Effects of oxygen-related damage on dwell-fatigue crack propagation in a P/M Ni-based superalloy: From 2D to 3D assessment
Effects of oxygen-related damage on dwell-fatigue crack propagation in a P/M Ni-based superalloy: From 2D to 3D assessment
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DOI：
10.1016/j.ijfatigue.2017.03.003
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发表时间：
2017-06-01
影响因子：
6
通讯作者：
Reed, P. A. S.
中科院分区：
文献类型：
--
作者：
Jiang, R.;Bull, D. J.;Reed, P. A. S.
在空气和真空中，在 725 摄氏度的驻留疲劳条件下，评估了氧相关损伤（即氧化和动态脆化）对高级盘合金疲劳裂纹扩展行为的影响。增强的疲劳裂纹扩展与裂纹尖端处/前方的氧相关损伤密切相关，这是由测试环境、驻留时间和裂纹扩展速率本身决定的，裂纹扩展速率本身基于光学显微镜和扫描电子显微镜对裂纹尖端的二维 (2D) 观察。 X 射线计算机断层扫描也已用于检查空气和真空条件下三维 (3D) 裂纹形态之间的差异，并且裂纹特征已根据裂纹张开位移、二次裂纹和未裂纹桥接韧带进行量化。结果表明，疲劳裂纹扩展速率与二次裂纹的数量有关，加载循环中的裂纹长度增量与裂纹尖端之前的不连续裂纹区内未裂纹桥接韧带的断裂/开裂有关，因为与氧相关的损伤优先发生在这些高度变形的区域。通过结合 3D X 射线计算机断层扫描和传统的 2D 观察，可以更深入地了解氧增强疲劳裂纹扩展行为的机制。 (C) 2017 Elsevier Ltd. 保留所有权利。
Effects of oxygen-related damage (i.e. oxidation and dynamic embrittlement) on fatigue crack propagation behavior in an advanced disc alloy have been assessed in air and vacuum under dwell-fatigue conditions at 725 degrees C. The enhanced fatigue crack propagation is closely related to oxygen-related damage at/ahead of the crack tip, which is determined by the testing environment, the dwell period and the crack propagation rate itself based on two dimensional (2D) observation of the crack tip in an optical microscope and scanning electron microscope. X-ray computed tomography has also been employed to examine the differences between three dimension (3D) crack morphology in air and vacuum conditions, and the crack features have been quantified in terms of crack opening displacements, secondary cracks and uncracked bridging ligaments. The results show that the fatigue crack propagation rate is related to the amount of secondary cracks, and the crack length increment in a loading cycle is related to the breaking/cracking of the uncracked bridging ligaments within the discontinuous cracking zone ahead of the crack tip as oxygen-related damage preferentially occurs in these highly deformed regions. By combination of 3D X-ray computed tomography and traditional 2D observation, a deeper understanding is provided of the mechanisms of oxygen-enhanced fatigue crack propagation behavior. (C) 2017 Elsevier Ltd. All rights reserved.