显微组织对X80钢疲劳裂纹扩展行为的影响

Effect of Microstructure on Fatigue Crack Propagation Behavior of Steel X80

疲劳性能是油气管道安全设计和评价的重要参考因素。在MTS伺服液压万能试验机上,测定了贝氏体/铁素体(B+F)双相X80管线钢在不同应力下的疲劳寿命;使用MTS Landmark 250KN型疲劳试验机对C(T)试样的疲劳裂纹扩展速率d a/d N进行了测定。结果表明,疲劳寿命随最大应力减小而增加,当最大应力降至最大工作应力460 MPa,疲劳寿命约为4.1×10^(5)循环周次;疲劳裂纹产生于钢板表面,然后向内扩展,直至断裂。在Paris区,当ΔK=30 MPa m^(1/2),疲劳裂纹扩展速率d a/d N与应力强度因子幅值ΔK的关系曲线图出现转折点。研究成果可为高强钢的疲劳寿命预测和疲劳性能评估提供参考。

Fatigue performance is an important reference factor for safety design and evaluation of oil and gas pipelines.The fatigue life of bainite/ferrite(B+F)phase pipeline steel X80 under different stresses was measured on MTS servo hydraulic universal test machine.The fatigue crack growth rate d a/d N of C(T)sample was measured by MTS Landmark 250KN fatigue testing machine.The results show that the fatigue life increases with the decrease of the maximum stress.When the maximum stress is reduced to the maximum working stress of 440 MPa,the fatigue life is about 4.2×10^(5)cycles.Fatigue cracks occur on the surface of the steel plate and then propagate inward until fracture.In the Paris zone,the relationship between fatigue crack growth rate d a/d N and stress intensity factor amplitudeΔK shows a turning point whenΔK=30 MPa m^(1/2).The research results can provide reference for fatigue life prediction and fatigue performance evaluation of high strength steel.