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RBF-Based Meshless Method for Large Deflection of Elastic Thin Rectangular Plates with Boundary Conditions Involving Free Edges.

1. Introduction

The nonlinear deflection problems arise when using the light weight structures. In several practical light weight structures applications such as fluid tank, aircraft, and hydrospace, flexible plates are commonly used and undergo large deflection. Consequently, the analysis of the plates becomes more difficult. The governing equations become coupled and highly nonlinear [1]. The available analytical methods are based on simplified assumptions and are limited to simple loading and boundary conditions [1-5]. For such complicated problems, numerical methods offer convenient and reliable solutions. The ideal numerical method for the solution of nonlinear partial differential equations (PDEs) such as the one considered here should be high-order accurate, flexible with respect to the geometry, computationally efficient, and easy to implement. The conventional numerical methods that are commonly used usually fulfill one or two of the above criteria, but not all. Finite difference methods (FDM), finite element methods (FEM), and boundary element methods (BEM) have been the dominating methods for the numerical solution of PDEs [6-13]. Referring to the most dominant approach, that is, FEM, it is highly flexible, but it is hard to achieve high-order accuracy and both coding and mesh generation become increasingly difficult as the problem dimension increases. The use of a mesh implies that specific procedures have to be devised just to define the mesh. Also, and to keep the order of the local approximation within reasonable limits, the element size has to be reduced, whenever better approximations are pursued. The extraordinary amount of work, which has been put into FEM research since its early years, has, one way or another, circumvented these and other problems associated with the existence of a mesh and made FEM the dominant approach for most problems in computational mechanics. Accordingly, many sophisticated powerful codes (e.g., ANSYS, ABACUS, and COMSOL) have been established and have proven to be reliable in solving almost any computational mechanics problem. FDM can be made high-order accurate in resolving PDEs but require a structured grid (or a collection of structured grids), which makes it difficult to model features of irregular domain. Furthermore, solutions of PDEs using FDM can be derived from the assumptions of the local interpolation schemes and require a mesh to support the localized approximations; however, the construction of a mesh in two or more dimensions is a nontrivial problem. In recent years, BEM has become a powerful alternative to FEM and FDM, especially for problems involving high gradients and stress concentrations. It has been successfully applied to solve the problems of large deflection of thin elastic plates. However, this was possible by devising some techniques to overcome the inherent deficiency of BEM as a self-standing numerical method in handling nonlinearities.

Nevertheless, the possibility of obtaining numerical solutions for PDFs without resorting to element frame has been the goal of many researchers throughout the computational mechanics community for the past three decades or so. One of the earliest meshless methods is the smoothed particle hydrodynamics (SPH) which was developed in 1977 by Lucy et al. [13,14]. Since then, many versions and types of the meshless methods have been proposed. Examples are the radial basis function-based collocation method (RBF) by Kansa [15,16], the diffuse element method (DEM) by Nayroles et al. [17], the element-free Galerkin (EFG) method by Belytschko el al. [18], the reproduced kernel particle method (RKPM) by Liu et al. [19], the finite point method by Onate et al. [20], the meshless local Petrov-Galerkin method (MLPG) by Atluri and Zhu [21], and the mesh-free weak-strong form (MWS) by Liu and Gu [22].

RBF method, as one of the efficient meshless methods, has attracted attention in recent years especially in the area of computational mechanics. In general, RBF method expands the solution of a problem in terms of RBFs and chooses expansion coefficients such that the governing equations and boundary conditions are satisfied at some selected domain and boundary points. This method does not require mesh generation which makes it advantageous for nonlinear problems that require frequent remeshing such as the one considered in this study. The roots of RBF go back to the early 1970s when it was first used for fitting scattered data [23]. In the early 1980s, it was coupled with BEM in a technique called dual reciprocity-boundary element method where the RBF was employed to transform the domain integrals into boundary integrals [24]. Thereafter, many researchers have used RBF in conjunction with BEM to solve various problems in computational mechanics. The method, however, has not been applied directly to partial differential equations until 1990 by Kansa [15, 16]. Since then, many researchers have suggested several variations to the original method [25-31].

