STABILIZED FINITE ELEMENT METHODS FOR THE REISSNER-MINDLIN PLATE

A new stabilized finite element method which is different from Hughes and Franco's (1988) is presented for the Reissner-Mindlin plate model. The least square mesh-dependent residual form of the shear constitute equation is added to the Partial Projection scheme to enhance the stability. Using piecewise polynomials of order k≥1 for the rotations, of order k+1 for the displacement and of order k-1 for the shear, the kth order error-estimates are obtained. Besides, our computing scheme can be also applied to some lower order elements. All error-estimates are obtained independent of the plate thickness, and the stability parameter is an arbitrary positive constant.     

TRAPEZOIDAL PLATE BENDING ELEMENT WITH DOUBLE SET PARAMETERS

Using double set parameter method, a 12-parameter trapezoidal plate bending element is presented. The first set of degrees of freedom, which make the element convergent, are the values at the four vertices and the middle points of the four sides together with the mean values of the outer normal derivatives along four sides. The second set of degree of freedom, which make the number of unknowns in the resulting discrete system small and computation convenient are values and the first derivatives at the four vertices of the element. The convergence of the element is proved.     

Reissner-Mindlin板问题带约束非协调旋转Q_1有限元方法

本文利用带约束非协调旋转Q_1元逼近Reissner-Mindlin板问题中旋度的两个分量.并分别选择Wilson元、双线性元和带约束非协调旋转Q_1元逼近挠度,相应地选取不连续的矢量值分片线性函数空间、最低阶旋转Raviart-Thomas元空间和矢量值分片常数函数空间为离散的剪应力空间,在矩形网格上构造了三个板元.通过证明一个离散的Korn不等式,并借助MITC4元的解构造了旋度、挠度和剪应力一个具有某种特殊且关键的可交换性的插值.再利用Helmholtz分解分析相容性误差.我们证明了这三个矩形元在能量范数意义下与板厚无关的一致最优收敛性.数值算例验证了我们的理论结果.     

ON THE CONVERGENCE OF NONCONFORMING FINITE ELEMENT METHODS FOR THE 2ND ORDER ELLIPTIC PROBLEM WITH THE LOWEST REGULARITY

1.IntroductionTheaimofthisnoteistoestablishtheconvergenceofthenonconformingfiniteelementmethodsforthesecondorderellipticproblemwiththelowestregularity.Theproofoftheconvergenceisnottrivial,althoughtheconvergenceresultsfortheconformingfiniteelementmeth...     

TWO-GRID DISCRETIZATION SCHEMES OF THE NONCONFORMING FEM FOR EIGENVALUE PROBLEMS

This paper extends the two-grid discretization scheme of the conforming finite elements proposed by Xu and Zhou （Math. Comput., 70 （2001）, pp.17-25） to the nonconforming finite elements for eigenvalue problems. In particular, two two-grid discretization schemes based on Rayleigh quotient technique are proposed. By using these new schemes, the solution of an eigenvalue problem on a fine mesh is reduced to that on a much coarser mesh together with the solution of a linear algebraic system on the fine mesh. The resulting solution still maintains an asymptotically optimal accuracy. Comparing with the two-grid discretization scheme of the conforming finite elements, the main advantages of our new schemes are twofold when the mesh size is small enough. First, the lower bounds of the exact eigenvalues in our two-grid discretization schemes can be obtained. Second, the first eigenvalue given by the new schemes has much better accuracy than that obtained by solving the eigenvalue problems on the fine mesh directly.     

SOME ESTIMATES WITH NONCONFORMING ELEMENTS IN DOMAIN DECOMPOSITION ANALYSIS

1.IntroductionFOrsimplicityoftheexposition,weconsidertheellipticboundaryvalueproblemonaboundedopenpolygonaldomainfiCEZwhereItiswell--knownthat(1.1)hasauniquesolutionueH'(fl)(of.[7,15,16]).Supposethatfib~{e}isaquajsi--uniformmeshoffi,i.e.,fibsatisfieswhere…     

A V-CYCLE MULTIGRID METHOD FOR THE PLATE BENDING PROBLEM DISCRETIZED BY NONCONFORMING FINITE ELEMENTS

1.IntroductionMultigridmethodshavebecomesomeofthemostpowerfulmethodsforsolvingpartialdifferentialequationsdiscretizedbythefiniteelementandfinitedifferencemethods.(of.[7][11][141andreferencetherein).Multigridmethodsforthenonconformingfiniteelementshav...     

A CLASS OF NEW NONCONFORMING FINITE ELEMENTS

A class of new nine-parameter nonconforming finite elements with convergent prop-erties are constructed in terms of the approach of interpolation methods in this paper. All of those finite elements can be viewed as the generalization of Zienkiewicz's finite element by dis-lurbing its parameters.     

ON THE ERROR ESTIMATE OF NONCONFORMING FINITE ELEMENT APPROXIMATION TO THE OBSTACLE PROBLEM

This paper is devoted to analysis of the nonconforming element approximation to the obstacle problem, and improvement and correction of the results in [11], [12].     

OPTIMAL ERROR ESTIMATES OF THE PARTITION OF UNITY METHOD WITH LOCAL POLYNOMIAL APPROXIMATION SPACES

In this paper, we provide a theoretical analysis of the partition of unity finite elementmethod (PUFEM), which belongs to the family of meshfree methods. The usual erroranalysis only shows the order of error estimate to the same as the local approximations[12].Using standard linear finite element base functions as partition of unity and polynomials aslocal approximation space, in 1-d case, we derive optimal order error estimates for PUFEMinterpolants. Our analysis show that the error estimate is of one order higher than thelocal approximations. The interpolation error estimates yield optimal error estimates forPUFEM solutions of elliptic boundary value problems.     

