# An Edge-Based Smoothed Finite Element for Free Vibration Analysis of Functionally Graded Porous (FGP) Plates on Elastic Foundation Taking into Mass (EFTIM)

Authors: Trung Thanh Tran; Quoc-Hoa Pham; Trung Nguyen-Thoi
Journal: Mathematical Problems in Engineering
 (2020)

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## Abstract

In this paper, free vibration analysis of the functionally graded porous (FGP) plates on the elastic foundation taking into mass (EFTIM) is presented. The fundamental equations of the FGP plate are derived using Hamilton’s principle. The mixed interpolation of the tensorial components (MITC) approach and the edge-based smoothed finite element method (ES-FEM) is employed to avoid the shear locking as well as to improve the accuracy for the triangular element. The EFTIM is a foundation model based on the two-parameter Winkler–Pasternak model but added a mass parameter of foundation. Materials of the plate are FGP with a power-law distribution and maximum porosity distributions in the forms of cosine functions. Some numerical examples are examined to demonstrate the accuracy and reliability of the proposed method in comparison with those available in the literature.


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## Body

## 1. Introduction

The plate resting on the elastic foundation (EF) is one of the most common types of structures which have practical applications in civil and industrial constructions, especially in transportation and irrigation. In particular, the structures of beams and plates on the EF are subjected to moving loads of means of transport such as roadbeds affected by vehicles, railway tracks, and aircraft runways. In most publications, when investigating the mechanical behavior of structures on the EF, the researchers mainly use the one-parameter Winkler foundation model [1] or two-parameter Winkler–Pasternak foundation model [2, 3]. The analysis of plates resting on the Winkler–Pasternak foundation was previously addressed by several authors. For instance, Fazzolari [3] used an analytical method to consider free vibration and buckling of porous FG Sandwich beams resting on the EF with the Winkler–Pasternak foundation model. Leissa [4] presented results for the free vibration of rectangular plates. Xiang et al. [5] studied free vibration for Mindlin plates on the Winkler–Pasternak foundation using an analytical method. Omurtag et al. [6] used the finite element method (FEM) for the free vibration analysis of the Kirchhoff plates resting on the EF. Özçelikörs et al. [7] analyzed the exact solutions of bending, buckling, and vibration problems of a Levy-plate on the two-parameter foundation. Matsunaga [8] used a special higher-order plate theory (HSDT) to analyze vibration and buckling of thick plates on the EF. Ayvaz et al. [9] developed a modified Vlasov model to consider the earthquake response of thin plates on the EF. Shen et al. [10] based on the Rayleigh–Ritz method to study free and forced vibration of the Reissner–Mindlin plates resting on the EF. Liew et al. [11, 12] and Han and Liew [13] analyzed the free vibration of rectangular plates resting on the EF using a differential quadrature method. Zhou et al. [14] considered the vibration of rectangular plates on the EF using the Ritz method. Chucheepsakul and Chinnaboon [15] investigated plates by a two-parameter foundation model using a boundary element method. Civalek and Acar [16] investigated the bending of Mindlin plates on the EF by developing a singular convolution method. Ferreira et al. [17] presented bending and free vibration analyses of the FGP plates on the Winkler–Pasternak foundation by using radial basis functions. Shahsavari et al. [18] used a new quasi-3D hyperbolic theory for the free vibration analysis of the FGP plates resting on the EF. Zenkour and Radwan [19] proposed an exact analytical approach for free vibration analysis of laminated composite and Sandwich plates resting on the EF using a four-unknown plate theory. Duc et al. [20] presented the analysis of nonlinear thermal dynamic response of shear deformable functionally graded plates on the EF. Mahmoudi et al. [21] developed a refined quasi-three-dimensional shear deformation theory to analyze the functionally graded Sandwich plates resting on the two-parameter EF under thermomechanical loading. Duc et al. [22] used an analytical method to calculate static bending and free vibration of FG carbon nanotube-reinforced composite plate resting on Winkler–Pasternak foundations. Thang et al. [23] considered the effects of variable thickness on buckling and postbuckling behavior of imperfect sigmoid FGM plates on elastic medium subjected to compressive loading. Banh-Thien et al. [24] developed the isogeometric analysis for buckling analysis of nonuniform thickness nanoplates in an elastic medium.In recent years, the FGP materials have attracted great interest from many researchers over the world due to their lightness and high strength. As a result, they are widely applied for civil engineering, aerospace structures, nuclear plants, and other applications. Kim et al. [25] investigated bending, vibration, and buckling of the FGP microplates using a modified couples stress based on the analytical method. Coskun et al. [26] presented analytical solutions to analyze the bending, vibration, and buckling of the FG microplates based on the third-order shear deformation theory (TSDT). Chen et al. [27] investigated the static bending and buckling of the FGP beams by using the Timoshenko beam theory. Rezaei and Saidi [28, 29] studied the vibration of rectangular and porous-cellular plates based on an analytical method. The vibration of the FGP shallow shells using an improve Fourier method was examined by Zhao et al. [30]. Moreover, the dynamics of the FGP doubly-curved panels and shells were also investigated in [31]. Li et al. [32] analyzed the nonlinear vibration and dynamic buckling of the Sandwich FGP plates with graphene platelet reinforcement (GPL) on the EF. For nonlinear problems, Sahmani et al. [33] used the nonlocal method to analyze nonlinear large-amplitude vibrations of the FGP micro-/nanoplates with GPL reinforce. Wu et al. [34] studied the dynamic of the FGP structures by using FEM. Thang et al. [35] investigated the elastic buckling and free vibration of porous cellular plates based on the first-order shear deformation theory (FSDT). Although the FGP materials have many different types, in this paper, the authors only use the distribution of porosity as presented in [25, 26].In the other front of the development of numerical methods for computational mechanics, Liu et al. [36] have recently proposed an edge-based smoothed FEM (ES-FEM) using triangular elements which show some following excellent properties for the 2D solid mechanics analyses such as (1) the numerical results are often found superconvergent and very accurate; (2) the method is stable and works well for dynamic analysis; and (3) the implementation of the method is straightforward and no penalty parameter is used. The ES-FEM has been developed for n-sided polygonal elements [37], viscoelastoplastic analyses [38], 2D piezoelectric [39], primal-dual shakedown analyses [40], fluid structure interaction [41, 42], and various applications [43–45]. Recently, in an effort to improve the accuracy of the plate and shell structural analyses, the classical MITC3 element [46] incorporated with the ES-FEM [36], has been proposed to give the so-called ES-MITC3 element [47–51]. In the formulation of the ES-MITC3, the system stiffness matrix is employed using strains smoothed over the smoothing domains associated with the edges of the MITC3 elements. The numerical results demonstrated that the ES-MITC3 has the following great properties [47]: (1) the ES-MITC3 can eliminate transverse shear locking even with the ratio of the thickness to the length of the structures reach 10−8 and (2) the ES-MITC3 has better accuracy than the existing triangular elements such as MITC3 [46], DSG3 [52], and CS-DSG3 [53] and is a good competitor with the quadrilateral element MITC4 element [54].The objective of this research now is to further extend the ES-MITC3 method for free vibration analyses of the FGP plates resting on the EFTIM. The governing equations are derived from the FSDT and the Reissner–Mindlin plate theory due to simplicity and computational efficiency. Besides, the EFTIM is modelled based on a two-parameter Winkler–Pasternak foundation model and added in a mass parameter of foundation. The plate is made from the FGP materials with a power-law distribution (k) and maximum porosity distributions (Ω) in the forms of cosine functions. The accuracy and reliability of the present formulation are verified by comparing with those of other available numerical results. Moreover, the effects of some geometric parameters and material properties on the free vibration of the FGP plates are also examined in detail.


