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Experimental and analytical investigation on service life of film cooling structure for single crystal turbine blade
International Journal of Fatigue ( IF 6 ) Pub Date : 2021-05-12 , DOI: 10.1016/j.ijfatigue.2021.106318
Zixu Guo , Ziyuan Song , Jun Fan , Xiaojun Yan , Dawei Huang

In this study, regarding the film cooling structure of single crystal (SC) turbine blade, the life tests simulating the service condition are conducted, and the life prediction modeling as well as damage mechanism analysis are carried out. In life test, the SC specimen with multiple film cooling holes is designed to simulate the geometrical characteristic of film cooling structure. The creep-fatigue loading spectrum characterizing a typical flight process is employed. The loading system is developed to simulate the cyclic service load in laboratory environment. Meanwhile, the strain distribution of film cooling structure is measured using digital image correlation (DIC) method. After that, the life tests are conducted, and eight groups of test lives are obtained. Taking the strain distribution measured by DIC as input, the model based on theory of critical distance (TCD) is improved to predict the service lives of film cooling structure. Furthermore, the crack nucleation mechanism of film cooling structure is discussed. Based on the microscopic observation, it can be found that the microcrack nucleation around hole edge is induced by persistent slip bands (PSBs). The matrix channel that significantly influences the dislocation accumulation rate and PSBs formation is chosen as the concerned microstructure. Under the effect of stress distribution of film cooling structure, the uneven spatial distributions of mean values and standard derivations for matrix channel width are quantificationally revealed. And the distribution of dislocation density on film cooling structure is measured using electron back-scatter diffraction (EBSD). It can be found that the concentration of dislocation density exists around the hole edge, and the distribution of dislocation density is quite unsmooth due to the scatter of matrix channel width. These findings can be employed in the life prediction and fault diagnosis for film cooling structure under service condition.



中文翻译:

单晶涡轮叶片薄膜冷却结构使用寿命的实验分析研究

本研究针对单晶(SC)涡轮叶片的薄膜冷却结构,进行了模拟使用寿命的寿命试验,并进行了寿命预测建模和损伤机理分析。在寿命测试中,设计了具有多个薄膜冷却孔的SC标本,以模拟薄膜冷却结构的几何特征。采用表征典型飞行过程的蠕变疲劳载荷谱。开发了加载系统,以模拟实验室环境中的周期性服务负载。同时,使用数字图像相关(DIC)方法测量膜冷却结构的应变分布。此后,进行寿命测试,并获得八组测试寿命。以DIC测得的应变分布作为输入,改进了基于临界距离理论的模型,以预测薄膜冷却结构的使用寿命。此外,还讨论了薄膜冷却结构的裂纹成核机理。基于显微镜观察,可以发现孔边缘周围的微裂纹成核是由持久滑移带(PSB)引起的。选择显着影响位错累积速率和PSBs形成的基质通道作为相关的微观结构。在薄膜冷却结构应力分布的影响下,定量地揭示了均值的不均匀空间分布和矩阵通道宽度的标准推导。并使用电子背散射衍射(EBSD)测量了薄膜冷却结构上的位错密度分布。可以发现,位错密度的集中存在于孔的边缘,并且由于基体通道宽度的分散,位错密度的分布非常不光滑。这些发现可用于在使用条件下薄膜冷却结构的寿命预测和故障诊断。

更新日期:2021-05-24
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