Failure propagation behavior of thermally sprayed coatings containing many random pores is investigated. The porous coatings are subjected to either external mechanical loads or residual stresses generated by temperature changes. The failure growth criterion is governed by the critical energy release rate. In our finite element analysis, the cohesive model is used to separate element boundaries during crack propagation in the inhomogeneous materials. The accuracy of the cohesive elements for the quasi-static crack growth is closely evaluated by an error analysis. We have observed that the cohesive elements may artificially increase the model compliance and introduce numerical errors. In order to minimize such errors, the parameters for cohesive model must be chosen carefully. Their numerical convergence and stability conditions with an implicit time integration scheme are also examined. In the porous material analysis, crack propagation is simulated to characterize its unique failure process. It appears a crack tends to propagate along the shortest path between neighboring pores. In addition, crack/pore coalescence mechanism causes the apparent crack length to increase discontinuously. Under thermally loaded conditions, the residual stresses generated by material mismatch in multilayered coatings drive cracks to grow. Using the present crack propagation model, the critical temperature leading to the complete porous coating failure can be approximated.

1.
Lin
,
C. K.
, and
Berndt
,
C. C.
,
1994
, “
Measurement and Analysis of Adhesion Strength for Thermally Sprayed Coatings
,”
J. Therm. Spray Tech.
,
3
, pp.
75
104
.
2.
Qian
,
G.
,
Nakamura
,
T.
,
Berndt
,
C. C.
, and
Leigh
,
S. H.
,
1997
, “
Tensile Fracture Toughness Test and High Temperature Fracture Analysis of Thermal Barrier Coatings
,”
Acta Mater.
,
45
, No.
4
, pp.
1767
1784
.
3.
Nakamura
,
T.
,
Qian
,
G.
, and
Berndt
,
C. C.
,
2000
, “
Effects of Pores on Mechanical Properties of Plasma Sprayed Ceramic Coatings
,”
J. Am. Ceramic Soc.
,
83
, pp.
578
584
.
4.
Leigh
,
S. H.
, and
Berndt
,
C. C.
,
2000
, “
Quantitative Evaluation of Void Distribution Within a Plasma Sprayed Ceramic
,”
J. Am. Ceram. Soc.
,
82
, pp.
17
38
.
5.
Xu
,
X.-P.
, and
Needleman
,
A.
,
1994
, “
Numerical Simulations of Fast Crack Growth in Brittle Solids
,”
J. Mech. Phys. Solids
,
42
, pp.
1397
1434
.
6.
Camacho
,
G. T.
, and
Ortiz
,
M.
,
1996
, “
Computational Modeling of Impact Damage in Brittle Materials
,”
Int. J. Solids Struct.
,
33
, pp.
2899
2938
.
7.
Guebelle
,
P. H.
, and
Baylor
,
J. S.
,
1998
, “
Impact-Induced Delamination of Composites: A 2D Simulation
,”
Composites, Part B
,
29
, No.
5
, pp.
589
602
.
8.
Miller
,
O.
,
Freund
,
L. B.
, and
Needleman
,
A.
,
1999
, “
Modeling and Simulation of Dynamic Fragmentation in Brittle Materials
,”
Int. J. Fract.
,
96
, pp.
101
125
.
9.
Needleman
,
A.
,
1987
, “
A Continuum Model for Void Nucleation by Inclusion Debonding
,”
ASME J. Appl. Mech.
,
54
, pp.
525
531
.
10.
Tvergaard
,
V.
, and
Hutchinson
,
J. W.
,
1992
, “
Relation Between Crack Growth Resistance and Fracture Process Parameters in Elastic-Plastic Solids
,”
J. Mech. Phys. Solids
,
40
, pp.
1377
1392
.
11.
Lin
,
G.
,
Kim
,
Y. J.
,
Comec
,
A.
, and
Schwalbe
,
K. H.
,
1997
, “
Fracture Toughness of a Constrained Metal Layer
,”
Comput. Mater. Sci.
,
9
, pp.
36
47
.
12.
Montavon
,
G.
,
Sampath
,
S.
,
Berndt
,
C. C.
,
Herman
,
H.
, and
Coddet
,
C.
,
1995
, “
Effects of Vacuum Plasma Spray Processing Parameters on Splat Morphology
,”
J. Therm. Spray Tech.
,
4
, pp.
67
74
.
13.
Bengtsson
,
P.
, and
Johannesson
,
T.
,
1995
, “
Characterization of Microstructural Defects in Plasma-Sprayed Thermal Barrier Coatings
,”
J. Therm. Spray Tech.
,
4
, pp.
245
251
.
14.
Wawrzynek
,
P. A.
, and
Ingraffea
,
A. R.
,
1989
, “
Interactive Approach to Local Remeshing Around a Propagating Crack
,”
Finite Elem. Anal. Design
,
5
, pp.
87
96
.
15.
Belytschko
,
T.
,
Lu
,
Y. Y.
, and
Tabbara
,
M.
,
1995
, “
Element-Free Galerkin Methods for Static and Dynamic Fracture
,”
Int. J. Solids Struct.
,
32
, pp.
2547
2570
.
16.
Dagher
,
H. J.
, and
Kulendran
,
S.
,
1992
, “
Finite Element Modeling of Corrosion Damage in Concrete
,”
ACI Struct. J.
,
89
, pp.
699
708
.
17.
Padovan
,
J.
, and
Guo
,
Y. H.
,
1994
, “
Moving Template Analysis of Crack Growth—I. Procedure Development
,”
Eng. Fract. Mech.
,
48
, pp.
405
425
.
18.
Padovan
,
J.
, and
Jae
,
J.
,
1997
, “
FE Modeling of Expansive Oxide Induced Fracture of Rebar Reinforced Concrete
,”
Eng. Fract. Mech.
,
56
, pp.
797
812
.
19.
Nakamura
,
T.
,
Shih
,
C. F.
, and
Freund
,
L. B.
,
1985
, “
Computational Methods Based on an Energy Integral in Dynamic Fracture
,”
Int. J. Fract.
,
27
, pp.
229
243
.
20.
Atluri
,
S. N.
, and
Nishioka
,
T.
,
1985
, “
Numerical Studies in Dynamic Fracture Mechanics
,”
Int. J. Fract.
,
27
, pp.
245
261
.
21.
Gao
,
H.
, and
Klein
,
P.
,
1998
, “
Numerical Simulation of Crack Growth in an Isotropic Solids With Randomized Internal Cohesive Bonds
,”
J. Mech. Phys. Solids
,
46
, pp.
187
218
.
22.
Zhang, P., Klein, P., Huang, Y., and Gao, H., 1999, “Numerical Simulation of Cohesive Fracture by Virtual-Internal-Bond Model,” Report by the Department of Mechanical and Industrial Engineering, University of Illinois.
23.
Shih
,
C. F.
,
Moran
,
B.
, and
Nakamura
,
T.
,
1986
, “
Energy Release Rate Along a Three-Dimensional Crack Front in a Thermally Stressed Body
,”
Int. J. Fract.
,
30
, pp.
79
102
.
24.
Needleman
,
A.
, and
Rosakis
,
A. J.
,
1999
, “
The Effect of Bond Strength and Loading Rate on the Conditions Governing the Attainment of Intersonic Crack Growth Along Interfaces
,”
J. Mech. Phys. Solids
,
47
, pp.
2411
2449
.
25.
Leigh
,
S. H.
, and
Berndt
,
C. C.
,
1997
, “
Elastic Response of Thermal Spray Deposits Under Indentation Tests
,”
J. Am. Ceram. Soc.
,
80
, pp.
2093
2099
.
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