40CrNi2MoA合金钢的弯曲微动疲劳特性

Bending Fretting Fatigue Characteristics of 40CrNi2MoA Alloy Steel

在不同弯曲载荷下,对40CrNi2MoA合金钢进行弯曲微动疲劳试验,建立其弯曲微动疲劳下的循环次数-应力曲线;通过对微动损伤区的微观分析,研究该合金钢的弯曲微动疲劳特性。结果表明:40CrNi2MoA钢弯曲微动疲劳应力曲线不同于常规疲劳应力曲线,呈现"C"型曲线特征;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;相对于另外两个区域,混合区试样的裂纹更易萌生、扩展且微动疲劳寿命最短;试样表面的磨损机制主要为磨粒磨损、氧化磨损和剥层;由于接触应力和弯曲应力的影响程度不同,弯曲微动疲劳裂纹的扩展分为三个阶段,即接触应力控制阶段、接触应力与弯曲疲劳应力共同控制阶段和完全受弯曲应力控制阶段。

Bending fretting fatigue tests of 40CrNi2MoA alloy steel were carried out under different bending loads, and its bendingfretting fatigue stress curve was built up. Through the micro-analyses of fretting damage zones, the bending fretting fatigue damage charac-teristics of the alloy steel were investigated. The results show that the bending fretting fatigue stress curve of 40CrNi2MoA steel with ashape of ＂C＂ is quite different from the plain fatigue stress curve. With the increase of the bending fatigue load, the fretting runs in thepartial slip regime （PSR）, mixed regime （MR）, and slip regime （SR）, respectively. Different from the other two regimes, the cracksare easier to initiate and propagate in the mixed regime, and the fretting fatigue life is the lowest. The wear mechanisms of sample surfacemainly are abrasive wear, oxidative wear and delamination. According to the different influence of contact stress and bending stress, thecrack propagation of bending fretting fatigue can be divided into three stages, which are respectively controlled by the contact stress, thecoupling of contact stress and bending stress, only the bending stress.