Most of previous applications of meshless methods to large deflection of plates are limited to simple and clamped boundary conditions. The inclusion of free edge boundary condition poses a challenge for both analytical and numerical methods. The difficulty of the free edge boundary condition is due to the enforcement of zero shear on the free boundary of the plate which, for large deflection, involves lengthy and highly nonlinear differential operators as explained in Section 2. In this paper, a multiquadric radial basis function-(MQ-RBF-) based meshless model is developed for the solution of large deflection of thin plates with different boundary conditions including free edges. The proposed method has the advantages of simplicity and ease of code implementation. The accuracy of the model is validated through several numerical examples.

2. Governing Equations

The governing equilibrium equations of a plate undergoing large deflection can be expressed in terms of the transverse displacement w and a stress function F or in terms of w and the in-plane displacements u and v. The summary of both formulations and their corresponding boundary conditions are given below.

2.1. w-F Formulation. In this formulation, the governing equations for large elastic deflection of thin plates are represented by two coupled nonlinear differential equations, known as Von Karamn equations, which are expressed in terms of the displacement w and a stress function F [1]:

[[nabla].sup.4] w = q/D + [t/D] NL (w, F), (1)

[[nabla].sup.4] F = -[E/2] NL (w, w), (2)

where q is the distributed load, t is the plate thickness, and D = ([Et.sup.3])/(12(1 - [v.sup.2])) is the flexural rigidity of the plate having elastic constants E and v, and NL(w, F) is a nonlinear differential operator given by

[mathematical expression not reproducible]. (3)

The stress function F is related to the membrane forces [N.sub.x], [N.sub.y], and [N.sub.xy] by the following differential operators:

[mathematical expression not reproducible]. (4)

The details for deriving (1) and (2) are given in the classical book by Timoshenko and Woinowsky-Kreiger [1]. The first equation describes the transverse or bending action whereas the second equation represents the in-plane action of the plate. In general, there are two types of in-plane boundary conditions, namely, movable and immovable. The w-F formulation can be utilized directly in the former type where the movable boundary condition is represented by F = [partial derivative]F/[partial derivative]n = 0. However, the immovable boundary condition (u = v = 0) cannot be accurately expressed in terms of the stress function F. To overcome this difficulty, (2) can be replaced by two partial differential equations in terms of the in-plane displacements, u and v, as described in the following section.

2.2. u-v-w Formulation. Excluding the body forces, the equilibrium equations along x and y are given by

[mathematical expression not reproducible]; (5)

the membrane strains are related to the membrane through the following equations:

[mathematical expression not reproducible]. (6)

The membrane strains are also related to the displacements by the following equations:

[mathematical expression not reproducible]. (7)

Using (7) into (6) and then in (5), we get

[mathematical expression not reproducible]. (8)

To complete the u-v-w formulation, (1) is rewritten after replacing the stress function F by the proper terms involving the displacements u, v, and w. Equation (1) becomes

[mathematical expression not reproducible] (9)

Equations (8) and (9) can be expressed in compact forms as follows:

[L.sub.11] (u) + [L.sub.12] (v) = [NL.sub.1] (w) (10)

[L.sub.21] (u) + [L.sub.22] (v) = [NL.sub.2] (w) (11)

[[nabla].sup.4]w = q/D + [NL.sub.3] (u, v, w), (12)

where

[mathematical expression not reproducible], (13)

In the above equations, subscript variables denote partial differentiation with respect to the variables.

2.3. Boundary Conditions. The general boundary conditions for large deflection of plates can be classified into two types.

