残余应力与拘束对GH4169合金疲劳及蠕变-疲劳裂纹扩展速率影响研究

为深入理解残余应力与拘束在疲劳载荷下的交互作用，以镍基高温合金GH4169为研究对象，选用紧凑拉伸(CT)试样，对不同拘束CT试样的上方施加不同大小的预加载荷从而在裂尖产生不同应力。将该应力作为残余应力，系统研究残余应力和拘束交互作用下GH4169合金的疲劳和蠕变–疲劳裂纹扩展速率。结果表明：随着裂尖残余压应力的增加，不同拘束下GH4169合金的疲劳和蠕变–疲劳裂纹扩展速率均降低。与低拘束试样相比，高拘束试样的疲劳和蠕变–疲劳裂纹扩展速率对残余应力的变化更加敏感，这主要与裂尖Mises应力和垂直于裂纹扩展方向的正应力有关。与疲劳裂纹扩展速率相比，蠕变-疲劳裂纹扩展速率对残余应力的变化更加敏感。

Study on the effect of residual stress and constraints on fatigue and creep-fatigue crack propagation rates

In order to deeply understand the interaction between residual stress and constraint under fatigue, taking GH4169 superalloy as the research object, compact tension (CT) specimens with different constraints were selected. Different loads were applied to CT specimens to produce different stresses at the crack tip, and the stresses were introduced into the CT specimen as residual stress. And then, the fatigue and creep-fatigue crack propagation rates of GH4169 superalloy were systematically studied under the interaction of residual stress and constraint. The results showed that the fatigue and creep-fatigue crack propagation rates of GH4169 alloy decreased with the increase of residual compressive stress at crack tip. In contrast to the specimen with low constraint, the fatigue and creep-fatigue crack propagation rates of the specimen with high constraint were more sensitive to the change in residual stress, and it was mainly related to the Mises stress at the crack tip and the normal stress perpendicular to the crack propagation direction. Compared with the fatigue crack propagation rate, the creep-fatigue crack propagation rate was more sensitive to the change of residual stress.