【作者】 王弘； 高庆； 闫桂玲；

【Author】 WANG Hong GAO Qing YAN GuiLing(Department of Applied Mechanical and Engineering, Southwest Jiaotong University, Chengdu 610031, China)

【机构】 西南交通大学应用力学与工程系；

【摘要】 用2 0kHz超声疲劳试验技术测试40Cr钢、5 0车轴钢在10 5～10 1 0 周次范围内的疲劳性能。结果表明,两种钢并不存在传统意义上的所谓“疲劳极限”。在超过10 7周次,甚至10 9周次的超长寿命范围内仍发生低应力疲劳断裂,其中40Cr钢的S—N曲线呈现“连续下降型”特征;5 0车轴钢呈现“阶梯下降型”特征。对两种钢缺口试样的疲劳性能测试表明,缺口应力集中对疲劳性能的影响呈现“阶段性特征”,在10 6 ～10 7周次内存在一个临界疲劳断裂循环周次Nc,当疲劳断裂循环数Nf<Nc,随Nf 的增加,缺口应力集中对疲劳性能的影响程度呈上升趋势;当疲劳断裂循环数Nf>Nc,随Nf 的增加,缺口应力集中对疲劳性能的影响程度呈逐渐下降的趋势更多还原

【Abstract】 Fatigue behaviors of 40Cr and 50 steel between 10⁵ and 10¹⁰ cycles were tested by ultrasonic fatigue method at a frequency of 20?kHz. The experimental results showed that fatigue failure can occur even at amplitudes below the conventional fatigue limit in the ultra-long life regime of N>10⁷ cycles, and the conventional fatigue limit could not be obtained until 10⁹ cycles. A continuously decreasing S—N curve in 40Cr steel and a stepwise shape S—N curve in 50 steel was observed. The effect of notch stress concentration on the fatigue behaves shows a stage shape and exist a critical number of cycles N_c. If cycle number N_f<N_c, fatigue notch factor K_f increase with increasing number of cycles, whereas, if N_f>N_c, fatigue notch factor K_f decrease with increasing number of cycles.更多还原