7. a cell-based smoothed discrete shear gap method (cs-dsg3) based on the c0 type higher order shear...
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7/29/2019 7. a Cell-based Smoothed Discrete Shear Gap Method (CS-DSG3) Based on the C0 Type Higher Order Shear Defor
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A cell-based smoothed discrete shear gap method (CS-DSG3) based
on the C0-type higher-order shear deformation theory for static and free
vibration analyses of functionally graded plates
P. Phung-Van a, T. Nguyen-Thoi a,b,, Loc V. Tran a, H. Nguyen-Xuan a,b
a Division of Computational Mechanics, Ton Duc Thang University, Nguyen Huu Tho St., Tan Phong Ward, Dist.7, Hochiminh City, Viet Namb Department of Mechanics, Facultyof Mathematics & ComputerScience,Universityof Science, Vietnam NationalUniversity HCMC, 227NguyenVan Cu,Dist. 5, HochiminhCity, VietNam
a r t i c l e i n f o
Article history:
Received 27 March 2013
Received in revised form 19 May 2013
Accepted 5 June 2013
Available online xxxx
Keywords:
Smoothed finite element methods
ReissnerMindlin plate
Cell-based smoothed discrete shear gap
technique (CS-DSG3)
Functionally graded plates (FGPs)
Thermo-mechanical loads
The higher-order shear deformation plate
theory (HSDT)
a b s t r a c t
A cell-based smoothed discrete shear gap method (CS-DSG3) based on the first-order shear deformation
theory was recently proposed for static and dynamics analyses of Mindlin plates. In this paper, the CS-
DSG3 is extended to the C0-type high-order shear deformation plate theory for the static and free vibra-
tion analyses of functionally graded plates (FGPs). In the FGPs, the material properties are assumed to
vary through the thickness by a simple power rule of the volume fractions of the constituents. In the sta-
tic analysis, both thermal and mechanical loads are considered and a two-step procedure is performed
includinga step of analyzing the temperature field along the thickness of the plate anda step of analyzing
the behavior of the plate subjected to both thermal and mechanical loads. The accuracy and reliability of
the proposed method is verified by comparing its numerical solutions with those of other available
numerical results.
2013 Elsevier B.V. All rights reserved.
1. Introduction
Being first proposed in Sendai (Japan) in 1984, functionally
graded materials (FGM) are then developed rapidly around the
world [14]. The FGMs are classified as special composites whose
material properties change continuously and smoothly along cer-
tain dimensions of the structure according to a predetermined for-
mula. This makes FGMs have many advantages in engineering
applications because the material properties of FGMs can be al-
tered according to the specific requirements. For the functionally
graded plates (FGPs), the volume fractions are derived from a func-
tion of position through their thickness. The FGPs usually consist of
metal and ceramic which make them both tough and resistant to
high temperatures. This property makes the FGPs become more
suitable to apply in aerospace structures, nuclear plants and
semi-conductor technologies.
With the advantageous features of FGPs in many practical appli-
cations and the limitations of analytical methods [59], many
effective numerical methods have been devised to analyse and
simulate the behavior of FGPs. For static analysis, Praveen [10]
investigated the static thermo-elastic response of FGPs using the fi-
nite element method. Lee [11] presented thermoelastic analysis of
FGPs using element-free kp-Ritz. Liew et al. [1215] studied the
thermal behavior of FGPs with temperature-dependent properties.
Reddy [16,17] presented finite element models for FGPs based on
the third-order shear deformation theory. Javaheri et al. [18] de-
rived equilibrium and stability equations of FGPs under thermal
loads based on a high-order shear deformation plate theory
(HSDT). Shen [19] studied the non-linear bending response of FGPs
subjected to thermalmechanical loads, and Woo and Merguid [20]
carried out the non-linear analysis of FGM plates and shells.
For dynamic and buckling analyses, Huang and Shen [21] pre-
sented the non-linear vibration and dynamic response of FGPs in
thermal environments. Yang and Shen [22] studied the free vibra-
tion and dynamic response of FGPs subjected to impulsive lateral
loads combined with initial in-plane actions in a thermal environ-
ment. Vel and Batra [23] provided a three-dimensional solution for
the free and forced vibration of simply supported FGPs by using
different plate theories. Efraim and Eisenberger [24] analysed the
frequency characteristics of thick annular FGPs of variable thick-
ness. Matsunaga [25,26] used a two-dimensional global higher-or-
der deformation theory to analyse free vibration and buckling of
FGPs. Najafizadeh [27] carried out a thermal buckling analysis of
0927-0256/$ - see front matter 2013 Elsevier B.V. All rights reserved.http://dx.doi.org/10.1016/j.commatsci.2013.06.010
Corresponding author at: Department of Mechanics, Faculty of Mathematics &
Computer Science, University of Science, Vietnam National University HCMC, 227
Nguyen Van Cu, Dist. 5, Hochiminh City, Viet Nam. Tel.: +84 942340411.
E-mail addresses: [email protected], [email protected](T.Nguyen-Thoi).
Computational Materials Science xxx (2013) xxxxxx
Contents lists available at SciVerse ScienceDirect
Computational Materials Science
j o u r n a l h o m e p a g e : w w w . e l s e v i e r . c o m / l o c a t e / c o m m a t s c i
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circular FGPs based on a HSDT. In addition, some finite element
methods [2830] or meshfree approaches [3135] were also de-
vised to solve the FGM structures. So far, based on the update of
authors, there have not yet been the papers presenting numerical
examples using three-node triangular plate elements based on
the C0-type HSDT [36] for analysis of functionally graded plates
(FGPs) subjected to thermo-mechanical loads. This paper hence
will try to fill this gap by using a new three-node triangular plate
element proposed recently.
In the other front of the development of numerical methods, Liu
and Nguyen-Thoi et al. [37] have integrated the strain smoothing
technique into the FEM to create a series of smoothed FEM (S-
FEM) [38] such as a cell/element-based smoothed FEM (CS-FEM)
[39], a node-based smoothed FEM [40], an edge-based smoothed
FEM [41] and a face-based smoothed FEM [42]. Each of these S-
FEM has different properties and has been used to produce desired
solutions for a wide class of benchmark and practical mechanics
problems. Several theoretical aspects of the S-FEM models have
been provided in Refs [43,44]. The S-FEM models have also been
further investigated and applied to various problems such as plates
and shells [4547], piezoelectricity [48], fluidsolid interaction
[49], visco-elastoplasticity [50,51], limit and shakedown analysis
for solids [52], etc.
