Macrophenomenological modeling to determine an efficient grain structure for the gas turbine engine disk

Abstract

The paper considers the issue of the influence of the average grain size on the complex of strength characteristics of the turbine disk of a gas turbine engine made of Inconel 718 alloy. For a structurally similar element in the conditions of stationary engine operation, the initial boundary value problem of determining temperature, strain and stress fields was posed and solved. The applied material model allows us to take into account the dependence of the fatigue properties and the plasticity limit of the material on the average grain size. A number of numerical experiments were carried out in which a gradient and uniform grain size distribution over the disk radius was set, and the fulfillment of static and kinematic fatigue strength criteria for various areas of the part was verified. The results of numerical modeling have shown that the gradient grain size distribution – from 30 microns near the hub to 60 microns near the rim – under the conditions under consideration shows better resistance to fatigue strength, and provides a greater margin of static strength compared with the uniform design of the average grain size. The comprehensive analysis showed the stability of the developed model to perturbations of the key parameters of exposure (temperature) and the state of the structure (grain size).