Three-dimensional crack propagation simulation on the aero-engine turbine blade under the thermo-mechanical loads

For an aero-engine in service, it is important to ensure the structural integrity for its main components to avoid possible failures. The security work, such as safe inspection, depends on the investigations of the crack propagation in these structures. As for the turbine blade, which is typically the most demanding structure in aero-engine, it is vital to conduct the prediction of the cracks accurately and efficiently in order to support the safe inspection. This paper presented a simulation framework through FEM (finite element method) to predict the crack growth on the turbine blade under complicated loads. In view of the complex three-dimensional geometry and multi-type loads endured, it is challenging to accurately predict the crack growth rate and direction. The combination of thermal and mechanical stresses results in mixed-mode crack growth, so that the crack propagation simulation in this paper included the effect of the KΙ, KⅡand KⅢ. The result that the path, in which the cracks on the blade grew, is not in a plane verify the mixed-mode effect. To deal with the thermal cycles together with mechanical ones in the crack propagation process, an actual flight rotating speed spectrum and time-varying temperature distribution of the blade were used. And some special methods were also adopted to simplify the simulation without losing accuracy. In this paper, cracks along leading edge of the blade, located on three different heights in radial direction, were calculated. The role of the thermal and mechanical loads in the crack propagation was evaluated. The methodology established here is helpful to better determine safe inspection and replacement intervals.