Wikov (Czechia)

This paper analyzes high-cycle fatigue degradation of turbine blade. The fatigue degradation is considerable problem in industry and can cause catastrophic accidents. Also, the fatigue damage of mechanical components leads to significant economic losses. The turbine blade is during it's working life subjected to the intensive multiaxial loading and broken blade is much more frequent cause of the turbine failure, than the fatigue fracture of rotor shaft. Therefore great effort is devout to the fatigue resistance improvement and proper method of fatigue life modeling. In recent work, relatively new approach for fatigue crack modeling is discussed and its application on specific problem of turbine blade. The majority of fatigue crack models are working with predefined boundary length of crack. This length makes possible to distinguish between the different phases of crack growth, i.e. different crack growth mechanism. The method used in this work is based on another approach. The fatigue crack is simulated in this way: (1) the crack grew throughout the whole blade volume controlled by nucleation mechanism, (2) by propagation mechanism. Thus two different fatigue curves are obtained and merged in one final fatigue curve. This method is in compliance with data obtained experimentally.