基于整机试车的涡轮叶片高低循环复合疲劳试验技术

针对航空发动机涡轮叶片同时承受高循环载荷和低循环载荷的特征,以小推力涡喷发动机为研究对象,搭建了基于引电器的涡轮叶片动应力测量系统,利用数值模拟和试验测试结合的方法,实现了高度为30mm的涡轮叶片在40000r/min转速、950℃环境温度条件下的动应力测量,并以此为基础发展了整机高低循环复合疲劳试验方法,开展了高压涡轮叶片高低复合疲劳整机试验。研究结果表明,该型发动机转速在34920r/min时,叶片高循环振动应力达到112.7MPa,带来了涡轮叶片的高循环疲劳损伤且是引起涡轮叶片产生裂纹的主要因素,低循环疲劳载荷是导致裂纹扩展的主要因素,两者综合作用会显著影响涡轮叶片寿命。 

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.