(1) The first is transverse boundary conditions which are encountered in both small and large deflection formulations. For this type, we will assume that, at each boundary point, there are two prescribed boundary conditions:

(a)

[mathematical expression not reproducible] (14)

(b)

[mathematical expression not reproducible] (15)

where [M.sub.n] is the normal bending moment which is given by

[mathematical expression not reproducible]. (16)

shear force [V.sub.n] is composed of a linear and a nonlinear part; that is, [V.sub.n] = [V.sup.L.sub.n] + [V.sup.NL.sub.n], where [V.sup.L.sub.n] is given by

[mathematical expression not reproducible]. (17)

The nonlinear part of the shear, [V.sup.NL.sub.n], is given by

[mathematical expression not reproducible]. (18)

The above nonlinear formula for the nonlinear part of the shear force is suitable for the w-F formulation. The nonlinear part of the shear corresponding to the u-v-w formulation can be obtained by replacing the stress function F with the proper derivatives of u, v, and w. The result is

[mathematical expression not reproducible], (19)

where [n.sub.x] and [n.sub.y] are the x and y components of the unit vector normal to the boundary, respectively.

(2) The second is in-plane boundary conditions which have to be addressed in the case of large deflection formulation. This type of boundary condition is further classified into two types of edge conditions:

(a) Movable edge (free to move in the in-plane directions) which is represented by the following equation:

F = [partial derivative]F/[partial derivative]n = 0. (20)

(b) Immovable edge which is represented by

u = v = 0. (21)

In summary, the plate problem with movable edges can be handled by the w-F formulation represented by the governing equations (1) and (2), the lateral boundary conditions (14) and (15), and the in-plane boundary conditions (20), while the plate problem with immovable edges can be handled by the u-v-w formulation represented by the governing equations (8) and (9), the lateral boundary conditions (14) and (15), and the in-plane boundary conditions (21).

3. RBF Formulation

Consider the 2D computational domain (Figure 1) that represents the plate geometry. For collocation, we use node points distributed both along the boundary ([[x.bar].sup.j.sub.B] , j = 1, ..., [N.sub.B]) and over the interior ([[x.bar].sup.j.sub.D] , j = 1,..., [N.sub.D]). Let [[bar.x].sub.p] = [[[x.bar].sub.B], [[bar.x].sub.D]], so that the total number of points called poles is [N.sub.P] = [N.sub.B] + [N.sub.D].

The transverse deflections w, the stress function F, and the in-plane deflections u and v are interpolated linearly by suitable radial basis functions, respectively:

[mathematical expression not reproducible], (22)

where

[mathematical expression not reproducible], (23)

[p.sub.j] is the magnitude of the concentrated load acting at the jth point ([[x.bar].sup.j.sub.C], [[y.bar].sup.j.sub.C])

0([parallel][x.bar] - [[x.bar].sup.j][parallel]) = [square root of ([([x.bar] - [[x.bar].sup.j]).sup.2] + [(y - [y.sup.j]).sup.2] + [c.sup.2])], (24)

with a multiquadratic radial basis function (MQ-RBF), c is the shape factor, and [a.sup.j.sub.w], [a.sup.j.sub.F], [a.sup.j.sub.u], and [a.sup.j.sub.v] are unknown coefficients to be determined by applying the governing equations at the domain points and satisfying the boundary conditions at the boundary points.

For the w-F formulation, the collocation of (1) and (2) yields the following coupled nonlinear algebraic equations:

[mathematical expression not reproducible]. (25)

Similarly, the collocation of (10), (11), and (12), for the u-v-w formulation, yields the following coupled nonlinear algebraic equations:

[mathematical expression not reproducible], (26)

[mathematical expression not reproducible], (27)

where the collocations of (10) and (11) have been combined to get (26). For the solution of (25), (26), and (27), the loads are applied incrementally and then solved by iterations until the convergence is satisfied for each incremental load. The nonlinear terms (NL(w,F),[V.sup.Nl.sub.n] and -(E/2)NL(w, w)) in (25) and [NL.sub.1](w), [NL.sub.2](w), and [NL.sub.3](m, v, w), in (26) and (27), are put equal to zero in the first iteration of the first incremental load and then (25), (26), and (27) are solved accordingly to get w, F, u, and v functions after the nonlinear terms are evaluated to be used in the next iteration. This procedure is iterated until convergence is satisfied; otherwise, the load increment is reduced. The iterative procedure is repeated by adding load increments and performing iterations until the total load is applied.