A TWO-GRID METHOD FOR THE C0 INTERIOR PENALTY DISCRETIZATION OF THE MONGE-AMP(E)RE EQUATION

The purpose of this paper is to analyze an efficient method for the solution of the nonlinear system resulting from the discretization of the elliptic Monge-Ampère equation by a $C^0$ interior penalty method with Lagrange finite elements. We consider the two-grid method for nonlinear equations which consists in solving the discrete nonlinear system on a coarse mesh and using that solution as initial guess for one iteration of Newton's method on a finer mesh. Thus both steps are inexpensive. We give quasi-optimal $W^{1,\infty}$ error estimates for the discretization and estimate the difference between the interior penalty solution and the two-grid numerical solution. Numerical experiments confirm the computational efficiency of the approach compared to Newton's method on the fine mesh.     

非协调区域分解Lagrange乘子法的超收敛

本文讨论分析非协调区域分解Ｌａｇｒａｎｇｅ乘子法对二阶椭圆型方程Ｄｉｒｉｃｈｌｅｔ问题的有限元超收敛现象。文中通过利用积分恒等式,适宜地引进Ｌ２投影过渡以及高次插值后处理等技巧,经过一系列误差分析及估计,得到了高出半阶的超收敛结果,实现了非协调区域分解法与高精度算法的结合。     

ON THE ANISOTROPIC ACCURACY ANALYSIS OF ACM''''S NONCONFORMING FINITE ELEMENT

The main aim of this paper is to study the superconvergence accuracy analysis of thefamous ACM's nonconforming finite element for biharmonic equation under anisotropicmeshes. By using some novel approaches and techniques, the optimal anisotropic inter-polation error and consistency error estimates are obtained. The global error is of orderO(h~2). Lastly, some numerical tests are presented to verify the theoretical analysis.     

Helmholtz方程外边值问题的基于修正的DtN边界条件的有限元方法

本文对于无界区域上的Helmholtz方程研究基于修正的Dirichlet-to-Neumann边界条件(MDtN)的有限元方法,得到了依赖于网格尺寸,MDtN边界条件的位置和MDtN中的级数截断项数的H~1-误差估计和L~2-误差估计.最后通过数值结果验证了误差分析的正确性以及所提方法的有效性.     

THE NONCONFORMING FINITE ELEMENT METHOD FOR SIGNORINI PROBLEM

We present the Crouzeix-Raviart linear nonconforming finite element approximation of the variational inequality resulting from Signorini problem. We show if the displacement field is of H2 regularity, then the convergence rate can be improved from O（h3/4） to quasi-optimal O（h｜log h｜1/4） with respect to the energy norm as that of the continuous linear finite element approximation. If stronger but reasonable regularity is available, the convergence rate can be improved to the optimal O（h） as expected by the linear approximation.     

完全三次非协调板元的误差估计

本文考虑以下重调和方程的边值问题:△~2u=f,在G上,u=?u/?n=0,在?G上,其中G为R~2上多边形区域,n为单位外法向量.此问题的变分形式为:找u∈H_0~2(G),使得: α(u,v)=(f,vv)?v∈ _0~~2(G),其中 α(u,v)=∫_G[△u△v+(1-σ)(2u_(x_1x_2)v_(x_1x_2)-u(x_1x_1)v_(x_2x_2)-u_(x_2x_2)v_(x_1x_1))]dx_1dx_2 设τ_h为G的一致正则矩形剖分,h为所有元的最大直径.文[5]中构造了一个完全三次非协调板元,它的形函数为完全三次多项式;自由度集合由函数在四个顶点之值及两个三阶     

A NONCONFORMING ANISOTROPIC FINITE ELEMENT APPROXIMATION WITH MOVING GRIDS FOR STOKES PROBLEM

This paper is devoted to the five parameters nonconforming finite element schemes with moving grids for velocity-pressure mixed formulations of the nonstationary Stokes problem in 2-D. We show that this element has anisotropic behavior and derive anisotropic error estimations in some certain norms of the velocity and the pressure based on some novel techniques. Especially through careful analysis we get an interesting result on consistency error estimation, which has never been seen for mixed finite element methods in the previously literatures.     

ON THE SELECTION OF SHAPE FUNCTION SPACES OF TRIANGULAR PLATE ELEMENTS

ＯＮＴＨＥＳＥＬＥＣＴＩＯＮＯＦＳＨＡＰＥＦＵＮＣＴＩＯＮＳＰＡＣＥＳＯＦＴＲＩＡＮＧＵＬＡＲＰＬＡＴＥＥＬＥＭＥＮＴＳＣｈｅｎＳｈａｏｃｈｕｎ；ＳｈｉＤｏｎｇｙａｎｇ（Ｄｅｐｔ．ｏｆＳｙｓ．Ｓｃｉ．＆Ｍａｔｈ．，ＺｈｅｎｇｚｈｏｕＵｎｉｖ．，Ｚｈｅ...     

SUPERCONVERGENCE ANALYSIS OF THE POLYNOMIAL PRESERVING RECOVERY FOR ELLIPTIC PROBLEMS WITH ROBIN BOUNDARY CONDITIONS

We analyze the superconvergence property of the linear finite element method based on the polynomial preserving recovery(PPR)for Robin boundary elliptic problems on triangulartions.First,we improve the convergence rate between the finite element solution and the linear interpolation under the H1-norm by introducing a class of meshes satisfying the Condition(α,σ,μ).Then we prove the superconvergence of the recovered gradients post-processed by PPR and define an asymptotically exact a posteriori error estimator.Finally,numerical tests are provided to verify the theoretical findings.