40CrNiMo钢工程短疲劳裂纹扩展规律

On the Propagation of Short Engineering Fatigue Cracks in 40CrNiMo

对调质40CrNiMo钢光滑及缺口试样进行了旋转弯曲疲劳试验,利用塑性复型技术实现了对工程短疲劳裂纹扩展过程的显微观测、由实验获得光滑试样的短裂纹扩展可由方程do/dN=Bσ~nα予以确定性描述。对于缺口试样的应力接近屈服极限时,疲劳损伤表现为萌生大量的短裂纹体系,利用等效裂纹概念进行统计,缺口试样的短裂纹扩展具有与光滑试样相似的规律。

Rotating-bending fatigue tests were performed on smoothed specimen and circumferentially notched specimen of steel 40CrNiMo. Plastic replica technique was used in microscopy to monitor the propagation of short engineering fatigue cracks. An expression of certainty is thus given from tests as da/dN=Ba*a which is available to the short crack propagation of smoothed specimen. For the notched specimen as its stress approaching to yield point. the fatigue failure appears as that there are a lot of short cracks initiated. As revealed in the statistics utilizing a concept of equivalent crack length, the behavior of short crack propagation in notched specimen is similar to that in smoothed specimen.