4. Numerical Examples

In order to examine the effectiveness of the proposed RBF method, the following three examples are considered. In all examples, the loads are assumed to be either uniformly distributed = q or concentrated = p, Poisson ratio v is assumed 0.3, and the analysis was performed for several combinations of boundary conditions and shapes. For generality of the solutions, all results are made dimensionless, so that the coordinates, the load, the deflection, and the stress are represented by [bar.x] = x/a, [~bar.y] = y/a, [bar.q] = [qa.sup.4]/[Et.sup.4], p = [pa.sup.2]/[Et.sup.4]; [bar.w] = w/t, [bar.[sigma]] = [sigma][a.sup.2]/[Et.sup.2], respectively. The shape factor, c, of the RBF is changed according to the boundary conditions and the type of load. Its optimum value ranged between 0.3 and 0.8.

Example 1. Consider a square plate with three simply supported edges and the fourth edge free (denoted by SSSF). All edges are allowed to move in the in-plane directions and hence, the w-F formulation is used. The plate is analyzed for two different load types: a uniformly distributed load [bar.q] ranging from 1.5 to 12 and a central concentrated load [bar.p] ranging from 1 to 8. The plate is discretized using a uniform node distribution consisting of 36 boundary nodes and 81 domain nodes as shown in Figure 2. The results of the deflections as obtained by RBF and FEM at the center and at the mid-point of the free edge are given in Tables 1 and 2 for the uniform and central concentrated load, respectively. The maximum differences in the deflection at the center of the plate are 1.25% and 3.95% for the uniform and concentrated load, respectively, whereas the differences at the free edge of the plate are 1.26% and 4.73% for the uniform and concentrated loads, respectively. The maximum differences in the bending stresses at the center of the plate are 2.93% and 4.49% for the uniform load and concentrated load, respectively. For the stresses at the mid-point of the free edge, the maximum differences are 3.75% and 4.95% for the uniform and concentrated load, respectively.

Example 2. Consider the plate of Example 1 with its simply supported edges replaced by clamped edges and let us denote it by CCCF. The uniform load [bar.q] is incrementally increased from 5 to 40 while the central concentrated load is incrementally increased from 2 to 16. The plate is discretized using a uniform node distribution similar to the one employed in Example 1. The results of the analysis of this example are given in Tables 3 and 4 for the uniform load and Tables 5 and 6 for the central concentrated load. The results show a good agreement between RBF and FEM solutions for the uniform load with a maximum difference of 1.61% in the deflection results and a maximum difference of 4.99% in the stress results. For the concentrated load, the results show a reasonable agreement between the two solutions with a maximum difference of 4.37% in the deflection results and a maximum difference of 4.88% in the stress results.

Example 3. Consider the plate of Example 2 but with immovable edges (CCCF-IM). The solution is obtained using u-v-w formulation. The plate is analyzed under two different load types: uniformly distributed load [bar.q] ranging from 15 to 75 and a central and concentrated load [bar.p] ranging from 4 to 20. The results (Tables 7-10), once again, show a good agreement between RBF and FEM solutions. For the uniform load, the maximum difference is 4.66% in the deflection results and 4.92% in the stress results while, for the concentrated load, the maximum difference is 4.25% in the deflection and 4.69% in the stress results.

5. Conclusions

An RBF-based meshless method has been presented for the solution of large deflection of thin plates with different boundary conditions including free edges. The method is based on collocation with MQ-RBF. The load types considered in the study are uniform and concentrated. The boundary conditions covered are clamped, simply supported, free, movable, and immovable conditions. The FEM-based software COMSOL has been used to verify the RBF results. The proposed RBF meshless method has the advantage of being simple, easy to implement in a computer code, and reasonably accurate and therefore can qualify as an alternative numerical technique for the solution of highly nonlinear boundary value problems.

http://dx.doi.org/10.1155/2016/6489375

Competing Interests

The authors declare that they have no competing interests.

Acknowledgments

The authors would like to express their appreciation to King Fahd University of Petroleum & Minerals for supporting this study.

