某些因素对30CrMnSiNi2A钢门槛值影响的研究

 本文研究了30CrMnSiNi2A超高强钢的降载方式,应力比、试样厚度及裂纹长度对门槛值及低速疲劳裂纹扩展行为的影响。氧化物诱发的闭合效应与氢脆机制的相互作用导致了高强钢的门槛值与应力比的弱相关性。证实了试样厚度及裂纹长度在所观察的范围内对门槛值及低速扩展无明显的影响。

EFFECT OF SOME FACTORS ON THE FATIGUE THRESHOLD OF 30CrMnSiNi2A STEEL

The effect of load-shedding sequences, stress ratio, specimen thickness and crack length on the fatigue threshold behaviour in a high-strength steel, 30CrMnSiNi2A, is investigated. Three load-shedding sequences are adopted, i. e. conventional manual load-shedding technique, computer-based k-gradient methods with constant load control and constant stress intensity factor control. The fracture surfaces in near threshold regime are examined by TEM and SEM. The examination demonstrates that there is little difference in the loadshedding sequences when a/w is not too large, but as a/w enlarges, the k-gradient method with constant stress intensity factor control is superior to the other two sequences in economy of test time and reliability of experimental data. No appreciable influence of the crack length or the specimen thickness on the fatigue threshold values is found in the investigation. The dependence of the fatigue threshold value on the stress ratio is also weakened in this high-strength steel. This fact is explained in terms of crack closure effect and hydrogen embrittlement enhanced by fretting oxidation process.