This work describes the application of two-dimensional finite element models with a cohesive zone to study quasi-static crack extension in functionally graded Yttria stabilized Zirconia (YSZ)-Bond Coat (BC) alloy (NiCoCrAlY) thermal barrier coatings (TBC). Crack growth under a single heating-cooling cycle simulating a laser thermal shock experiment is considered. The traction-separation relations for YSZ and BC alloy are coupled to yield a traction-separation relation for the individual layers of the graded TBC. Results from laser thermal shock experiments are then used for a systematic evaluation of the material properties in this traction-separation relation. The effective work of separation for YSZ-BC alloy composites, which is indicative of the material’s fracture toughness, is then computed. The model is then used to predict the surface thermal fracture response in a graded TBC having an architecture different from the coatings that were used to evaluate the cohesive properties. These model predictions are then compared with results from laser thermal shock experiments.
A Study of Thermal Fracture in Functionally Graded Thermal Barrier Coatings Using a Cohesive Zone Model
Contributed by the Materials Division for publication in the JOURNAL OF ENGINEERING MATERIALS AND TECHNOLOGY. Manuscript received by the Materials Division November 1, 2002; revision received April 1, 2003. Associate Editor: A. Rajendran.
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Rangaraj , S., and Kokini, K. (January 22, 2004). "A Study of Thermal Fracture in Functionally Graded Thermal Barrier Coatings Using a Cohesive Zone Model ." ASME. J. Eng. Mater. Technol. January 2004; 126(1): 103–115. https://doi.org/10.1115/1.1631028
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