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借助疲劳试验机及SEM,研究了应力比对J55钢级疲劳裂纹扩展性能的影响,并对断口形貌进行分析。结果表明:随着应力比增大,进入快速裂纹扩展区的ΔK变小;对于应力比0.1,低Paris区断裂模式为沿晶体学平面发生的穿晶断裂,Paris线性部分为由双滑移机制控制的疲劳条带断裂,高Paris区为疲劳条带断裂和延性静态断裂相结合的断裂模式;应力比为0.3、0.5与应力比为0.1的断裂模式相似;对于应力比0.7,沿晶体学平面发生穿晶断裂模式贯穿整个Paris区。
With the help of fatigue tester and SEM, the effect of stress ratio on fatigue crack growth of J55 steel grade was studied and the fracture morphology was analyzed. The results show that as the stress ratio increases, ΔK decreases into the rapid crack growth zone. For the stress ratio of 0.1, the lower Paris zone fracture mode is transgranular fracture along the crystallographic plane. The linear part of Paris is dominated by double slip mechanism The fatigue zone was controlled by the fracture zone. The high Paris zone was the fracture mode combining the fatigue fracture with the ductile static fracture. The fracture modes with stress ratio of 0.3 and 0.5 were similar to the stress ratio of 0.1. For the stress ratio of 0.7, Transgranular fracture mode occurs throughout the Paris area.