Among these S-FEM models, the CS-FEM [38,39] shows some
interesting properties in the solid mechanics problems. Extendingthe idea of the CS-FEM to plate structures, Nguyen-Thoi et al. [54]
have recently formulated a cell-based smoothed stabilized discrete
shear gap element (CSDSG3) for static, and free vibration analyses
of isotropic Mindlin plates by incorporating the CS-FEM with the
original DSG3 element [53]. In the CS-DSG3, each 3-node triangular
element will be divided into three sub-triangles, and in each sub-
triangle, the stabilized DSG3 is used to compute the strains. Then
the strain smoothing technique on whole the triangular element
is used to smooth the strains on these three sub-triangles. The
numerical results showed that the CSDSG3 is free of shear locking
and shows four superior properties such as: (1) be a strong
competitor to many existing three-node triangular plate elements
in the static analysis; (2) can give high accurate solutions for
problems with skew geometries in the static analysis; (3) can givehigh accurate solutions in free vibration analysis; (4) can provide
accurately the values of high frequencies of plates by using only
coarse meshes.
Due to these advantages, in this paper, the CS-DSG3 is further
extended to the C0-HSDT [36] for the static and free vibration anal-
yses of FGPs. In the FGPs, the material properties are assumed to
vary through the thickness by a simple power rule of the volume
fractions of the constituents. In the static analysis, both thermal
and mechanical loads are considered and a two-step procedure is
performed including a step of analyzing the temperature field
along the thickness of the plate and a step of analyzing the behav-
ior of the plate subjected to both thermal and mechanical loads.
The accuracy and reliability of the proposed method is verified
by comparing its numerical solutions with those of other availablenumerical results.
2. Functionally graded plates and thermal distribution
A functionally graded plate made of ceramic and metal is shown
in Fig. 1. The material property is assumed to be graded through
the thickness by the power law distribution expressed as
Pz Pc PmVc Pm 1
Vc 1
2
z
t
nnP 0 2
where subscripts m and c refer to the metal and ceramic constitu-ents, respectively; P represents the effective material properties,
including the Youngs modulus E, density q, Poissons ratio m, ther-mal conductivity k and thermal expansion a; Pc and Pm denote theproperties of the ceramic and metal, respectively; Vc is the volume
fraction of the ceramic; z is the thickness coordinate of plate and
varies from t/2 to t/2; n is the volume fraction exponent. The vol-
ume fraction through the thickness for different volume fraction
exponents n is illustrated in Fig. 2.
In the thermal analysis of the FGPs, it is assumed that the tem-
perature distributions of the ceramic (top) surface and metal (bot-
tom) surface are the constant temperature, and the temperature
varies only through the thickness direction. The temperature vari-
ation along the thickness is attained by solving the one-dimen-
sional steady state heat conduction equation, which is given by
d
dzkz
dT
dz
0 3
with boundary conditions
T Ttop at z t=2
T Tbot at z t=24
Fig. 1. Functionally graded plate.
Fig. 2. Volume fraction Vc versus the thickness.
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7/29/2019 7. a Cell-based Smoothed Discrete Shear Gap Method (CS-DSG3) Based on the C0 Type Higher Order Shear Defor
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where Ttop and Tbot are the top and bottom surface temperatures,
respectively; and k(z) represents the thermal conductivity coeffi-cient at z and is also defined similarly as Eq. (1).
Fig. 3 illustrates the temperature distributions through the
thickness of a FGP made by the Aluminum-Ziconia (Al/ZnO2-1)
for the various value of n, where the top and bottom surfaces are
hold at 300 C and 20 C, respectively. It is evident that tempera-
ture in the FGPs constituted by both ceramic and metal
components.
3. C0type higher-order shear deformation theory and
weakform for FGM Mindlin plates
3.1. C0type HSDT for FGM Mindlin plates
According to C0-type HSDT model [36], the displacements of an
arbitrary point in the plate are expressed by
ux;y;z u0 z4z3
3t2
bx
4z3
3t2/x
vx;y;z v0 z4z3
3t2
by
4z3
3t2/y h=2 6 z6 h=2
wx;y w
5
where tis thickness of plate, u0 = {u0 v0}T and w0 are the membrane
displacements and the transverse displacement of the mid-plane;
and b = {bx by}T are the rotations around y-axis and x-axis, respec-
tively, with the positive directions defined as shown in Fig. 4. Eq.
(5) is developed from Reddys higher-order theory [55] in which,derivative of deflection is replaced by warping function / = {/x/y}
T. Thus, the generalized displacement vector with 5 degrees of
freedom for C1 continuity element can be transformed into the vec-
tor with 7 degrees of freedom for C0 continuity element as
u u0 v0 w0 bx by /x /y T
.
For a FGM Mindlin plate, the strains in plain is expressed by the
following equation
exx eyy cxyT
e0 zj1 z3j2 6
where the membrane strains are obtained from the symmetric dis-
placement gradient
e0
@u0@x
@v0@y
@u0@y
@v0@x
8>>>:9>>=>>; rs u0 7
and the bending strains are given by
j1 12 frb rbTg
j2 k6 fr/ r/T rb rbTg
with k 4
t28
and the transverse shear strains are basically defined as
cxz cyzT es z
2js 9
with
es rw b
js cb /10
where r = [@/@x @/@y]T is the gradient operator.Under the temperature condition, the thermal strain of plate is
expressed as
eth azDTz 1 1 0 11
where DT is the temperature change from a stress-free state.
From Hooks law, the stress in plane is given by
r Ee0 zj1 z3j2 eth 12
and the shear stress is expressed as
s Ges z2js 13
where the material matrices are given by
E Ez
1 mz2
1 mz 0
mz 1 0
0 0 1 mz=2
264375 14
G Ez
21 mz
1 0
0 1
!15
in which E(z) is Youngs modulus; m(z) is the Poissons ratio varyingaccording to the power law as in Eq. (1).
Note that the transverse shear strains in Eq. (9) and the shearstress in Eq. (13) are represented parabolically, hence the shear
correction factor in the C0-type HSDT formulation [36] is not nec-
essary as shown in Eq. (15).
Fig. 3. Temperature distribution through the thickness of the Al/ZnO2-1 FGM plate.
Fig. 4. Positive directions of displacement u, v, w and two rotations bx, by in Mindlin plate.
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3.2. Weakform equation for FGM Mindlin plates
The standard Galerkin weakform of the static equilibrium equa-
tions [56] for the FGM Mindlin plate subjected to thermo-mechan-
ical loads can be written as
ZXdeTp D
epdX
ZXdcTDScdX
ZXdwpdX
ZXdeTrthdX 16
in which p is the transverse loading per unit area; ep, c and rth areexpressed by
ep e0 j1 j2f gT; c es jsf g
T; rth Nth Mth Pth
T
17
and material constant matrices D and DS have the forms of
D
A B E
B D F
E F H
264375; DS AS BS
BS
DS
" #; 18
where
Aij; Bij; Dij; Eij; Fij; Hij Zh=2
h=2
1;z;z2;z3;z4;z6Qijdz i;j 1; 2; 6
Asij; B
sij; D
sij
Zh=2h=2
1;z2;z4Qijdz i;j 4; 5
19
and Nth, Mth, Pth are thermal force and moment resultants and com-
puted by
Nth 1 1 0 T
Zt=2t=2
Ez
1 mzkzDTdz
Mth 1 1 0 T
Zt=2t=2
Ez
1 mzkzzDTdz
Pth 1 1 0 T
Zt=2
t=2
Ez
1 mzkzz3DTdz
20
4. FEM formulation the FGM ReissnerMindlin plate
Now, discretize the bounded domain X into Ne finite elements
such that X SNe
e1Xe andXi \Xj = ;, ij, then the finite element
solution uh u0 v0 w0 bx by /x /y T
of a displacement
model for the FGM Mindlin plate is expressed as
uh
XNn
i1
Nix 0 0 0 0 0 0
0 Nix 0 0 0 0 0
0 0 Nix 0 0 0 0
0 0 0 Nix 0 0 0
0 0 0 0 Nix 0 0
0 0 0 0 0 Nix 0
0 0 0 0 0 0 Nix
2666666666664
3777777777775
di Nd
21
where Nn is the total number of nodes of problem domain discret-
ized; Ni(x) is shape function at the ith node;
di ui vi wi bxi byi /xi /yi T
is the displacement vector
of the nodal degrees of freedom of uh associated to the ith node,
respectively.
