一种单晶涡轮叶片热机械疲劳寿命评估方法

针对单晶涡轮叶片热机械疲劳(TMF)问题,围绕单晶涡轮叶片TMF试验,结合单晶变形、损伤理论及数值模拟,建立了一套单晶涡轮叶片TMF寿命评估方法.利用空心气冷涡轮叶片TMF试验系统,对单晶涡轮片考核截面在服役条件下所产生的交变应力场和交变温度场进行模拟,确定了裂纹萌生部位及其TMF寿命.考虑单晶涡轮叶片变形和损伤行为的特征,分别建立了基于滑移系的Walker黏塑性本构模型和基于临界平面的循环损伤累积(CDA)模型.利用上述本构和寿命模型,完成了单晶涡轮叶片TMF试验的数值模拟.结果表明:叶片理论危险点与试验结果一致,且计算寿命基本落在试验寿命的3倍分散带内. 

A thermo-mechanical fatigue life assessment method for single crystal turbine blades

A thermo-mechanical fatigue (TMF) life assessment method of single crystal turbine blades was developed based on TMF experiments of single crystal turbine blades combined with deformation and damage theory of single crystal as well as numerical simulation for thermo-mechanical fatigue problem of single crystal turbine blades. Firstly, the cyclic stresses and temperatures generated on the critical section in the single crystal turbines during service were simulated with the TMF experimental system of hollow air-cooled turbine blades, and the position of crack initiation and the TMF life were determined. Then, the Walker viscoplastic constitutive model based on slip systems and cyclic damage accumulation (CDA) model based on critical plane were proposed considering the features of deformation and damage behavior of single crystal turbine blades. Finally, the numerical simulation of TMF of single crystal turbine blades under the experimental conditions was performed with the above-proposed constitutive model and life model. Results show that the theoretical dangerous point is consistent with the experimental results, and the calculated life is basically within three times scatter band of the experimental life.