## 2. Functionally Graded Porous Material Plates on Elastic Foundation

Let us consider an FGP plate resting on EFTIM, as shown in Figure1. The FGP materials with a variation of two constituents and three different distributions of porosity through-thickness are presented as follows [25, 26]:(1)Case1:Λz=Ωcosπzh,Case2:Λz=Ωcosπ2zh+0.5,Case3:Λz=Ωcosπ2zh−0.5,where Ω is the maximum porosity value. A typical material property of the FGP materials can be considered as in the following power-law relations:(2)Pz=Pt−Pbzh+0.5k+Pb1−Λz,where Pt and Pb are the typical material properties at the top and the bottom surfaces, respectively; and k is the power-law index. The normalized distributions of porosity through the thickness are shown in Figure 2(a). As shown in Figure 2(a), the porosity distribution of Case 1 is symmetric with respect to the midplane of plates. Case 2 and Case 3 are bottom and top surface-enhanced distributions, respectively. Besides, Figures 2(b)–2(d) show the distributions of a normalized typical property associated with three different cases of porosity distributions with parameters: Ω=0.5, k = 1, 5, 10, and Pt/Pb = 10.Figure 1
Modeling the FGP plate resting on EFTIM.Figure 2
Distributions of porosity and typical material property. (a) Distribution of porosity along ofz-axis, (b) distribution material property with k = 1, (c) distribution material property with k = 5, and (d) distribution material property with k = 10.
(a)
(b)
(c)
(d)The EFTIM is built based on the Winkler–Pasternak foundation by adding a mass parameter of foundation:(3)qe=k1wx,y,t−k2∂2∂x2+∂2∂y2wx,y,t+mf∂2wx,y,t∂t2,where w is the displacement of FGP plate; k1 and k2 are, respectively, Winkler foundation stiffness and shear layer stiffness of the Pasternak foundation. In order to mention the effectiveness of the foundation mass involved in the oscillation as well as the continuous interaction of the spring with the plate, the parameter β with unit kg−1 is added. It characterizes the effective level of the foundation mass involved in vibration, which is determined based on an experimental basis and the ratio of the density of the foundation to the density of plate material which is defined as μF=ρF/ρ. Thus, the density of mass mf involved vibration with the foundation is determined mf=βμFρ. From equation (3) we see that, for the static problem, the EFTIM model and Winkler–Pasternak foundation model are the same. But, for the dynamic problems, these two models have differences, and when omitting the influence parameters of the foundation mass, the EFTIM model is equivalent to the Winkler–Pasternak foundation model. In addition, this foundation model also covers the Winkler foundation model when the influence of shear parameters and foundation mass parameters ignored. It was found that the EFTIM model closely resembles the true feature of the foundation, including the Pasternak and Winkler foundation models.


## 3. The First-Order Shear Deformation Theory and Weak Form of the FGP Plates

### 3.1. First-Order Shear Deformation Theory for FGP Plates

The displacement of the FGP plates in the present work based on the FSDT model can be expressed as(4)ux,y,z=u0x,y+zθxx,y,vx,y,z=v0x,y+zθyx,y,wx,y,z=w0x,y,where u, v, w, θx, and θy are five unknown displacements of the midsurface of the plate. For a bending plate, the strain field can be expressed as follows:(5)ε=εm+zκ,where the membrane strain is given as(6)εm=u0,xv0,yu0,y+v0,x.The bending and transverse shear strains are written as(7)κ=θx,xθy,yθx,y+θy,x,(8)γ=w0,x+θxw0,y+θy.From Hooke’s law, the linear stress-strain relations of the FGP plates can be expressed as(9)σxσyτxyτxzτyz=Q11Q12000Q21Q2200000Q6600000Q5500000Q44εxεyγxyγxzγyz,where(10)Q11=Q22=Ez1−υ2,Q12=Q21=υEz1−υ2,Q44=Q55=Q66=Ez21+υ.where Ez presents for effective Young’s modulus and υ represents Poisson’s ratio.


### 3.2. Weak Form Equations

To obtain the motion equations of the FGP plates for the free vibration analysis, Hamilton’s principle is applied with the following form:(11)∫t1t2δU−δKdt=0,where U and K are the strain and kinetic energies, respectively. The strain energy is expressed as(12)U=Up+Uf,where Uf is the strain energy(13)Uf=12∫ψk1w2−k2∂2w∂x22+∂2w∂y22dψ,and Up is the strain energy(14)Up=12∫ψεTDε+γTCγdψ.where ε=εmκT and(15)D=ABBF,and A, B, F, and C can be given by(16)A,B,F=∫−h/2h/21,z,z2Q11Q120Q21Q22000Q66dz,(17)C=∫−h/2h/2Q5500Q44dz.The kinetic energy in equation (11) is given by(18)K=Kp+Kf,where Kp is the kinetic energy(19)Kp=12∫ψu˙mpudψ,where uT=u0v0w0θxθyϕxϕy is the displacement field and mp is the mass matrix defined by(20)mp=I100I20I100I2I100I30I3,where I1,I2,I3=∫−h/2h/2ρ1,z,z2dz.In equation (11), the kinetic energy of the mass of foundation Kf is defined as(21)Kf=12∫ψw˙mfwdψ.Substituting equations (12) and (18) into equation (11), the weak formulation for the free vibration of the FGP plate is finally obtained as(22)∫ψδεTDεdψ+∫ψδγTCγdψ+∫ψδwTk1w−k2∂2w∂x2+∂2w∂y2dψ=∫ψu˙mpudψ+∫ψw˙mfwdψ.