Substituting Eq. (21) into Eqs. (7), (8), (10), then the strains in
Eq. (17) can be expressed in the general forms of nodal displace-
ments as
eh ep cT X
Nn
i1
B
id
i22
where eh is the compatible strain and Bi is the generalized straindisplacement matrix expressed by
Bi B
mi
TB
b1i
TB
b2i
TB
s0i
TB
s1i
T !23
in which
Bmi
Ni;x 0 0 0 0 0 0
0 Ni;y 0 0 0 0 0
Ni;y Ni;x 0 0 0 0 0
264 375;B
b1
i
0 0 0 Ni;x 0 0 0
0 0 0 0 Ni;y 0 0
0 0 0 Ni;y Ni;x 0 0
264375;
Bs0i
0 0 Ni;x Ni 0 0 0
0 0 Ni;y 0 Ni 0 0
!;
Bs1i c
0 0 0 Ni 0 Ni 0
0 0 0 0 Ni 0 Ni
!;
24
Bb2
i
c
3
0 0 0 Ni;x 0 Ni;x 0
0 0 0 0 Ni;y 0 Ni;y0 0 0 Ni;y Ni;x Ni;y Ni;x
264 375where Ni,x and Ni,y are the derivatives of the shape functions in x-
direction and y-direction, respectively.
The discretized system of equations of FGM Mindlin plate using
the FEM for static analysis then can be expressed as
Kd F 25
where F is the load vector computed by
F
ZX
pN BmI T
Nth Bb1I
TMth B
b2I
TPth
!dX f
b26
in which fb is the remaining part of F subjected to prescribed
boundary loads; and K is the global stiffness matrix assembled from
the element stiffness matrices Ke as
K XNee1
Ke XNee1
ZXe
BTi D
BjdX
ZXe
STi D
s SjdX
|fflfflfflfflfflfflfflfflfflfflfflfflfflfflfflfflfflfflfflfflfflfflfflfflfflfflfflfflfflfflffl{zfflfflfflfflfflfflfflfflfflfflfflfflfflfflfflfflfflfflfflfflfflfflfflfflfflfflfflfflfflfflffl}
Ke
27
where Bi and Si are defined by
Bi Bmi
TB
b1
i
TB
b2
i
T !28
Si Bs0i
TB
s1i
Th i29
For free vibration analysis, we have
K x2Md 0 30
where x is the natural frequency and M is the global mass matrixcomputed by
M
ZX
NT
mNTdX 31
in which m is the matrix defined as
m
I1 0 0 I2 0c3
I4 0
I1 0 0 I2 0c3
I4
I1 0 0 0 0
I3 0c3
I5 0
I3 0c3
I5
c3
2I7 0
sym c3 2I7
26666666666664
37777777777775
32
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with
I1; I2; I3; I4; I5; I7
Zh=2h=2
qz1;z;z2;z3;z4;z6dz 33
5. Formulation of a cell-based smoothed discreate shear gap
(CS-DSG3) method based on the C0-type HSDT for FGM Mindlin
plates
5.1. Formulation of the DSG3 based on the C0 -type HSDT
In the original DSG3 [53], the problem domain is discretized
into Nn nodes and Ne three-node triangular elements. The first-or-
der shear deformation plate theory (FSDT) is used for Mindlin
plates behavior and each node only has 3 degrees of freedom
di wi bxi byi T
. The formulation of the DSG3 is based on the
concept shear gap of displacements along the edges of the ele-
ments. In the DSG3, the shear strain is linear interpolated from
the shear gaps of displacement by using the standard element
shape functions. The DSG3 element is shear-locking-free and has
several superior properties as presented in Ref [53]. In the
present paper, the DSG3 is extended to the C0-type HSDT formula-
tion [36] and each node will have 7 degrees of freedom
di ui vi wi bxi byi /xi /yi T
as mentioned in Section 4.
Using a mesh of 3-node triangular elements, the approximation
ue ue ve we bex be
y /e
x /e
y
Tfor a 3-node triangular
element Xe for Mindlin FGM plates can be written as
uex
X3i1
Nei x 0 0 0 0 0 0
0 Nei x 0 0 0 0 0
0 0 Nei x 0 0 0 0
0 0 0 Nei x 0 0 0
0 0 0 0 Nei x 0 0
0 0 0 0 0 Nei x 0
0 0 0 0 0 0 Nei x
2666666666664
3777777777775
|fflfflfflfflfflfflfflfflfflffl fflfflfflfflfflfflfflfflfflfflfflffl fflfflfflfflfflfflfflfflfflffl fflfflfflfflfflfflfflfflfflfflfflffl fflfflfflfflfflfflfflfflfflffl fflffl{zfflfflfflfflfflfflfflfflfflfflffl fflfflfflfflfflfflfflfflfflfflfflffl fflfflfflfflfflfflfflfflfflfflffl fflfflfflfflfflfflfflfflfflfflfflffl fflfflfflfflfflfflfflfflfflffl}Nei x
dei
X3i1
Nei xd
ei
34
where de
i uei v
ei w
ei b
exi b
eyi /
exi /
eyi
Tare the nodal degrees
of freedom of ue associated to ith node and Nei x
diag Nei x; Nei x; N
ei x; N
ei x; N
ei x; N
ei x; N
ei x
, i = 1, 2, 3, in
which Nei x are the linear shape functions of the 3-node triangular
elementXe.
