内部萌生疲劳裂纹扩展速率定量表征

Quantitative characterization of internal initiation fatigue crack growth rate

3Cr13高强钢是航空航天飞行器中常见的结构承力材料,本文对3Cr13高强钢进行超声疲劳试验,结果表明:当超声疲劳循环周次超过10^7后,3Cr13仍会发生疲劳断裂,不存在传统理论的疲劳极限。3Cr13高强钢的超高周疲劳裂纹常从内部夹杂等位置萌生,由于内部萌生裂纹难以直接观测,表征裂纹扩展速率更是存在困难。我们通过阶梯加载获得疲劳弧线以计算裂纹扩展速率,利用Paris公式反推裂纹扩展寿命,发现超高周疲劳寿命主要消耗在裂纹萌生阶段,扩展阶段所占比例很小。

3Cr13 high-strength steel is a common structural load-bearing material in aerospace vehicles. In this paper, ultrasonic fatigue test of 3Cr13 high-strength steel is carried out. The results show that when the ultrasonic fatigue cycle exceeds 10^7, 3Cr13 still undergoes fatigue fracture, and there is no traditional Fatigue limit. The ultra-high cycle fatigue cracks of 3Cr13 high-strength steel often originate from internal inclusions. It is difficult to directly observe the internal cracks, and it is difficult to characterize the crack growth rate. We obtained the fatigue arc by step loading to calculate the crack growth rate, and used the Paris formula to reverse the crack propagation life. It was found that the ultra-high cycle fatigue life was mainly consumed in the crack initiation stage, and the proportion in the expansion stage was small.