Mathematical Modeling of Failure Process of AlMg2.5 Alloy in High and Very High Cycle Fatigue

Abstract

Prediction of the endurance limit in the high and very high cycle loading range (102−1010) is an important problem in aircraft engine construction and high-speed rail transport. It involves the development of models and their experimental verification taking into account damage evolution stages and fatigue crack growth in a damaged medium. A damage evolution model that takes into account the kinetics of defects and microplasticity effects was proposed. The model was used to study the process of fatigue failure of an AlMg2.5 structural alloy. The model parameters were identified and verified using experimental data on static, dynamic, and fatigue loading, as well as tests at various temperatures. The numerical results were used to construct the Wohler curve, which was found to agree well with experimental data in the range of high cycle fatigue. The duality effect of the S-N curve was described. A computational experiment was performed to study the effect of dynamic loading on the fatigue strength. It was found that the fatigue limit depends weakly on the preliminary dynamic strain, which was confirmed by experimental data. Various mathematical packages and numerical methods for solving the constructed system of differential equations were compared. The Adams method and its modifications were shown to be optimal for the numerical integration of the problem under consideration. Wolfram Mathematica was found to be a preferred software package for numerical solution. The convergence of the numerical solution was investigated.