Substituting Eq. (34) into Eqs. (23) and (24), we obtained the
membrane strain ee0, the curvatures of the deflection je1; j
e2 and
the shear strains ch [53] of the element in the forms of
ee0 Bm
de
35
je1 Bb1 d
e; je2 B
b2 de
36
ce ee
s
jes& ' Bs0
Bs1
& 'de 37where d
e d
e1 d
e2 d
e3
Tis the nodal displacement vector of
element; andBm, Bb1 ; Bb2 ; Bs0 , Bs1 arethe gradient matricesexpressed
by
Bm
1
2Ae
b c 0 0 0 0 0 0
0 d a 0 0 0 0 0
d a b c 0 0 0 0 0|fflfflfflfflfflfflfflfflfflfflfflfflfflfflfflfflfflfflfflfflfflfflfflfflfflfflfflfflffl{zfflfflfflfflfflfflfflfflfflfflfflfflfflfflffl fflfflfflfflfflfflfflfflfflfflfflfflfflffl}B
m1
c 0 0 0 0 0 0
0 d 0 0 0 0 0
d c 0 0 0 0 0|fflfflfflfflfflfflfflfflfflfflfflfflfflfflfflfflfflfflfflfflfflfflfflfflffl{zfflfflfflfflfflfflfflfflfflfflfflfflfflfflfflfflfflfflfflfflfflfflfflfflffl}B
m2
b 0 0 0 0 0 0
0 a 0 0 0 0 0
a b 0 0 0 0 0|fflfflfflfflfflfflfflfflfflfflfflfflfflfflfflfflfflfflfflfflfflfflfflfflffl{zfflfflfflfflfflfflfflfflfflfflfflfflfflfflfflfflfflfflfflfflfflfflfflfflffl}B
m3
266664377775 12Ae Bm1 Bm2 Bm3 38
Bb1
1
2Ae
0 0 0 b c 0 0 00 0 0 0 d a 0 0
0 0 0 d a b c 0 0|fflfflfflfflfflfflfflfflfflfflfflfflfflfflfflfflfflfflfflfflfflfflfflfflfflfflfflfflffl{zfflfflfflfflfflfflfflfflfflfflfflfflfflfflfflffl fflfflfflfflfflfflfflfflfflfflfflfflffl}B
b11
0 0 0 c 0 0 00 0 0 0 d00
0 0 0 d c00|fflfflfflfflfflfflfflfflfflfflfflfflfflfflfflfflfflfflfflfflfflfflfflfflfflfflffl{zfflfflfflfflfflfflfflfflfflfflfflfflfflfflffl fflfflfflfflfflfflfflfflfflfflfflffl}B
b12
0 0 0 b 0 0 00 0 0 0 a00
0 0 0 a b00|fflfflfflfflfflfflfflfflfflfflfflfflfflfflfflfflfflfflfflfflfflfflfflfflfflfflffl{zfflfflfflfflfflfflfflfflfflfflfflfflfflfflfflfflfflfflfflffl fflfflfflfflfflfflffl}B
b13
266664377775 12Ae Bb11 Bb12 Bb13
h i39
Bb2
1
2Ae
0 0 0 b c 0 b c 0
0 0 0 0 d a 0 d a
0 0 0 d a b c d a b c|fflfflfflfflfflfflfflfflfflfflfflfflfflfflfflfflfflfflfflfflfflfflfflfflfflfflfflfflfflfflfflfflfflfflffl fflfflffl{zfflfflfflfflfflfflfflfflfflfflfflfflfflfflfflfflfflfflfflfflfflfflfflfflfflfflfflfflfflfflfflfflfflfflfflfflfflffl}B
b21
0 0 0 c 0 c 0
0 0 0 0 d 0 d
0 0 0 d c d c|fflfflfflfflfflfflfflfflfflfflfflfflfflfflfflfflfflfflfflfflfflfflfflfflfflfflfflffl{zfflfflfflfflfflfflfflfflfflfflfflfflfflfflfflfflfflfflfflfflfflfflfflfflfflffl fflffl}B
b22
0 0 0 b 0 b 0
0 0 0 0 a 0 a
0 0 0 a b a b|fflfflfflfflfflfflfflfflfflfflfflfflfflfflfflfflfflfflfflfflfflfflfflfflfflfflfflffl{zfflfflfflfflfflfflfflfflfflfflfflfflfflfflfflfflfflfflfflfflfflfflfflfflfflfflfflffl}B
b23
266664377775 12Ae Bb21 Bb22 Bb23
h i
40
Bs0 12Ae
0 0 b c Ae 0 0 0
0 0 d a 0 Ae 0 0|fflfflfflfflfflfflfflfflfflfflfflfflfflfflfflfflfflfflfflfflfflfflfflfflfflfflffl{zfflfflfflfflfflfflfflfflfflfflfflfflfflfflfflfflfflfflfflfflfflfflfflfflfflfflffl}B
s01
0 0 c ac=2 bc=2 0 0
0 0 d ad=2 bd=2 0 0|fflfflfflfflfflfflfflfflfflfflfflfflfflfflfflfflfflfflfflfflfflfflfflfflfflfflfflfflfflfflfflfflfflffl{zfflfflfflfflfflfflfflfflfflfflfflfflfflfflfflfflfflfflfflfflfflfflffl fflfflfflfflfflfflfflfflfflfflffl}B
s02
0 0 b bd=2 bc=2 0 0
0 0 a ad=2 ac=2 0 0|fflfflfflfflfflfflfflfflfflfflfflfflfflfflfflfflfflfflfflfflfflfflfflfflfflfflfflfflfflfflfflfflfflffl{zfflfflfflfflfflfflfflfflfflfflfflfflfflfflfflfflfflfflfflfflfflfflfflfflfflfflfflfflfflfflfflfflfflffl}B
s03
264 375 12Ae Bs01 Bs02 Bs03 41
Bs1
1
2Ae
0 0 0 1 0 1 0
0 0 0 0 1 0 1
|fflfflfflfflfflfflfflfflfflfflfflfflfflfflfflfflfflfflfflfflffl{zfflfflfflfflfflfflfflfflfflfflfflfflfflfflfflfflfflfflfflfflffl}B
s11
0 0 0 1 0 1 0
0 0 0 0 1 0 1|fflfflfflfflfflfflfflfflfflfflfflfflfflfflfflfflfflfflfflfflffl{zfflfflfflfflfflfflfflfflfflfflfflfflfflfflfflfflfflfflfflfflffl}B
s12
0 0 0 1 0 1 0
0 0 0 0 1 0 1|fflfflfflfflfflfflfflfflfflfflfflfflfflfflfflfflfflfflfflfflffl{zfflfflfflfflfflfflfflfflfflfflfflfflfflfflfflfflfflfflfflfflffl}B
s13
266664377775 12Ae Bs11 Bs12 Bs13 42
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in which a, b, c, d arecomputed from the coordinates of three nodes of
theelement as shown in Fig. 5, andAe is thearea of thetriangular ele-
mentXe.
Substituting Eqs. (38)(42) into Eq. (27), the global stiffness ma-
trix now becomes
KDSG3
XNe
e1
KDSG3e 43
where KDSG3e is the element stiffness matrix of the DSG3 element,
and is computed by
KDSG3e
ZXe
BTi D
BjdX
ZXe
STi D
s SjdX B
Ti D
BjAe S
Ti D
s SjAe
44
From Eqs. (38)(42) and (44), it is seen that the element stiff-
ness matrix in the DSG3 depends on the sequence of node numbers
of elements, and hence the solution of DSG3 is influenced when the
sequence of node numbers of elements changes, especially for the
coarse and distorted meshes. The CS-DSG3 is hence proposed to
overcome this drawback and also to improve the accuracy as well
as the stability of the DSG3.
