13th International Conference on Fracture June 16–21, 2013, Beijing, China -7- Transient Thermal Loading The boundary conditions for this loading case are depicted in Figure 5. Fig 5- Thermal boundary conditions for the FGM coating, bond coat and substrate structure It is assumed that the composite medium is initially stress-free at a high processing temperature of ܶ = 1200 K. Then, the other face of solid is left in an environment which has a temperature of ܶ = 100 K. The boundary conditions for this loading case are depicted in Figure 5. The thermo mechanical parameters used in the transient thermal analyses are described before. For the transient thermal analyses, inclination angles of 45semi-elliptic surface crack are considered. It is seen that the normalized stress intensity factors rates go through a maximum in a short time period and then starts to decrease (Figures 6, 7 and 8) for different ratio of ܧ ଶ ܧ ଵ ൗ . Figures 9 show the distribution of energy release around the crack front. Fig 6- Distribution of normalized mode I stress intensity factors around crack front Fig 7- Distribution of normalized mode II stress intensity factors around crack front
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