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Mohammed M. Hussein Al-Tholaia and Husain Jubran Al-Gahtani

Civil & Environmental Engineering Department, King Fahd University of Petroleum & Minerals (KFUPM), Dhahran 31261, Saudi Arabia

Correspondence should be addressed to Husain Jubran Al-Gahtani; hqahtani@kfupm.edu.sa

Received 17 February 2016; Revised 22 April 2016; Accepted 12 May 2016

Academic Editor: Evangelos J. Sapountzakis

Caption: Figure 1: Domain and boundary nodes.

Caption: Figure 2: Boundary and domain node distribution for the SSSF plate ([N.sub.B] = 36; [N.sub.D] = 81).
Table 1: Deflections and stresses for SSSF plate under a uniform load.

              [bar.w](a/2, a/2)         [bar.w](a, a/2)

[bar.q]    FEM     RBF    Diff.%    FEM     RBF    Diff.%

1.5       0.130   0.129   0.880    0.211   0.210   0.487
3.0       0.260   0.258   0.855    0.422   0.420   0.507
4.5       0.390   0.387   0.852    0.633   0.630   0.558
6.0       0.519   0.515   0.878    0.844   0.839   0.641
7.5       0.648   0.642   0.933    1.055   1.047   0.755
9.0       0.777   0.769   1.016    1.267   1.255   0.896
10.5      0.904   0.894   1.118    1.477   1.462   1.057
12.0      1.032   1.019   1.253    1.688   1.667   1.255

             [bar.[[sigma].sub.y]]   [bar.[[sigma].sub.y]]
                   (a/2,a/2)                (a,a/2)

[bar.q]    FEM     RBF    Diff.%    FEM     RBF    Diff.%

1.5       0.720   0.700   2.784    1.008   0.971   3.746
3.0       1.440   1.400   2.732    2.017   1.941   3.745
4.5       2.156   2.099   2.672    3.026   2.914   3.703
6.0       2.869   2.794   2.631    4.037   3.890   3.638
7.5       3.578   3.485   2.587    5.048   4.869   3.542
9.0       4.281   4.170   2.611    6.060   5.850   3.462
10.5      4.979   4.844   2.719    7.073   6.830   3.430
12.0      5.671   5.505   2.928    8.086   7.805   3.475

Table 2: Deflections and stresses for SSSF plate under a central
concentrated load.

              [bar.w](a/2, a/2)         [bar.w](a, a/2)

[bar.p]    FEM     RBF    Diff.%    FEM     RBF    Diff.%

1         0.182   0.18    1.099    0.182   0.179   1.648
2         0.361   0.357   1.108    0.366   0.361   1.366
3         0.536   0.537   0.187    0.551   0.534   3.085
4         0.705   0.718   1.844    0.74    0.729   1.486
5         0.869   0.902   3.797    0.932   0.941   0.966
6         1.027   1.063   3.505    1.128   1.173   3.989
7         1.18    1.219   3.305    1.328   1.384   4.217
8         1.330   1.383   3.954    1.532   1.605   4.731

             [bar.[[sigma].sub.y]]     [bar.[[sigma].sub.y]]
                   (a/2,a/2)                  (a,a/2)

[bar.p]    FEM      RBF     Diff.%    FEM     RBF    Diff.%

1         3.207    3.089    3.668    0.926   0.921   0.509
2         6.382    6.167    3.381    1.859   1.843   0.838
3         9.502    9.188    3.304    2.805   2.761   1.582
4         12.551   12.010   4.310    3.770   3.664   2.812
5         15.526   14.829   4.493    4.759   4.578   3.797
6         18.430   17.581   4.611    5.775   5.501   4.748
7         21.269   20.280   4.650    6.821   6.523   4.356
8         24.050   22.983   4.436    7.895   7.504   4.949

Table 3: Central and free edge deflections for CCCF plate subjected
to a uniform load [bar.q].

