Fatigue crack propagation analysis in an aero-engine turbine disc using computational methods and spin test

Abstract

This article presents a study on applying the fracture mechanics-based method to predict the fatigue crack growth (FCG) characteristics of the turbine disc in a turboshaft engine. According to the stress analysis results, the electric discharge machining (EDM) method introduced notches for initiating cracks of a specific size into the critical locations of the turbine disc. The FCG of these cracks under cyclic load was predicted utilising a three-dimensional (3D) numerical analysis method and a simplified rectangular plate model with relevant fracture mechanics properties. Meanwhile, the full-scale spin test was performed using a pre-flawed turbine disc under intentional loads at an isothermal temperature. After the test, the crack surface fractography and the quantitative fracture striation analysis revealed the practical crack propagation behaviour. There was a relatively small difference between the experimental results and the 3D finite element method, which indicated the good predictability of FEM for turbine disc crack growth. Furthermore, the rectangular plate models could predict the front stage of steady-state crack growth but were overall conservative due to their inability to precisely calculate the effects of crack growth and structure geometry on the stress intensity factor.