缺口应力集中对40Cr钢高周疲劳性能的影响

Influence of Notch Stress-concentration on the Ultra-high-cycle Fatigue Behaviors of 40Cr Steel

用超声疲劳试验方法测定了40Cr钢光滑试样和缺口试样在105-1010周次范围内的疲劳寿命(S-N)曲线,研究了缺口应力集中对疲劳性能的影响。结果表明:两种试样的S-N曲线呈现连续下降特征;缺口应力集中对材料疲劳性能的影响表现出阶段性特征,存在一个临界疲劳断裂循环数Nc,当疲劳断裂周次Nf<Nc,疲劳缺口系数Kf随Nf增加而增大;当Nf>Nc,Kf随Nf的增加而减小。在107以上超高周范围内,Kf和疲劳缺口敏感系数g与Nf具有线性关系。

The fatigue life (S-N) curves of 40Cr steel for smooth specimens and two kinds of notched specimens, in the 105 - 1010 cycles region, were determined using ultrasonic fatigue testing technique. The experimental results showed that the S-N curves of smooth specimens and notched specimens had a continuously decreasing response in the 105 ?1010 cycles region, and the effect of notch stress concentration on the fatigue behaviors showed a stage shape and a critical number of cycles Nc. If cycle number Nf<Nc, fatigue notch factor Kf increased with increasing number of cycles, whereas, if Nf>Nc, fatigue notch factor Kf decreased with increasing number of cycles. The relationship between the fatigue-notch factor Kf or the fatigue-notch sensitivity factor q and the number of cycles Nt to failure in the ultra-high-cycle-fatigure (UHCF) region was givea