超载对X52管线钢疲劳裂纹扩展速率的影响

Effect of overload on fatigue crack growth rate for X52 pipeline steel

用紧凑拉伸试样研究了不同应力比和超载比对X52管线钢疲劳裂纹扩展速率的影响,并对疲劳断口形貌进行SEM分析。结果表明,拉伸超载有阻滞X52钢疲劳裂纹扩展的作用,使疲劳裂纹扩展由超载扩展,减速扩展和恢复扩展三个阶段组成。在恒定的应力比下,超载比越大,裂纹扩展的阻滞效应也越明显,超载前后形貌差别越大;在恒定超载比下,低应力比的裂纹扩展阻滞现象更明显。

The effect of overload on fatigue crack growth rate for X52 pipeline steel under different stress ratio and overload ratio was studied. The fatigue fracture surface morphology of X52 pipeline steel was analyzed by means of scanning electron microscopy, The results show that the tensile overload has the retardation effect on fatigue crack propagation, and the crack propagation curve after overload includes three processes： accelerated growth, retardation growth and recovery growth. Under a constant stress ratio, with the increasing of overload ratio the retardation effect on fatigue crack propagation is more significant and the fatigue fracture surface morphology changes a lot before and after overloading. However, when the overload ratio is kept unchanged the crack growth retardation is more significant at a lower stress ratio.