13th International Conference on Fracture June 16–21, 2013, Beijing, China -5- can affect the interface distortions. Compared to the crack “b”, the crack “a”, which is more close to the base of the instability zone, results in a more significant distortion. Therefore, the existing of crack, especially the crack close to the base of instability site, can induce larger "up" and "down" displacements. The distribution of out-of-plane stress ( 22 ) in the intact TC presents in Fig. 4b. The tensile stresses mainly concentrate on the region above the instability site. When the tensile stress develop to a sufficient level, it can induce the cracks within the TC above the instability site and the delamination at the interface[5, 16]. The compressive stresses mainly appear in a relatively small zone near the periphery of instability zone and this compressed zone can prevent the crack initiation. Fig. 5A demonstrates the distribution of out-of-plane stress in TC along TC-TGO interface when a crack exists within TC. It can be seen clearly that the tensile stress level near the instability region would increase when the crack exists at location “a” and this increase recedes when the crack is far away from the instability region (location “b”). In other regions, the effect of crack on 22 is small and can be ignored. Figure 4. Stress distribution within TC when the TC is intact. (a) in-plane stress ( 11 ) and (b) out-of-plane stress ( 22 ). Figure 5. Stress distribution in TC along TC-TGO interface. (A) The out-of-plane stress ( 22 ). (B) The in-plane stress ( 11 ).
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