5.2. Formulation of CS-DSG3 based on the C0-type HSDT
In the CS-DSG3 [54] using the C0-type HSDT formulation [36],
the domain discretization is the same as that of the DSG3 using
Nn nodes and Ne triangular elements. However in the formulation
of the CS-DSG3, each triangular element Xe is further divided into
three sub-trianglesD1,D2 andD3 by connecting the central point O
of the element to three field nodes as shown in Fig. 6.
In the CS-DSG3, we assume that the displacement vector deO at
the central point O is the simple average of three displacement vec-
tors de1; d
e2 and d
e3 of three field nodes
deO 13de1 d
e2 d
e3
45On the first sub-triangleD1(triangle O-1-2), a linear approxima-
tion ueD1 ueD1 veD1 weD1 beD1x beD1
y /eD1
x /eD1
y
h iTis con-
structed by
ueD1 NeD11 deO N
eD12 d
e1 N
eD13 d
e2 N
eD1 deD1 46
where deD1 d
eO d
e1 d
e2
Tis the vector of nodal degrees of free-
dom of the sub-triangle D1 and NeD1 NeD11 N
eD12 N
eD13
contains
the linear shape functions created by the sub-triangle D1.
Using the DSG3 formulation based on the C0-type HSDT pre-
sented in Section 5.1 for the sub-triangle D1, the membrane strain
eD10 , the bending strains jD11 ; jD12 and the shear strains eD1s ; jD1s inthe sub-triangle D1 are then obtained, respectively, by
eD10 bmD11 b
mD12 b
mD13
|fflfflfflfflfflfflfflfflfflfflfflfflfflfflfflfflfflffl{zfflfflfflfflfflfflfflfflfflfflfflfflfflfflfflfflfflffl}bmD1
deO
de1
de2
26643775 bmD1 deD1 47
jeD11 bb1D11 b
b1D12 b
b1D13
h i|fflfflfflfflfflfflfflfflfflfflfflfflfflfflfflfflfflfflfflffl{zfflfflfflfflfflfflfflfflfflfflfflfflfflfflfflfflfflfflfflffl}
bb1D1
deO
de1
de2
264375 bb1D1 deD1 ;
jeD12 bb2D11 b
b2D12 b
b2D13h i|fflfflfflfflfflfflfflfflfflfflfflfflfflfflfflfflfflfflfflffl{zfflfflfflfflfflfflfflfflfflfflfflfflfflfflfflfflfflfflfflffl}bb2D1
deO
de1
d
e2
264
375
bb2D1 d
eD1
48
eeD1s bs0D11 b
s0D12 b
s0D13
|fflfflfflfflfflfflfflfflfflfflfflfflfflfflfflfflfflfflffl{zfflfflfflfflfflfflfflfflfflfflfflfflfflfflfflfflfflfflffl}b
s0D1
deO
de1
de2
264375 bs0D1 deD1 ;
jeD1s bs1D11 b
s1D12 b
s1D13
|fflfflfflfflfflfflfflfflfflfflfflfflfflfflfflfflfflfflffl{zfflfflfflfflfflfflfflfflfflfflfflfflfflfflfflfflfflfflffl}b
s1D1
deO
de1
de2
264375 bs1D1 deD1
49
where bmD1 ; b
b1D1 ; bb2D1 ; b
s0D1 and bs1D1 are, respectively, com-
puted similarly as the matrices Bm; Bb1 ; Bb2 ; Bs0 and Bs1 of the
DSG3 in Eqs. (38)(42) but with two following changes: 1) the coor-
dinates of three nodexi xi yi T; i 1; 2; 3 are replaced byxO, x1
andx2, respectively; and 2) the areaAe is replaced by the areaAD1 ofsub-triangle D1.
Substituting deO in Eq. (45) into Eqs. (47)(49), and then rear-
ranging we obtain
eD10 13
bmD11 b
mD12
13
bmD11 b
mD13
13
bmD11
h i|fflfflfflfflfflfflfflfflfflfflfflfflfflfflfflfflfflfflfflfflfflfflfflfflfflfflfflfflfflfflfflfflfflffl fflfflfflffl{zfflfflfflfflfflfflfflfflfflfflfflfflfflfflfflfflfflfflfflfflfflfflfflfflfflfflfflfflfflfflfflfflfflfflfflfflfflffl}
BmD1
de1
de2
de3
264375 BmD1 de
50
jD11 13
bb1D11 b
b1D12
13
bb1D11 b
b1D13
13
bb1D11
h i|fflfflfflfflfflfflfflfflfflfflfflfflfflfflfflfflfflfflfflfflfflfflfflfflfflfflfflfflfflfflfflfflfflfflfflfflfflfflffl fflffl{zfflfflfflfflfflfflfflfflfflfflfflfflfflfflfflfflfflfflfflfflfflfflfflfflfflfflfflfflfflfflfflfflfflfflffl fflfflfflfflfflffl}Bb1D1
de1
de2
de3
264
375
Bb1D1 de
jD12 13
bb2D11 b
b2D12
13
bb2D11 b
b2D13
13
bb2D11
h i|fflfflfflfflfflfflfflfflfflfflfflfflfflfflfflfflfflfflfflfflfflfflfflfflfflfflfflfflfflfflfflfflfflfflfflfflfflfflffl fflffl{zfflfflfflfflfflfflfflfflfflfflfflfflfflfflfflfflfflfflfflfflfflfflfflfflfflfflfflfflfflfflfflfflfflfflffl fflfflfflfflfflffl}
Bb2D1
de1
de2
de3
264 375 Bb2D1 de51
eD1s 13
bs0D11 b
s0D12
13
bs0D11 b
s0D14
13
bs0D11
h i|fflfflfflfflfflfflfflfflfflfflfflfflfflfflfflfflfflfflfflfflfflfflfflfflfflfflfflfflfflfflfflfflfflffl fflfflfflfflffl{zfflfflfflfflfflfflfflfflfflfflfflfflfflfflfflfflfflfflfflfflfflfflfflfflfflfflfflfflfflffl fflfflfflfflfflfflfflfflffl}
Bs0D1
de1
de2
de3
264375 Bs0D1 de
jD1s 13
bs1D11 b
s1D12
13
bs1D11 b
s1D13
13
bs1D11
h i
|fflfflfflfflfflfflfflfflfflfflfflfflfflfflfflfflfflfflfflfflfflfflfflfflfflfflfflfflfflfflfflfflfflfflfflfflfflfflffl{zfflfflfflfflfflfflfflfflfflfflfflfflfflfflfflfflfflfflfflfflfflfflfflfflfflfflfflfflfflfflfflfflfflfflfflfflfflfflffl}Bs1D1
de1
de2
de3
264375 Bs1D1 de
52
Fig. 5. Three-node triangular element and local coordinates in the DSG3.
Fig. 6. Three sub-triangles (D1, D2 and D3) created from the triangle 1-2-3 in theCS-DSG3 by connecting the central point O with three field nodes 1, 2 and 3.
