Reliability analysis of francis turbine blade against fatigue failure under stochastic loading

Due to blade cracks existing on a worldwide scale and to the lack of system method for hydraulic turbine during their lifetime, it is necessary to develop a system method to evaluation their reliability. This work presents a simple and efficient framework for fatigue reliability assessment of a blade. The paper makes a study on dynamic characteristic, statistical characteristics of stress load, fatigue property parameters of material and dynamic fatigue reliability analysis method so as to develop the dynamic fatigue reliability method of complex curved surface under the dynamic pressure on surface, and an practical analysis model of fatigue reliability design method is established for a blade of hydraulic turbine. A numerical experiment of the damaged blade in some plant as an example is analyzed, which indicated that the system method of fatigue reliability is closed to those obtained from experiment and it is feasible.