## 3.1. First-Order Shear Deformation Theory for FGP Plates

The displacement of the FGP plates in the present work based on the FSDT model can be expressed as(4)ux,y,z=u0x,y+zθxx,y,vx,y,z=v0x,y+zθyx,y,wx,y,z=w0x,y,where u, v, w, θx, and θy are five unknown displacements of the midsurface of the plate. For a bending plate, the strain field can be expressed as follows:(5)ε=εm+zκ,where the membrane strain is given as(6)εm=u0,xv0,yu0,y+v0,x.The bending and transverse shear strains are written as(7)κ=θx,xθy,yθx,y+θy,x,(8)γ=w0,x+θxw0,y+θy.From Hooke’s law, the linear stress-strain relations of the FGP plates can be expressed as(9)σxσyτxyτxzτyz=Q11Q12000Q21Q2200000Q6600000Q5500000Q44εxεyγxyγxzγyz,where(10)Q11=Q22=Ez1−υ2,Q12=Q21=υEz1−υ2,Q44=Q55=Q66=Ez21+υ.where Ez presents for effective Young’s modulus and υ represents Poisson’s ratio.


## 3.2. Weak Form Equations

To obtain the motion equations of the FGP plates for the free vibration analysis, Hamilton’s principle is applied with the following form:(11)∫t1t2δU−δKdt=0,where U and K are the strain and kinetic energies, respectively. The strain energy is expressed as(12)U=Up+Uf,where Uf is the strain energy(13)Uf=12∫ψk1w2−k2∂2w∂x22+∂2w∂y22dψ,and Up is the strain energy(14)Up=12∫ψεTDε+γTCγdψ.where ε=εmκT and(15)D=ABBF,and A, B, F, and C can be given by(16)A,B,F=∫−h/2h/21,z,z2Q11Q120Q21Q22000Q66dz,(17)C=∫−h/2h/2Q5500Q44dz.The kinetic energy in equation (11) is given by(18)K=Kp+Kf,where Kp is the kinetic energy(19)Kp=12∫ψu˙mpudψ,where uT=u0v0w0θxθyϕxϕy is the displacement field and mp is the mass matrix defined by(20)mp=I100I20I100I2I100I30I3,where I1,I2,I3=∫−h/2h/2ρ1,z,z2dz.In equation (11), the kinetic energy of the mass of foundation Kf is defined as(21)Kf=12∫ψw˙mfwdψ.Substituting equations (12) and (18) into equation (11), the weak formulation for the free vibration of the FGP plate is finally obtained as(22)∫ψδεTDεdψ+∫ψδγTCγdψ+∫ψδwTk1w−k2∂2w∂x2+∂2w∂y2dψ=∫ψu˙mpudψ+∫ψw˙mfwdψ.


## 4. Formulation of an ES-MITC3 Method for FGP Plates

### 4.1. Formulation of the Finite Element Using the MITC3 Element

The middle surface of plateψ is discretized into ne finite three-node triangular elements with nn nodes such that ψ≈∑e=1neψe and ψi∩ψj=∅,i≠j. Then, the generalized displacements at any point ue=uje,vje,wje,θxje,θyjeT of element ψe can be approximated as(23)uex=∑j=1nneNIx00000NIx00000NIx00000NIx00000NIxdje=∑j=1nneNxdje,where nne is the number of nodes of ψe; Nx is the shape function matrix; and dje=uje,vje,wje,θxje,θyjeT is the nodal degrees of freedom (d.o.f) associated with the jth node of ψe.The membrane bending strains of MITC3 element can be expressed in matrix forms as follows:(24)εme=Bm1eBm2eBm3ede=Bmede,(25)κe=Bb1eBb2eBb3ede=Bbede,where(26)Bm1e=12Aeb−c00000d−a000d−ab−c000,(27)Bm2e=12Aec00000−d000−dc000,(28)Bm3e=12Ae−b00000a000a−b000,(29)Bb1e=12Ae000b−c00000d−a000d−ab−c,(30)Bb2e=12Ae000c00000−d000−dc,(31)Bb3e=12Ae000−b00000a000a−b,To eliminate the shear locking phenomenon as the thickness of the plate becomes small, the formulation of the transverse shear strains of the MITC3 element based on FSDT [36] in this study can be written as follows:(32)γe=Bsede,where(33)Bse=Bs1eBs2eBs3e,with(34)Bs1e=J−100−1a3+d6b3+c600−1d3+a6c3+b6,(35)Bs2e=J−1001a2−d6b2−c6000d6c6,(36)Bs3e0=J−1000a6b6001d2−a6c2−b6,where(37)J−1=12Aec−b−da.Here,a=x2−x1, b=y2−y1, c=y3−y1, and d=x3−x1 are pointed out in and Ae is the area of the three-node triangular element as shown in Figure 3.Figure 3
Three-node triangular element in the local coordinates.Substituting the discrete displacement field into equation (22), we obtained the discrete system equations for free vibration analysis of FGP plate resting on the EF, respectively, as(38)K−ω2Md=0,where K and M are the stiffness and mass matrices, respectively.The stiffness matrix in equation (38) can be written as(39)K=∑e=1neKpe+Kfe,where(40)Kpe=∫ψeBTDBdψe+∫ψeBsTCBsdψe,(41)Kfe=k1∫ψeNwTNwdψe+k2∫ψe∂Nw∂xT∂Nw∂x+∂Nw∂yT∂Nw∂ydψe,where(42)Be=BmeBbe,(43)Nw=00N100,00N200,00N300.Next, the mass matrix in equation (38) can be defined as(44)M=∑e=1neMpe+Mfe,where(45)Mpe=∫ψeNTmpNdψe,(46)Mfe=mf∫ψeNwTNwdψe.


### 4.2. Formulation of an ES-MITC3 Method for FGP Plates

The smoothing domainsψk is constructed based on edges of the triangular elements such that ψ=∪k=1nkψk and ψik∩ψjk=∅fori≠j. An edge-based smoothing domain ψk for the inner edge k is formed by connecting two end-nodes of the edge to the centroids of adjacent triangular MITC3 elements, as shown in Figure 4.Figure 4
The smoothing domainψk is formed by triangular elements.Applying the edge-based smooth technique [36], the smoothed membrane, bending, and shear strain ε˜mk,κ˜k, γ˜k over the smoothing domain ψk can be created by(47)ε˜mk=∫ψkεmΦkxdψ,(48)k˜k=∫ψkκΦkxdψ,(49)γ˜k=∫ψkγΦkxdψ,where εm, κ, and γ the compatible membrane, bending, and the shear strains, respectively; Φkx is a given smoothing function that satisfies at least unity property ∫ψkΦkxdψ=1.In this study, we use the constant smoothing function(50)Φkx=1Ak,x∈ψk,0,x∉ψk,where Ak is the area of the smoothing domain ψk and is given by(51)Ak=∫ψkdψ=13∑i=1nekAi,where nek is the number of the adjacent triangular elements in the smoothing domain ψk; and Ai is the area of the ith triangular element attached to the edge k.By substituting equations (47)–(49) into equations (24), (25), and (32), the approximation of the smoothed strains on the smoothing domain ψk can be expressed as follows:(52)ε˜mk=∑j=1nnkB˜mjkdjk;k˜k=∑j=1nshnkB˜bjkdjk;γk=∑j=1nshnkB˜sjkdjk;where nshnk is the total number of nodes of the triangular MITC3 elements attached to edge k (nshnk=3 for boundary edges and nshnk=4 for inner edges as given in Figure 4; djk is the nodal d.o.f associated with the smoothing domain ψk; and B˜mjk, B˜bjk, and B˜sjk are the smoothed membrane, bending, and shear strain gradient matrices, respectively, at the jth node of the elements attached to edge k computed by(53)B˜mjk=1Ak∑i=1nek13AiBmje,(54)B˜bjk=1Ak∑i=1nek13AiBbje,(55)B˜sjk=1Ak∑i=1nek13AiBsje.The stiffness matrix of the FGP plate using the ES-MITC3 is assembled by(56)K˜=∑k=1nshkK˜k,where K˜k is the ES-MITC3 stiffness matrix of the smoothing domain ψk and given by(57)K˜k=∫ψkB˜KTDB˜k+B˜sktCB˜skdψ=B˜KTDB˜kAk+B˜sktCB˜skAk,where(58)B˜kT=B˜mjkB˜bjk.


