30CrNiMo8合金钢的弯曲微动疲劳特性

Bending Fretting Fatigue Characteristics of 30CrNiMo8 Alloy Steel

在不同弯曲载荷水平下,对30CrNiMo8合金钢进行了系统的弯曲微动疲劳试验,建立了其微动疲劳S-N曲线,讨论了其弯曲微动疲劳特性及相关规律。结果表明:30CrNiMo8钢弯曲微动疲劳的S-N曲线明显不同于常规疲劳的,呈现"C"曲线特征;随着弯曲载荷的增加,微动依次运行于部分滑移区、混合区和滑移区;在混合区,裂纹最易萌生且微动疲劳寿命最短;微动损伤区的磨损机制主要为磨粒磨损、氧化磨损和剥层;弯曲微动疲劳裂纹的扩展表现为三个不同的阶段,第一阶段裂纹斜向扩展,以接触应力控制为主,第二阶段裂纹转向,受接触应力和弯曲应力共同控制,第三阶段裂纹扩展方向变为垂直方向,以弯曲应力控制为主。

Bending fretting fatigue tests of 30CrNiMo8 alloy steel were carried out at different bending loads, and the S-N curve of bending fretting fatigue was also built up, then the bending fretting fatigue characteristics and related laws of the steel were discussed. The results show that the S-N curve of the steel presented a shape of ＂C＂ curve, which was different from the curve of plain fatigue. With the increase of the bending fatigue loads, the fretting successively run in the partial slip regime （PSR）, mixed regime （MR）, and slip regime （SIR）, respectively. In the mixed regime, the cracks initiated most easily and the fatigue life was the lowest. The wear mechanisms in the fretting damage zones were mainly abrasive wear, oxidative wear and delamination. The propagation of the bending fretting fatigue cracks showed three stages, in the first stage, the crack extended obliquely at an angle and was controlled by the contact pressure, the crack turned in the second stage and was controlled by both contact stress and bending stress, and in the third stage, the crack propagated along vertical direction and was controlled by bending stress.