45钢的疲劳裂纹扩展速率及其工程构件的寿命预测

Fatigue Crack Growth Rate of 45 Steel and Fatigue Life Prediction of Its Engineering Components

在常温下对调质态和正火态45钢紧凑拉伸试样进行了疲劳裂纹扩展速率试验,并根据Paris公式确定了两种状态试样在稳定扩展阶段的疲劳裂纹扩展速率;分析了含缺陷的45钢工程构件的张开型（Ⅰ型）裂纹尖端的应力强度因子,然后采用损伤容限设计原则,根据断裂力学试验结果计算了构件的疲劳裂纹扩展寿命,并进行了含缺陷45钢构件的动态弯曲疲劳试验,以验证理论推算的合理性。结果表明：正火态45钢的疲劳裂纹扩展速率略大于调质态45钢的;采用损伤容限设计原则估算的含缺陷45钢构件的疲劳裂纹扩展寿命为2.3×10^6次,与动态弯曲疲劳试验结果相吻合。

The fatigue crack growth rate （FCGR） test of 45 steel CT specimens （quenching and tempering condition and normalizing condition） was clone at room temperature, and the FCGR equation in the stably expanding stage was determined By Paris formula. The stress intensity factor of open-type （type I） crack tip of 45 steel engineering components with defects was analyzed, and then according to the test results of FCGR and using the design method of damage tolerance, the fatigue lifetime for crack growth was calculated. At the same time, dynamic bending fatigue test on 45 steel components with defects was also done to validate the correctness of theoretical analysis. The results show that the FCGR of normalizing 45 steel was greater than that of quenching and tempering 45 steel. The calculated fatigue lifetime for crack growth of 45 steel components with defects by the design method of damage tolerance was 2.3 × 10^6 times, which agreed with the results of dynamic bending fatigue test.