## 4.1. Formulation of the Finite Element Using the MITC3 Element

The middle surface of plateψ is discretized into ne finite three-node triangular elements with nn nodes such that ψ≈∑e=1neψe and ψi∩ψj=∅,i≠j. Then, the generalized displacements at any point ue=uje,vje,wje,θxje,θyjeT of element ψe can be approximated as(23)uex=∑j=1nneNIx00000NIx00000NIx00000NIx00000NIxdje=∑j=1nneNxdje,where nne is the number of nodes of ψe; Nx is the shape function matrix; and dje=uje,vje,wje,θxje,θyjeT is the nodal degrees of freedom (d.o.f) associated with the jth node of ψe.The membrane bending strains of MITC3 element can be expressed in matrix forms as follows:(24)εme=Bm1eBm2eBm3ede=Bmede,(25)κe=Bb1eBb2eBb3ede=Bbede,where(26)Bm1e=12Aeb−c00000d−a000d−ab−c000,(27)Bm2e=12Aec00000−d000−dc000,(28)Bm3e=12Ae−b00000a000a−b000,(29)Bb1e=12Ae000b−c00000d−a000d−ab−c,(30)Bb2e=12Ae000c00000−d000−dc,(31)Bb3e=12Ae000−b00000a000a−b,To eliminate the shear locking phenomenon as the thickness of the plate becomes small, the formulation of the transverse shear strains of the MITC3 element based on FSDT [36] in this study can be written as follows:(32)γe=Bsede,where(33)Bse=Bs1eBs2eBs3e,with(34)Bs1e=J−100−1a3+d6b3+c600−1d3+a6c3+b6,(35)Bs2e=J−1001a2−d6b2−c6000d6c6,(36)Bs3e0=J−1000a6b6001d2−a6c2−b6,where(37)J−1=12Aec−b−da.Here,a=x2−x1, b=y2−y1, c=y3−y1, and d=x3−x1 are pointed out in and Ae is the area of the three-node triangular element as shown in Figure 3.Figure 3
Three-node triangular element in the local coordinates.Substituting the discrete displacement field into equation (22), we obtained the discrete system equations for free vibration analysis of FGP plate resting on the EF, respectively, as(38)K−ω2Md=0,where K and M are the stiffness and mass matrices, respectively.The stiffness matrix in equation (38) can be written as(39)K=∑e=1neKpe+Kfe,where(40)Kpe=∫ψeBTDBdψe+∫ψeBsTCBsdψe,(41)Kfe=k1∫ψeNwTNwdψe+k2∫ψe∂Nw∂xT∂Nw∂x+∂Nw∂yT∂Nw∂ydψe,where(42)Be=BmeBbe,(43)Nw=00N100,00N200,00N300.Next, the mass matrix in equation (38) can be defined as(44)M=∑e=1neMpe+Mfe,where(45)Mpe=∫ψeNTmpNdψe,(46)Mfe=mf∫ψeNwTNwdψe.


## 4.2. Formulation of an ES-MITC3 Method for FGP Plates

The smoothing domainsψk is constructed based on edges of the triangular elements such that ψ=∪k=1nkψk and ψik∩ψjk=∅fori≠j. An edge-based smoothing domain ψk for the inner edge k is formed by connecting two end-nodes of the edge to the centroids of adjacent triangular MITC3 elements, as shown in Figure 4.Figure 4
The smoothing domainψk is formed by triangular elements.Applying the edge-based smooth technique [36], the smoothed membrane, bending, and shear strain ε˜mk,κ˜k, γ˜k over the smoothing domain ψk can be created by(47)ε˜mk=∫ψkεmΦkxdψ,(48)k˜k=∫ψkκΦkxdψ,(49)γ˜k=∫ψkγΦkxdψ,where εm, κ, and γ the compatible membrane, bending, and the shear strains, respectively; Φkx is a given smoothing function that satisfies at least unity property ∫ψkΦkxdψ=1.In this study, we use the constant smoothing function(50)Φkx=1Ak,x∈ψk,0,x∉ψk,where Ak is the area of the smoothing domain ψk and is given by(51)Ak=∫ψkdψ=13∑i=1nekAi,where nek is the number of the adjacent triangular elements in the smoothing domain ψk; and Ai is the area of the ith triangular element attached to the edge k.By substituting equations (47)–(49) into equations (24), (25), and (32), the approximation of the smoothed strains on the smoothing domain ψk can be expressed as follows:(52)ε˜mk=∑j=1nnkB˜mjkdjk;k˜k=∑j=1nshnkB˜bjkdjk;γk=∑j=1nshnkB˜sjkdjk;where nshnk is the total number of nodes of the triangular MITC3 elements attached to edge k (nshnk=3 for boundary edges and nshnk=4 for inner edges as given in Figure 4; djk is the nodal d.o.f associated with the smoothing domain ψk; and B˜mjk, B˜bjk, and B˜sjk are the smoothed membrane, bending, and shear strain gradient matrices, respectively, at the jth node of the elements attached to edge k computed by(53)B˜mjk=1Ak∑i=1nek13AiBmje,(54)B˜bjk=1Ak∑i=1nek13AiBbje,(55)B˜sjk=1Ak∑i=1nek13AiBsje.The stiffness matrix of the FGP plate using the ES-MITC3 is assembled by(56)K˜=∑k=1nshkK˜k,where K˜k is the ES-MITC3 stiffness matrix of the smoothing domain ψk and given by(57)K˜k=∫ψkB˜KTDB˜k+B˜sktCB˜skdψ=B˜KTDB˜kAk+B˜sktCB˜skAk,where(58)B˜kT=B˜mjkB˜bjk.


