, n 6, 1976, pp. 1131–1135

An expression for the energy flux vector of plate bending vibrations is obtained in invariant form. The derivation of expressions for the transverse force, bending and twisting moments in an arbitrary orthogonal coordinate system and the derivation of an orthogonality type condition for normal waves being propagated in a thin elastic strip with free edges are considered as applications.In a number of cases it turns out to be useful to consider the energy flux vector in analyzing the vibrations in systems with distributed parameters. The expressions for the Umov-Poynting vector in electrodynamics and for the energy flux vector in acoustics are well-known. An analogous vector for the bending Vibrations of a plate was mentioned only in [1 – 3], This vector is used in [1] to prove a uniqueness theorem for a two-component acoustic model consisting of an ideal compressible fluid and elastic plates in contact with it. However, the expression for the energy flux in [1] (it was later cited in [2, 3] with a reference to [1]) is erroneous. An exact expression (within the framework of the applicability of the Kirchhoff equation) is found below for the energy flux vector of the bending vibrations of a plate and some applications of the formulas obtained are mentioned.     

Optimal control of a variational inequality with applications to structural analysis. II. Local optimization of the stress in a beam. III. Optimal design of an elastic plate

Optimal design with respect to the variable thickness of an elastic beam with unilateral supports under the criterion of minimal value of the maximal stress is presented in Part I. A dual formulation of the state problem (in terms of bending moments) is used and the convergence of some approximations proved.In Part III the variable thickness of an elastic or elasto-plastic plate unilaterally supported on a part of its edge is optimized. For elastic plates with parallel edges a primal finite element model is applied and a convergence result obtained.     

Cylindrical bending of a cusped plate with big deflections

The present paper deals with big deflections by the cylindrical bending of a cusped plate with the variable flexural rigidity vanishing at the cusped edge. The setting of boundary conditions at the plate edges depends on the geometry of sharpening of the cusped edges. All the admissible classical bending boundary-value problems are formulated. Existence and uniqueness theorems for the solutions of these boundary-value problems are proved. Translated from Sovremennaya Matematika i Ee Prilozheniya (Contemporary Mathematics and Its Applications), Vol. 51, Differential Equations and Their Applications, 2008.     

Accurate bending analysis of rectangular plates with two adjacent edges free and the others clamped or simply supported based on new symplectic approach

The symplectic geometry approach is introduced for accurate bending analysis of rectangular thin plates with two adjacent edges free and the others clamped or simply supported. The basic equations for rectangular plates are first transferred into Hamilton canonical equations. Using the symplectic approach, the analytic solution of rectangular thin plate with two adjacent edges simply supported and the others slidingly supported is derived. Accurate bending solutions of title problems are then obtained using the superposition method. The approach used in this paper eliminates the need to pre-determine the deformation function and is hence more reasonable than conventional methods. Numerical results are presented to demonstrate the validity and efficiency of the approach as compared with those reported in other literatures.     

双参数弹性地基上自由边矩形板

本文以迭加法[1]给出在V. Z. Vlazov双参数弹性地基上自由边矩形板的精确解.文中导出了在各种边界条件下的基本解式,迭加这些基本解式,求得了在双参数弹性地基上自由边矩形板的最一般的精确解.它严格满足双参数弹性地基上板的控制微分方程和自由边的边界条件和角点条件.给出了数值结果.计算结果表明:当板的平面尺寸一定,地基深度与板厚度之比H/h=15时,双参数弹性地基与Winkler弹性地基相接近,证明了Winkler地基模式适用于压缩尺寸比较薄的弹性地基.     

夹层圆板轴对称非线性弯曲和屈曲的样条函数解法

以三次B样条函数为试函数,用配点法计算夹层圆板的非线性弯曲．支座可以是弹性的．夹层板采用Reissner模型．荷载可为多项式型的分布荷载、均布边缘力矩、均布径向压力或均布径向预应力及它们的组合．首次用非线性理论计算了夹层圆板的压曲临界荷载．在均布荷载作用下的结果同幂级数解的结果作了比较,说明样条配点法具有收敛范围大、精度高、编写程序通用的优点．     

非均匀弹性地基圆板轴对称弯曲的一般解

本文在阶梯折算法的基础上,提出一个新的方法——精确解析法,得到了非均匀弹性地基圆板弯曲的一般解.文中导出了在任意轴对称载荷和边界条件下求解非均匀弹性地基圆板和中心带孔圆板弯曲的一般公式,并给出一致收敛于精确解的证明.文中得到的一般解可直接计算无弹性地基圆板的弯曲问题.问题最后归结为求解一个二元一次代数方程.文末给出算例,算例表明无论内力和位移均可得到满意的结果.     

On the plane deformation of fibre-reinforced viscoelastic plates

The realization method of elastic solutions is used to solve the problem of bending of a viscoelastic plate reinforced unidirectionally by elastic fibres. Numerical computations are carried out for three kinds of external load. The plane deformation of this plate is discussed.     

An extended edge-based smoothed discrete shear gap method for free vibration analysis of cracked Reissner–Mindlin plate

An extended edge-based smoothed discrete shear gap method (XES-DSG3) is proposed for free vibration analysis of cracked Reissner–Mindlin plate by implementing the edge-based strain smoothing operation into the discrete shear gap-based extended finiteelement method (XFEM-DSG3). In present method, the strain smoothing operation is implemented into the bending strain gradient matrices, in which the enriched functions are included. Then, the derivatives of element shape functions and derivatives of crack-tip singular enriched functions are not required in the computation. The calculation of element matrices is performed over the smoothing domains which are associated with edges of elements. The transverse shear locking of Reissner–Mindlin plate can be avoided by using the integration of discrete shear gap (DSG) method. Several numerical examples are investigated to illustrate the accuracy of XES-DSG3 for the free vibration analysis of cracked Reissner–Mindlin plate. Moreover, numerical results show that the present method is insensitive to mesh distortion and it is more stable than the pervious XFEM-DSG3.