Method of integro-differential relations in linear elasticity

Boundary-value problems in linear elasticity can be solved by a method based on introducing integral relations between the components of the stress and strain tensors. The original problem is reduced to the minimization problem for a nonnegative functional of the unknown displacement and stress functions under some differential constraints. We state and justify a variational principle that implies the minimum principles for the potential and additional energy under certain boundary conditions and obtain two-sided energy estimates for the exact solutions. We use the proposed approach to develop a numerical analytic algorithm for determining piecewise polynomial approximations to the functions under study. For the problems on the extension of a free plate made of two different materials and bending of a clamped rectangular plate on an elastic support, we carry out numerical simulation and analyze the results obtained by the method of integro-differential relations.     

Geometric elasticity problem of stress concentration in a plate with a circular hole

We use the geometric elasticity equations [1], which permit relating the medium stress state to the geometry of the Riemannian space generated by the stresses, to consider the plane problem of stress concentration near a circular hole in a thin unbounded plate loaded by normal and tangential stresses. The Riemannian space metric coefficient corresponding to the coordinate normal to the plate plane is treated as the variable thickness of the plate in three-dimensional Euclidean space, which determines the optimal law for the plate material distribution. We consider plates in uniaxial tension, biaxial tension, and shear. For the plate with thickness variation laws thus obtained, we construct direct numerical solutions of the corresponding classical elasticity problems and determine the stress concentration factors.     

Dispersion and polarization of surface Rayleigh waves for the Cosserat continuum

In the framework of the nonsymmetric theory of elasticity (the Cosserat contimum), we consider the problem of propagation of a surface acoustic Rayleigh wave in the half-space. The wave is represented as a wave packet of arbitrary form bounded both in the time space and the Fourier space. We assume that the material strain is described by not only the displacement vector but also an independent rotation vector. The general analytic solution of this problem is obtained in displacements. We perform comparative analysis of the obtained solution and the corresponding solution for the classical elastic medium. We introduce and analyze macroparameters characterizing the difference between the stress-strain state and the state predicted by the classical theory of elasticity: the elasticity coefficient, the wave number, and the phase and group velocities. It should be noted that these parameters can be measured experimentally.     

CIRCULAR WELDING PROBLEMS WITH A CRACK

In this paper,the problem of an infinite plane with acircular hole welded by a nearly circular plate with a crackof different material is considered.The problem is tran-sformed into solving a certain boundary value problem ofanalytic functions and then reduced to solving a singularintegral equation along the crack.The formulas and somenumerical results of the factors of stress intensityfor the cases Mode Ⅰ and Mode Ⅱ are obtained at the endof this paper.     

Exact Analytical Solution of the Kirsch Problem within the Framework of the Cosserat Continuum and Pseudocontinuum

The Kirsch problem of onesided tension of a plate with a circular hole is considered within the framework of the nonsymmetric theory of elasticity under the assumption that material deformation is described not only by the displacement vector but also by the rotation vector. The general analytical solution of this problem is expressed in terms of the Bessel functions. The resulting solution is compared with the corresponding solutions for a symmetric medium and Cosserat pseudomedium. A macroparameter characterizing the distortion of the boundary of the circular hole upon deformation is introduced.     

多圆孔圆板问题的数值解

提出了一种求解多圆孔圆板问题的新方法。首先引入了基本特解，它由主要部分和附加部分组成。主要部分为带奇点无限平板的一个特殊弹性力学解，奇点取在内圆孔的中心处。附加部分为实心圆饭的一个特解。整个基本特解满足外圆周界为自由条件。文中把待求解取为特解系的形式，其中待定系数可用变分原理得出。最后给出了算例。     

Fundamental-solution-based finite element model for plane orthotropic elastic bodies

A new hybrid finite element formulation is presented for solving two-dimensional orthotropic elasticity problems. A linear combination of fundamental solutions is used to approximate the intra-element displacement fields and conventional shape functions are employed to construct elementary boundary fields, which are independent of the intra-element fields. To establish a linkage between the two independent fields and produce the final displacement-force equations, a hybrid variational functional containing integrals along the elemental boundary only is developed. Results are presented for four numerical examples including a cantilever plate, a square plate under uniform tension, a plate with a circular hole, and a plate with a central crack, respectively, and are assessed by comparing them with solutions from ABAQUS and other available results.     

The asymptotic analyeical solution of the strain-hardening elasto-plastic plate containing A circular hole under simple tension

In this paper the general asymptotic analytical solution of plane problem of elasto-plasticity with strain-hardening^[2] is used in solving the problem of an infinitely large plate containing a circular hole under simple tension, and the analytical expressions of stress components of the first two approximations are given. These results are compared with the numerical and the experimental results given by other authors^{[4, 5]}, and a good agreement is obtained. At the end of this paper the authors inspect the correctness of Neuber's formula^[9] for this problem.     

敷去耦层有限加筋板声辐射近似解析解

本文主要研究了流体负载下敷设去耦阻尼层的加筋板，在外界激励力作用下的振动和声辐射，推导出了敷设去耦层有限长加筋板的振动响应和水下辐射噪声近似解析解。采用弹性理论来描述去耦层，并采用模态迭加理论构造响应函数，将加强筋等效为线力的作用，以复模量形式计及去耦阻尼层损耗因子，建立了敷设去耦阻尼层加筋板的理论解析模型，结合加筋板与去耦层变形连续条件、结构与流体连续性条件组成了声-流体-结构的耦合方程，结合数值计算方法，得到了有限长加筋板结构的振动位移及水下辐射噪声。开展相应数值算例与模型试验结果吻合较好，验证本文方法的正确性。     

Rubber-like elasticity by boundary element method: Finite deformation of a circular elastic slice

We briefly review the phenomenological theory of rubber-like elasticity and report a microstructural model that leads us to eventually adopt a particular constitutive equation, which includes the Neo-Hookean and the Mooney materials. A numerical implementation of the Boundary Element method for solving a general two-dimensional or axisymmetric finite deformation problem is described and tested with some simple deformations. The resulting program is used to analyse the finite deformation of a circular elastic slice perfectly bonded to two parallel rigid end plates; the bottom plate is stationary and the top plate is given a constant displacement. The problem has a free surface which must be found as part of the solution. The results indicate that the Boundary Element method can be an efficient tool for stress-strain analyses with rubber-like materials.