## 5. Accuracy of the Proposed Method

In this section, the various numerical examples are solved to verify the reliability and accuracy of the proposed method. For convenience, the stiffness factors and nondimensional frequencies of the plates are defined as the following equations:(59)K1=k1a4H;K2=k2a2H;λ=ωa2π2ρhH,withH=Eh3121−ν2.To demonstrate the performance of numerical results, the relative frequency error is defined by(60)Δ%=100×λpr−λreλre,where λpr and λre are nondimensional frequencies of present method and nondimensional frequencies in [17, 18], respectively.The results of the convergence of the first two nondimensional frequencies of the plate in the case of fully simple support (SSSS) plate and a fully clamped (CCCC) plate withh/a = 0.1, K1 = 100, K2 = 10, respectively, are shown in Figure 5. From these results, it can be seen that almost all frequencies corresponding to different cases of boundary conditions (BC) converge with 18 × 18 element mesh. For 18 × 18 mesh, we compare the first three nondimensional frequencies of a plate resting on the Winkler–Pasternak foundation with the published results as shown in Table 1. It can be seen that the present results agree well with the results of the authors using analytical methods [5, 14, 17] and are more accurate than those using the original MITC3 element and FEM [6]. In addition, from Table 2, it is obvious that the relative error of the present results compared to [18] is less than 2%. In [18], they used a new quasi-3D hyperbolic theory to investigate the free vibration of the FGP plate resting on the EF. These results are the basis to analyze the free vibration of FGP plates on the EFTIM.Figure 5
The convergence of element mesh to nondimensional frequency of plate. (a)λ1 and (b)λ2.
(a)
(b)Table 1
Nondimensional frequencies of plates.
Plates
K
1
K
2
Author
λ
1
Δ
%
λ
2
Δ
%
λ
3
Δ
%
SSSSυ=0.3h/a = 0.01
100
10
Ferreira et al. [17]
2.6559
5.5718
8.5384
Zhou et al. [14]
2.6551
0.03
5.5717
0.00
8.5406
0.03
Xiang et al. [5]
2.6551
0.03
5.5718
0.00
8.5405
0.02
MITC3
2.6604
0.17
5.6103
0.70
8.6296
1.07
Present
2.6590
0.12
5.5920
0.37
8.6017
0.74
500
10
Ferreira [17]
3.3406
5.9285
8.7754
Zhou et al. [14]
3.3398
0.02
5.9285
0.00
8.7775
0.02
Xiang et al. [5]
3.3400
0.02
5.9287
0.00
8.7775
0.02
MITC3
3.3441
0.10
5.9649
0.61
8.8642
1.01
Present
3.3430
0.07
5.9477
0.32
8.8370
0.70
SSSSυ=0.3h/a = 0.1
200
10
Ferreira et al. [17]
2.7902
5.3452
7.8255
Zhou et al. [14]
2.7756
0.52
5.2954
0.93
7.7279
1.25
Xiang et al. [5]
2.7842
0.22
5.3043
0.77
7.7287
1.24
MITC3
2.7874
0.10
5.3258
0.36
7.7719
0.68
Present
2.7887
0.05
5.3362
0.17
7.7971
0.36
1000
10
Ferreira et al. [17]
3.9844
6.0430
8.3112
Zhou et al. [14]
3.9566
0.70
5.9757
1.11
8.1954
1.39
Xiang et al. [5]
3.9805
0.10
6.0078
0.58
8.2214
1.08
MITC3
3.9827
0.04
6.0266
0.27
8.2619
0.59
Present
3.9836
0.02
6.0358
0.12
8.2856
0.31
CCCCυ=0.15h/a = 0.015
1390.2
166.83
Ferreira et al. [17]
8.1669
12.821
16.842
Zhou et al. [14]
8.1675
0.01
12.823
0.02
16.833
0.05
Omurtag et al. [6]
8.1375
0.36
12.898
0.60
16.932
0.53
MITC3
8.1842
0.21
12.909
0.69
17.010
1.00
Present
8.1729
0.07
12.872
0.40
16.939
0.58Table 2
The first nondimensional frequencies of FGP plate according to the Winkler–Pasternak foundation stiffness (k = 1).
(K1, K2)
h/a
ξ
=
0
ξ
=
0.2
Present
[18]
Δ
%
Present
[18]
Δ
%
(0, 0)
0.05
9.010
9.020
0.11
8.485
8.370
1.37
0.10
8.823
8.818
0.06
8.319
8.203
1.41
0.15
8.541
8.516
0.29
8.069
7.950
1.50
0.20
8.196
8.151
0.55
7.762
7.641
1.58
(100, 0)
0.05
9.389
9.430
0.43
9.020
8.917
1.16
0.10
9.207
9.231
0.26
8.858
8.753
1.20
0.15
8.933
8.934
0.01
8.614
8.505
1.28
0.20
8.599
8.577
0.26
8.315
8.203
1.37
(100, 100)
0.05
15.383
15.439
0.36
16.338
16.320
0.11
0.10
15.213
15.245
0.21
16.175
16.148
0.17
0.15
14.962
14.966
0.03
15.932
15.895
0.23
0.20
14.664
14.640
0.16
15.639
15.595
0.28Next, we consider an SSSS FGP plate (Al/Al2O3) with its material properties as follows: metal (Al) Eb=70GPa, ρb=2702kg/m3 and ceramic (Al2O3) Et=380GPa, ρt=3800kg/m3. Poisson’s ratio is fixed at υ=0.3. The FGP plate with even porosities is expressed as in [18]:(61)Pz=Pb+Pt−Pbzh+0.5k−ξ2Pt+Pb,where ξξ≤1 presents the porosity volume fraction. The stiffness factor and nondimensional frequencies of the plates are shown in equation (58) with Hb=Ebh3/121−υ2 and ω∗=ωa2/hρb/Eb. The first nondimensional frequencies of present work compared with [18] are shown in Table 2.


## 6. Numerical Results and Discussions

For free vibration problems, a fully simple support (SSSS) FGP plate is considered, whereina=b,h=a/10,Ω=0.5, k=1, Et=10Eb, ρt=10ρb, υ=0.38, and μF=0.5. The first six nondimensional frequencies of the FGP plate with porosity distribution of Case 1 and stiffener of foundation K1=100,K2=10 are shown in Table 3; and the first six mode shapes are presented in Figure 6. The stiffness factors and nondimensional frequencies of FGP plate are shown in equation (58) with Hb=Ebh3/121−υ2.Table 3
Nondimensional frequencies of the FGP plate on EFTIM.
λ
1
λ
2
λ
3
λ
4
λ
5
λ
6
0.8583
1.8118
1.8157
2.8015
3.3898
3.4248Figure 6
The first six mode sharps the FGP plate on EFTIM.
(a)
(b)
(c)
(d)
(e)
(f)


