Volume 38, Number 6, December 2020
|Page(s)||1291 - 1298|
|Published online||02 February 2021|
Initiation and Propagation Characteristics of Multi-Source Fatigue Crack in Superalloy Disk
College of Energy Engineering, Zhejiang University, Hangzhou 310027, China
2 College of Mechanical and Electrical Engineering, Wenzhou University, Wenzhou 325035, China
The multi-source fatigue crack growth characteristics of a turbine disk were studied via high-speed rotating low cycle fatigue test, fracture analysis and crack growth simulation analysis. The results show that the fatigue initiation life N0 of Superalloy disk and its simulation parts is less dispersive and similar, and the S-N0 curve of the material is not conservative to predict the N0 of the disk. The fracture of eccentric hole of disk is multi-source fatigue fracture, and the surface characteristic of the crack L/D decreases rapidly from 7.5 to 2, which is obviously different from the single source fatigue crack growth. Because of the long and thin stress distribution at the eccentric hole and the small dispersivity of GH698 crack initiation life, it's relatively easy to crack on the plane A of the eccentric hole, which is prone to multi-source fatigue. At the stage of a ≥ 1.23 mm, the reverse life of crack propagation fracture of 2# and 5# eccentric holes is consistent, and the error between the simulation value of single source fatigue crack propagation life and the reverse life is below 5%. In the stage of 0.61 mm ≤ a < 1.23 mm, the simulation crack growth rate of 5# eccentric hole of multi-source is close to that of fracture inversion. Accurate simulation analysis of multi-source crack growth needs to define the initial crack accurately, at the same time, consider the influence of existing fatigue damage on crack growth.
通过高速旋转低周疲劳实验及断口分析、裂纹扩展仿真分析，研究了某涡轮盘多源疲劳裂纹扩展特征。结果显示高温合金盘及其模拟件的疲劳萌生寿命N0分散性较小且相近；直接采用材料的S-N0曲线预测轮盘N0时偏不保守。轮盘偏心孔断口均为多源疲劳断口；裂纹表面特征L/d从7.5快速减小至2，明显不同于单源疲劳裂纹扩展。由于偏心孔处应力分布细长、GH698裂纹萌生寿命分散性小，偏心孔A面各处各自萌生裂纹相对容易，易出现多源疲劳。a≥1.23 mm阶段，2#、5#偏心孔裂纹扩展断口反推寿命变化较一致，单源疲劳裂纹扩展寿命仿真值与之误差在5%以内。0.61 mm≤a < 1.23 mm阶段，5#偏心孔多源裂纹扩展速率仿真值与断口反推值接近。准确的多源裂纹扩展仿真分析不仅需要准确定义初始裂纹，同时还需考虑各处已有的疲劳损伤对裂纹扩展的影响。
Key words: superalloy / turbine disk / LCF / damage tolerance / multi-source initiation
关键字 : 高温合金 / 涡轮盘 / 低周疲劳 / 损伤容限 / 多源起裂
© 2020 Journal of Northwestern Polytechnical University. All rights reserved.
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