考虑温度梯度作用的涡轮盘损伤容限评估方法研究

In order to determine the failure risk caused by the initial defects such as inclusions and voids, the turbine disk made of powder metallurgy superalloy must be evaluated based on damage tolerance method. In view of the fact that the existing damage tolerance method does not consider the effect of temperature gradient on the crack growth behavior of materials, a heating and cooling module capable of forming a stable temperature gradient will be constructed in this project. The fatigue crack propagation test under temperature gradient will be conducted to reveal the influence mechanism of temperature gradient on the crack growth path and rate, and study the crack propagation behavior under cyclic tension load and temperature gradient. Based on the theories of thermodynamics and fracture mechanics, a mathematical description of the crack tip control parameters is given. In combination with the crack propagation test results, a crack growth model which considers the influence of temperature gradient on powder metallurgy superalloy will be built up. On these bases, the methods to characterize the temperature gradient and calculate the crack growth in turbine disk will be developed. At last, the damage tolerance evaluation of turbine disk considering the effect of temperature gradient will be carried out. In summary, this project can improve the current knowledge system of fracture mechanics, and provide support and basis for the design of the advanced aero-engine turbine disk and the safety maintenance of aero-engine turbine disk in service.

为确定夹杂、空洞等初始缺陷导致的失效风险，粉末合金涡轮盘必须开展损伤容限评估，但现有损伤容限方法未考虑温度梯度作用对材料裂纹扩展的影响。针对这一问题，本项目通过搭建可形成稳定温度梯度的加热和冷却模块，开展温度梯度作用下的裂纹扩展试验，揭示温度梯度对裂纹扩展速率和扩展路径的影响机理，掌握循环机械载荷与温度梯度作用下的裂纹扩展规律；基于热力学和断裂力学理论，给出裂纹尖端控制参量的数学描述，结合裂纹扩展试验结果，建立考虑温度梯度作用的粉末高温合金裂纹扩展模型；在此基础上，建立涡轮盘温度梯度表征方法，发展温度梯度作用下的裂纹扩展数值计算方法，实现考虑温度梯度作用的涡轮盘损伤容限评估。本项目的实施可完善当前的断裂力学理论，同时为我国先进航空发动机涡轮盘的设计、现役航空发动机涡轮盘的安全维护提供理论依据和方法支撑。

在航空燃气涡轮发动机的涡轮盘、涡轮叶片等高温结构中，不同部位的温度差异会导致显著的温度梯度，并影响结构的安全性和可靠性。本项目围绕温度梯度对高温合金疲劳裂纹扩展行为的影响，设计并搭建了两类温度梯度试验加载系统，包括针对空心圆棒试件的电磁感应加热系统、针对薄板试件的电阻加热系统；开展了不同温度梯度下的薄板试件裂纹扩展试验，获取了温度梯度下的裂纹扩展数据和规律，并与理论预测结果进行了对比分析；利用电磁感应加热系统开展了空心圆棒试件及高温结构的高温失效试验，获取了温度载荷与机械载荷作用下的变形、裂纹萌生和扩展规律，并建立了相应的寿命预测模型和寿命计算方法；在此基础上，提出了考虑温度梯度作用的轮盘损失容限评估方法，并发展了高效的失效概率计算方法。