Fatigue limit of Ni-based superalloy 718 relative to the shear-mode crack-growth threshold: A quantitative evaluation considering the influence of crack-opening and -closing stresses
Fatigue limit of Ni-based superalloy 718 relative to the shear-mode crack-growth threshold: A quantitative evaluation considering the influence of crack-opening and -closing stresses
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DOI：
10.1016/j.ijfatigue.2021.106228
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发表时间：
2021-04-03
影响因子：
6
通讯作者：
Matsunaga, Hisao
中科院分区：
文献类型：
--
作者：
Tanaka, Yuya;Okazaki, Saburo;Matsunaga, Hisao
研究了ni基高温合金718的疲劳强度与剪切型裂纹扩展阈值的关系，评价了垂直于剪切型裂纹面的裂纹开闭应力对疲劳强度的影响。还研究了沉淀硬化的影响。采用固溶处理和沉淀硬化材料，进行了三种不同类型的疲劳试验：(i)推拉；(2)纯扭;（iii）具有叠加静张力的扭转。所有试验均显示剪切型小裂纹不扩展，同时证实沉淀硬化对剪切型裂纹扩展阈值的影响可以忽略不计。此外，裂纹打开/关闭应力被确定为仅难以察觉地改变剪切模式阻力。基于这些发现，提出了一种新的策略来量化合金？S疲劳强度。
Fatigue strength of Ni-based superalloy 718 was investigated relative to shear-mode crack-growth thresholds, to evaluate the influence of crack-opening/-closing stresses perpendicular to shear-mode crack-planes. The impact of precipitation-hardening was also examined. Using solution-treated and precipitation-hardened materials, three different types of fatigue tests were performed: (i) push?pull; (ii) pure-torsion; (iii) torsion with superposed static tension. All tests revealed non-propagation of small, shear-mode cracks, while confirming the negligible impact of precipitation-hardening on shear-mode crack-growth threshold. Additionally, crack-opening/-closing stresses were determined to only imperceptibly alter shear-mode resistance. Based on these findings, a novel strategy was proposed to quantify the alloy?s fatigue strength.