6 P. Phung-Van et al. / Computational Materials Science xxx (2013) xxxxxx
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Similarly, by using cyclic permutation, we easily obtain the bending
and shear strains eDj0 ; j
Dj1 ; j
Dj2 ; e
Djs ; j
Djs and matrices
BmDj ; Bb1Dj ; Bb2Dj ; Bs0Dj ; Bs1Dj ; j 2; 3, for the second sub-triangle
D2 (triangle O-2-3) and third sub-triangle D3 (triangle O-3-1),
respectively.
Now, applying the cell-based strain smoothing operation in the
CS-FEM [38,39], the membrane strain eDj0 , bending strains j
Dj1 ; j
Dj2
and shear strainse
Dj
s ; j
Dj
s ;j
1;
2;
3 are, respectively, used to cre-
ate a smoothed membrane strain ~ee0, smoothed bending strains~je1; ~j
e2 and smoothed shear strains ~e
es ; ~j
es on the triangular element
Xe, such as:
~ee0 ZXe
eh0UexdX X3j1
eDj0
ZDj
UexdX 53
~je1 ZXe
jh1UexdX X3j1
jDj1
ZDj
UexdX;
~je2 ZXe
jh2UexdX X3j1
jDj2
ZDj
UexdX 54
~ees ZXeebsUexdX X
3
j1 ZDjeDjs UexdX;
~jes ZXe
jhsUexdX X3j1
ZDj
jDjs UexdX 55
where Ue(x) is a given smoothing function that satisfies the unity
propertyRXeUexdX 1. Using the following Heaviside constant
smoothing function
Uex 1=Ae x 2 Xe
0 x R Xe
&56
where Ae is the area of the triangular element, the smoothed mem-
brane strain ~ee0, the smoothed bending strains ~je1; ~j
e2 and the
smoothed shear strains ~ees ; ~jes in Eqs. (53)(55) become
~ee0 1
Ae X3
j1ADje
Dj0 57
~je1 1
Ae
X3j1
ADjjDj1 ;
~je2 1
Ae
X3j1
ADjjDj2 58
~ees 1
Ae
X3j1
ADjeDjs ; ~j
es
1
Ae
X3j1
ADjjDjs 59
Substituting eDj0L; j
Dj1 ; j
Dj2 ; e
Djs , and j
Djs ; j 1; 2; 3, into Eqs. (57)
(59), the smoothed bending strain ~ee0, the smoothed bending strains~je1; ~j
e2 and the smoothed shear strains ~e
es ; ~j
es are expressed by
~ee0 eBmde; ~je1 eBb1 de; ~je2 eBb2 de; ~ees eBs0 de;
~jes eBs1 d
e60
where eBm; eBb1 ; eBb2 ; eBs0 and eBs1 are the smoothed bending andshear strain gradient matrices given by
eBm 1Ae
X3j1
ADj BmDj ; eBb1 1
Ae
X3j1
ADj Bb1Dj ; eBb2 1
Ae
X3j1
ADj Bb2Dj
eBs0 1Ae
X3j1
ADj Bs0Dj ; eBs1 1
Ae
X3j1
ADj Bs1Dj
61
Therefore the global stiffness matrix of the CS-DSG3 are assembledby
eK XNee1
eKe 62where eKe is the element smoothed stiffness matrix for FGMMindlinplates given by
~Ke
ZXe
eBTi DeBjdX ZXe
~STi Ds~SjdX eBTi DeBjAe ~STi Ds~SjAe 63
in which
eBi
eB
mi
TeB
b1
i
TeB
b2
i
T !;
eSi
eB
s0i
TeB
s1i
T !64
From Eqs. (61) and (63), it is clearly seen that the element stiff-ness matrix in the CS-DSG3 does not depend on the sequence of
node numbers, and hence the solution of CS-DSG3 is unchanged
when the sequence of node numbers changes. In addition, due to
using the cell-based strain smoothing technique in the CS-FEM
[38,39], the CS-DSG3 can help to improve the accuracy as well as
the stability of the DSG3 [54].
6. Numerical results
In this section, various numerical examples are performed to
show the accuracy and stability of the CS-DSG3 compared to re-
sults to several published ones in the literature. The ceramicmetal
FGM plates are used, and their material properties, including
Youngs modulus, Poissons ratio, thermal expansion coefficient,conductivity and density of pure plates are given in Table 1.
6.1. Temperature field distribution in the FGPs subjected to only
surface temperatures
A functionally graded plate shown in Fig. 1 is made of
Aluminum-Ziconia (Al/ZnO2-2). The thermal analysis is conducted
by imposing constant surface temperatures at the Aluminum
(metal) at 20 C and Ziconia (ceramic) surface at 300 C. The varia-
tion of temperature varies only through the thickness direction.
The distribution of temperature through the thickness is attained
by solving the one-dimensional steady state heat conduction
equation, which is shown in Eq. (3). In this analysis, the standard
Table 1
Material properties of FGM components.
Properties Aluminum Alumina
(Al2O3)
Zirconia (ZrO2-
1)
Zirconia (ZrO2-
2)
E (GPa) 70 380 200 151
m 0.3 0.3 0.3 0.3k (W/mK) 204 10.4 2.09 2.09
a (106/C)
23 7.2 10 10
q (kg/m3) 2707 3800 5700 3000Fig. 7. Two square plate models: (a) clamped plate; (b) simply supported plate.
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Fig. 8. Four lowest frequencies of square plates by the CS-DSG3 corresponding to different values of volume fraction exponents: (a) n = 0; (b) n = 0.5; (c) n = 1; (d) n = 2.
Fig. 9. Effect of volume fraction exponent n to four lowest frequencies of square FGM plates: (a) Mode 1; (b) Mode 2; (c) Mode 3; (d) Mode 4.
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one-dimensional finite element method is used.
Fig. 3 illustrates the temperature distributions through the
thickness Aluminum-Ziconia (Al/ZnO2-2) FGM plate for the various
value of volume fraction exponent n. With the results of the tem-
perature through the thickness, the thermal force and moment
resultants Nth, Pth and Mth can be computed according to Eq. (20).
6.2. Free vibration analysis of FGPs
In this section, we investigate the accuracy and efficiency of theCS-DSG3 element for analyzing natural frequencies of plates. The
plate may have simply (S) supported or clamped (C) edges. The
symbol, CCCC or SSSS, for instance, represents clamped or simply
supportted boundary conditions along the four edges of the
rectangular plate, respectively. A non-dimensional frequency
parameter - is often used to stand for the frequencies. The numer-ical results by the CS-DSG3 are then compared to analytical solu-
tions and other available numerical results in the literature.
6.2.1. Square FGM plates
We now consider two square Al/Al203 plates of length L = 10and thickness t= 1 with two boundary conditions, CCCC and SSSS,
Fig. 10. Shape of six lowest eigenmodes of a clamped square FGM plate by the CS-DSG3: (a) Mode 1; (b) Mode 2; (c) Mode 3; (d) Mode 4; (e) Mode 5; (f) Mode 6.
