Modeling of oxidation and its effect on crack growth in titanium alloys

Abstract

The effect of oxidation on the crack growth resistance of titanium alloys is investigated in this work. The oxidation process is modeled by modifying the Fickian diffusion problem in order to account for the chemical reaction (phase change) in the material. Two different variants of a fixed grid finite element method for numerical simulation of oxidation are used. The first approach taken is to locate the oxidation front and split the domain into metal and oxide subdomains. The second approach is based on reformulating the diffusion equations in both the oxide and metal, resulting in a single non-linear equation for the whole domain. After the oxidation process is modeled, the mechanical analysis is performed. In the finite element formulation of the mechanical problem, the influence of oxidation is introduced by the change of the elastic constants and the oxidation-induced eigenstrain. The applicability of both the oxidation and mechanical models is tested by simulating oxidation of a pre-cracked Ti-15-3 compact tension specimen which is then subjected to monotonic loading.