### 6.1. Influence of the Parameters of the EFTIM to the Free Vibration for the FGP Plate

Firstly, in order to investigate the effect of the featured-index of the mass of foundationβ to free vibration of the FGP plate, the featured-index of mass is changed from 0 to 1. In Figure 7 and Table 4, it is seen that all cases of porosity distribution featured-index of the mass of foundation β significantly influence to free vibration of the FGP plate. As β increases, the mass of the plate increases, and the frequencies of the plate decrease. For all cases of porosity distribution of the FGP plate, the porosity distribution of Case 3 leads to the maximum values of frequencies of the plate, while the porosity distribution of Case 2 leads to the minimum values. It can be observed that the FGP plate with porosity distribution Case 3 is stiffer than plates with other porosity distributions.Figure 7
Nondimensional frequencies of the eFGP plate with difference of featured-indexβ: (a) nondimensional frequency λ1; (b) nondimensional frequency λ2; and (c) nondimensional frequency λ3.
(a)
(b)
(c)Table 4
The first three nondimensional frequencies of FGP on EFTIM.
Parameter of plate
β
0
0.25
0.5
0.75
1
Case 1
λ
1
1.1015
0.9575
0.8583
0.7847
0.7273
(K1 = 100, K2 = 10)
λ
2
2.3078
2.0156
1.8118
1.6595
1.5400
(SSSS)
λ
3
3.5651
3.1154
2.8015
2.5665
2.3822
Case 2
λ
1
1.0225
0.8988
0.8113
0.7453
0.6931
(K1 = 100, K2 = 10)
λ
2
2.0774
1.8350
1.6612
1.5289
1.4239
(SSSS)
λ
3
3.2410
2.8630
2.5921
2.3859
2.2221
Case 3
λ
1
1.2537
1.0735
0.9538
0.8669
0.8001
(K1 = 100, K2 = 10)
λ
2
2.7399
2.3531
2.0942
1.9054
1.7599
(SSSS)
λ
3
4.1972
3.6097
3.2152
2.9269
2.7044Next, the influence of nondimensional parameters of foundation stiffnessK1 and K2 is investigated. We change K1 from 100 to 1000 and K2 from 10 to 100 with respect to β=0.5 and μF=0.5. The first nondimensional frequency of the FGP plate with three cases of porosity distribution is presented in Table 5 and shown in Figure 8. As shown in these figure and table, when K1 and K2 increase, the nondimensional frequency of plate also increases. We also examine the effect of (β, K1) and (β, K2) parameters to nondimensional frequency. The numerical result is presented in Table 6 and Figure 9. Consequently, Winkler foundation stiffness K1 and shear layer stiffness of Pasternak foundation K2 make stiffness of plate become greater and the mass of the EF involved in the plate’s vibration makes reduce frequencies.Table 5
Nondimensional frequencies of the FGP plate with differentK1 and K2.
Case of Porosity distribution
K
2
K
1
100
250
500
750
1000
Case 1(SSSS)
10
0.8583
0.8929
0.9477
0.9995
1.0488
25
0.9258
0.9579
1.0092
1.0580
1.1047
50
1.0285
1.0575
1.1042
1.1490
1.1921
75
1.1218
1.1485
1.1916
1.2332
1.2734
100
1.2079
1.2327
1.2730
1.3120
1.3499
Case 2(SSSS)
10
0.8113
0.8452
0.8988
0.9493
0.9973
25
0.8775
0.9089
0.9589
1.0064
1.0518
50
0.9778
1.0061
1.0515
1.0950
1.1369
75
1.0687
1.0947
1.1365
1.1769
1.2160
100
1.1525
1.1765
1.2156
1.2534
1.2902
Case 3(SSSS)
10
0.9538
1.0009
1.0747
1.1438
1.2090
25
1.0452
1.0883
1.1566
1.2211
1.2823
50
1.1819
1.2202
1.2815
1.3400
1.3960
75
1.3044
1.3392
1.3953
1.4492
1.5011
100
1.4163
1.4484
1.5004
1.5507
1.5993Figure 8
Nondimensional frequencies of FGP plate with differentK1 and K2. (a) Case 1; (b) Case 2; and (c) Case 3.
(a)
(b)
(c)Table 6
Nondimensional frequencies of FGP plate with differentK1, K2, and β.
β
K
1 (K2 = 10)
K
2 (K1 = 100)
Case 1
100
250
500
750
1000
10
25
50
75
100
0
1.1015
1.1459
1.2163
1.2828
1.3460
1.1015
1.1882
1.3199
1.4397
1.5502
0.25
0.9575
0.9961
1.0572
1.1150
1.1700
0.9575
1.0328
1.1473
1.2514
1.3475
0.5
0.8583
0.8929
0.9477
0.9995
1.0488
0.8583
0.9258
1.0285
1.1218
1.2079
0.75
0.7847
0.8163
0.8664
0.9138
0.9588
0.7847
0.8464
0.9403
1.0256
1.1043
1
0.7273
0.7566
0.8030
0.8469
0.8887
0.7273
0.7844
0.8715
0.9505
1.0235
Case 2
0
1.0225
1.0652
1.1327
1.1964
1.2569
1.0225
1.1059
1.2323
1.3469
1.4525
0.25
0.8988
0.9363
0.9957
1.0517
1.1049
0.8988
0.9721
1.0833
1.1840
1.2768
0.5
0.8113
0.8452
0.8988
0.9493
0.9973
0.8113
0.8775
0.9778
1.0687
1.1525
0.75
0.7453
0.7763
0.8256
0.8720
0.9161
0.7453
0.8060
0.8982
0.9817
1.0586
1
0.6931
0.7220
0.7677
0.8109
0.8519
0.6931
0.7496
0.8353
0.9129
0.9845
Case 3
0
1.2537
1.3156
1.4127
1.5035
1.5891
1.2537
1.3739
1.5536
1.7146
1.8617
0.25
1.0735
1.1265
1.2096
1.2874
1.3607
1.0735
1.1764
1.3303
1.4681
1.5941
0.5
0.9538
1.0009
1.0747
1.1438
1.2090
0.9538
1.0452
1.1819
1.3044
1.4163
0.75
0.8669
0.9097
0.9768
1.0396
1.0988
0.8669
0.9500
1.0742
1.1855
1.2872
1
0.8001
0.8395
0.9015
0.9595
1.0141
0.8001
0.8767
0.9914
1.0942
1.1880Figure 9
Nondimensional frequencies of FGP plate with differentK1, K2, and β. (a) Case 1; (b) Case 2; and (c) Case 3.
(a)
(b)
(c)


