Computational Model of the Propagation of Stress-Corrosion Cracks at High Temperatures

We propose a mathematical model for the investigation of the fracture of thin-walled structural elements with cracks under the action of long-term static loads and aggressive media. The model is based on the energy approach and the basic ideas of fracture mechanics. We deduce an equation for the analysis of the kinetics of growth of stress-corrosion cracks, which forms, together with the initial and final conditions, a mathematical model for the determination of the period of subcritical growth of these cracks in metallic materials. We determine the influence of acid corrosive media on the lifetime of thin-walled plates of 20 steel weakened by cracks (an analog of the Griffith problem) under the action of static loads and high-temperature creep. The dependences of the lifetime of the plate on the initial size of the defect are plotted both in corrosive media and in air. It is shown that corrosive media increase the rate of propagation of creep cracks, which leads to a decrease in the lifetime of structural elements.