两种不同碳含量铁素体+珠光体型非调质钢的缺口高周疲劳破坏行为

采用旋转弯曲疲劳实验和疲劳裂纹扩展速率实验研究了两种不同碳含量的铁素体+珠光体型非调质钢30MnVS和49MnVS的光滑样和缺口样(应力集中系数Kt=4)的高周疲劳破坏行为。结果表明,缺口对实验钢的疲劳极限具有显著的影响,30MnVS和49MnVS钢缺口样的疲劳极限较光滑样降低了约69%,呈现出较高的疲劳缺口敏感性。与49MnVS钢相比,30MnVS钢的光滑疲劳极限提高了11.0%,缺口疲劳极限提高了8.5%,但30MnVS钢的疲劳缺口敏感性及疲劳裂纹扩展速率均略高。两种实验钢的疲劳裂纹往往萌生于试样或缺口根部表面基体组织中的铁素体/珠光体边界,并优先沿着该边界扩展。实验结果及文献数据的拟合分析表明,可采用Kt的二次多项式拟合公式来简便地计算Kf值。

Notch high-cycle fatigue behavior of two ferritic-pearlitic non-quenched and tempered steels with different carbon content

The high-cycle fatigue behavior of smooth and notched samples(stress concentration coefficient Kt=4)of two kinds of ferritic-pearlitic non-quenched and tempered steels 30 MnVS and 49 MnVS with different carbon content was studied by rotating bending fatigue test and fatigue crack growth rate experiment.The results show that the notch has significant effect on the fatigue limit of the experimental steels.The fatigue limit of the notched samples of the 30 MnVS and 49 MnVS steels is about 69%lower than that of the smooth sample,which shows that the tested steels have high fatigue notch sensitivity.Compared with the 49 MnVS steel,the smooth fatigue limit and notched fatigue limit of the 30 MnVS steel are increased by 11.0%and 8.5%,respectively,but the fatigue notch sensitivity and fatigue crack growth rate of the 30 MnVS steel are slightly higher than that of the 49 MnVS steel.The fatigue cracks of the two kinds of experimental steel often originate from the ferrite/pearlite boundary in the matrix structure of the specimen or notched root,and propagate along the boundary first.The experimental results and the fitting analysis of the literature data show that the quadratic polynomial fitting formula of Kt can be used to calculate the value of the fatigue notch factor Kf conveniently.