              [bar.w](a/2, a/2)         [bar.w](a/a/2)

[bar.q]   FEM     RBF     Diff.%   FEM     RBF     Diff.%

5         0.103   0.102   1.266    0.161   0.159   1.469
10        0.207   0.204   1.225    0.323   0.318   1.508
15        0.310   0.306   1.201    0.485   0.477   1.549
20        0.412   0.407   1.204    0.647   0.637   1.584
25        0.514   0.508   1.234    0.810   0.797   1.606
30        0.616   0.608   1.292    0.973   0.958   1.610
35        0.717   0.707   1.372    1.137   1.119   1.590
40        0.817   0.805   1.471    1.302   1.282   1.543

Table 4: Central, clamped, and free edge stresses for CCCF plate
subjected to a uniform load [bar.q].

             [bar.[[sigma].sub.y]]    [bar.[[sigma].sub.x]]
                   (a/2,a/2)                (0,a/2)

[bar.q]    FEM     RBF    Diff.%    FEM      RBF     Diff.%

5         0.943   0.941   0.258    1.727    1.641    4.979
10        1.884   1.880   0.178    3.452    3.281    4.967
15        2.820   2.816   0.114    5.177    4.920    4.959
20        3.749   3.747   0.068    6.900    6.558    4.955
25        4.671   4.669   0.041    8.620    8.193    4.956
30        5.583   5.581   0.034    10.338   9.825    4.962
35        6.486   6.483   0.043    12.053   11.454   4.973
40        7.378   7.373   0.064    13.767   13.080   4.986


             [bar.[[sigma].sub.y]]      [bar.[[sigma].sub.y]]
                   (a/2,0)                    (a,a/2)

[bar.q]    FEM      RBF     Diff.%    FEM      RBF     Diff.%

5         2.014    1.940    3.657    1.317    1.272    3.386
10        4.026    3.880    3.631    2.635    2.545    3.429
15        6.034    5.817    3.611    3.957    3.819    3.465
20        8.038    7.749    3.598    5.283    5.098    3.491
25        10.037   9.676    3.592    6.614    6.383    3.500
30        12.028   11.596   3.593    7.951    7.674    3.486
35        14.013   13.509   3.599    9.294    8.974    3.443
40        15.991   15.414   3.609    10.642   10.283   3.368

Table 5: Central and free edge deflections for CCCF plate subjected
to a central concentrated load [bar.p].

              [bar.w](a/2, a/2)         [bar.w](a/a/2)

[bar.p]   FEM     RBF     Diff.%   FEM      RBF      Diff.%

2         0.145   0.144   0.759    0.059    0.059    0.421
4         0.288   0.286   0.694    0.119    0.119    0.268
6         0.425   0.429   0.941    0.181    0.179    1.137
8         0.557   0.570   2.334    0.246    0.241    2.101
10        0.683   0.701   2.635    0.314    0.304    3.070
12        0.802   0.831   3.616    0.385    0.369    3.989
14        0.915   0.946   3.331    0.459    0.439    4.372
16        1.023   1.057   3.357    0.538    0.515    4.201

Table 6: Central, clamped, and free edge stresses for CCCF plate
subjected to a central concentrated load [bar.p].

             [bar.[[sigma].sub.y]]     [bar.[[sigma].sub.x]]
                   (a/2,a/2)                  (0,a/2)

[bar.p]    FEM      RBF     Diff.%    FEM      RBF     Diff.%

2         5.587    5.434    2.741    1.648    1.656    0.530
4         11.117   10.696   3.794    3.275    3.313    1.158
6         16.544   15.895   3.928    4.866    4.970    2.145
8         21.840   21.151   3.153    6.411    6.629    3.412
10        26.992   26.107   3.276    7.905    8.231    4.125
12        31.999   31.009   3.093    9.350    9.758    4.357
14        36.870   35.710   3.145    10.749   11.230   4.481
16        41.614   40.216   3.361    12.105   12.682   4.764

             [bar.[[sigma].sub.y]]     [bar.[[sigma].sub.y]]
                   (a/2,0)                    (a,a/2)

[bar.p]    FEM      RBF     Diff.%    FEM     RBF    Diff.%

2         1.829    1.793    1.924    0.607   0.591   2.680
4         3.631    3.569    1.709    1.221   1.183   3.128
6         5.386    5.256    2.405    1.849   1.780   3.699
8         7.080    7.249    2.394    2.496   2.397   3.955
10        8.708    8.975    3.064    3.167   3.037   4.112
12        10.271   10.599   3.189    3.867   3.694   4.481
14        11.772   12.324   4.686    4.600   4.377   4.837
16        13.217   13.834   4.672    5.368   5.106   4.881

Table 7: Central and free edge deflections for CCCF-IM plate under a
uniform load.