Fig. 11. (a) a skew plate model; (b) a discretization of skew plate using triangular elements.
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Fig. 12. Four lowest frequencies of the Al/ZrO2-2 skew plates with h = 15: (a) n = 0; (b) n = 0.5; (c) n = 1; (d) n = 3.
Fig. 13. Four lowest frequencies of skew plates with h = 45: (a) n = 0; (b) n = 0.5; (c) n = 1; (d) n = 3.
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as shown in Fig. 7a and b. A regular discretization using 144 3-node
triangular elements and a non-dimensional frequency parameter
- xL2=tffiffiffiffiffiffiffiffiffiffiffiffiqc=Ec
pare used. Fig. 8 shows the four first non-dimen-
sional frequencies of the FGM plate by the CS-DSG3 corresponding
to different values of volume fraction exponents, n = 0, n = 0.5, n = 1
and n = 2. It is seen that the present results match well with those
ofkp-Ritz [33].
Next, the effect of volume fraction exponent n to the non-
dimensional frequency of Al/Al203 plate is investigated and the re-
sults are shown in Fig. 9. Again, it is seen that the present results
match well with those by kp-Ritz [33]. Fig. 10 plots the shape of
six lowest eigenmodes of the clamped square FGM plates by the
CS-DSG3. It is observed that the shapes of eigenmodes express cor-rectly the real physical modes of the plate.
Fig. 14. Shape of six lowest eigenmodes of a clamped skew plate by the CS-DSG3: (a) Mode 1; (b) Mode 2; (c) Mode 3; (d) Mode 4; (e) Mode 5; (f) Mode 6.
Table 2
Non-dimensional center deflection w 100wcEmt3=121 m2qL4 of a Al/ZrO2-1
plate (L/t= 5) subjected to a uniform load.
Boundary condition Method n
0 0.5 1 2
CCCC DSG3 0.0731 0.0970 0.1137 0.1334
CS-DSG3 0.0732 0.0972 0.1139 0.1336
MLPG 0.0718 0.1073 0.1253 0.1444
kp-Ritz 0.0774 0.1034 0.1207 0.1404
SSSS DSG3 0.1768 0.2336 0.2679 0.3051
CS-DSG3 0.1774 0.2343 0.2688 0.3060
MLPG 0.1671 0.2505 0.2505 0.3280
kp-Ritz 0.1722 0.2403 0.2403 0.3221
Fig. 15. Non-dimensional central deflection w 100wcEmt3=121 m2qL4
of asimply supported FGM plate subjected to a uniform load by the CS-DSG3.
Fig. 16. Non-dimensional central deflection w 100wcEmt3=121 m2qL4 of a
clamped FGM plate subjected to a uniform load by the CS-DSG3.
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6.2.2. Skew FGM plates
We now consider a Al/ZrO2-2 skew plate with various skew an-
gles h as shown in Fig. 11a. Two boundary conditions (SSSS and
CCCC) are studied, and the plate is discretized into 144 three-node
triangular elements as shown in Fig. 11b.
Figs. 12 and 13 show the first four non-dimensional frequencies
of the Al/ZrO2-2 skew plate with skew angles h = 15 and h = 45 by
the CS-DSG3, corresponding four different values of volume frac-
tion exponents, n = 0, 0.5, 1.0 and 3.0. It is seen that the results
by the CS-DSG3 agree well with those by kp-Ritz [33]. Furthermore,
Fig. 14 plots the shape of six lowest eigenmodes of the clamped
skew plate with skew angle h = 60 by the CS-DSG3. It is again ob-
served that the shapes of eigenmodes express correctly the real
physical modes of plate.
6.3. Static analysis
6.3.1. Square FGM plates
6.3.1.1. Behavior of FGM plates subjected to only the mechanical
load. We now perform a static analysis for two square Al/ZrO2-1
plates (length L, thickness t) with clamped and simply supported
boundary conditions as described in Fig. 7a and b. The plate is sub-
jected to a uniform load q = 1 and the volume fraction exponent n
ranges from 0 to 2. Using the uniform discretization of 13 13
nodes, the non-dimensional center deflectionsw 100wcEmt
3=121 m2qL4 of the plate (L/t= 5) by the CS-DSG3 are presented in Table 2, and compared with those of Mesh-
less Local Petrov Galerkin (MLPG) [31] and kp-Ritz [11]. It is seen
that the numerical results by the CS-DSG3 agree well to reference
solutions. In addition, the ability of overcoming the shear locking
of the CS-DSG3 for the cases of FGM plates with different boundary
conditions is illustrated clearly in Figs. 15 and 16. It isseen thatthe
non-dimensional central deflection of the FGM plate is almost
independent with the change of the length-to-thickness ratio L/t
when the plates become thin. The conclusion is correct for the
plates with two simply supported and clamped boundary condi-
tions, and also for four different volume fraction exponents, n = 0,
0.5, 1.0 and 2.0.
Next, Fig. 17 shows the effect of volume fraction exponent n to
the deflection of the center line position of simply supported FGM
plate by the CS-DSG3. It is seen that when the volume fraction
Fig. 17. Effect of volume fraction exponent n to the non-dimentional deflectionw wcEmt
3=121 m2qL4 of the center line position of a simply supported FGMplate by the CS-DSG3.
Fig. 18. Non-dimentional axial stress profile rx rxt2=qL2
through thethickness of a simplysupported FGM plate subjectedto a uniformload by the CS-DSG3: (a) n = 0;(b)n = 0.5; (c) n = 1; (d) n = 2.
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exponent n increases, the deflection also increases, as expected.
This result is quite similar to those by MLPG [31] and kp-Ritz [11].
6.3.1.2. Behavior of FGM plates subjected to the thermo-mechanical
load. In this example, the proposed CS-DSG3 is used to analyse the
behavior of the FGPs subjected to both mechanical and thermal
loadings. The temperature is assumed to be constant in the plane
of the plate and varies through the thickness. The FGM plate (Al/
ZrO2-2) is made from aluminum at the bottom surface and the Zir-conia at the top surface with the length L = 0.2 m and thickness
t= 0.01 m. Material properties vary through the thickness of plate
with respect to the power law as shown in Eqs. (1) and (2).
We first investigate the behavior of the FGM plate subjected to a
uniform mechanical load q, and the volume fraction exponents n of
the plate are varied by n = 0, 0.5, 1 and 2. Figs. 18 and 19 show the
axial stress profile through the thickness of FGM plates
corresponding to two boundary conditions, simply supported and
clamped ones. It is seen that the present results by the CS-DSG3
match well with those by MLPG [31]. Fig. 20 shows the effect ofthe volume fraction exponent and the mechanical load parameter
Fig. 19. Non-dimensional axial stress profile rx rxt2=qL2 through the thickness of a clamped FGM plate subjected to a uniform load by the CS-DSG3: (a) n = 0; (b) n = 0.5;
(c) n = 1; (d) n = 2.
Fig. 20. Effect of the volume fraction exponent and the mechanical load parameter
P qL4=Emt4 (without thermal load) to non-dimensional central deflection
wc wc=t of a simply supported FGM plate by the CS-DSG3.
