温度梯度-应力梯度耦合作用单晶热机械疲劳损伤机理研究

Research practice on the development of advanced high pressure turbine blades and its related experiments shows that the life of nickel based single crystal hollow turbine blade is closely linked to the thermo-mechanical fatigue(TMF) of its feature structures, e.g. the film cooling holes. In service, there are complex flow and heat transfer conditions around the film cooling holes because of the combined effects of internal air cooling and external high-temperature gas heating, and hence cracks always initiate in the hole edge regions first. This investigation focuses on the TMF damage mechanism of the film cooling holes where the stress and temperature distribution presents the features of strong time-varying and large gradient. Based on the TMF experiments on single crystal standard smooth specimens, tube specimens with film cooling holes and real turbine blades combined with the multidisciplinary coupling analysis, the TMF damage mechanism under the coupling effect of temperature gradient and stress gradient is studied，and then a new life prediction method for advanced single crystal hollow turbine blade is developed to support the development of advanced military and commercial aeroengines.

某型先进航空发动机研制和为之进行的相关试验都表明：镍基单晶空心气冷涡轮叶片的服役寿命与其结构特征部位的热机械疲劳(TMF)密切相关。考虑到涡轮叶片气膜冷却孔等典型结构特征部位的应力场、温度场呈现出强时变、大梯度特点，由此提出采用单晶标准圆管试件、具有气膜冷却孔的单晶结构特征模拟件、真实单晶涡轮叶片的多层次TMF试验，并结合气-热-固多学科耦合分析，研究揭示温度梯度-应力梯度耦合作用单晶TMF损伤机理，并进而提出一种单晶TMF寿命预测新方法，以期更为清晰的理解和逼真的刻画单晶空心气冷涡轮叶片服役损伤情景，为彻底解决军、民先进航空发动机气冷涡轮叶片研制瓶颈难题提供技术支撑。

由于结构和服役条件的极端复杂性，单晶空心气冷涡轮转子叶片寿命设计涉及的很多问题尚未得到清晰理解和有效解决，成为制约军、民先进航空发动机研制的瓶颈难题。本项目针对涡轮叶片气膜冷却孔等典型结构特征部位应力场、温度场强时变、大梯度的特点，分别开展了单晶标准圆管试件、单晶结构特征模拟件、真实单晶气冷空心涡轮叶片试验。通过标准件热机械疲劳试验，揭示了单晶热机械疲劳损伤机理，完善了基于滑移系的Walker模型，并建立了基于主成分分析的镍基单晶高温疲劳寿命模型；通过模拟件热机械疲劳试验，进一步修正了寿命预测模型，发展了虑及结构特征影响的镍基单晶高温合金寿命分析方法；通过真实单晶气冷空心涡轮叶片热机械疲劳试验，确定了真实涡轮叶片考核截面的易失效部位以及热机械疲劳寿命，结合所发展的基于滑移系的Walker模型、基于主成分分析的镍基单晶高温疲劳寿命模型、虑及结构特征影响的寿命分析方法，对涡轮叶片考核截面进行了热机械疲劳数值模拟，并完成了寿命评估，结果表明，叶片危险位置位于尾缘扰流柱根部，与试验结果一致，且预测寿命与试验寿命吻合良好。本项目提出了一种单晶气冷空心涡轮叶片寿命分析新方法，有利于提高涡轮叶片强度设计水平及寿命预测精度，可以为我国先进航空发动机研制提供技术支撑，经济效益和军事意义重大。