              [bar.w](a/2, a/2)          [bar.w](a/a/2)

[bar.q]    FEM     RBF    Diff.%    FEM     RBF    Diff.%

15        0.292   0.284   2.730    0.426   0.412   3.318
30        0.518   0.500   3.411    0.699   0.667   4.530
45        0.694   0.670   3.475    0.887   0.846   4.658
60        0.836   0.799   4.488    1.032   0.985   4.506
75        0.957   0.913   4.601    1.150   1.100   4.415

Table 8: Central, clamped, and free edge stresses for CCCF-IM plate
under a uniform load.

            [bar.[[sigma].sub.y]]    [bar.[[sigma].sub.x]]
                   (a/2,a/2)                (0,a/2)

[bar.q]    FEM     RBF    Diff.%    FEM      RBF     Diff.%

15        2.625   2.561   2.411    5.029    4.903    2.517
30        4.579   4.424   3.394    9.517    9.160    3.756
45        6.004   5.772   3.858    13.505   12.959   4.048
60        7.088   6.815   3.849    17.122   16.378   4.347
75        7.949   7.610   4.260    20.460   19.557   4.414

            [bar.[[sigma].sub.y]]     [bar.[[sigma].sub.y]]
                   (a/2,0)                  (a,a/2)

[bar.q]    FEM      RBF     Diff.%    FEM     RBF    Diff.%

15        5.804    5.653    2.595    3.452   3.349   2.997
30        10.815   10.425   3.604    5.637   5.440   3.498
45        15.165   14.500   4.388    7.121   6.860   3.654
60        19.058   18.164   4.691    8.247   7.943   3.692
75        22.622   21.509   4.921    9.168   8.816   3.837

Table 9: Central and free edge deflections for CCCF-IM plate under
a central concentrated load.

              [bar.w](a/2, a/2)         [bar.w](a/a/2)

[bar.p]    FEM     RBF    Diff.%    FEM     RBF    Diff.%

4         0.281   0.282   0.204    0.114   0.114   0.369
8         0.521   0.534   2.550    0.214   0.218   1.884
12        0.717   0.739   3.062    0.297   0.304   2.334
16        0.880   0.912   3.627    0.367   0.376   2.412
20        1.020   1.064   4.251    0.429   0.446   4.048

Table 10: Central, clamped, and free edge stresses for CCCF-IM plate
under a central concentrated load.

             [bar.[[sigma].sub.y]]     [bar.[[sigma].sub.x]]
                   (a/2,a/2)                  (0,a/2)

[bar.p]    FEM      RBF     Diff.%    FEM      RBF     Diff.%

4         11.034   10.873   1.460    3.210    3.160    1.559
8         21.373   21.053   1.498    6.023    5.898    2.074
12        30.946   30.469   1.542    8.408    8.143    3.150
16        39.913   39.171   1.860    10.470   10.121   3.334
20        48.420   47.213   2.492    12.296   11.719   4.692

             [bar.[[sigma].sub.y]]     [bar.[[sigma].sub.y]]
                   (a/2,0)                    (a,a/2)

[bar.p]    FEM      RBF     Diff.%    FEM     RBF    Diff.%

4         3.560    3.467    2.602    1.165   1.149   1.454
8         6.665    6.461    3.061    2.135   2.103   1.487
12        9.289    8.988    3.246    2.899   2.960   2.085
16        11.556   11.165   3.386    3.516   3.599   2.364
20        13.569   14.075   3.727    4.029   4.210   4.505
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Title Annotation:Research Article
Author:Tholaia, Mohammed M. Hussein Al-; Gahtani, Husain Jubran Al-
Publication:Mathematical Problems in Engineering
Date:Jan 1, 2016
Words:5950
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