Hybrid contact stress analysis of a turbine engine blade to disk attachment

Abstract

The present investigation examines an analysis methodology for fretting fatigue in a turbine engine fan disk. This is an important problem for the operators of turbine engines, since it is a significant driver of fatigue damage and failure risk of disks. Fretting fatigue in turbine engines occurs when the blade and disk are pressed together in contact and experience a small oscillating relative displacement due to variations in engine speed and vibratory loading. Fretting causes a very high local stress near the edge of contact resulting in wear, nucleation of cracks, and their growth, which can result in significant reduction in the life of the material. It is dependent on geometry, loading conditions, residual stresses, and surface roughness, among other factors. These complexities are not just physically based, but also computationally challenging. For example, the determination of the local contact stresses accurately depends on the mesh resolution of the finite element method (FEM) model. This has been addressed using various approaches. Recently, a computational hybrid technique was implemented successfully to investigate fretting fatigue of turbine engine blade and disk attachments. The present work extends application to specifically investigate the effects of surface contact in an actual blade and disk assembly using a representative loading mission. The results show consistency with available experimental data. Finally, the knowledge gained from this investigation could be used as a basis for uncertainty analyses of an actual blade and disk assembly.