A Three Dimensional Finite Element Analysis for Contact Stress and Fatigue near the Fir-Tree Region in a Gas Turbine Blade

Abstract

In this work an attempt is made to simulate the life of a rotating element subjected to the phenomenon of fatigue fretting using finite element analysis. A numerical model is being proposed to analyse the fretting failure phenomenon. The model explores the physics of the problem with a view to capture micro slip at the interface between the root and the disc. Some of the parameters that affect fretting are dissimilar material component types, kinds of fit, geometry of the mating part etc. The effect of these parameters on the extent of fretting is being analysed using the commercial finite element tool ANSYS. This will enable one to gauge failure criterion of the part to be designed under different cyclic loading conditions subjected to fatigue fretting failure. It is found out from the present analysis that the bottom tooth of the fir tree structure experiences the maximum stress induced at the interface. Also the stress increases non-linearly as the speed increases. As the flank angle is increased, the fatigue life at higher speeds decreases. Also the equivalent stress decreases as the number of teeth increases.