### 6.2. Influence of the Parameters-FGP to Free Vibration of the Plate on EFTIM

Let us consider the effect of materials property to free vibration of the FGP plate. The power-law indexk is changed from 0 to 10, and maximum porosity distributions Ω has the value from 0 to 1. We examine the SSSS FGP plate and fully clamped (CCCC) plate resting on EFTIM. The parameters of EFTIM are given by β=0.5, μF=0.5, K1=100, and K1=10. The first nondimensional frequencies of plate with three cases of porosity distribution is shown in Table 7 and Figure 10.Table 7
Nondimensional frequencies of the FGP plate as a function ofk and Ω.
Ω
SSSS
CCCC
k
k
0
2.5
5
7.5
10
0
2.5
5
7.5
10
Case 1
0
0.6146
0.8460
0.9468
1.0184
1.0706
1.0275
1.2153
1.3432
1.4571
1.5444
0.25
0.6584
0.8830
0.9777
1.0469
1.0984
1.0935
1.2518
1.3694
1.4783
1.5633
0.5
0.7126
0.9238
1.0105
1.0767
1.1273
1.1732
1.2869
1.3930
1.4958
1.5780
0.75
0.7820
0.9677
1.0446
1.1070
1.1564
1.2711
1.3154
1.4102
1.5061
1.5848
1
0.8745
1.0105
1.0776
1.1357
1.1836
1.3924
1.3226
1.4130
1.5021
1.5766
Case 2
0
0.6146
0.8460
0.9468
1.0184
1.0706
1.0275
1.2153
1.3432
1.4571
1.5444
0.25
0.6609
0.8604
0.9563
1.0288
1.0833
1.0977
1.2011
1.3156
1.4273
1.5162
0.5
0.7162
0.8685
0.9569
1.0299
1.0871
1.1707
1.1651
1.2611
1.3675
1.4564
0.75
0.7777
0.8600
0.9357
1.0073
1.0671
1.2179
1.0868
1.1556
1.2496
1.3342
1
0.7852
0.7972
0.8420
0.9009
0.9580
1.0347
0.9106
0.9310
0.9904
1.0547
Case 3
0
0.6146
0.8460
0.9468
1.0184
1.0706
1.0275
1.2153
1.3432
1.4571
1.5444
0.25
0.6609
0.9413
1.0475
1.1196
1.1714
1.0977
1.3661
1.5012
1.6147
1.6994
0.5
0.7162
1.0785
1.1908
1.2621
1.3122
1.1707
1.5836
1.7243
1.8317
1.9084
0.75
0.7777
1.3066
1.4256
1.4917
1.5363
1.2179
1.9297
2.0656
2.1484
2.2018
1
0.7852
1.8589
1.9631
1.9772
1.9807
1.0347
2.4083
2.4138
2.3588
2.3246Figure 10
Nondimensional frequencies vibration of the FGP plate as a function ofk. (a) Case 1; (b) Case 2; and (c) Case 3.
(a)
(b)
(c)As shown in these figures and tables, whenk and Ω change, the values of nondimensional frequency change with no rule. It is understandable because with each case of change in porosity distributions k and Ω, the stiffness and the weight of the plate changes. From Figure 10, in the case of the CCCC plate, nondimensional frequency depending on k and Ω value varies more complex than the case of the SSSS plate. If k and Ω values are same, the frequency of the CCCC plate is larger than that of the SSSS plate. The results are quite reasonable because the SSSS boundary condition inherently offers more flexible boundary conditions than the CCCC boundary condition.


## 6.1. Influence of the Parameters of the EFTIM to the Free Vibration for the FGP Plate

Firstly, in order to investigate the effect of the featured-index of the mass of foundationβ to free vibration of the FGP plate, the featured-index of mass is changed from 0 to 1. In Figure 7 and Table 4, it is seen that all cases of porosity distribution featured-index of the mass of foundation β significantly influence to free vibration of the FGP plate. As β increases, the mass of the plate increases, and the frequencies of the plate decrease. For all cases of porosity distribution of the FGP plate, the porosity distribution of Case 3 leads to the maximum values of frequencies of the plate, while the porosity distribution of Case 2 leads to the minimum values. It can be observed that the FGP plate with porosity distribution Case 3 is stiffer than plates with other porosity distributions.Figure 7
Nondimensional frequencies of the eFGP plate with difference of featured-indexβ: (a) nondimensional frequency λ1; (b) nondimensional frequency λ2; and (c) nondimensional frequency λ3.
(a)
(b)
(c)Table 4
The first three nondimensional frequencies of FGP on EFTIM.
Parameter of plate
β
0
0.25
0.5
0.75
1
Case 1
λ
1
1.1015
0.9575
0.8583
0.7847
0.7273
(K1 = 100, K2 = 10)
λ
2
2.3078
2.0156
1.8118
1.6595
1.5400
(SSSS)
λ
3
3.5651
3.1154
2.8015
2.5665
2.3822
Case 2
λ
1
1.0225
0.8988
0.8113
0.7453
0.6931
(K1 = 100, K2 = 10)
λ
2
2.0774
1.8350
1.6612
1.5289
1.4239
(SSSS)
λ
3
3.2410
2.8630
2.5921
2.3859
2.2221
Case 3
λ
1
1.2537
1.0735
0.9538
0.8669
0.8001
(K1 = 100, K2 = 10)
λ
2
2.7399
2.3531
2.0942
1.9054
1.7599
(SSSS)
λ
3
4.1972
3.6097
3.2152
2.9269
2.7044Next, the influence of nondimensional parameters of foundation stiffnessK1 and K2 is investigated. We change K1 from 100 to 1000 and K2 from 10 to 100 with respect to β=0.5 and μF=0.5. The first nondimensional frequency of the FGP plate with three cases of porosity distribution is presented in Table 5 and shown in Figure 8. As shown in these figure and table, when K1 and K2 increase, the nondimensional frequency of plate also increases. We also examine the effect of (β, K1) and (β, K2) parameters to nondimensional frequency. The numerical result is presented in Table 6 and Figure 9. Consequently, Winkler foundation stiffness K1 and shear layer stiffness of Pasternak foundation K2 make stiffness of plate become greater and the mass of the EF involved in the plate’s vibration makes reduce frequencies.Table 5
Nondimensional frequencies of the FGP plate with differentK1 and K2.
Case of Porosity distribution
K
2
K
1
100
250
500
750
1000
Case 1(SSSS)
10
0.8583
0.8929
0.9477
0.9995
1.0488
25
0.9258
0.9579
1.0092
1.0580
1.1047
50
1.0285
1.0575
1.1042
1.1490
1.1921
75
1.1218
1.1485
1.1916
1.2332
1.2734
100
1.2079
1.2327
1.2730
1.3120
1.3499
Case 2(SSSS)
10
0.8113
0.8452
0.8988
0.9493
0.9973
25
0.8775
0.9089
0.9589
1.0064
1.0518
50
0.9778
1.0061
1.0515
1.0950
1.1369
75
1.0687
1.0947
1.1365
1.1769
1.2160
100
1.1525
1.1765
1.2156
1.2534
1.2902
Case 3(SSSS)
10
0.9538
1.0009
1.0747
1.1438
1.2090
25
1.0452
1.0883
1.1566
1.2211
1.2823
50
1.1819
1.2202
1.2815
1.3400
1.3960
75
1.3044
1.3392
1.3953
1.4492
1.5011
100
1.4163
1.4484
1.5004
1.5507
1.5993Figure 8
Nondimensional frequencies of FGP plate with differentK1 and K2. (a) Case 1; (b) Case 2; and (c) Case 3.
(a)
(b)
(c)Table 6
Nondimensional frequencies of FGP plate with differentK1, K2, and β.
β
K
1 (K2 = 10)
K
2 (K1 = 100)
Case 1
100
250
500
750
1000
10
25
50
75
100
0
1.1015
1.1459
1.2163
1.2828
1.3460
1.1015
1.1882
1.3199
1.4397
1.5502
0.25
0.9575
0.9961
1.0572
1.1150
1.1700
0.9575
1.0328
1.1473
1.2514
1.3475
0.5
0.8583
0.8929
0.9477
0.9995
1.0488
0.8583
0.9258
1.0285
1.1218
1.2079
0.75
0.7847
0.8163
0.8664
0.9138
0.9588
0.7847
0.8464
0.9403
1.0256
1.1043
1
0.7273
0.7566
0.8030
0.8469
0.8887
0.7273
0.7844
0.8715
0.9505
1.0235
Case 2
0
1.0225
1.0652
1.1327
1.1964
1.2569
1.0225
1.1059
1.2323
1.3469
1.4525
0.25
0.8988
0.9363
0.9957
1.0517
1.1049
0.8988
0.9721
1.0833
1.1840
1.2768
0.5
0.8113
0.8452
0.8988
0.9493
0.9973
0.8113
0.8775
0.9778
1.0687
1.1525
0.75
0.7453
0.7763
0.8256
0.8720
0.9161
0.7453
0.8060
0.8982
0.9817
1.0586
1
0.6931
0.7220
0.7677
0.8109
0.8519
0.6931
0.7496
0.8353
0.9129
0.9845
Case 3
0
1.2537
1.3156
1.4127
1.5035
1.5891
1.2537
1.3739
1.5536
1.7146
1.8617
0.25
1.0735
1.1265
1.2096
1.2874
1.3607
1.0735
1.1764
1.3303
1.4681
1.5941
0.5
0.9538
1.0009
1.0747
1.1438
1.2090
0.9538
1.0452
1.1819
1.3044
1.4163
0.75
0.8669
0.9097
0.9768
1.0396
1.0988
0.8669
0.9500
1.0742
1.1855
1.2872
1
0.8001
0.8395
0.9015
0.9595
1.0141
0.8001
0.8767
0.9914
1.0942
1.1880Figure 9
Nondimensional frequencies of FGP plate with differentK1, K2, and β. (a) Case 1; (b) Case 2; and (c) Case 3.
(a)
(b)
(c)


