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本文研究了35CrMo钢在室温空气中近门槛疲劳裂纹扩展特性。实验结果表明:R=0.1时,随着回火温度升高,疲劳门槛值提高,疲劳裂纹扩展速率降低;R=0.7时,疲劳门槛值及疲劳裂纹扩展速率并不随回火温度改变而改变;R=0.1时,在近门槛区域,发现有黑色氧化带;R=0.7时,在近门槛区域,基本上没有氧化物产生。实验结果可用裂纹闭合机制予以解释。根据实验结果,作者认为:对于淬火回火钢,当奥氏体晶粒尺寸一致时,真实断裂应变是影响疲劳门槛值的主要因素。
This paper studies the near-threshold fatigue crack growth of 35CrMo steel in air at room temperature. The experimental results show that the fatigue threshold increases with the increase of tempering temperature and the fatigue crack growth rate decreases with R = 0.1. The fatigue threshold and the fatigue crack growth rate do not change with the tempering temperature at R = 0.7. At R = 0.1, a black oxidation zone was found in the near-sill area; at R = 0.7, there were essentially no oxides in the near-sill area. The experimental results can be used to explain the crack closure mechanism. According to the experimental results, the author thinks: For quenched and tempered steel, when the austenite grain size is consistent, the true fracture strain is the main factor that affects the fatigue threshold value.