(1. School of Civil Engineering and Architecture, Chongqing University of Science and Technology, Chongqing 401331, China) (2. College of Aerospace Engineering, Chongqing University, Chongqing 400030, China)
Thermal barrier coating (TBC) is one of the essential technologies to ensure the safety of gas turbine blades and rocket engines under the service condition of extremely high temperature and oxidation atmosphere. However, the damage failure mechanism of TBCs is still a challenge in this field. In this paper, a temperature-dependent damage failure criterion for TBCs considering the plastic deformation energy under thermal cycling was proposed based on the force-heat equivalence energy density principle. Meanwhile, combined with the finite element method, the failure energy density distribution in TBCs under thermal cycling was analyzed. The differences of the failure energy density distribution in ceramic top coat (TC) layer during three typical stages as heating, holding and cooling between two different simulations, one considering the plastic deformation energy and the other only with the tensile elastic strain energy were discussed, respectively. Moreover, the damage failure behaviors of TBCs under thermal cycling were simulated. The results showed that the cracks which caused the damage failure of TBCs did not always propagate along the boundary of TC / TGO to the trough, and it was not easy for cracks to appear on the top of the wave crest of TGO layer. These two key phenomena were consistent with the experimental results, which verified the accuracy of the temperature dependent damage failure criterion derived in this paper. The deduced criterion could overcome the limitations involved in VCCT technology, cohesive element method and extended finite element method based on traditional fracture mechanics, and provide a scientific basis for strength and safety evaluation of TBC.