## 6.2. Influence of the Parameters-FGP to Free Vibration of the Plate on EFTIM

Let us consider the effect of materials property to free vibration of the FGP plate. The power-law indexk is changed from 0 to 10, and maximum porosity distributions Ω has the value from 0 to 1. We examine the SSSS FGP plate and fully clamped (CCCC) plate resting on EFTIM. The parameters of EFTIM are given by β=0.5, μF=0.5, K1=100, and K1=10. The first nondimensional frequencies of plate with three cases of porosity distribution is shown in Table 7 and Figure 10.Table 7
Nondimensional frequencies of the FGP plate as a function ofk and Ω.
Ω
SSSS
CCCC
k
k
0
2.5
5
7.5
10
0
2.5
5
7.5
10
Case 1
0
0.6146
0.8460
0.9468
1.0184
1.0706
1.0275
1.2153
1.3432
1.4571
1.5444
0.25
0.6584
0.8830
0.9777
1.0469
1.0984
1.0935
1.2518
1.3694
1.4783
1.5633
0.5
0.7126
0.9238
1.0105
1.0767
1.1273
1.1732
1.2869
1.3930
1.4958
1.5780
0.75
0.7820
0.9677
1.0446
1.1070
1.1564
1.2711
1.3154
1.4102
1.5061
1.5848
1
0.8745
1.0105
1.0776
1.1357
1.1836
1.3924
1.3226
1.4130
1.5021
1.5766
Case 2
0
0.6146
0.8460
0.9468
1.0184
1.0706
1.0275
1.2153
1.3432
1.4571
1.5444
0.25
0.6609
0.8604
0.9563
1.0288
1.0833
1.0977
1.2011
1.3156
1.4273
1.5162
0.5
0.7162
0.8685
0.9569
1.0299
1.0871
1.1707
1.1651
1.2611
1.3675
1.4564
0.75
0.7777
0.8600
0.9357
1.0073
1.0671
1.2179
1.0868
1.1556
1.2496
1.3342
1
0.7852
0.7972
0.8420
0.9009
0.9580
1.0347
0.9106
0.9310
0.9904
1.0547
Case 3
0
0.6146
0.8460
0.9468
1.0184
1.0706
1.0275
1.2153
1.3432
1.4571
1.5444
0.25
0.6609
0.9413
1.0475
1.1196
1.1714
1.0977
1.3661
1.5012
1.6147
1.6994
0.5
0.7162
1.0785
1.1908
1.2621
1.3122
1.1707
1.5836
1.7243
1.8317
1.9084
0.75
0.7777
1.3066
1.4256
1.4917
1.5363
1.2179
1.9297
2.0656
2.1484
2.2018
1
0.7852
1.8589
1.9631
1.9772
1.9807
1.0347
2.4083
2.4138
2.3588
2.3246Figure 10
Nondimensional frequencies vibration of the FGP plate as a function ofk. (a) Case 1; (b) Case 2; and (c) Case 3.
(a)
(b)
(c)As shown in these figures and tables, whenk and Ω change, the values of nondimensional frequency change with no rule. It is understandable because with each case of change in porosity distributions k and Ω, the stiffness and the weight of the plate changes. From Figure 10, in the case of the CCCC plate, nondimensional frequency depending on k and Ω value varies more complex than the case of the SSSS plate. If k and Ω values are same, the frequency of the CCCC plate is larger than that of the SSSS plate. The results are quite reasonable because the SSSS boundary condition inherently offers more flexible boundary conditions than the CCCC boundary condition.


## 7. Conclusions

In this paper, new numerical results of free vibration of the FGP plate resting on EFTIM are studied. We used the ES-MITC3 to establish the fundamental equation of the FGP plate. The computed results obtained by this approach are in excellent agreement with others published. Our work has the following advantages.The novel ES-MITC3 which computes the free vibration of the plate on EF takes into account the mass of foundation.The numerical results obtained by ES-MITC3 show good agreement with the reference solutions and are more accurate than those obtained by the original MITC3.The elastic foundation of Pasternak with three-parameters is developed by adding the featured-index of massβ to accurately describe the actual elastic foundation.The mass of the elastic foundation involved in the vibration of the plate reduces the frequency of vibration, while two parametersK1 and K2 effect the stiffness of the plate.The material parametersk, Ω and the case of porosity distribution effect of vibration of the plate. Numerical results are useful for calculation, design, and testing of material parameters in engineering and technologies.This study suggests some further works on the dynamic response and heat transfer problems of the FGP plate resting on EF using different plate theories.



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*Source: 8278743-2020-04-25.xml*