喷丸对渗碳件接触疲劳及裂纹萌生扩展的影响

通过一系列试验表明,渗碳后喷丸可使接触疲劳强度提高,在低接触应力下接触疲劳寿命明显增加。对接触疲劳裂纹萌生。扩展至失效全过程所进行的连续追踪观测发现,裂纹萌生于渗碳过渡区;渗碳喷丸后比未喷丸的裂纹萌生寿命增加,扩展速率减小;由钢丸坑连接而成的浅小裂纹为非扩展裂纹;在喷丸影响区,裂纹扩展不同于未喷丸试件,即主裂纹平行于表面扩展;分叉裂纹发生再次分叉向下扩展,从而使裂纹扩展后期速率减小。

Influence of Shot Peening on Contact Fatigue Crack Initiation and Propagation of Carburized Steel

A series of rolling contatct fatigue tests have been done by using a carburized steel with and without shot peening. The results showed that, after shot peening, the rolling contact fatigue strength can be raised, and the fatigue life elongated remarkably under lower contact stress. After continuous observing and detecting for the initiation and propagation of fatigue cracks, it was found that the microcracks were initiated at hte transitional layer of carburized specimen. The life of initiation was increased, the velocity of crack propagation was decreased after shot peening. There were some sallow short microcracks found on the rim surface after shot peening, but they were never propagated. In the shot-peened effected layer, the ways of crack propagation were different from specimens without shot peening, that is, the main cracks propagated parallel to the surface of specimen, some new secondary branching cracks initiated from the old branching cracks and propagated downward. This caused that the velocity of crack propagation in shot peening specimens decreased during the later stage.