Test method for the combined high and low cycle fatigues of turbine blade based on the whole engine operation

The turbine blade is subjected to both high cycle and low cycle loads synchronously during aero-engine operation. Therefore, using a low thrust turbojet engine as research platform, a test scheme based on the electrical leads on how to assess the blade dynamic stress was put forward in particular for the blades used in harsh conditions i.e. high rotation speed, small size and high temperature. The dynamic stress of 30mm height turbine blades operated at the rotation speed of 40000r/min and in 950℃ was obtained by use of a combined value simulation and experiment measurement method. Moreover test methods of the combined high cycle and low cycle fatigues based on the whole engine operation, including the methods on how to obtain the resonance vibratory stress and to compose the load spectrum, were developed. The engine test was carried out and the combined high cycle and low cycle fatigues of high pressure turbine blade were investigated. The results show that blade dynamical stress reaches 112.7MPa at the rotation speed of 34920r/min, which may lead to the high cycle fatigue failure of the turbine blade and the high cycle load is the major reason for the initialization of the crack, and the low cycle load is the major reason to result in the crack propagation, and both of them will affect the life of the turbine blade synthetically.