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Metals (superalloys) and Metal Matrix Composites (MMC) are being used for elevated temperature applications such as leading edge components in hypersonic aircraft or turbine blades, which undergo highly variable mechanical loads in corrosive environments. Even though protective coatings are used to prevent oxidation, surface wear and microcracks may lead to oxygen penetration into the metallic substrate and subsequent chemical reaction, transforming the metal into a brittle oxide, with detrimental consequences for the integrity and life of the structure. The oxidation of the metal matrix is modeled in the present work by modifying the Fickian diffusion problem in order to simulate the chemical reaction (phase change) in the metal. Two different variants of a fixed grid finite element method for numerical simulation of oxidation are used. The first approach is based on reformulating the governing equation in both the oxide and matrix, resulting in a single, non-linear equation for the whole domain. The second approach tracks the oxidation front and splits the domain into metal and oxide subdomains. In both approaches, the accuracy of the numerical method is measured by comparing the numerical results with the exact solution for specific cases. Coupled with the mechanical analysis, the model is used to estimate the effect of the oxide layer on the energy release rate. 1998 Elsevier Ltd. All rights reserved.
Studies in Applied Mechanics
author list (cited authors)
Lagoudas, D. C., Entchev, P., & Triharjanto, R.