Fig. 21. Effect of the volume fraction exponent and the thermal load Tc to non-
dimensional central deflection wc wc=t of a simply supported FGM plate by the
CS-DSG3.
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Fig. 22. Effect of the volume fraction exponent and the mechanical load parameter
P qL4=Emt4 (with thermal loads, Tm = 20 C and Tc = 300 C) to non-dimen-
sional central deflection wc wc=t of a simply supported FGM plate by the CS-
DSG3.
Fig. 23. Non-dimensional deflection wc wc=t of the central line position of a
simply supported FGM plate subjected to a mechanical, thermal and thermo-
mechanical loads by the CS-DSG3.
Fig. 24. Effect of the thermal load Tc on central deflection wc wc=t of a simply
supported FGM plate (with n = 1) subjected to a thermo-mechanical load by the CS-DSG3.
Fig. 25. Effect of the skew angle on the axial stress through the thickness of a
simply supported Al/ZnO2-1 plate (n = 0.5) subjected to a mechanical load by the
CS-DSG3.
Fig. 26. Effect of the skew angle on the axial stress through the thickness of a
simply supported Al/ZnO2-1 plate (n = 2) subjected to a mechanical load by the CS-
DSG3.
Fig. 27. Effect of the skew angle on the axial stress through the thickness of a
simply supported Al/ZnO2-1 plate (n = 0.5) subjected to a thermo-mechanical loadby the CS-DSG3.
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P qL4=Emt4 to non-dimensional central deflection wc wc=t
of the simply supported FGM plate. It is observed that the central
deflection of the plate varies linearly with respect to the change
of the load parameter. In addition as expected, the central deflec-
tion increases correspondingly to the increase of the volume frac-
tion exponent n. This is because a FGM plate with a larger volume
fraction exponent means that it has a smaller ratio of ceramic com-
ponent, and hence its stiffness is reduced.
We next study the behavior of the FGM plate subjected to the
thermal load. The temperature at the bottom surface is hold at
Tm = 20 C and the temperature at the top surface is varied from
0 C to500 C. Fig. 21 shows the effect of the volume fraction expo-
nent and the thermal load to non-dimensional central deflection
wc wc=t of the simply supported FGM plate. It is observed thatthe central deflection of the plate also varies linearly with respect
to the change of the thermal load. In addition, when the thermal
load increases highly at the top surface, the deflection of the plate
increases upwardly. This implies that the FGM plates subjected to
mechanical loads in the high temperature condition will have the
deflection smaller than that of the FGM plates subjected to only
mechanical loads in the normal temperature conditions. In other
words, the FGM plates can resist mechanical loads in the high tem-
perature conditions very well, as illustrated in the following
numerical results.
We nowinvestigate the behavior of FGM plates subjected to the
thermo-mechanical load. The temperature is now holdTm = 20 C at
the bottom surface and Tc = 300 C at the top surface. Fig. 22 shows
the effect of the volume fraction exponent and the mechanical load
parameter
P qL
4
=Emt
4
(from
14 to 0) to non-dimensional cen-
tral deflection wc wc=t of the simply supported FGM plate. It is
seen that the behavior of deflection under thermo-mechanical load
is quitedifferent fromthe pure mechanical load. When the mechan-
ical load parameter equals to zero,the deflection of FGMplate is dif-
ferent from zero. This is because the high temperature at the top
surface causes the thermal expansion, and hence makes the plates
deflect upwardly. In addition as expected, the central deflection in-
creasescorrespondinglyto the increaseof the volumefractionexpo-
nent. Next, Fig. 23 shows the non-dimensional deflection of the
central line position of a simply supported FGM plate subjected to
a mechanical, thermal and thermo-mechanical loads. As expected,
it is observedthat when theplate is subjectedto the themo-mechan-
ical load, thedeflection of plate is smaller than that of the plate sub-
jected to onlythe mechanical load. Lastly, Fig. 24 shows theeffect of
the temperature Tc on the central deflection of a simply supported
FGM plate subjected to a thermo-mechanical load and the volume
fraction exponent n = 1. Again, it is seen that when the temperature
Tcat the topsurfaceof FGMplate increases, the upwarddeflection by
the thermal load is also increased and hence the total deflection of
FGM plate becomes smaller than those of the FGM plate subjected
to only pure mechanical loads.
6.3.2. Skew FGM plate
Wenow applytheproposedCS-DSG3to analysea simplysupported
Al/ZrO2-1 skewplate as shown in Fig. 11a. The geometry of plate is gi-
ven by length L = 10, thickness t= 0.1 and the plate is discretized by a
uniformmesh of 13 13 nodes as shown in Fig. 11b. Wefirstconsider
the effect of the skew angleh
to the axial stress of the FGM plate sub-
jectedto a uniformmechanical load q = 104 N/m2. The resultsfor three
volume fraction exponents at n = 0.5 and n = 2.0 are shown in Figs. 25
and 26, respectively. It is seen that when the skew angle becomes lar-
ger, the absolute axial stress induced in the plate becomes higher.
These results agree very well with those given in the reference [11].
A similar observation for thecase of the FGM plate subjected to a ther-
mo-mechanical load is also illustrated in Figs. 27and28. Lastly, Fig. 29
shows the effect of the temperature on the axial stress through the
thickness of the FGM plate subjected to a thermo-mechanical load at
the volume fraction exponent n = 1. It is again observed that when
the temperature becomes larger, the absolute axial stress induced
in the plate becomes higher.
7. Conclusions
The paper presents an extension of the CS-DSG3 using three-
node triangular elements to the C0-type high-order shear deforma-
tion plate theory for the static and free vibration analyses of func-
tionally graded plates (FGPs). In the FGPs, the material properties
are assumed to vary through the thickness by a simple power rule
of the volume fractions of the constituents. In the static analysis,
both thermal and mechanical loads are considered and a two-step
procedure is performed including a step of analyzing the tempera-
ture field along the thickness of the plate and a step of analyzing
the behavior of the plate subjected to both thermal and mechanical
loads. The accuracy and reliability of the proposed CS-DSG3 is ver-
ified by comparing its numerical solutions with those of other
available numerical results. In addition, the numerical results bythe CS-DSG3 confirm that the FGM plates can resist mechanical
Fig. 28. Effect of the skew angle on the axial stress through the thickness of a
simply supported Al/ZnO2-1 plate (n = 2.0) subjected to a thermo-mechanical load
by the CS-DSG3.
Fig. 29. Effect of the thermal load Tc on the axial stress through the thickness of a
simply supported Al/ZnO2-1 plate (n = 1.0) subjected to a thermo-mechanical loadby the CS-DSG3
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loads in the high temperature conditions very well. This is due to
the opposite responses of the FGM plate to the thermal loads and
mechanical loads.
Acknowledgements
This work was supported by Vietnam National Foundation for
Science & Technology Development (NAFOSTED), Ministry of Sci-
ence & Technology, under the basic research program (Project
No.: 107.02-2012.05).
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