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Probabilistic Failure Analysis of a Ceramic Turbine Vane

The CARES/LIFE life prediction code, developed by NASA Lewis Research Center, was used to evaluate the fast fracture life of a ceramic turbine vane subjected to thermal loads. The probabilistic life prediction is performed by first analyzing the structure using ANSYS. Macros and translators are used to obtain geometry and result information from the ANSYS model, such as surface and interior stresses, temperatures, and surface area and volume information. With this information and fracture data for the ceramic material, CARES can predict the overall probability of failure for both surface and volume flaws, as well as contours of the risk of rupture intensities for determining the critical regions of the structure.

The analysis and subsequent probabilistic life prediction of the ceramic turbine vane in this project has demonstrated the feasibility of using ceramic components in a turbine engine environment. Further research is underway to continue development of ceramic vanes, with the goal of replacing heavier metals with lower temperature capability.

The full vane model was analyzed by CARES using the above procedure. Using both surface and volume flaw data, CARES predicted a probability of survival of 0.99990. The highest risk of rupture intensity values occur near mid-span of the airfoil, with the critical region for volume flaws predicted at the leading edge. For surface flaws, the critical location was found to be the trailing edge region. The two figures show the volume and surface risk of rupture intensities at the mid-span.

 

Volume Risk of Rupture Surface Risk of Rupture