Effects of creep-plastic behavior on stress development in TBCs during cooling

The stress development, as the main cause of TBCs failure, can be significantly influenced by the non-linear behaviors of TBCs materials (e.g. plastic and creep deformations). Description of the non-linear behaviors of TBCs materials is crucial to accurate stress evaluation. However, conventional constitutive models couldn't distinguish the role of the nonlinear plastic and creep deformations in the stress evaluation, which may lead to obvious difference. This work employs the creep-plastic constitutive model to study the effects of creep-plastic behavior of BC and TGO on the TC/TGO/BC interface stress development. This creep-plastic model reveals that the stress can be identified in three sections when BC creep properties varies in wide margins: In the first section with a small BC creep rate, plastic deformation mainly influences the interface stresses; in the second section with a medium creep rate, both creep and plastic deformations affect the stress development; in the third section with a larger creep rate, creep becomes the main factor dominating the relaxing process. It is also found that if the creep in TGO is considered, the stresses will be overall relaxed no matter if BC is plastic, creep or creep-plastic. Based on this three-section phenomenon, the influence of TGO thickness, interface roughness and cooling rate on the stress development is investigated.