利用电液伺服疲劳试验机及扫描电镜研究了应力比对J55钢疲劳裂纹扩展行为的影响.结果表明:在相同裂纹扩展长度处,随着应力比R的增大,疲劳裂纹扩展速率明显减小;在较低的△Keff区,应力比R对裂纹扩展速率的影响不显著,随着△Keff的升高,应力比对裂纹扩展速率的影响越来越显著;在相同的Kmax下,裂纹扩展速率随着应力比的增加而明显减小;随着应力比的增大,在高Kmax区,韧性断口的韧窝逐渐由抛物线状转变为等轴状.
The effect of stress ratio on the fatigue crack growth behavior of J55 steel was studied by using SEM and electrohydraulic servo fatigue testing equipment. The results show that the fatigue crack growth rate decreased obviously with the increase of stress ratio R at the same crack growth length. The effect of stress ratio R on fatigue crack growth rate was not obvious at lower △Keff stage, but it was more and more remarkable with △Keff increasing. At the same Kmax stage, fatigue crack growth rate decreased with the increase of stress ratio R. Ductile fracture dimple gradually changed from parabolic shape to equiaxed shape at the high Kmax stage with increasing stress ratio.
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